eChapters

Phosphorus in soil present both in inorganic form and organic form. The inorganic P can be divided into different pools. The major active inorganic forms are: P bound to aluminium (Al-P), iron (Fe-P), calcium (Ca-P) and silicate minerals and relatively less active forms are occluded and reductant soluble forms of P. On the other hand the principal organic P compounds present in soil are (i) inositol phosphate, (ii) phospholipids, (iii) nucleic acid and other unidentified esters and phosphoproteins.

15.1. Determination of Available Soil P

The availability of soil P to plant varies greatly depending upon the reaction, minerological composition and amount of the soil colloid. Very little P is present in the soil solution except in recently fertilized or sodic soils. The type of phosphate ions present in the soil solution depends on the soil pH. In soils of neutral to slightly alkaline pH, HPO₄^2- ion is the dominant form. In slightly or moderately acidic soils, both H₂PO₄^- and HPO₄^2- ions prevail. At strongly acidic soil H₂PO₄^- ion tends to dominate, while above pH 9.0, the PO₄^3- ion becomes more important than H₂PO₄^-.

14.1. Determination of Total Nitrogen in Soil (Modified Kjeldahl Method)

Nitrogen mostly present in soil in organic form. Relatively small amount of nitrogen usually occur in ammonium and nitrate form, the available form. The Kjeldahl method of total N determination includes both organic and ammonium form and with modification nitrate form of N can also be included.

13.1 Exchange Capacity

Soil colloidal particles carry both negative and positive charges on their surface which attract and hold equivalent amount of oppositely charged ions to their surface. The total number of negative charges present on a given mass of soil or capacity of a given mass of soil to exchange cations or total number of cation held by a given mass of soil is termed as cation exchange capacity (CEC). Similarly, the capacity of a soil to retain anions is known as anion exchange capacity (AEC). The ion exchange capacity of a soil depends upon the type and amount of colloidal particle (clay and organic matter) present in the soil. Ion exchange capacity (CEC / AEC) is expressed as milliequivalent ion (cation / anion, respectively) per 100 g of soil (meq / 100g). It is also expressed as centimoles of charge (positive / negative) per kg of soil [cmol (±) / kg]. Meq / 100g = cmol (±) / kg of soil.

Carbon may present in soil in four different forms:

1. Carbonates: Mainly as CaCO₃ and MgCO₃, active CO₃^2- and HCO₃^- ions and gaseous CO₂.
2. Highly condensed elemental organic form: Charcoal, graphite.
3. Completely decomposed resistant organic residues: Humus.
4. Undecomposed and partially decomposed organic residues.

11.1. Determination of Electrical Conductivity of Soil Solution

The conductivity or more precisely the specific conductance of a soil at a given soil-water ratio is the reciprocal of the specific resistance offered by the solution at 25ºC between the electrodes of 1 sq cm cross section kept 1 cm apart. Thus, the electrical conductivity of any solution depends on the amount of soluble salt present in it. Knowledge on the extent of salinity is important for management of saline soil including the choice of the crop suitable for that soil. Soluble salt content in saturation extract is more reliable index of salinity level than in soil: water ratio of 1: 2 or 1: 2.5 because it simulates the extent of salinity experienced by crop in field moisture condition.

Salinity class of soil is based on the electrical conductivity (EC) of saturation extract at 25ºC. However, EC of water extract from 1:2 soil-water suspension can be transformed into the EC of saturation extract following the formula (except for soil containing gypsum).

10.1. Determination of Soil pH

The soil pH value is the measure of hydrogen or hydroxyl ion activity in the soil solution and it indicates whether the soil is acidic, neutral or alkaline in reaction. The pH is the most important property of soil as it controls the availability of plant nutrients, microbial activity and physical condition of soil. Since crop growth is affected both under very low (strongly acidic) and very high (strongly alkaline) soil pH, reclamation of these soils are necessary. Soil pH in fact indicates the extent of active acidity (activity of hydrogen ion in soil solution) of soil. Depending upon the purpose of measurement and soil condition, soil pH is measured in several soil-water or soil-salt solution ratios. The saturated paste is used for identifying specific soil problems like degree of acidity or alkalinity. For making fertilizer recommendation, 1: 2 soil-water suspension is generally adopted. To mask the variability in salt content of the soil, the pH is measured in soil-CaCl₂ suspension (1:2 soil-0.1 M CaCl₂ solution). The soil pH value is independent of dilution over a wide range of soil-salt solution ratio, thus more reproducible than those obtained with soil-water suspension.

9.1. Balance and Weighing

9.1.1. Principle of Functioning of a Balance

It is one of the important tools used in the laboratory and one should have thorough knowledge about its assembly, use and care, otherwise it may be the initial step for introducing error in any physical or chemical analysis. Every balance has its maximum load limit and sensitivity depending upon its construction.

Essentially balance may be regarded as a rigid beam, BC having a central fulcrum, O and two arms of equal length, d₁, d₂ (Fig.9.1). The both ends of beam have prism edges upon which the balance pans are suspended by means of suitable suspension.

8.1. Law of Mass Action

Gulberg and Waage, the two Norwegian chemists in the year 1864 stated the law of mass action in this form: ‘The velocity of any chemical reaction at any instant at a given temperature is proportional to the active mass of each of the reactants at that instant present in the system, the active mass in a homogeneous system is defined as the number of gram molecule of the substance present per unit volume i.e., the molar volume’.

Mathematical Formulation of the Law of Mass Action

Let us take a simple case of a reversible reaction at constant temperature represented by the equation:

Soil consistency is a term used to designate the manifestation of different physical forces acting within the soil at various moisture levels. The consistency limits, also known as ‘Atterberg Limits’ (Atterberg, 1911; 12) are defined by the water content of the soil to create specified degree of consistency. These limits are – (i) Liquid limit or upper plastic limit, (ii) Plastic limit or lower plastic limit and (iii) Sticky limit.

7.1. Determination of Liquid Limit or Upper Plastic Limit

Equipments and Materials

Liquid limit device (Casagrande, 1932) and accessories, spatula, dish, oven, moisture box, balance, desiccator

6.1. Determination of Hydraulic Conductivity of Saturated Soil: Laboratory Methods

Hydraulic conductivity of a saturated soil indicates the ease with which water is transmitted through the soil pores. If a constant water head (h) is maintained on a saturated soil column of length (L) and the volume of water (V) percolating per unit time (t) through per unit cross sectional area (A) to the other end, then according to Darcy’s Law the rate of flow of liquid or flux (q) is proportional to the hydraulic gradient (ΔH/L) across the length of soil column.

5.1. Determination of Soil Moisture

5.1.1. Determination of Soil Moisture Content by Gravimetric Method (Direct method)

Traditionally water content in soil is expressed as the ratio of the weight of water present in the soil to the weight of dry soil. When this ratio is multiplied by 100, it becomes the percentage of water in the soil sample on dry weight basis.

In natural condition primary soil particles cohere to each other to form a cluster or an aggregate through the cementing action of various agents like organic matter, oxides of iron and aluminium, carbonates, etc. Aggregate analysis tells one about the structural status, pore geometry which in turn influences the movement of air and water in soil, amount of water stable secondary particles (aggregate) as well as the extent of finer particles aggregated to the coarser particles and the erodibility status of surface soil against wind and water.

Methods of Analysis

Among the several methods of aggregate analysis the commonly used methods practiced in agriculture and related fields are wet sieving and dry sieving method of aggregate analysis.

3.1. Determination of Bulk Density of Soil

3.1.1. Determination of Bulk Density of an Undisturbed Soil

Bulk density of soil is expressed as the ratio of the mass (weight) of soil particle to their total volume including the pore space between the soil particles. Alternately, it is the weight of unit volume of dry soil. It is usually expressed in the unit of gram per cubic centimeter (g/cc) or mega gram per cubic meter (Mg/m³). In fine textured soil bulk density varies from 1.00 to 1.60 g/cc, whereas in coarse textured soil from 1.20 to 1.80 g/cc.

2.1. Particle Size Distribution Analysis

Soil is composed of particles of varying size and shape. The expression of the proportion of the different size particles is termed as ‘soil texture’. It is one of the most important basic characters being little changed by cultivation or other practices. Particles are arbitrarily distinguished into following groups on the basis of their diameters.

Soil is a mass of large variability and thus its sampling is the most challenging problem for any soil analyst. Practically, soil sampling is a two step process which includes (i) collection of soil from homogeneous unit and (ii) processing which in turn includes drying, grinding, sieving, mixing, partitioning and storing.

1.1. Sources of Error in Soil Chemical Analysis

Different sources of error involved starting from soil sampling to chemical analysis of a sample can be divided into three main groups:

1. Sampling error : This error results from variability among the different samples drawn from same soil unit with respect to the objective of sampling.
2. Sub-sampling error : This error is due to variability introduced among sub samples of the same soil sample.
3. Analytical error : This error introduced due to variability from one chemical determination to another on same sub sample.

An extraordinary variety of viruses, bacteria, and organisms stand ready to attack us and feed off our bodies’ cells. Using microscopes of varying power, photographers show us a teeming microbial world that we could barely imagine without their help.

INTRODUCTION

A parasite is an organism which exploits another organism for the purpose of staying alive. Some parasitic relationships are harmless, while in other cases a parasite can damage or even kill its host. The word is borrowed from the Greek word ‘‘parasitos’’, meaning “one who eats at the table of someone else.” In case of exotic carps parasites causes a great loss by reducing economy. Some, cannot live once their host dies, while others can continue thriving on dead hosts until their nutrients are consumed. Parasites live inside a host are called endoparasites or internal parasites. Ectoparasites live outside the host, and are generally more capable of switching hosts. A parasite preys on other parasites, is called epiparasite (Anderson, 1974).

Silver Carp

The silver carp (Hypophthalmichthys molitrix) is a species of freshwater cyprinid fish, a variety of Asian carp native to north and northeast Asia. It is cultivated in China. Pound for pound, more silver carp are produced worldwide in aquaculture than any other species. Silver carp are usually farmed in polyculture with other Asian major carps, or sometimes Indian major carps or other species. It has been introduced to, or spread into via connected waterways, at least 88 countries around the world.Introduced in india in 1959 at the pond culture division of CIFRI. In India in 1963 breed sucessfully by hypophysation. The silver carp is a filter feeder, and possesses a remarkably specialized filtration apparatus capable of filtering particles as small as 4 µm. The gill rakers are fused into a sponge-like filter, and an epibranchial organ secretes mucus which assists in trapping small particles. A strong buccal pump forces water through this filter. Silver carp, like all Hypophthalmichthys species, have no stomachs; they are thought to feed more or less constantly. Silver carp are thought to feed largely on phytoplankton; they also consume zooplankton and detritus. It is used in controlling water quality, especially control of noxious cyanobacteria (blue-green algae), microcystis .

Occasionally anglers catch fish that show signs of infection or parasitism. Is the fish safe to eat? The usual and safest response to this question is, “When in doubt - don’t.” However, very few fish diseases can be transferred to humans. Almost all fish are safe to eat when thoroughly cooked, smoked or frozen.

Fishes are a valuable resources for hill streams and temperate region people. Not only do they provide important recreation, but they are also a valuable supplement to the family food budget. The anticipation of any fisherman, whether he be a young boy with a cane pole and a can of worms or an “old pro,” is a quality fish for the table. It is the unwritten law of any true sportsman to utilize the fish he catches. The purpose of this publication is to help you, the angler, determine if the fish you’ve caught is worthy of your skillet. Remember, a sick fish will not take the hook (Taraschewski, 2000).

For most people in their right mind, parasites are disgusting little creatures. The mention of them evokes images of tiny crawlers entering the body of innocent victims by devious means, encrusting themselves within various organs (often with very unpleasant effects), living off their host’s tissues, and then exiting the body, sometimes through scatological avenues, leaving behind hosts that are incapacitated, if not mere shells of their former selves (as is literally the case for some insects). The true facts are not always that gruesome (after all, parasites that have to spend a long time inside a host do not benefit if this host kicks the bucket, because then they die as well) but often enough parasitic reality is not pretty. Ask biology students about their parasitology course, and they will tell you that attending class is like visiting a little shop of horrors. I, for one, came out of my parasitology course with newly developed phobias (mercifully temporary) of such innocuous activities as eating meat and bathing in streams – they represent ways of transmission for some parasites. But students will also tell you that parasites are fascinating because of the complexity of their life cycles and the intricate ways in which they complete these cycles. So fascinating, in fact, that many students eventually become parasitologists and devote their entire lives to studying the little critters. Most of these people work with parasites of livestock or humans, but a few with an equal taste for ethology and ichthyology pursue the more esoteric questions that occupy this page: how fishes avoid getting parasitized, and how fishes alter their behaviour once they get parasitized (Barber et al., 2000)

INTRODUCTION

Zoonoses are diseases and infections which are naturally transmitted between vertebrate animals and humans. The pathogens that cause zoonotic diseases are bacteria, fungi, viruses, parasites or protozoa. Disease transfer occurs via direct or indirect exposure to the pathogen. A pathogen is contracted directly through skin to skin contact of an infected animal or through ingestion of diseased animal products (infected faeces, urine, saliva, blood, milk or other bodily fluids). A bite or sting from a diseased animal or through an infected invertebrate host directly transfers the pathogen to humans as well. Indirect exposure occurs through air, water or soil in which the pathogen can survive for a limited period of time without a host ( Acha, et al., 2003).

CLASSIFICATION OF ZOONOSES

The World Health Organization (WHO) Expert Committee on Zoonoses came up with the following classification system of zoonoses based on the type of life cycle of the pathogen.

INTRODUCTION:

An association of two organisms, one living at the expense of other for food and shelter is called parasitism. Parasite factors associated with recognition and selection of the host and the mechanisms in the host responsible for acceptance or rejection of the invading organism were evaluated. Sensory structures in parasites are able to detect differences between different fish species and this ability to discern between fishes may be based on both chemical and mechanical stimuli on the host surface. Complex glycoproteins, proteins, carbohydrates and simple molecules attract parasites or modify their behaviour. (Kurt Buchmann and T. Lindenstrom, 2002)

INTRODUCTION

It can be added that physiological stress as well as the physical offences contribute as primary factor for disease occurrence and fish mortality. Many parasitic diseases due to fluctuation in water quality leads to deplition of stock, and some times total stock will go eg. yellow grub disease.

EFFECT OF TEMPERATURE ON PARASITES

Heterophyid Trematode

Cyprinodon variegatus, an estuarine fish, is heavily parasitized in the bulbus arteriosus by the heterophyid trematode Ascocotyle pachycystis. Parasitized fish ventricles were hypertrophied due to mechanical blockage of normal blood flow by metacercariae in the bulbus Swimming performance generally was reduced by the presence of parasites, which had their most significant negative effect at cold temperatures and low dissolved oxygen level ( Felicia C. Coleman , 1993)

PREVENTION

This section will discuss ailments that affect the fish kept in our aquariums. We will simply not call them diseases because most are not true diseases but a response to some sort of stimuli such as poor tank water management or the presence of actual parasites. A list of the most common ailments, the reasons behind them and the appropriate action needed to “fix” the problem is given in this Chapter.

If you maintain good water quality, keep the right kind of fish together, feed good quality food and monitor all your water properties you will rarely have any problems. A few common sense precautions when you purchase new fish can save you a lot of trouble.

INTRODUCTION

Fish culture as a hobby or business is well established in India. Increased interest in fish culture has also increased awareness and experience with parasites that affect fish health, growth, and survival. Information provided in this chapter is intended for the novice fish culturist as a guide to common parasites of freshwater fish. Identification of parasites and their basic treatment is included; however, any herbal treatment alone or biological cum chemical treatment may be choosen for eradication purpose (Das et al., 1995a).

WHY, WHEN AND HOW FISH GET PARASITES

Parasites pose a real risk to fishes

All fish are potential hosts to many different species of parasites. Small numbers of parasites are common and probably do little harm. However, all parasites have tremendous reproductive potential and can, under ideal conditions, quickly overwhelm fish in the confines of a tank or pond.

Types of parasites

We can broadly class parasites into two groups. Ectoparasites are found on the external surfaces such as skin, fins and gills, while endoparasites are found in the internal tissues and organs.

Endoparasites are uncommon in ornamental fish. However, there is a wide diversity of blood parasites, worms that colonize the intestines and other parasites that can invade various organs and tissues. Many require an intermediate host, such as snails, birds or the introduction of an infected fish, and so are rare in pond/ aquarium fish. There are a variety of clinical signs which might indicate the presence of endoparasites. Lethargy accompanied by emaciation is a common sign, as are worms protruding from the anus. Identification of sporozoan and protozoan endoparasites often requires microscopic examination of tissues (Chanratchakool et al. 1994).

The Distributed Information Sub Center at Kerala Agricultural University, Thrissur was set up in May 1995 as the 23^rd center of the BTISNet of DBT, Government of India. The area of specilisation of the Centre is Agricultural Biotech- nology. The Centre passed through several phases involving Internet connectivity through the ordinary C band connectivity, then the Ku band connectivity etc. Now the commu- nication facilities of the Centre have been strengthened by procuring an ISDN Internet connection and a connection through ASIANET. The Center caters to the needs of the students (UG, M Sc & Ph D) and faculty of all departments of the Colleges in the main campus as well as of the other nearby academic and research centers of the University. Over the years, DISC has come to occupy a position in the KAU in the area of Infor- mation Technology , information sources and services based on Internet, CD-ROMs etc. The Centre has procured databases in the field of Biotechnology and developed several databases in the field of Agriculture and related fields. The center regularly conducts training programmes in Bioinformatics. The research activities in the field of Bioinformatics have been enhanced. The Centre has now been upgraded to DIC to facilitate intensive research on Bioinformatics in an effective manner. During the year 2004, the Centre has also started offering a course on Bioinformatics for the M.Sc Biotechnology students of the College of Horticulture.

Biotechnology research in KAU spread over various research stations and cam- puses includes Plant Biotechnology, Animal Biotechnology and Fisheries Biotechnol- ogy. Thrust areas for Plant Biotechnology include developing in vitro protocols for mass multiplication of elite types of fruit plants, ornamentals, medicinal plants, spices, plantation crops and forest species. The other thrust areas include checking clonal stability and genetic fidelity of in vitro derived plants using molecular markers, DNA finger printing and characterisation of germplasm with molecular markers, imparting biotic and abiotic stress tolerance in otherwise accepted crop varieties, genetic trans- formation for imparting/ improving expression of desired traits, in vitro germplasm conservation, enhancement of secondary metabolites production etc.

The crops identified for biotechnology research at KAU include spice crops like black pepper, ginger, turmeric, vanilla, cardamom; plantation crops like cashew, coco- nut and medicinal & aromatic plants such as Kaempferia, Trichopus, Gymnema, Holostemma and Coscinium. For improvement of such crops through molecular breed- ing, it is highly essential to identify/design specific probes/primers, micro-satellites, etc. By combining the research results generated at the Biotechnology Centre and informa- tion retrieved from the Bioinformatics Centre, suitable probes, primers are being de- signed for characterization and improvement of these unique crops through molecular breeding.

ABSTRACT

The Cry2A proteins are promising candidates for managing the development of Cry1Ac resistance in insects. The Cry2A class of proteins is different from that of Cry1A, and experiments have shown that insects resistant to Cry1Ac are not cross-resistant to Cry2A proteins. However, the Cry2A proteins are less toxic than Cry1Ac to the polyphagous pest Helicoverpa armigera. Structure-based protein engineering of Cry toxins may pave the way for directed evolution of variants with broad spectrum of insect species specificity, enhanced potency, and stability. In the present study homology modeling of Cry2Ac was done using DeepView software. The template for Cry2Ac protein sequence (accession number X57252) was selected using ExPdb template search. The raw sequence of the Cry2Ac was superimposed over the Cry2Aa PDB template (1I5P). The superimposed model was submitted to the SWISS Model server. After receiving the Cry2Ac model, energy minimization was done using Gromos96. The threading energy and force field energy were calculated. The homology model of Cry2Ac made by us along with the Cry2Ac model from the SWISS-MODEL Repository was used for comparative analysis of receptor binding regions of Cry2Aa. Results showed variation between the two highly homologous Cry2A proteins in their receptor binding regions which may account for differences in spectrum of insecticidal activity.

ABSTRACT

Astudy was undertaken at Department of Soil Science & Agrl. Chemistry, College of Horticulture, Vellanikkara to standardize different amelioration techniques to prepare enriched coirpith compost. Twelve treatments were tried using different combinations of coirpith, Pleurotus spp., Schizophyllus spp., urea, rock phosphate, cowdung slurry, mushroom waste, goat manure, glyricidia and water hyacinth. The results of the various enrichment techniques revealed that the temperature in the compost in general, increased to a peak value of 47oC on the 22nd day of composting and later decreased to a stabilized value. The observed temperature of 40-50 °C found during the thermophilic stage is essential for the rapid degradation of lignocellulose, as the thermophilic microfungi and actinomycetes involved in this process thrive at that temperature. Though the pH show a hike at the initial stage of composting, it decreased and stabilized at the later stage of composting which is conducive for growth and proliferation of microbes. The treatment coirpith with Pleurotus spp., glyricidia +20% cowdung slurry and goat manure was found to be ideal for compost preparation.

ABSTRACT

Biological lipids are chemically diverse group of compounds. Lipids serve two major biological roles namely a structural one as component of membrane, and storage function, particularly in certain seed tissues. Fats and oils are the principal stored form of energy in many organism, and phospholipids and sterols makeup about half of the mass of biological membranes.

An experiment was conducted to study phospholipids composition qualitatively as well as quantitatively in the roots of mung bean seedlings. Among the four solvents used for phospholipids isolation, solvent II (methanol) and solvent III (chloroform: methanol: NH₃ salt) were proved to be the major phospholipids eluting solvents. The results indicated that Phosphatidyl Choline (PC), Phosphatidyl Inositol (PI), Phosphatidyl Serine (PS), Phosphatidyl Ethanolamine (PE) and Di Phospho Glyceride (DPG) were present in significant amount in the roots of ten days old mung bean seedlings. These phospholipids were also identified by their Rf values using thin layer chromatography. Among all the phospholipids isolated, PI showed the minimum Rf value, whereas PS showed the maximum Rf value. On the basis of column chromatography, four fractions of phospholipids were isolated. The highest amount of phospholipids was found in fraction II and the lowest in fraction I. Fraction II and fraction III contained the maximum phospholipids. In the fraction II PC showed the highest content (μg g-1) and one unidentified phospholipids showed the lowest content (μg g-1), whereas in fraction III, PI showed the maximum content (μg g-1) and PS showed the minimum content (μg g-1).

ABSTRACT

The potato is one of the most important food crops both in developed as well as in developing countries. Developing countries today produce 37 per cent of world’s output of potatoes. Potato is an important food crop in India. Both area under potato cultivation and production has increased manifolds during past decades. The efforts are being made to improve potato quality and its post harvest life as well.

An experiment was conducted to isolate mitochondria from potato tubers and succinate dehydrogenase (SDH) assay and protein profiling were performed in the tissue. Three varieties namely, Kufri Bahar, Kufri Lauvkar and Kufri Jyoti were taken into consideration for the present investigation. Kufri Bahar showed the minimum values for SDH activity and Kufri Jyoti the maximum SDH activity. On the basis of SDH activity, the mitochondria in Kufri Jyoti were seemed to be more viable, functional and coupled as compared to Kufri Bahar and Kufri Lauvkar. This finding also suggested that the respiratory degradation of starch in Kufri Jyoti was higher as compared to Kufri Bahar and Kufri Lauvkar. Thus these result showed that the shelf life of Kufri Jyoti was less as compared to Kufri Bahar and Kufri Lauvkar. Protein profiling performed by SDS-PAGE was found to be similar in all the potato tubers.

ABSTRACT

Apot culture experiment was conducted on tomato with cadmium and lead to identify the selective retention sites of the metals. For this a completely randomized design with five treatments and four replications were laid out at the College of Horticulture, Vellanikkara. The different levels of treatment ranged from 0.5 to 2.0 mg kg -1 soil. Cadmium and lead were directly supplied as a water-soluble source through cadmium chloride and lead nitrate respectively. In tomato the growth and fruiting was permitted only at lower levels of cadmium application. At 1.5 mg kg-1 soil, fruiting failed. While at 2.0 mg kg-1 soil, the very establishment of plant was totally affected. At higher levels of application, cadmium preferred to get accumulated in roots while on the contrary at lower levels, cadmium uptake increased in shoots than in roots with the least content of the metal in fruits. However, in the case of lead, all levels of application in soil permitted growth and fruiting. With increase in rate of lead application, significant selective retention was observed in roots (1.48-6.69 ppm), shoot (0.29-1.62 ppm) and fruits (0.39-1.45 ppm). On comparison of retention sites of lead in tomato, it could be seen that fruits maintained the maximum lead uptake (637.2-2933.0 mg pot-1). Hence, the consumption of such tomato fruits contaminated with heavy metals may result in kidney damage, lack of memory, dissolution of phosphorus in the bones etc.

ABSTRACT

Detection of disease tolerance with enhanced defense mechanism is a practical approach in crop variety improvement programme. Toxins being responsible for pathogenicity and virulence of the fungi, regenerating plants from toxin treated calli is an effective and easy approach. The response of tomato calli to the crude toxins of the foliar pathogens viz., Alternaria solani and Septoria lycopersici was studied and the changes in phenol metabolism due to toxin treatment were analysed. Crude toxins of A. solani and S. lycopersici extracted under optimum conditions were serially diluted and tomato calli were treated with different dilutions of the toxins to find out the optimum dilution at which minimum survival percentage was obtained, based on a 1-4 score. Minimum score of 1 was obtained at 1:10 dilution for A. solani and at 1:20 for S. lycopersici.

The calli of resistant (LE-625) and susceptible (CO-3) tomato varieties were treated with desired dilutions of the toxins of A. solani and S. lycopersici. Total phenolics and ortho- dihydroxy (OD) phenolics were estimated at 24 h interval to study the extent of necrosis on resistant and susceptible calli due to toxin treatment. The total and OD-phenol contents of calli of susceptible cultivar (CO-3) progressively decreased with increase in time interval consequent to the treatment of toxins of A. solani and S. lycopersici. In the resistant calli of LE-625, an initial reduction of total phenol and OD-phenol content was observed following the application of the toxins of A. solani and S. lycopersici at 24 hours after treatment. Later with lapse of time, the total phenol content and OD-phenol contents progressively increased reaching a maximum at 120 h after treatment. The results clearly indicated the enhancement of biochemical defense in the resistant calli and a fall in defense mechanism in the susceptible calli due to toxin treatment. Such techniques are useful in the preliminary screening of resistant genotypes in crops like tomato.

ABSTRACT

In Kerala, apart from cultivated sesame species (Sesamum indicum L.) three wild species were identified viz. Sesamum malabaricum, Sesamum mulayanum and Sesamum radiatum. An investigation was carried out to determine the intensity of arbuscular mycorrhizal fungal colonization in cultivated and wild species of sesame. The percentage of arbuscular mycorrhizal fungal infection in roots of different sesame species were found to be variable. The highest percentage of root colonization of arbuscular mycorrhial fungi was found in wild species S. malabaricum, which promotes tolerance to the plant under drought stress conditions.

ABSTRACT

Atotal of 45 Gram positive, spore forming and rod shaped bacteria identified as Bacillus species were isolated from the rhizosphere of Chickpea plants. They were studied for their interaction with root borne fungal pathogens was studied using spot test method. Isolates CBS 29, CBS 113, CBS 123, CBS 132, CBS 153 and CBS 155 inhibited the growth of four or more fungi with inhibition zones varied from 1-5 mm. Two isolates CBS 153 and CBS 155 produced siderophores on CAS supplemented agar medium. Further inoculation of these Bacilli on seeds of Chickpea cultivar C235 and H8618 showed inhibitory, stunting or stimulatory effects on plumule and radicle growth depending upon cultivar, bacterium used and stage of seedling growth. Studies on co-inoculation of these isolates with Mesorhizobium and their plant growth promoting activity are being carried out. These co-inoculation studies are important areas of exploitation to improve crop productivity.

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.

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

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

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

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 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

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

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

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

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

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

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

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

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

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

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.