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.