Why high yield QTLs did not succeed in preventing yield stagnation in rice?

Rice plays a vital role in global food security, and its yield needs to be increased to meet escalating demand. Although many high yield quantitative trait loci (QTLs) have been identified in the last decades, rice grain yield in the main rice-producing countries is stagnating since the middle of the 1990s. By summarizing the yield performance of high-yielding QTL lines, we found that almost all the high-yielding QTL introduced lines had no practical usage in current high yield breeding programs, due mainly to their low absolute grain yield. Further analysis showed that scientists primarily focused on spikelets number per panicle alone rather than other yield traits, and, in most of the studies, the yield increase was referenced to very old cultivars. By analyzing the yield traits correlations across cultivars in both field and pot conditions, and yield traits correlations across different eco-sites using the same cultivars, we demonstrated that the rice high yield will be rarely achieved by using single-trait approaches due to the traits trade-offs. Building on this, several recommendations are provided to the next generation of biotechnological breeding in rice.