Increasing grain yield is a long-term goal in crop breeding and a key to ensure global food security. Heterosis—when a hybrid shows higher performance for a trait than both parents—offers an important strategy for crop breeding. 

To identify the genetic basis of heterosis for yield in rice, Prof. HAN Bin's group and Prof. HUANG Xuehui's group from the Institute of Plant Physiology and Ecology (SIPPE), Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences (CAS), in cooperation with Prof. YANG Shihua's group from the China National Rice Research Institute, conducted genotype and phenotype analyses of 10,074 F₂ lines from 17 representative hybrid rice crosses.

The researchers systemically identified the genetic loci related to heterosis for yield in rice. They found that modern rice varieties can be classified into three major types, reflecting the major breeding systems. Within each group, the researchers identified a few genomic regions and gene alleles from female parents that were associated to heterosis effects for improved yields. However, these loci varied across the three groups. 

This discovery will facilitate the optimization of hybridization in order to quickly obtain hybrid varieties with high yield, high quality, and stress resistance. 

The results were published in Nature on Sept. 7, 2016.