Reproductive characters of three species of Cyamopsis were studied to find out barriers to interspecific crosses between Cyamopsis tetragonoloba × Cyamopsis serrata and C. tetragonoloba × C. senegalensiswhich may serve as a stepping stone for development of extra early varieties of guar. Pollen grains of C. tetragonoloba and C. senegalensis showed more than 95% of viability while those of C. serrata had 87% viability. Nutritive requirement for in vitro germination of pollen revealed that pollen of C. tetragonoloba required 25% sucrose + 100 ppm boric acid + 300 ppm calcium nitrate while C. senegalensis pollen needed 35% sucrose with same basal medium. On the other hand, C. serrata pollen required 35% maltose + 6% PEG 6000 along with above dose of boric acid and calcium nitrate. Moreover, pollen germination in C. serrata was initiated after 30 h of incubation and its pollen tubes were slow growing attaining 174.7 µm length in 48 h. The length of style of C. tetragonoloba and C. serrata was nearly identical (2.6 mm) while C. senegalensispossessed longest style (3.8 mm). Interspecific hybridization between C. tetragonoloba x C. serrata was successful through the use of stub smeared with pollen germination medium (PGM) and as a consequence 10.43% of pod setting was observed. Colour and shape of hybrid seeds was similar to the female parent (C. tetragonoloba), hybrid plants showed early flowering just like male parent (C. serrata) whereas the plant height was intermediate between the two parents.
Key words: Interspecific hybrids, pollen, in vitro germination, stub pollination, in vivo tube growth.
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