Characterization of qPL5: a novel quantitative trait locus (QTL) that controls panicle length in rice (Oryza sativa L.)

Panicle length (PL) is an important trait that determines panicle architecture and strongly affects grain yield and quality in rice. However, this trait has not been well characterized genetically, and its contribution to yield improvement is not well understood. Characterization of novel genes related to PL is of great significance for breeding high-yielding rice varieties. In our previous research, we identified qPL5, a quantitative trait locus for PL. In this study, we aimed to determine the exact position of qPL5 in the rice genome and identify the candidate gene. Through substitution mapping, we mapped qPL5 to a region of 21.86 kb flanked by the molecular marker loci STS5-99 and STS5-106 in which two candidate genes were predicted. By sequence analysis and relative expression analysis, LOC-Os05g41230, which putatively encodes a BRASSINOSTEROID INSENSITIVE 1-associated receptor kinase 1 precursor, was considered to be the most likely candidate gene for qPL5. In addition, we successfully developed a pair of near-isogenic lines (NILs) for qPL5 in different genetic backgrounds to evaluate the genetic effects of qPL5. Agronomic trait analysis of the NILs indicated that qPL5 positively contributes to plant height, grain number per panicle, panicle length, grain yield per plant, and flag leaf length, but it had no influence on heading date and grain-size-related traits. Therefore, qPL5 and the markers tightly linked to it should be available for molecular breeding of high-yielding varieties.