Molecular dissection of the primary sink size and its related traits in rice

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Abstract
The genetic mechanism underlying the relationship between three traits of the primary sink size ‐ spikelet number per panicle (SNP), panicle number per plant (PN), and 1000‐grain weight (GWT), and their 10 component traits in rice was dissected in 292 F13 recombinant inbred lines using a complete linkage map. A total of 43 genomic regions on 12 rice chromosomes were found to contain quantitative trait loci (QTLs) affecting the sink size traits, which revealed several important aspects of the genetic basis of sink capacity in rice. First, QTLs for SNP, PN and GWT were largely independent. Secondly, most QTLs affecting SNP and GWT showed close characteristics in both genomic locations and directions of effects to QTLs for their components, suggesting that pleiotropy, rather than linkage, was the primary genetic basis of the correlated panicle and grain traits. Thirdly, some QTLs affecting component traits did not contribute to SNP or GWT. In these cases, two or more QTLs with opposite effects on their component traits were detected, which could be due to either linkage or pleiotropy. Fourthly, some QTLs had large effects on panicle number (QPn4), panicle branching and length (QPbn3a, QPbn3b and QPb14), grain length and volume (QG13, QG15 and QGv2), and grain shape (QGs1 and QGs7), which were consistently detected in the related rice mapping populations and in different environments, providing good candidates and useful information for marker‐aided improvement of sink size and yield potential of rice.