| Most heterotic hybrids for grain yield also showed heterosis for harvest index or
biological yield per plant, the latter being more frequent. Number of tillers per plant and
1000 grain weight also expressed more or less similar trend. Heterosis in F1 could be explained on the basis of dominance, overdominance, nonallelic interactions (MACKEY 1976), and pure additive gene action at individual loci coupled with favourable additive x additive interaction (ARUNACHALAM 1976). It will, therefore, be possible to recover homozygous lines as good as heterotic hybrids if the heterosis is caused by fixable gene action. However, our earlier studies, using these hybrids, revealed preponderance of nonadditive gene action for most of the characters including grain yield and overdominance being most possible reason could not be oversighted (BEHL & SINGH 1984). Thus, the chances of exploitation of heterosis at commercial level appear to be dim, at least in present case, because of moderate heterosis and its genetic control. Heterosis, being deviation of F1 from mid or better parent value, can be high or low depending on the average performance of the parents. Therefore, heterosis coupled with high per se performance should be considered while selecting cross combinations for population improvement work. Though, none of the cross, as expected, manifested heterosis for all the component attributes of grain yield and quality, yet few crosses expressed high heterosis for two to five characters. In that context, crosses viz., T24 x St69-1 for tillers per plant, biological yield and grain yield per plant, T134 x 6TA204 for grain density, biological yield and harvest index ; UPT74364 x 6TA204 for days to spike emergence, plant height, 1000 grain weight, grain density and biological yield ; Arm147 x 6TA204 for grain weight, grain crushing hardness and grain protein content ; Koala x T122 for harvest index and grain yield ; Cinnamon x T122 for number of grains per spike, biological yield and grain yield per plant ; T134 x UPT74535 for tillers per plant, and grain protein content ; T103 x 6TA204 for grain crushing hardness and grain yield per plant ; UPT74536 x St69-1 for floret fertility and UPT74418 x UPT74535 for number of spikelets per spike figured important. Pairwise or multiple crosses involving these hybrids offer some promise to facilitate synthesis of dynamic population and to recover better homozygous lines in progeny generations with improved plant type, grain yield and better nutritional and end use grain quality as parents involved in their synthesis were genetically divergent and either good or average general combiner (BEHL & SINGH 1984). Our results are in partial confirmity with that of SRIVASTAVA & ARUNACHALAM (1977), ANSINGKAR et al., (1978) and ROSENKOVA & MASTENPOVA (1981). However, for physico-chemical characters such as grain density, grain crushing hardness and grain protein content available information is scanty. Since triticale has to compete with wheat, it would be logical to emphasize heterosis over best wheat checks. Highest standard heterosis for grain yield was recorded for T130 x 6TA204, followed by Cinnamon x UPT74535, T139 x T122, T139 x UPT74535 and Koala x T122 etc. while crosses viz., T24 x 6TA204, T103 x 6TA204 and Koala x T122 depicted considerable standard heterosis for biological yield per plant and harvest index. Inclusion of these crosses for breeding better triticale lines might be fruitful. References ANSINGKAR, A.S., P.R. CHOPDE & L.A. DESPANDE 1978. Note on heterosis in triticale. Indian J, agric Sci., 48 : 503-504. ARUNACHALAM, V. 1976. Heterosis for characters governed by two genes. J. Genet., 63 : 15-24. BEHL, R.K. & V.P. SINGH 1984. Genetics of harvest index and related characters in hexaploid triticale. Cereal Res. Communication (Accepted). GUPTA, P.K. & P.M. PRIYADARSHAN 1982. Triticale : Present status and future prospects. Advances in Genet., 21 : 255-345. MACKEY, I. 1976. Genetics and Evolutionary Principles of Heterosis. Proc. VIII Congr. EUCARPIA : 17-33. ROSENKOVA, V.E. & M.V. MASTEPANOVA 1981. Use of spring forms of triticale in hybridization with winter forms. Puti Povysh Urozhainosti Polev Kultur. 12 : 10-19. SRIVASTAVA, P.S.L. & V. ARUNACHALAM 1977. Heterosis as a function of genetic divergence in triticale. Z. Pflanzenzuchtg, 78 : 269-275. |
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