| The heterosis (Table 1) for plant height, spikes
per plant, spike length and grains per spike is of common occurrence in
wheat (AL-SAHEAL & GAMIL 1981, BEHL 1985). It is concluded that the increased
height and spike length of hybrids over parents may be due to the interaction
of complementary growth genes. Deviation of hybrids from mid parent values
suggests dominance due to positive dominant genes, whereas deviation of
crosses from better parent values indicate over dominance due to positive
dominant genes. Among the traits studied maximum heterosis manifested was for yield per plant (Table 1). The hybrid advantage for yield per plant varied from 38.80 to 44.18 percent over commercial check and better parent respectively. Highest heterobeltiosis values for yield per plant was recorded by cross combination Pak-70 x Sonalika. All the hybrids on an average out yielded their parents. An explanation of yield heterosis encompasses the contribution of its various physiological components. A close persual of Table 1 indicate that yield heterosis was mainly due to heterosis for grains per spike ranging from 22.18 to 25.64 percent and spike length 18.27 to 20.70 percent for better parent and commercial check respectively. It may be mentioned that the contribution of grains per spike to grain yield per plant was comparatively higher than the spike length in yield heterosis of both better parent and the commercial check. Number of reports highlight the positive contribution of these traits to yield heterosis (BAILEY et al. 1980, GIRIRAZ & GOUD 1981. BITZER et al. 1982, UDDIN & JOARDER 1986). Heterosis for four F2 hybrids alongwith their component characters is presented in Table 2. Although the components of heterosis were specific for each cross, yield heterosis in general is largely due to heterosis in yield components. The best hybrid in our study gave as much as 44.18 percent more yield than the regional check Pak-70. This, coupled with other reports of substantial yield heterosis, presents an encouraging picture for exploiting heterosis by producing F2 hybrids in bread wheat. References BEHL, R.K. 1985. Wheat Inform. Serv. 60: 10-14. AL-SAHEAL, Y.A. and K.H. GAMIL. 1981. Wheat Inform. Serv. 53: 16-20. BANAGA, S.S. and K.S. LABANA. 1984. Z. Pflanzenzuchtg 92: 61-70. BAILEY, Jr. T.B., C.O. QUALSET and D.R. COX. 1980. Crop Sci. 20: 339-42. BITZER, N.J., PATTERSON and W.E. NYQUIST, 1982. Crop Sci. 22: 1126-1128. GIRIRAJ, K. and J.V. GOUD. 1981. SABRO J. 13(2): 92-97. UDDIN, M.M. and O.I. JOARDER. 1986. Pak. J. Agric. Res. 7: 1-9. |
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