Compatibility studies in monopodial orchids

Abstract

A research programme "Compatibility studies In monopodia! orchids" was carried out in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani during 2001-2003 with the objective of undertaking intra and intergeneric hybridization and in vitro embryo culture in monopodial orchids. Twelve monopodial orchid genotypes comprising of six mono generic and six bigeneric hybrids were selected as parents after initial evaluation. They were evaluated adopting completely randomized design with six replications. Analysis of variance revealed significant differences for almost all the characters studied. Genotypic and phenotypic coefficients of variation were high for number of aerial roots, leaf area and width of leaf. Characters like number of aerial roots, width of leaf, leaf area and number of flowers per inflorescence had high heritability coupled with high genetic advance. Significant positive inter-correlation at genotypic and phenotypic levels was observed for length of flow'er and width of flower with number of leaves per cane, number of aerial roots, number of spikes per cane, length of inflorescence and length of scape. The 12 parental genotypes were crossed in all possible combinations (144) after preliminary studies on floral biology. A total of 116 crosses were done including 50 crosses, 54 reciprocals and 12 selfs. Incompatibility reaction was noticed at different stages ranging from flower abscission before the onset of any visible post pollination change to instances where seeds geminated but aborted in culture. A total of 58 combinations attempted succumbed to incompatibility at these different

stages from pollination to deflasking. Harvestable green capsules were obtained from 58 combinations and they were inoculated in MS half strength basal medium. Percentage capsule yield ranged from 8 to 38 in the various hybrid combinations. Percentage filled seeds ranged from 18 to 76 in the various combinations. Capsules from twelve combinations did not contain seeds and seeds from ten combinations did not germinate on inoculation. Protocorms of developing seedlings from twelve combinations aborted at various stages of in vitro development. The remaining 24 cross combinations were taken through three to four subculture passages. Seedlings having 2-3 leaves and 2-4 roots were deflasked. Significant differences among the combinations were observed with respect to number of days taken for germination initiation, number of days taken for development of protocorms, chlorophyll, first leaf and first root primordia and for deflasking. Significant differences in seedling morphology were observed among the 24 hybrid combinations at deflasking with respect to all the seven vegetative characters studied.