eChapters

ABSTRACT

Genetic relationships were estimated among twenty five ashgourd (Benincasa hispida (Thunb.) Cogn.) landraces of different types using PCR-based random amplified polymorphic DNA (RAPD) markers. The molecular survey of the ashgourd germplasm by RAPD using three random primers resulted in twenty scorable bands (average of 6.66 bands per primer) of which two were monomorphic and rest, 18 were polymorphic (90.0%). Pair-wise genetic similarities among the landraces determined using Jaccard’s coefficient ranged from 0.14 to 1.00. The dendrogram based on clustering matrix separated the landraces with morphologically distinct smooth textured fruits from waxy textured fruits and the former group showed less divergence than the latter. With in the group of waxy textured fruits, limited variation was detected among landraces with small and medium sized fruits. Further, morphologically similar landraces with large fruits form distinct clusters with in the major clusters. The study demonstrated the usefulness of the RAPD marker analysis in effectively assessing the genetic relationship present among the ashgourd landraces examined.

Introduction

Genetic markers have assisted in genomic characterization of various crops species (Rafalski and Tingey, 1993). Most of the genetic marker systems rely upon DNA sequence polymorphisms (Staub et al., 1996). Each system has unique advantages and disadvantages based on cost, experimental objectives and type of information desired. Regardless of its inherent methodology, the effective use of any marker system for genetic analysis requires reliability and consistency.

The random amplified polymorphic DNA i.e. RAPD (Williams et al., 1990) or arbitrarily primed polymerase chain reaction (Welsh and McClelland, 1990) marker identifies DNA sequence polymorphisms. In this technique, segments of genomic DNA are amplified in a polymerase chain reaction i.e. PCR (Mullis et al., 1986) with random primers followed by agarose gel electrophoresis. This is simple, relatively inexpensive and is amenable to high throughput investigation. RAPD markers are usually dominant and polymorphisms are observed as the presence or the absence of DNA bands of a particular size. RAPDs are common molecular approaches employed in plant breeding, genotypic differentiation, gene linkage analysis, assigning evolutionary and taxonomic affinities and relatedness and DNA fingerprinting analysis (Lin et al., 1996).

ABSTRACT

Genetic variability was assessed among twenty five distinct drumstick (Moringa oleifera Lam.) landraces using PCR based random amplified polymorphic DNA (RAPD) markers. Genomic DNA extracted from tender leaves was used for RAPD analysis. Thirty five primers were screened and based on the number of bands three primers were selected. The primers produced 34 bands, of which 58 % (20 bands) were polymorphic. The data were analysed using NTSYS pc 2.1 software. The similarity matrix constructed using Jaccard’s coefficient method was subjected to cluster analysis using UPGMA (Unweighted Pair Group Method with Arithmetic Mean) and dendrogram was generated. The pair wise coefficient values in the genetic similarity matrix among the landraces varied between 0.28 and 1.00. The dendrogram based on the matrix separated the landraces with distinct morphological characters and it was noted that the cluster formation was not fully in agreement with the geographical location. The study showed the use of RAPD markers in detecting genetic variability present among the drumstick landraces studied.

ABSTRACT

There is a wide variability in the contents of the commercially important chemical compounds of Centella asiatica depending on the source / ecotypes of the plants. The glycosides found in Indian plants include brahmoside, brahminoside and minor amounts of asiaticosides, which vary in their relative contents depending on the ecotypes. An RAPD marker assisted study of ten accessions, collected from different geographical locations of Kerala, viz., Parumala (Kottayam District), Kottayam, Nagercoil (Tamil Nadu), Mananthala (Trivandrum District), Vlathankara (Trivandrum District), Ponmudi (High range, Trivandrum District), Angamaly (Ernakulam District), Punalur (Kollam district), Pattambi (Palakkad district) and Calicut, was conducted. DNA amplification of the accessions was studied using forty decamer primers, involving 43 cycles. Based on the number of bands four primers were selected. The least similarity coefficient of 0.71 was shown by the Pattambi accession, which formed a separate cluster with all other accessions. Nagercoil and Ponmudi accessions showed the highest similarity coefficient of 0.88 with each other.

ABSTRACT

Exploitation of genetic resistance available in the local germplasm provides a rational solution to most deadly purple blotch disease problem associated with onion production in India. Keeping this in view, efforts have been made to characterize the identified sources of resistance available in the local germplasm. Three lines namely, MS-65-268, PBR-287 and Arka Kalyan-704 that were identified as resistant after screening, were subjected to Random amplified polymorphic DNA (RAPD) analysis for their precise identification and estimation of genetic relationship among them. Highly susceptible variety Arka Niketan was also included in the study for better interpretation. A total of 160 ten- mer random primers were used in the analysis, out of which, 41 exhibited polymorphism among the accessions. Out of these DNA profile with 5 primers namely, OPB02, OPB13, OPC09, OPC12 and OPF08 distinguished the three resistant accessions clearly from the susceptible one. On an average of 2.65 polymorphic, 11.65 monomorphic and 14.3 total bands were produced per primer. The amplified PCR products were of the range from 300 bp to 2 kbp and were consistent, unambiguous and repeatable. Further genetic dissimilarity analysis based on the Ward’s method using minimum variance algorithm and Principal Component Analysis (PCA) of these genotypes using the data generated from RAPD markers revealed high genetic diversity. Dendrogram clustered these four genotypes into two main clusters containing two each. PCA also confirmed high genetic dissimilarity. The least genetic dissimilarity (40.0%) was between PBR-287 and MS-65-268 where as the maximum (65.0%) was found between genotypes Arka Niketan-709 and MS-65-268.

ABSTRACT

In oil palm there are three fruit forms viz. dura, tenera and pisifera. The commercial planting material is tenera produced by crossing dura and pisifera (D X P). Dura has thick shell and less economic part, where as pisifera is an abortic, female sterile type and cannot be reproduced in the normal ways. When tenera is selfed, segregation takes place in the monogenic Mendelian ratio; 1 dura: 2 tenera: 1 pisifera. Since all these palm types are morphologically alike, they can be confirmed only after fruiting, and verifying the internal fruit morphology. Fruiting in pisifera is highly erratic and often prolonged to several years. Proper technique in identifying these palms has been puzzling the breeder all over. Hence, a shell thickness marker is very important for early identification of the oil palm varieties.

An attempt has been taken to screen PCR primers and select the probable primers linked to the shell thickness in the present study. ‘Bulk segregation analysis’ approach was adopted for the study and DNA isolation was carried out from 25 dura and 25 pisifera palms. All the palms were developed from same tenera x tenera crosses. DNA from all the 25 duras and 25 pisiferas were pooled separately. Two pooled DNA samples were subjected to RAPD analysis with 50 random primers using the standard RAPD protocol. The amplified samples were electrophoresed and documented.

Both the pooled samples showed same banding pattern with all the primers, except 10 primers showing differences. Since the genetic configuration of the pooled dura DNA was likely to be same as that of the pisifera pooled DNA, the primers showing difference in banding pattern were the putative primers linked to shell thickness. All the 10 primers would be used for amplification of individual dura and pisifera DNA for confirmation of shell thickness marker.

ABSTRACT

Owing to paucity of available genetic / molecular markers, onion breeding still relies heavily on phenotypic selection methods. DNA markers can provide plant breeders genetic information for indirect selection of plants. All the DNA based procedures require high quality plant genomic DNA. Abundance of polysaccharides and phenolics present in plant tissue often impede PCR amplification. The polysaccharide contaminants can also produce downstream problems by inhibiting many of the enzymes that are employed in subsequent analysis and cloning. RFLP based markers in Allium species pose certain problems due to relatively large size of the genome compared to most other herbaceous crops. As an alternative, RAPD would prove advantageous in genetic analysis of Allium. Here we present our results on optimization of DNA extraction in onion to get amplifiable quality of DNA for further RAPD analysis. Leaf samples were collected from the onion germplasm maintained at Indian Institute of Horticultural Research (IIHR), Bangalore. Dried leaf protocol was suitably modified to obtain fair quality of DNA. After varying each of the ingredients of the extraction buffer we arrived at the optimal extraction buffer, which resulted in good quality DNA. Quality was analyzed by subjecting the DNA to agarose gel electrophoresis and restriction digestion. Extracted genomic DNA was quantified with ‘Hoefer’s Dynaquant’ (Pharmacia, USA). The DNA quantity ranged between 160-2400mg/gm of dried powder. The standardized 25ml PCR mixture contained template DNA (25ng), 5 pmol of primer (Operon Tech. Inc., Alameda), 2mM MgCl₂, I unit of Taq polymerase (Bangalore Genei), with 10x buffer along with 200 mM each of dNTPs. Amplifications were performed in thermal cycler (MJ Research, PTC 100) for 45 cycles after an initial denaturation of 95°C for 3 minutes. In each cycle denaturation for one minute at 95°C, annealing for one minute at 35°C and extension for two minute at 72°C was programmed with final extension step at 72°C for 5 minutes. This fine tuned protocol resulted in clear, informative RAPD profile.

ABSTRACT

The present investigation was undertaken to standardize the DNA extraction methods, to optimize the PCR conditions and generate RAPD’s to study the genetic variability in chrysanthemum. Total genomic DNA was extracted from freshly emerged leaves of chrysanthemum cultivars (Flirt, Nagpur Red, Snow Ball) using different DNA extraction methods (CTAB method, SDS potassium acetate method, SDS miniprep method and urea phenol method). The highest amount of DNA (349μg/g of leaves) was extracted using CTAB method, while it was lowest (130 μg/g of leaves) in SDS miniprep method. The absorbance ratio was high for DNA extracted by CTAB method (1.82) followed by SDS- potassium acetate (1.65) and SDS miniprep (1.60) methods. For standardization of PCR ampl ification conditions, optimization was carried out to determine the optimal concentrations of template DNA, MgCl₂, Taq DNA polymerase and annealing temperature. In general, either no products or products with inconsistent bands were obtained when the concentration of template DNA was 25 ng or MgCl₂ was 1.0 mM with high annealing temperature of 45°C.

ABSTRACT

Of the several PCR techniques developed during the last two decades, random amplified polymorphic DNA (RAPD) offers a simple and economical means of genotype characterization. The information obtained through RAPD characterization is extensively used for the identification of genotypes, screening of duplicates, assessing genetic diversity and monitoring the genetic stability of conserved germplasm. The present study is a report on the DNA fingerprinting of P. nigrum and P. longum cultivars. Fourteen land races and three advanced cultivars of P. nigrum and eleven land races and one advanced cultivar of P.longum were used in the present study. Forty decamer primers from Operon Tech were screened using two representative genomic DNA samples of black pepper. Of these, 10 primers that yielded clear and dominant band patterns were selected for the final analysis of the 29 accessions. These generated 119 amplification products. The total number of markers per primer varied with respect to both P. nigrum and P. longum. Cultivar specific single bands were obtained for a few land races and accessions of both the Piper species.

ABSTRACT

Though the genetic control of sex determination is being explored in several animal systems, no much information is available on the genetic basis for sex specificities in dioecious or sexually polymorphic plant species. Date palm is a unique member of the family Palmaceae which exhibits dioecy. Here we report the sex-specific variation in the genomic DNA of male and female date palms as revealed from an extensive study conducted with palms representing different date palm growing regions of the Kingdom of Saudi Arabia. The genomic DNA content in females was less than 60 per cent compared to those of the male genotypes. Polymerase chain reactions carried out to amplify different segments of the alcohol dehydrogenase (AdhA) gene from the date palm genomic DNA yielded two DNA fragments each in the female genotypes where as the same primers amplified a single fragment in male plants. Genomic Southern analysis of Eco R1 restriction digests showed RFLP between the male and female genotypes with the male plants showing a single hybridization signal of approximately 14 kb size and the females showing six additional bands of varying molecular weights. The results of our investigations reveal the potential of molecular biology in differentiating the sex in date palm at DNA level. Further research is needed to develop DNA markers that will help to unequivocally identify the sex of dioecious plants at the seedling stage.

Introduction

Musa species and cultivars are identified mainly on the basis of morphological characters. Somatic mutations and changes brought about by environment are major obstacles to the accurate identification of clones (Kaemmer et al., 1992). Isoenzymatic markers provide an additional tool for the characterization of germplasm and have been successfully employed in banana to provide better understanding of somaclonal variants and to detect genetic differences at clonal level.

Being located within the center of diversity of cultivated banana, the South Indian state of Kerala accounts for a large share of variability, especially the AA, AB, AAB and ABB genomic groups.Nendran, the French plantain cultivar indigenous to Kerala (Jacob, 1952) is represented by many ecotypes/clones. Other prominent cultivar groups include Mysore (AAB), Rasthali (AAB), Neypoovan (AB), Kunnan (AB), Monthan (ABB) and Karpooravalli (ABB). The variability has been collected and conserved in the field at the Banana Research Station, Kannara. These have been characterized morphologically employing per INIBAP/IPGRI Musa descriptors, facilitating the identification of distinct cultivars, clones and synonyms.This project was initiated to survey the isozyme polymorphism in the cultivar groups and to select suitable system for clonal identification.Results of the study employing three enzymatic systems -esterase, diaphorase and peroxidase are presented

ABSTRACT

Amajor goal of plant biotechnology is to develop effective and lasting means to reduce crop losses due to stress caused by biological organisms. In Indian context, fungal diseases are rated as the most important factor contributing to yield losses. Although, conventional programmes towards development of disease resistant cultivars have been successful , they suf fer from limitations of human health consequences, potential degradation of environment etc. In this scenario, introduction of specific genes encoding for disease resistance through genetic engineering seems to be a viable alternative. Among the various genes that are induced in response to plant defense, chitinases are the most widely studied and used for development of transgenic crops. Keeping this in view, attempt was made to isolate chitinase genes from four fungal species viz., Trichoderma harzianum, Metarhizum anisopliae, Nomuraea rileyi and Alternaria solani by designing primers based on sequence information available in the database. RT-PCR was done using the RNA isolated from the fungal species using the designed primers. Amplified products were eluted, cloned into pTZ57R vector and sequenced. Characterization of sequenced cDNA was done using the BLAST (x) programme of NCBI site. The amplified product (261 bp) from T. harzianum showed 90 per cent homology to endochitinases from T. asperellum and T. viridae. Using this cDNA, full-length chitinase gene of 1556 bp from T. harzianum could be accomplished through RACE (Rapid amplification of cDNA Ends). In M. anisopliae the amplified product of 1500 bp matched the full length gene of 1500 bp and showed 99 per cent homology to M. anisopliae and 96 per cent homology to M. flavoviride. In other two fungal species, viz., Nomuraea rileyi and Alternaria solani, the amplified products did not show any homology to chitinase gene

ABSTRACT

Piper colubrinum is a wild relative of the cultivated species of black pepper, Piper nigrum. The enzyme hydroxy methyl glutaryl Co A reductase which catalyses mevalonate synthesis, is the key enzyme in isoprenoid biosynthesis.This is the rate limiting step in the pathway which leads to the formation of sesquiterpene phytoalecins, a group of plant defense metabolites. Piper colubrinum is known to be tolerant to the dreaded disease called foot rot, incited by Phytophthora capsici. The hmgr gene is reported to confer resistance to fungal pathogens. Hence we made an attempt to isolate gene encoding this enzyme. cDNA was synthesised by reverse transcription from total RNA of P.colubrinum using oligo dt primers. Specific degenerate primers designed based on the conserved boxes among various plant species were used for amplifying hmgr gene from the cDNA. The 700 bp amplicon was cloned in pGEMT vector and sequenced with T7 primer. Multiple sequence alignment using clustal W 1.8 revealed homology of the cDNA fragment with hmgr genes in several other plant species. Maximum similarity was observed among P. colubrinum, Solanum xanthocarpum and Nicotiana tabacum. The cDNA library of P. colubrinum constructed in lTriplEx2 when screened with radiolabelled hmgr amplicon, yielded positive signals. Attempts are being made to isolate full length gene from these clones, which could be later used for imparting biotic stress tolerance to cultivated crop species.

ABSTRACT

The present study was conducted to screen fungal isolates for chitinolytic activity and to clone full-length endochitinase gene from fungus. Among the ten isolates tested (Trichoderma harzianum 1, 2, 3, Trichoderma koningii, Trichoderma virens, Trichoderma viride, Aspergillus oryzae Metarshizium verrucasia, Bauveria bassiana, Nomuraea releyi), Trichoderma koningii showed higest colloidal chitin hydrolysis when screened in Mandels and Reese (1969) salts supplemented with colloidal chitin as the sole carbon source followed by Aspergillus oryzae. Nomuraea releyi showed least chitinolytic activity. Other isolates were on par with each other. The use of diagnostic primers showed specific amplification of 260 bp in Trichoderma harzianum isolates 1,2 and3, Trichoderma koningii and Trichoderma virens, which confirmed presence of endochitinase gene.

Attempts were made to clone full-length endochitinase gene from isolates showing chitinolytic activity. A unique amplicon of 1.7Kb from Trichoderma virens was cloned into linear pTZ57R/T vector with T over hangs. The confirmation of clones was made through blue/white colony assay, plasmid mini-preparation and PCR amplification of these plasmids, sequencing and BLAST search at NCBI. Among the clones confirmed, pSAV804 was sequenced that showed 98% homology with other reported endochitinase genes from Trichoderma spp at DNA and protein level. 85.7% of the protein is conserved. The ORF of the sequence comprises of 822 bases, which deduces 274 amino acids. The position of primer sequence in the insert and BLAST results confirmed the reverse orientation in the vector. The endochitinase gene now needs to clone into the expression and plant expression vectors for further studies.

ABSTRACT

There has been conscious effort to discover and apply biological pesticides for the control of insect predation. Insecticidal proteins/ genes from Bacillus thuringiensis have been deployed as sprays and through transgenic route for crop protection against insect attack and have been successful in protecting the crop damage and environment pollution. However, impending fear of development of resistance to Bt proteins by insects has prompted search for new insecticidal proteins. In this context we are exploring and analysing components of insect immunity as targets for restricting insect feeding behaviour. Insects encounter several microbes during different stages of growth and development. Incidental entry of these microbes elicits a host defense response, which mainly consists of a phenoloxidase (PO) pathway. The invasion of the microbe is recognized by a specific protein, which activates the PO pathway consisting of prophenoloxidase (PPO) & prophenoloxidase activating enzyme (PPAE). Understanding the mechanism of insect immunity will allow us to discover potential targets for inactivating the mechanism of immune action in insects and make them vulnerable to natural microbial infection.

An agronomically important polyphagous pest, Heliothis armigera (Bollworm) was chosen in the present work for studying the components of insect immunity. H. armigera is the most important insect pest of the developing world accounting for heavy damage on various crops including cotton, vegetables, tobacco, potato, groundnut, chickpea and pigeon pea. We have isolated full-length cDNA encoding prophenoloxidase (PPO) and a partial cDNA encoding PPAE from haemocytes of 5th instar larvae of H. armigera. The open reading frame (ORF) of PPO gene is 2.1 kb, which encodes for a 698 amino acid protein with a molecular mass of 77 kDa. Computer-assisted analysis revealed the presence of 60 amino acid long propeptide at the N terminus of protein and 2 copper binding motifs but no signal peptide was detected. The gene was cloned and expressed in a bacterial expression vector pET43b under the induction of IPTG. The SDS-PAGE analysis showed that the protein is expressing in the supernatant in its native form. The expressed enzyme is catalytically active on 4-Methylcatechol upon activation by cetyl pyridinium chloride (CPC). The regulatory role played enzyme in insect immunity is being examined.

ABSTRACT

Production of cardamom in India has been greatly affected by Cardamom mosaic virus (CdMV). The conventional breeding program to develop resistance is a lengthy process. An alternative approach is to develop transgenic cardamom through introduction and expression of viral sequences in the plant. The coat protein (CP) gene of all the CdMV isolates have been cloned in pGEMT vector and sequenced. Sequence comparison studies of the eight isolates of CdMV in their CP and 3’UTR showed that, Kursupara isolate is highly variable from the rest of the isolates (Jacob et al., 2003). Hence the present study was undertaken to introduce the Kursupara CP gene of CdMV into cardamom plants in order to develop pathogen-derived resistance in cardamom. The CP gene of the Kursupara isolate of the virus was amplified with and without the 3’untranslated region (3’UTR) from the viral clone. These PCR products were cloned into the pXcmkn12 vector and sub cloned in to a plant expression vector (pAHC17) at the BamHI site, under maize ubiquitin promoter. Work is in progress towards the biolistic transformation of cardamom with these constructs.

ABSTRACT

The cry1A genes of Bacillus thuringiensis (Bt) are widely used to engineer lepidopteran insect resistance in crop plants including horticultural crops. Continuous exposure of a single kind of Bt toxin can lead to resistance development in insect pest. Due to the difference in structure and unique insecticidal mechanism, cry2A genes are promising candidates for management of resistance development. Since India is rich in biodiversity and genetic resources, indigenous Bt strains are valuable tool for identification of novel cry genes. The present study describes the cloning of cry2Ab from a new indigenous strain of Bt, 14RI. The presence of cry2Ab gene in Bt strain 14RI was confirmed by PCR with primers specific to its internal region. Primers corresponding to the flaking region of cry2Ab were used for amplification of cry2Ab orf from the Bt strain 14RI. The amplified cry2Ab orf was first cloned into the T/A cloning vector, and then fused to the downstream of the cry2Aa promoter along with its orf1 and orf2 in the Bt shuttle vector pHT1301. Acrystalliferous Bt strain 4Q7 has been transformed with recombinant pHT1301 to express the cry2Ab of Bt strain 14RI.

ABSTRACT

Basic understanding of plant cell proliferation and differentiation is essential for applying modern techniques of genetic transformation. The lack of understanding about the physiological and molecular mechanisms underlying in vitro morphogenesis, together with the non-availability of reliable morphogenetic markers, is one of the most serious constraints for application of gene transfer technology to plant improvement. Plant tissue culture has therefore remained an empirical science. In recent years, concerted efforts are being made to understand the molecular control of cell differentiation. In light of this, present work was carried out to study the role of CKI1 (cytokinin independent 1) gene, one of the genes implicated in shoot regeneration, by transforming the tomato cotyledons through Agrobacterium mediated transformation with two different gene constructs one with CKI 1 gene and another without CKI1 gene. In both the constructs, nptII gene was used as a selectable marker. Transformation of tomato cotyledon explants with CKI 1 gene resulted in higher regeneration of putative transformant s (8.0%) as compared to transformation of explants without CKI1 gene (2.1%). The results show that CKI1 gene has a role in increasing the regeneration frequency in tomato.

ABSTRACT

Rapid optimization and improvement of papaya transformation necessacitates, a quick, non-destructive marker, which permits early detection of transformed tissue. We assessed the ability of a modified version of the green fluorescent protein gene (GFP) to act as the reporter. Transgenic papaya (Carica papaya L.) plants were developed using immature zygotic embryo as the expl ants and Agrobacterium tumefaciens as the transformation inducer. GFP gene (pBIN35Smgfp-ER) under the control of the Cauliflower Mosaic Virus (CaMV) 35S promoter was used as the reporter gene. Media P (modified MS basal medium with B vitamins supplemented with picloram 1 mg/l) and BN (modified MS basal medium with B vitamins supplemented with BAP: NAA 1:0.1 mg/l) supplemented with kanamycin (50 mg/l) were used for regeneration of transgenic papaya under selection pressure. GFP gene expression was detected at the juvenile stages viz. at early stages of somatic embryogenesis. 35S promoter driven GFP gene activity was also detected in the epidermis and the vascular tissues of the leaf petiole. Visualization under microscope and subsequent DNA analysis (Southern hybridization) showed that kanamycin resistant plants carried and expressed the GFP transgene. Expression of the GFP as green fluorescence served as a useful non-destructive indicator of successful transformation.

ABSTRACT

Zingiber officinale is a herbaceous perennial. The absence of seed set in ginger makes conventional breeding methods inapplicable. Genetic modification through biotechnological means is the only way for introducing novel genes into the cultivated types. Transient expression of the gus reporter gene was used in preliminary experiments. Agrobacteruim tumefaciens strains EHA105/p35SGUS Int. effective in expressing b- glucuronidase activity was used for standardizing the optimum conditions for effecting transformation, such as preculture of explants, bacterial dilution, infection time, co-cultivation period etc. In addition, effects of acetosyringone and explant wounding were evaluated using the same strain. Genetic transformation of bud and regenerated plantlets was confirmed by their ability to grow on MS medium containing kanamycin 100 mg l-1 + cefotaxime 300 mg l-1 by histochemical b-glucuronidase assays.

ABSTRACT

Role of cytokinins in the regulation of sink development in potato was studied by transgenic approach. Transgenic potato plants over-expressing Agrobacterium native ipt (gene for isopentenyl transferase, rate limiting enzyme in cytokinin biosynthesis) under the transcriptiona l regulation of tuber specific patatin promoter were developed. Transformants obtained showed normal phenotype, while the cytokinin levels showed significant increase over the control plants for the various cytokinins tested, viz., trans zeatin riboside (tZR), dihydrozeatin riboside (DHZR) and isopentenyl adenosine (iPA). The primary transformants were hardened and tested under green house conditions. Green house studies showed a significant increase in the number of tubers in ipt transformants when compared to the wild plant as well as GUS transformant. However, the total weight of tubers did not show appreciable difference between transformants and control plants. Reduction in the weight of individual tubers appears to be due to source limitation.

ABSTRACT

Astudy was undertaken with the main objective to standardise the Agrobacterium mediated genetic transformation technique in Dendrobium Sonia 17. Protocorms and protocorm like bodies (PLBs) of Dendrobium orchid were transformed by Agrobacterium tumefaciens strains LBA4404 and EHA105 harbouring the plasmids pCAMBIA2301, pCAMBIA1301 and PBI121. The PLBs were generated in vitro by culturing the shoot apices in half strength MS medium. The protocorms were obtained by culturing the seeds in vitro. The sensitivity of orchid tissues to various antibiotics viz., ampicilin, rifampicin, cefotaxime, carbenicillin, kanamycin and hygromycin was evaluated to use the antibiotics as selection agents. The sensitivity was studied in detail by scoring the tissues, based on the morphological changes as those remaining fully green, partially discoloured, bleached, completely turning brown and dead. The various requirements for transformation viz., the type and size of explant, infection time, wounding, co-cultivation and incubation period, concentration of acetosyringone required, elimination of bacteria, and the selection of transformants were optimised to establish a successful transformation system. The pre- cultured explants were mixed thoroughly by gentle swirling with the bacterial cells obtained by centrifuging the bacterial suspension, and also with the bacterial suspension diluted to 1/5 with fresh medium. Then the explants were cocultivated with the bacteria for 2 days at 28°C. The transformation was performed through two consecutive stages of cultivation, the first stage on half strength MS medium containing cefotaxime and subsequent stage on selection medium containing kanamycin. Initially recovered PLBs following co-cultivation, were allowed for further selection with kanamycin. New PLBs and leaves were formed from the transformed PLBs when they were regenerated under kanamycin selection. Successful transformants were obtained with a maximum transformation efficiency of 3.0 per cent with the addition of acetosyringone 100 mM. Out of the kanamycin resistant PLBs 69.23 per cent were GUS positives. The newly formed PLBs and leaves when subjected to histochemical GUS assay indicated successful transformation and it was detected as distinct blue spots on the PLBs after 24’ hours. The PLBs which were not co-cultivated with Agrobacterium were green in colour. The transformation were further confirmed by PCR analysis.

ABSTRACT

Cassava has developed importance mainly as an industrial crop due to its ability to store large quantities of starch (74% to 85% of dry weight) within secondary root structures. Cassava starch is exploited as a source of human food, feed for livestock and as raw material for the food processing and chemical industries. Research accomplishments during the last four decades helped India to have the top position among cassava growing countries with an average yield of 24 t ha-1. However several traits like starch quality, high protein , post harvest deterioration etc can be altered only through the development of transgenics. The present study summarizes the results of the experiments undertaken to optimize the protocol for the development of transgenic cassava through Agrobacterium mediated gene transfer. Friable Embryogenic Callus (FEC) was developed in the cassava var. TMS 60444 us ing Murashige and Skoog (MS) media with picloram (50μM). Experiments were conducted to study the efficiency of different Agrobacterium stains viz, AGL 8, GV3101, C58C1, LBA 4404 and EH105 in transforming FEC. The strains differed in their growth rate. The strains EH105 and AGL were slower in growth as compared to other strains and the protocol was modified accordingly. Among all the strains, EH105 resulted in maximum recovery of transgenic tissues. The paper also summarizes the present status of development of transgenic cassava along with future thrusts.

ABSTRACT

Coleus forskohlii Briq. is a threatened medicinal plant , susceptible to fungal disease. The regeneration of this plant has been achieved on MSo medium supplemented with 2 mg/l or 3 mg/l BAP and 0.2 mg/l 2,4-D for callus induction using leaf as explants. Multiple shoot production from the leaf-derived transformed callus of coleus has been standardized using the various concentration of NAA with 2 mg/l BAP. The combination of 2 mg/l BAP and 0.5 mg/l NAA was found to be best for multiple shoot production. Rooting was found to be best on MS medium supplemented with 0.7 mg/l NAA. Coleus forskohlii was transformed with glucanase-chitinase gene along with npt-II gene. The presence of npt-II genes in the leaves of putative transformants were confirmed by PCR analysis. SDS- PAGE analysis and glucanase assay revealed the over expression of glucanase enzyme in the transgenic plants. The transgenic coleus plants survived the infection caused by Fusarium chlamydosporium due to the accumulation of glucanase-chitinase enzyme, where as control plants were susceptible to the disease.

ABSTRACT

An efficient in vitro micro propagation protocol was developed for direct shoot produc tion of Contoloupe (Cucumis melo variety (NS Abhijit) using cotyledons as explant. The excised cotyledons were cultured on Murashige and Skoog’s medium (MS) contain- ing plant growth regulator, 6 Benzyl adenine with various concentrations for the study of shoot production. The best condition for the shoot production was with 1.2mg/l Benzyl adenine (BA) in MS medium. The shooting frequency was 65% and three shoots were obtained from each explant after 14 days of culture. The shoots (~1.5 cm length) were rooted most effectively on 0.1mg/l of α Naphthalene acetic acid (NAA) supplemented MS medium. We have also standardized the transformation protocol for GUS gene in the muskmelon variety Eden Gem to see test the feasibility of this variety for Agrobacterium mediated transformation. The transformed explants were confirmed through Indigogenic GUS assay.

ABSTRACT

Chilli (Capsicum annuum L.) is a vegetable and spice crop of worldwide importance. Despite the fact that other closely related members of the Solanaceae family are easily transformed by genetic engineering, capsicum still remains recalcitrant to in vitro manipulation, due to lack of proper elongation of multiple shoot initials. An attempt has been made to standardize transformation protocol in two local cultivars of capsicum viz., Byadgi dabbi and Sankeshwar, using shoot tip explants.

The Shoot tip explants were co-cultivated (for 2 days) with Agrobacerium strain EHA105 harboring pBinBt3 plasmid having cry1AC gene and nptII marker linked to the CaMV 35S promoter and nos terminator. After co-cultivation shoot tips were transferred to MS medium containing 2mg/l IBA, 100mg/l kanamycin and 300mg/l cefotaxime. Survived plants were checked for the presence of transgene using cry1 AC and npt II specific primers. Expression of cry1AC gene in these plants was checked using DesiGen Xpresstrips.

ABSTRACT

Chilli is the universal spice of Kerala, known for its pungency, flavour and colour of fruits. Of the five domesticated species of Capsicum, C. annuum is the most extensively cultivated one. Bell pepper (C. annuum L.) is mainly used as a vegetable, because of its low pungency and good flavour. It is used as raw in salads, and also in cooked form. Application of biotechnological tools in this crop for improving the quality, shelf life and tolerance of the crop to stress conditions has been limited. This is mainly due to lack of an efficient regeneration system. We reported a viable protocol for the regeneration of whole plant from the hypocotyl earlier. We also succeeded in developing a protocol for genetic transformation of bell pepper using Agrobacterium tumefaciens. The strain EHA 105 containing gus intron and npt II was used for co-cultivation. The dilution of bacterial culture and time of infection were standardised. This was followed by killing the bacterial cells using cefotaxim @ 250ppm. Transformants were selected on MS medium supplemented with kanamycin. Staining of the regenerants with X-gluc revealed presence of blue spots, confirming transformation. This protocol could be exploited for improving the commercial traits of bell pepper by incorporating desirable genes through Agrobacterium mediated transformation.

ABSTRACT

Holostemma ada-kodien K. Schum, is a laticiferous climber belonging to the family Asclepiadaceae. The root tubers of the plant are medicinally important and are utilized as a major ingredient of the drug, Jivanti. The roots of Holostemma are sweet, ophthalmic, emmolient, alterant, tonic stimulant, aphrodisiac, expectorant and galactagogue and are useful in ophthalmopathy, orchitis, cough, burning sensation, stomachalgia, fever and to cure ‘tridosha’ (Warrier et al., 1995). The sugars and amino acids present in the tuberous roots are responsible for the medicinal properties (Ramiah et al., 1981). There is a huge demand for the root tubers of Holostemma in the South Indian pharmacies and more than 150 metric tons of roots are needed every year (Nair et al., 1992). The destructive and ruthless collection of tuberous roots in recent times has led to acute scarcity of the plant and consequently it has been listed as vulnerable and rare in the FRLHT red list of medicinal plants (FRLHT, 1997). Extending the commercial cultivation of Holostemma is practically impossible due to the increasing land pressure and the perennial nature of the crop. An alternative to meet the increasing demand is to produce the active chemicals in Holostemma through in vitro techniques. In vitro techniques have been extensively studied to produce the different secondary metabolites from various medicinal plants. A strong correlation between secondary metabolite production and morphological differentiation gives more impetus to the application of organized cell culture particularly the root cultures for the large-scale production of phytochemicals in vitro. Transformed root cultures - the so called hairy root cultures obtained after the insertion of T-DNA from the root inducing (Ri) plasmid of the Agrobacterium rhizogenes into the plant genome (Ackermann, 1977) has emerged as an important tool for the production of secondary metabolites in vitro (Rhodes et al., 1987). Hairy roots have advantages of fast growth, organ differentiation and stable secondary metabolite production (Banerjee et al., 1995). We report here the hairy root induction from shoot buds and seedling hypocotyls in infection with A. rhizogenes useful in exploring the possibilities of large-scale in vitro secondary metabolite production in this rare medicinal plant.

ABSTRACT

The black pepper, ‘the king of spices’ cultivation fetches foreign exchange worth millions of rupees annually, has been constrained by the quick wilt disease caused by the fungal pathogen Phytophthora capsici. Peptides with systematic variations in cationicity, hydrophobicity and amphipathicity were designed based on Chou-Fasmann parameters and sequential alterations of amino acids were tested for antifungal activity against Phytophthora. The antifungal properties of these biodegradable and ecofriendly peptide peptides were evaluated following in vitro microplate titre assay using Phytophthora zoospores. Two peptides LD1 and LD4 showed very low MIC value as compared to that of well-known antifungal peptides and standard chemical fungicides. Fluorescent staining technique using fluorescent brightener-28 and propidium iodide dyes has revealed that the site of action of the designed peptides is the cell membrane. These peptides showed very low haemolytic potential inspite of their potent antifungal activity. The in vivo evaluation of the peptides on fungi infected detached pepper leaves has demonstrated their high antifungal potential.

ABSTRACT

Fruit rot and die back caused by Colletotrichum capsici is the destructive disease in chillies. The potential of Pseudomonas fluorescens for the management of fruit rot of chillies was evaluated under greenhouse and field conditions. Among the various strains of P. fluorescens tested in vitro, the strain Pf1 significantly inhibtied the mycelial growth of C. capsici. Combined application of talc-based powder formulation of P. fluorescens to seed (10 g/kg seed) and foliage (1 kg/ha) effectively controlled the fruit rot disease. Early and high induction of various defense compounds were observed due to P. fluorescens treatment.

ABSTRACT

Biofertilizers can supplement the chemical nutrients and helps in reducing the production expenditure in agriculture. Crop biofertilization with microbial consortia is an important strategy to improve the physical, chemical and biological conditions of the soil. The facultative methylotrophs are capable of fixing atmospheric nitrogen, besides it produces phytohormones viz; IAA, GA and cytokinin, vitamin B₁₂, polysaccharides, PHB, and siderophores. The essential nutrients are considered as the most important, among the factors limiting growth and yield of the tomato crop. The application of adequate amount of fertilizers is a pre-requisite for exploiting the genetic potential of tomato variety. Therefore, efficient and economic use of the fertilizer with microbial consortia would help in decreasing the input costs for raising bumper crop.

More number of studies carried out on the effect of facultative methylotrophs in different parts of the world and in India. The results confirmed that the facultative methylotrophs have a greater importance in increasing the growth and yield of various crop plants. Keeping this in view an experiment was conducted to find out the interaction effect of facultative methylotrophs with other bioinoculants viz., Azospirillum, Azotobacter, PSB and VAM (by seedling dip method followed by PPFM phyllosphere spray) on yield of tomato var Ruchi. The results showed that the treatment with above microbial consortia (50.71 t/ha) was found to increase the yield of the tomato crop by 62.73 percent over uninoculated control (18.90 t/ha) and individual treatments.

ABSTRACT

Phytophthora rot is the most destructive disease of black pepper nursery inflicting heavy crop losses. Considering the seriousness of the disease, the present study was undertaken to isolate and select the efficient antagonists from pepper nurseries raised in Government farms at Chelakkara, Pazhayannur, Mannuthy and Pananchery of Thrissur district. A quantitative estimation of the rhizosphere microflora from different nurseries revealed more abundance of soil bacteria followed by fungi and actinomycetes. Based on cultural characters of the rhizosphere microflora, 22 fungi, 20 bacteria and five actinomycetes were selected for further studies. Antagonistic action of soil microflora against Phytophthora capsici was studied by dual culture method in comparison with that of standard culture of T. harzianum. The study revealed that all fungal isolates and five bacterial isolates were antagonistic towards the pathogen with varying degrees. Among the fungal isolates, 13 isolates including T.harzianum recorded cent per cent inhibition of P.capsici. From among the fungal isolates that showed antagonistic reaction in dual culture, further selection of efficient ones was carried out based on the antagonistic index (AI). The isolate 22 F₂ (Trichoderma sp.) showed the maximum AI of 3000 followed by isolate 34 F₂ (Trichoderma sp.) and T. harzianum with an AI of 1500 each. The cultural and morphological characters of the efficient native isolates (22 F₂ and 34 F) were studied and were identified as Trichoderma longibrachiatum Rifai aggr. and Trichoderma viride Pers. ex S.F. Gray aggr. The three antagonists were found parasitic on P.capsici as evidenced by excessive coiling, penetration and disintegration of the hyphae and thereby these Trichoderma spp. used in the study is found to have effective parasitic effect on the pathogen in addition to some degree of antibiosis and these fungi could be utilised for the management of Phytophthora rot in black pepper nursery.

ABSTRACT

Studies on the impact of bio-fertilizers with levels of NPK on bulb yield, dry matter production, nutrient uptake and cost: benefit ratio in onion (cv. Bellary Red) were conducted in medium black soils during kharif and rabi seasons of 1999 and 2000 both under irrigated and rainfed conditions at the Agricultural Research Station, Hiriyur located under Central Dry Zone of Karnataka. The treatments were; T₁-Control, T₂-Azotobacter, T₃-Azotobacter+75% N+PK, T₄-Azotobacter +100%N+PK, T₅-Azospirillum, T₆-Azospirillum+75% N+PK, T₇-Azospirillum+100%N+PK, T₈-VAM, T₉-VAM 75% P+NK, T₁₀- VAM+100%P+NK, T₁₁ ? recommended NPK(125:50:125 kgha-1) and T₁₂-75% recommended NPK. The experiments were laid out in RBD in three replications.

The bio-fertilizers Azospirillum brasilence (500g ha-1) and Azotobacter vinelandii(500g ha-1) were applied to seedlings at transplanting separately by dipping the roots in the slurry for 15 minutes. The VAM fungi - Glomus mossae was applied to soil @ 1 kilogram per square meter area of nursery bed. The recommended dose of FYM @ 25 t ha-1 was applied to all the treatments as basal dose.

The results of the investigations revealed that the plants provided with Azospirillum + 100% N+PK (T₇) produced highest bulb yield (250.29;339.02;232.98 q/ha), highest total dry matter production (7053.96;8992.78;6287.03 kg/ha), maximum uptake of N, P a nd K ( 1 5 7 . 8 8 : 7 3 . 5 6 ; 7 0 . 4 6 N PK k g / ha ) , ( 2 0 6 . 8 6 : 9 6 . 2 5 : 9 1 . 1 0 N PK k g / ha ) , (131.81:50.25:71.24 NPK kg/ha) and also the maximum cost:benefit ratio of 4.00 (1:400), 5.42 (1:5.42), 3.94 (1:3.94) under irrigated condition during kharif and rabi seasons and under rainfed situation during kharif season respectively.

Thus, among all the treatments, application of Azospirillum + 100% N + PK (Azospirillum + 125:50:125 NPK kg/ha) was found to be most remunerative considering the nutrient uptake, bulb yield and total dry matter production and cost:benefit ratio, which gave the highest returns. This level can be followed for Bellary Red onion irrespective of seasons both under irrigated and rainfed conditions in the Central Dry Zone of Karnataka.

ABSTRACT

Soft rot of ginger caused by the fungus Pythium aphanidermatum is a major disease affecting ginger cultivation. To combat invading pathogen in the event of infection plants are known to produce antimicrobial pathogenesis related proteins (PR proteins) prominent among which are antifungal hydrolases like glucanases and chitinases. Since Pythium lacks chitin in its cell wall, increase in level of glucanase in the plant may enhance the resistance of ginger to soft rot disease. Signal molecule like ethylene plays a prominent role in the defense response of plants. The present study was undertaken to investigate the role of ethylene in enhancing the level of glucanase in the ginger system. Detached leaves of Rio de Janeiro variety of ginger were used in different experiments. Leaves were treated with ethephon at different concentrations and different time intervals. Increase in the glucanase activity by ethephon treatment was quantified by enzyme assay using crude protein extract. Glucanase levels showed an initial increase with increasing concentration of ethephon but decreased at higher concentration (5 mg/ml). A longer exposure of detached leaves to ethephon (48 h) resulted in 3.7 fold increase in glucanase activity compared to control. The level of enhancement of the glucanase transcript also followed a similar trend as revealed by RT PCR analysis. Two acidic isoforms of glucanase were detected using native PAGE and their levels were found to be enhanced by treatment with ethephon. An increase in the levels of glucanase may contribute to the plant’s ability to resist infection by Pythium.

ABSTRACT

Chickpea is an important pulse crop of India and most suited to the use of rhizobia for its nitrogen requirement. Mesorhizobium ciceri which interact with the crop are poorly understood. Attempt has been made to select M. ciceri with several beneficial properties. Sixty four isolates of M. ciceri collected from the nodules of several chickpea varieties and mutant lines were screened for their growth properties on nitrogen free medium. Isolates MC59 and MC 18-7 showed normal growth and had ARA values at half level to that of Azotobacter. PCR amplification results suggested the presence of ACC deaminase gene sequence both in Azotobacter and M. ciceri. Invariably all isolates showed the presence of one plasmid in the range of 35 kb to 40 kb size.

ABSTRACT

Bacterial wilt caused by Ralstonia solanacearum is the major constraint for cultivation of tomato in Kerala. Biocontrol of plant pathogens is becoming an important component of integrated disease management. Among the various antagonists tested against R. solanacearum of tomato, fungi were more effective than bacterial and actinomycetes organisms. Among them, Trichoderma virens, T. viride (Ozhalapathy and Vellanikkara) and T. pseudokoningii were the effective ones, recording the maximum antagonism index (AI) value of 6000 under in vitro condition. They inhibited the pathogen completely by the mechanism of both lysis and overgrowth. In pot culture study, T. viride and T. pseudokoningii and commercial Pseudomonas fluorescens gave maximum protection against wilt incidence. Under field condition, T. viride (Ozh), T. pseudokoningii and P. aeruginosa showed the lowest wilt incidence of 50.0, 58.3 and 58.3 respectively against cent per cent incidence in the control plot.

ABSTRACT

Brinjal is an important solanaceous vegetable, which holds coveted position among the different vegetables. Developing hybrids with high yield and resistance to borer would be highly beneficial. The biochemical parameters are used to study the mechanism of resistance to pests and diseases. With this aim, the biochemical constituents were estimated in five intervarietal hybrids and their parents with susceptible variety. The study on biochemical basis of resistance to shoot and fruit borer showed that among the parents of intervarietal crosses, EP 65 had the highest level of peroxidase, polyphenol oxidase and total phenol content in both shoot and fruit and it also recorded high content of solasodine next to APAU Bagmathi. Among the hybrids, the cross EP 65 x Pusa Uttam had the highest level of peroxidase and polyphenol oxidase activity in both shoot and fruit and high level of total phenols and solasodine content next to EP 104 x APAU Bagmathi . The susceptible check (CO 2) registered the lowest value for all the biochemical constituents .The study revealed that the genotypes with high or moderate level of these biochemical constituents suffered less for shoot and fruit borer infestation.

The native gel electrophoretic study showed that for peroxidase enzyme, the intervarietal hybrids EP 65 x Pusa Uttam, EP 12 x MDU 1 and EP 104 x APAU Bagmathi and the susceptible variety CO 2 did not show difference in the induction of isoform (PO-1) and all were single and thick. For polyphenol oxidase (PPO), the intervarietal hybrids and the variety CO 2 showed single and strong band induction

The evaluation of genotypes based on biochemical constituents and isozyme studies revealed the superiority of the parents EP 65, APAU Bagmathi and MDU 1and the hybrids EP 65 x Pusa Uttam, EP 12 x MDU 1 and EP 104 x APAU Bagmathi. The identified hybrids with high yield and resistance to shoot and fruit borer could be exploited for commercial cultivation.

ABSTRACT

Vesicular arbuscular mycorrhizal (VAM) fungi are known to improve the mineral nutrient and water status of the plants even under various abiotic stresses. During present investigations VAM fungus Glomus fasciculatum was used for developing mycorrhizal association with Sesbania sesban (L.) Merrill. In general mycorrhizal (M) plants exhibited better growth and development and showed significantly higher chlorophyll content, better PS II as well as PS I activities when compared to NM plants.

In general, both M and NM plants invariably showed reduced growth and development upon exposure to drought stress. However, the M plants could confront this abiotic stress more effectively than the NM plants. This was vindicated by the faster decline in the chlorophyll content and the photochemical activities in NM plants in comparison to the M plants upon exposure to drought stress. The higher photosynthetic efficiency of the M plants under drought stress indicate the presence of certain adaptive strategies in the form of osmotic adjustment operational in these plants through VAM association. The osmotic potential of the leaf cell sap in M plants was significantly lower than that of NM plants of Sesbania sesban, when exposed to either drought stress. The lower y of M plants as compared to NM plants under drought stress could be due to the accumulation of compatible solutes such as proline and sugars. A higher level of proline accumulation in the leaves of M plants than NM plants exposed to drought stress help them to counteract the adverse effects of stress better than NM plants.

ABSTRACT

Anursery experiment was conducted to study the effect of solarization, selected native antagonists viz., T. viride and T. longibrachiatum and the standard culture of T. harzianum for assesseing the growth enhancement and management of Phytophthora rot in black pepper nursery. The experiment was laid out at College of Horticulture with 20 different treatments and replicated thrice. The sprouting percentage of cuttings in different treatments was worked out at different intervals, which showed significant difference. In general, it was observed that the maximum sprouting percentage was noticed in treatments where solarized potting mixture and biocontrol agents were used. The population of soil microflora viz., fungi, bacteria and actinomycetes in different treatments were also estimated. The study indicated a fluctuation in the population of soil microbes in various treatments at different periods of observation. The observations on height and number of leaves of pepper cuttings in different treatments were recorded. It was noticed that cuttings raised in solarized potting mixture incorporated with native antagonists, especially T. viride, exerted a significant effect in increasing the height of cuttings. With regard to total number of leaves, it was also observed that addition of native antagonists in solarized potting mixture had a positive effect in increasing the leaf production. Thus, the effect of solarization enhanced the growth parameters in crop plants by making available the required nutrients. The increased growth response of plants by soil application of Trichoderma spp. may be due to the production of growth promoting substances by the antagonists. Thus, the nursery experiment revealed that, in general, soil solarization and incorporation of antagonists had a favourable effect in promoting the growth of pepper plants besides checking the Phytophthora rot in black pepper nursery.

ABSTRACT

Microbial antagonists not only reduce the soil borne disease, but also influence the growth of crop plants. In a study conducted for five years on the effect of microbial antagonists on damping off incidence and biometric characters of solanaceous seedlings, it was observed that seed treatment and soil application of Trichoderma viride, T. harzianum, Pseudomonas fluorescens, Azotobacter chroococcum reduced the damping off incidence considerably in brinjal, chilli and tomato. Application of these microbes also increased the per cent germination and promoted vigour of solanaceous seedlings as compared to control. Among the various antagonists, T. viride was the most effective one reducing the damping off diseases as well as promoting the growth of solanaceous vegetables.

ABSTRACT

Banana is one of the most accepted and versatile fruit crops across the globe and in Kerala, it is the most important economically profitable fruit crop grown, mainly by small and marginal farmers, providing a vital source of income. However, the productivity of this crop is very much reduced due to various diseases of which rhizome rot disease is an important one. In recent years, this disease has become a serious problem to the commercial cultivation of banana in southern states of India like Kerala, Karnataka, and Tamil Nadu.In Kerala the disease incidence is found to be nearly 30% and it will soon become cent percent if unnoticed since the disease is more seen in banana cultivated in paddy fields, and the area under the cultivation of banana in paddy fields in Kerala is rapidly increasing. The disease is caused by a gram negative bacterium, Erwinia carotovora. Developing an integrated management package involving biocontrol methods is the only remedy for managing the disease within the financial limits of the marginal farmers. With this intension a pot culture experiment was conducted to study the inhibitory effect of different biocontrol agents and botanicals in the incidence of the disease after testing their efficacy under in vitro cond itions. The results revealed that the biocont rol agent Pseudomonas flourescens (commercial preparation @ 7g /plant) was found to effective in managing the disease. The co- efficient of infection was found to be13.9% as against the control pot where it was 56.24%. With regard to the growth parameters also, the treatment with this biocontrol agent gave superior results. Thus it was proved that Pseudomonas flourescens (commercial preparation @ 7g /plant) could be successfully utilized in the integrated disease management making it cost effective.

ABSTRACT

To study the antagonistic potential of rhizobacteria against the soil borne pathogen Rhizoctonia solani, soil bacteria were isolated from the rice fields of Agricultural Research Station, Mannuthy and screened against R. solani. Out of the 22 rhizosphere bacteria, 10 were found to be antagonistic to R. solani. Seven belonged to the genera Bacillus, Pseudomonas, Clostridium and Sporosarcina and the rest three being unidentified. The bacterial isolates viz., 2B, 4B, 19B (Bacillus sp.), 28B and 10B (Sporosarcina sp.) showed increase in inhibition on extending the period of incubation. Maximum inhibition was expressed by 2B on the third day of inoculation followed by 4B, 10B (Sporosarcina sp.), 7B (Bacillus sp.) and Pseudomonas fluorescens. The bacterial isolate 4B and 7B (Bacillus sp.) and 10B (Sporosarcina sp.) completely prevented the sclerotial production of R. solani whereas 1B (Clostridium sp.), 2B, 19B (Bacillus sp.) and P. fluorescens delayed the sclerotial production. Pot culture studies also confirmed the superiority of these rhizobacteria in controlling the infection by R. solani. The potentiality of these rhizobacterial antagonists can be exploited for the management of soil borne pathogens like R. solani.

ABSTRACT

Phytophthora pod rot (PPR) incited by Phytophthora palmivora is the most serious disease of cocoa, inflicting heavy crop losses. Since, antagonistic microbes are useful in ecofriendly management of plant diseases, the present study was undertaken to harness the potential of antagonistic epiphytic microflora isolated from cocoa pods for the management of PPR of cocoa. A quantitative estimation of the epiphytic microflora from pods collected from different locations of cocoa gardens of Thrissur district revealed more abundance of bacteria followed by fungi, actinomycetes and fluorescent pseudomonads. The in vitro antagonistic effect of 16 isolates of fungi, 22 isolates of bacteria, five isolates of actinomycetes and two isolates of fluorescent pseudomonads from pod surface against P. palmivora was carried out in comparison with standard cultures of Trichoderma harzianum and Pseudomonas fluorescens. The study revealed that all the epiphytic fungal and bacterial isolates including standard cultures of T. harzianum and P. fluorescens were antagonistic to P. palmivora in varying degrees. Based on the in vitro screening seven promising epiphytic fungal isolates and five bacterial isolates along with standard cultures of T. harzianum and P. fluorescens were evaluated for their efficiency in reducing the infection by P. palmivora on detached pods. The pathogen was inoculated on the pods one hour after application of antagonists. Observations taken 10 days after inoculation of the pathogen revealed that one isolate of T. viride and two isolates of P. fluorescens obtained from pod surface exerted more than 40 per cent efficiency over control in reducing the infection. The standard cultures of fungal and bacterial antagonists recorded 33-35 per cent efficiency. Hence, these efficient epiphytic and standard cultures could be utilized for the management of PPR of cocoa.

ABSTRACT

Interaction of cationic dye acridine orange with lipopolysaccharide (LPS) isolated from Rhizobium strains specific (IC59) and non-specific (TAL1000) to chickpea (Cicer arietinum.L L.) has been investigated by spectrophotometric measurements. The strain specific (IC59) lipopolysaccharide induced decrease in absorbance of the α-band of acridine orange at 490 nm and finally upon further addition of LPS /Dye ratio in the range of 30~60 giving rise to α-polymeric metachromatic band at 660 nm. In contrast the LPS from non-specific strain (TAL1000) induces a decrease in absorbance at the α-band till LPS / Dye ratios are 0~50. This suggest that the anionic changes of strain specific LPS is different from non-specific strain enabling formation of large acridine orange aggregate on the surface of specific strain.

ABSTRACT

An In vitro study was conducted to evaluate the fungicidal efficiency of four selected fungal antagonists against leaf spot pathogens of ivy gourd by dual culture method. The antagonists evaluated were Trichoderma viride, Trichoderma harzianum, Aspergillus niger and Chaetomium globosum. The major leaf spot pathogens of ivy gourd used for the study were Cercospora cocciniae, Colletotrichum gloeosporioides and Alternaria alternata, causing severe infection on the foliage. Among the four antagonists tested, T. viride and T. harzianum were found to be the most effective recording the highest AI value of 1500 against all the three pathogens followed by A. niger. C. globosum was least inhibitory on C. gloeosporioides and A. alternata, but was effective against C. cocciniae. A complete overgrowth of the antagonists on all these pathogens were observed in the case of T. viride, T. harzianum and A.niger. C. globosum showed aversion to the hyphal growth of C. gloeosporioides and A. alternata, whereas in C. cocciniae, a homogenous growth was observed.

ABSTRACT

The antagonistic organisms are known to bring out action on the pathogen by various mechanisms. Based on in vitro screening of epiphytic microbes from cocoa pod surface against Phytophthora palmivora, the incitant of pod rot of cocoa, a promising isolate of Trichoderma viride and two isolates of Pseudomonas fluorescens were selected. The mechanisms of antagonistic action of these selected epiphytic antagonists against P. palmivora were studied in comparison with the standard cultures of T. harzianum and P. fluorescens. The selected epiphytic fungal antagonist T. viride and standard culture of T. harzianum were found to be efficient parasites of P. palmivora. The hyphae of the pathogen were seen tightly held by coiling with hyphae of the fungal antagonists. The hyphae of the antagonists penetrated the host hyphae at several points and grew to its inner cavity. The fungal antagonists also caused disintegration of the pathogen hyphae, besides free intermingling, which resulted in malformation of host hyphae. The ability of the two epiphytic P. fluorescens isolates and standard culture of P. fluorescens in producing HCN and siderophores was assessed. It was found that these isolates produced HCN and siderophores in appreciable levels thereby suppressing the P. palmivora. Though, more than one mechanism may operate in suppressing the pathogen, the relative importance of a particular mechanism may vary with different conditions, which needed to be further investigated.

ABSTRACT

An in vitro evaluation was carried out to find out the efficiency of bacterial and fungal antagonists in checking the growth of pathogens of Kacholam. Out of the two methods tried to find out the effectiveness of Pseudomonas fluorescens against the two isolates of Ralstonia solanacearum, cross streaking produced lysis at the juncture and point inoculation produced clear inhibition zones. Among the two fungal antagonists tested Trichoderma viride was more efficient than Aspergillus niger because of its faster growth over the pathogen. However, both the antagonists showed complete overgrowth and dense sporulation on the area where the pathogen was streaked. To find out the efficacy of Pseudomonas fluorescens against leaf spot pathogens like Colletotrichum gloeosporioides and C. capsici, streaking on both sides yielded more than 50 per cent reduction in growth of both the fungal pathogens. The fungal antagonist T. viride showed a faster growth over pathogens than A. niger eventhough both recorded an antagonism index of 1500. Dense sporulation was seen over the pathogens in case of T. viride. The ability of fungal antagonists to produce volatiles and their effect on fungal pathogens were also assessed. It was noticed that the volatiles produced by T. viride was more effective than that of A. niger. Even though the extent of inhibition was less compared to direct action, this could also be one of the mechanisms of action of both the antagonists. The study revealed that all the three antagonists were effective against both bacterial and fungal pathogens and they could be utilized under field conditions.

ABSTRACT

Soil samples from pepper growing tracts of six districts of Kerala viz., Ernakulam, Idukki, Kollam, Kottayam, Thrissur and Pathanamthitta were assessed for total microbial population. Thirty two fungi, 17 bacteria and three actinomycetes were isolated and studied for their antagonistic potential against the foot rot pathogen, Phytophthora capsici. All the 32 fungal isolates were found antagonistic to the pathogen and majority of them belonged to the genera Trichoderma, Aspergillus, Penicillium, Fusarium, Pythium, Cunninghamella and Rhizopus. Among these maximum inhibition was recorded by Trichoderma spp. which included T. pseudokoningii, T. longibrachiatum, T. polysporum and T. harzianum. The laboratory studies were followed by field trials laid out in farmers’ fields (newly planted pepper gardens) in six districts of Kerala. Effect of biocontrol agents in wilt incidence revealed that the two-time treatment of combined application of Trichoderma local isolate and potassium phosphate was superior in checking the foot rot incidence. The treatment, Trichoderma local isolate + Bordeaux mixture applied twice came in the second position. Data on biometric observations revealed a significant increase in the number of laterals in plots treated with Trichoderma local antagonist and potassium phosphate as compared to plots treated with Bordeaux mixture and copper oxychloride. Results of quality analysis of berries revealed that oleoresin content ranged from 6.98 - 11.84 per cent and piperine content from 3.61 - 5.92 per cent and the quality remain unchanged due to various treatments. The study has provided an ‘eco and health friendly’ biological control for the management of Phytophthora foot rot, the most devastating disease of pepper.

ABSTRACT

Trichoderma spp. are important group of fungi which are mycoparasitic on several plant pathogenic fungi. Trichoderma spp. are, therefore, used as commercial biofungicides. Genetic manipulation through induced mutagenesis and molecular cloning are two important tools in improving the biocontrol potential of Trichoderma spp. In the present study, attempts were made to induce genetic variability in Trichoderma virens using UV- induced mutagenesis. In the process, a simple protocol was developed for obtaining high frequency mutations in Trichoderma virens. Using a UV-crosslinker, four stable mutants of T. virens have been developed, which are distinctly different from the wild type in appearance and in antagonism against Rhizoctonia solani and Sclerotium rolfsii. One of the mutants, designated as TI is very slow in growth, but sporulates densely, and retained its mycoparasitic potential against R. solani. Though all the mutants were able to antagonize R. solani, all of them were overgrown by the test pathogen S. rolfsii. These mutants could be used to identify genes involved in growth and conidiation in T. virens.

ABSTRACT

Black pepper (Piper nigrum L.), known as the ‘King of Spices’ is an important export- oriented spice crop, valued for its medicinal and condimental properties. A perfect protocol for the rapid in vitro multiplication of this plant is available. However, systemic bacterial contamination is the single major constraint in the large scale in vitro production of plantlets. Based on morphological and biochemical characters, this bacterium was identified as Beijerinckia indica It grows profusely on nitrogen-free Jensen’s agar and solubilizes CaCO in the medium by acid production. It is resistant to a range of antibiotics and produces indole acetic acid. The bacterium is slow growing and has pH optima of 5.5 and temperature optima of 27oC. It has both endophytic as well as epiphytic association with the plant, the colonization being more in the stem and petiole. A single plasmid of 4.0 kb size was isolated from the bacterium and characterized. Competent cells of E. coli DH5a, transformed with this plasmid survived on Jensen’s nitrogen free agar, indicating its ability to fix atmospheric nitrogen. We stipulate that the nif genes are located on the plasmid of the bacterium. Since endophytic bacteria are known to stimulate plant growth through antagonistic activity against pathogens, production of growth promoting substances and inducing systemic resistance in several other agricultural crop species, the symbiotic association between Bejerinckia indica and black pepper could be further exploited through integrated nutrient management for improved growth and yield of this spice crop.