Heterosis in Rice

The nature and extent of heterosis was estimated for grain yield and its related characters in 10 parent diallel crosses in rice. The performance of their F₂’s was also studied at two locations. The high heterotic effects for grain yield were observed in IR 8 X Sona and Jhona 349 X Basmatti 370 hybrids which gave 42–44 and 56• 35 percent heterosis, respectively over better parent and 42–44 and 31–53 percent heterosis, respectively over the best variety IR-8. The high positive heterotic effectsfor spikelets/panicle and high negative heterotic effects for grains/panicle indicated occurrence of high percentage of spikelets sterility which contributedto the lack of heterosis in grain yield in many crosses. The crosses C 12329 x BJ-1, Jhona 349 x TK. M-6 and TKM-6 x Basmati 370 showed very highlevel of negative heterosis for grains/panicle which was due to very high spikelet sterility in these crosses On the basis of yield performance of F₂’s at two locations, the crosses IR 8 x Sona, IR 8 x Jhona 349, Sona X BJ-1 and IR 2153-43-2-5-4 X BJ-1 appeared to be promising and need the attention of the breeder for their exploitation.