New insights into the genetic basis for improved yield in rice hybrids over their parent varieties, reported in Nature this week, may help to further optimize breeding strategies designed to meet global food demands.

Breeding practices often use strategies to select for crops where crosses of two different varieties perform better than either of their parents in terms of yield; for example, commonly used hybrid rice varieties display increased yields that are around 10-20% higher than that of their inbred parents. However, the genetic basis for this phenomenon, known as heterosis, has been unclear.

Bin Han and colleagues report large-scale genomic mapping for yield related traits and heterotic effects by analysing over 10,000 rice lines produced from 17 elite rice lines. They find that modern rice varieties can be classified into three major types, reflecting the major breeding systems. Within each group a few genomic regions from female parents linked to heterosis effects for improved yields were identified, but these loci varied across the three groups.

These results inform on the genomic architecture of heterosis for yield traits in rice, which will be useful information for crop improvement programmes.