Natural variations in the promoter of Stay-green gene, TaSGR associated with yield-related traits in wheat

Abstract

AbstractStay-green ( SGR ) gene is crucial for degradation of chlorophyll in Arabidopsis but remained elusive in wheat, especially the effects of their allelic variations on leaf senescence and grain yield. Here, systematic analysis of chlorophyll content and TaSGR expression in wheat flag leaves during natural senescence revealed that the higher expression of TaSGR-5A and TaSGR-5B leads to faster chlorophyll degradation and endogenous hormones and dark treatment could induce TaSGR-5A and TaSGR-5B transcriptions. Single nucleotide polymorphism (SNP) assays identified eight allelic variation sites in the promotor of TaSGR-5A and four haplotypes were detected in wheat populations. Two markers SNP-A-1 or SNP-A-2 were designed to differentiate four haplotypes. Besides, two allelic variation sites were identified in the promotor of TaSGR-5B and three haplotypes were detected in wheat populations. Two markers SNP-B-1 or SNP-B-2 were designed to differentiate three haplotypes . Association analysis suggested that accessions with Hap-5A-1 had higher spikelet number per spike (SNS), grain per spike (GPS), thousand-grain weight (TGW), yield per plant and chlorophyll content along with reduced TaSGR-5A transcription compared to accessions with other haplotypes. Accessions with Hap-5B-2 of TaSGR-5B had higher chlorophyll content and Normalized Difference Vegetation Index (NDVI) relative to the accessions with other haplotypes. However, silencing of TaSGR significantly delayed leaf senescence without affecting SNS, TGW and yield suggesting that allelic variations in TaSGR promoter might regulate increased SNS and grain yield in wheat. Overall, functional markers developed in this study could be utilized for screening stay-green phenotype with increased grain yield in wheat breeding.