Manifestation of Hybrid Vigor in Rice

Abstract

The manifestation of heterosis for grain yield, yield components and several important agronomic characters by a group of 265 F1 hybrids of rice over a six-crop period from the second crop of 1967 to the first crop of 1970 are reported. Among 265 F1 hybrids evaluated, a total of 192 or 72.5% of the total hybrids outyielded their mid-parent and check varieties while grain yield of 145 or 54.7% of the hybrids exceeded their respective high-parent. The average heterosis for these outstanding F1 hybrids was 20.3, 19.1 and 18.3% in relation to mid-parent, check varieties and high-parent, respectively. However, the magnitude of hybrid advantage over the mid-parent and check varieties reduced to 10.6 and 6.3% respectively when the average data of the six crops were considered. The superiority of F1 hybrids over high-parent was also reduced to nil when averaged over all entries. The number of panicles per plant and the number of grains per panicle were found to be the most important components associated with the manifestation of heterosis for grain yield. The correlation coefficient between mid-parent yield and yield of the hybrids was large enough to indicate that mid-parent value would be highly effective indicator of hybrid performance. However, mean square associated with F1 hybrids vs. parents also attained significance in some cases. There was no evidence of maternal effect on the grain yield of the hybrids. The heterosis expresses for grain yield in the first crop was generally larger than that in the second crop. F1 hybrids also exhibited large leaf area index, earlier heading, taller plant, longer and heavier panicle in comparison with mid-parent and check varieties. The expression of heterosis for plant height and number of tillers per plant was not affected appreciably by the stages of rice growth.