Mutation of Ehd1 prolongs basic vegetative growth periods to boost biomass and grain yield in rice

Abstract

Heading date is a pivotal agronomic trait that influences grain yield, and it is determined by florigen genes. However, the regulation of heading date and its impact on other agronomic traits remain to be fully understood. In this study, we identified a mutant named late-flowering and big panicle 1 (lbp1) in rice; we surveyed the growth and yield traits in lbp1. Changes in gene expression between lbp1 and wild type (WT) were determined by RNA-seq. lbp1 exhibits delayed heading of 1 month and enhancements in various agronomic traits. Compared with WT plants, lbp1 showed 336.9% higher biomass production, 27.7% longer panicle length, 41.2% higher grain numbers, 29.4% and 56.6% more primary and secondary branch numbers, and an overall 58.7% higher grain yield. Map-based cloning pinpointed that the mutant phenotypes stemmed from a mutation in the early heading date 1 (Ehd1) gene. Through RNA-seq and quantitative reverse transcription-polymerase chain reaction analysis, we observed significantly lower expression levels of heading date 3a (Hd3a) and RICE FLOWERING LOCUS T 1 (RFT1) in lbp1 compared to WT plants. Additionally, the expression levels of several MADS-box genes were downregulated in the mutant. Our findings indicate that negative regulation of the Ehd1-Hd3a/RFT1 pathway leads to delayed heading, enhanced biomass production, and increased grain yield. This discovery presents an effective breeding strategy for developing new japonica rice varieties with prolonged vegetative growth periods suitable for cultivation in southern China and other low-latitude regions.