eChapter Name: Heterosis Breeding in Flower Crops
9789389130812
eBook Name: BREEDING AND BIOTECHNOLOGY OF FLOWERS: SET OF 2 VOLS. (SET PRICE)
by Anil K. Singh, Dr. A.K. Singh
INTRODUCTION
Heterosis has contributed significantly towards increased crop production and it has become the basis of multibillion dollar agro-businesses in the world (Phillips, 1999). Hybridization is the important way that can create genetic variability and make new options. The F1 population is obtained from the crossing of two homozygous but genetically dissimilar gametes or individuals (purelines in self pollinated crops or inbred lines in cross pollinated crops) that shows increased or decreased vigour over the better or mid parent value. Heterosis is maximum in F1, generation which diminishes gradually in later generations. Hence, production of F1, hybrid seeds of different flower crops is considered as the extreme focused area in floriculture industry.
Production of F1 hybrids in ornamental crops was carried out even before Shull’s classical theory of hybrid vigour which was reported in 1971 for the first time in plant breeding. Benary Seed Company in Germany released F1 hybrid in begonia (Begonia semperflorens) in the name of Prima Donna in 1909 (Reimann-Philip, 1983). But that time it did not attract the attention of plant breeders. It was during Second World War in 1942, when flower breeders were attracted towards heterosis breeding and started systematic F1 hybrids. From 1950 onwards, numerous outstanding hybrids have been developed in many other flower crops in several countries like USA, The Netherlands, Denmark, Germany, United Kingdom and Japan, etc. First hybrid in single geranium was produced in 1960, in other flower crops like antirrhinum, pansy, marigold and zinnia in 1965, ageratum in 1966, geranium double in 1970, dianthus, begonia, impatiens and portulaca in 1976-77, gerbera in 1980 and carnation in 1981. In the present scenario of developed floriculture industry, in many countries F1, hybrids are available in a number of annual flowers like ageratum, antirrhinum, anemones, calceolaria, dianthus, hollyhock, gazania, marigold, flowering tobacco, pansy, portulaca, stock, wall flower, zinnia, etc.
As emasculation is having the maximum share in cost of hybrid seed production, researchers have found several techniques in different flower crops as the alternative of emasculation and that can help in reducing the cost of hybrid seed production. The list of techniques being utilized commercially in different flower crops (Janakiram, 2004) is as follows: