Prospects of Developing Hybrid Rice with Super High Yield

Approaches to develop hybrid rice ( Oryza sativa L.) with super high yield involve the improvement of plant type, the exploitation of intersubspecific heterosis, the pyramiding of heterosis genes in different rice ecotypes, and the utilization of favorable genes from distant relatives. Three main plant types have been suggested in the literature for improving hybrid rice yield: (i) heavy panicle type, (ii) super high yielding plant type, and (iii) super high yielding ideotype. Recently, intersubspecific heterosis has been partially exploited with three strategies: (i) developing parental lines of indica‐japonica intermediate type with favorable genes from both parents, (ii) introgressing intersubspecific gene with the help of wide compatibility and thermosensitive genic male sterility (TGMS) genes, and (iii) breeding pro‐indica japonica lines. It is also possible to pyramid different heterosis genes from various rice ecotypes through molecular marker aided reciprocal recurrent selection. The identification of yield enhancing genes from wild rice, the construction of autoregulated senescence delaying gene, and the cloning of key enzymes related to C4 pathway have been accomplished using molecular biotechnology. By introducing these genes into the parents of the hybrid rice, the heterosis of the hybrid rice can be dramatically improved.