Yield-related QTLs and their applications in rice genetic improvement.

Grain yield is one of the most important indexes in rice breeding, which is governed by quantitative trait loci (QTLs). Different mapping populations have been used to explore the QTLs controlling yield related traits. Primary populations such as F(2) and recombinant inbred line populations have been widely used to discover QTLs in rice genome-wide, with hundreds of yield-related QTLs detected. Advanced populations such as near isogenic lines (NILs) are efficient to further fine-map and clone target QTLs. NILs for primarily identified QTLs have been proposed and confirmed to be the ideal population for map-based cloning. To date, 20 QTLs directly affecting rice grain yield and its components have been cloned with NIL-F(2) populations, and 14 new grain yield QTLs have been validated in the NILs. The molecular mechanisms of a continuously increasing number of genes are being unveiled, which aids in the understanding of the formation of grain yield. Favorable alleles for rice breeding have been 'mined' from natural cultivars and wild rice by association analysis of known functional genes with target trait performance. Reasonable combination of favorable alleles has the potential to increase grain yield via use of functional marker assisted selection.