A natural allele of TAW1 contributes to high grain number and grain yield in rice

Grain number per panicle (GNP) is a complex trait controlled by quantitative trait loci (QTL), directly determining grain yield in rice. Identifying GNP-associated QTL is desirable for increasing rice yield. A rice chromosome segment substitution line (CSSL), F771, which showed increased panicle length and GNP, was identified in a set of CSSLs derived from a cross between two indica cultivars, R498 (recipient) and WY11327 (donor). Genetic analysis showed that the panicle traits in F771 were semidominant and controlled by multiple QTL. Six QTL were consistently identified by QTL-seq analysis. Among them, the major QTL qPLN10 for panicle length and GNP was localized to a 121-kb interval between markers N802 and N909 on chromosome 10. Based on quantitative real-time PCR and sequence analysis, TAWAWA1 (TAW1), a known regulator of rice inflorescence architecture, was identified as the candidate gene for qPLN10. A near-isogenic line, NIL-TAW1, was developed to evaluate its effects. In comparison with the recurrent parent R498, NIL-TAW1 showed increased panicle length (14.0%), number of secondary branches (20.9%) and GNP (22.0%), and the final grain yield per plant of NIL-TAW1 was increased by 18.6%. Transgenic experiments showed that an appropriate expression level of TAW1 was necessary for panicle development. Haplotype analysis suggested that the favorable F771-type (Hap 13) of TAW1 was introduced from aus accessions and had great potential value in high-yield breeding both in indica and japonica varieties. Our results provide a promising genetic resource for rice grain yield improvement.