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

Tiller number is a key factor influencing wheat plant architecture and yield potential. This study analyzed the variation in tiller number among 323 wheat accessions across nine environmental conditions. The results revealed a significant decrease in tiller number in modern cultivars compared to traditional landraces, indicating a trend in selective breeding for fewer tillers. Genome-wide association studies (GWASs) identified four quantitative trait loci (QTLs) associated with tiller number on chromosomes 2D, 5A, and 6A. Haplotypes linked to reduced tiller number at three of these QTLs have been significantly selected and are predominantly found in various Chinese agroecological zones, positively affecting grain number and/or weight. These findings suggest that contemporary Chinese wheat breeding strategies have prioritized reducing tiller number while improving spike yield. Identifying selected haplotype combinations can further enhance breeding efforts aimed at optimizing the tiller number trait. This study provides insights into the genetic basis of tiller number QTLs and their relevance to wheat breeding practices.