The selection and application of tiller number QTLs in modern wheat breeding

Abstract Tiller number is a critical factor influencing wheat plant structure and yield potential, yet the genetic underpinnings and implications for tiller breeding selection remain elusive. This study extensively investigates tiller number across 323 wheat accessions within nine diverse environments, unveiling a significant reduction in modern wheat cultivars compared to landraces, demonstrating a prevalent preference for lower tiller numbers in modern breeding. Through genome-wide association study (GWAS), four pivotal quantitative trait loci (QTLs) associated with tiller number were identified, with three extensively selected and preferentially integrated into diverse Chinese agroecological zones. Notably, haplotype analysis revealed that lower tiller haplotypes also have significant genetic effects in enhancing grain number and/or weight. These findings suggest a co-selection of lower tiller numbers and higher spike yield was adopted in modern high-yield breeding programs in China. Additionally, the proposed combinations of these haplotypes aim to optimize tiller numbers for wheat breeding. This study provides novel insights into the genetic basis and selection of tiller number QTLs for modern wheat breeding.