Natural variation in the THICK TASSEL DWARF1 (TD1) gene in the regulation of maize (Zea mays L.) ear-related traits

THICK TASSEL DWARF1 (TD1) is a critical gene that negatively modulates meristem size during maize inflorescence development and may also regulate ear-related traits. In the present study, the whole genomic DNA sequences and the promoter regions of TD1 were analyzed in 165 diverse maize inbred lines. Polymorphism analysis identified 39 SNPs and five InDels in the genic region of TD1 and allowed 23 haplotypes to be classified. Among these sites, eight SNPs and one InDel were significantly associated with kernel number (KN) (p < 0.05), seven SNPs and one InDel were significantly associated with kernel number per row (KNPR) (p < 0.05), and three SNPs were significantly associated with kernel row number (KRN) (p < 0.05). In addition, 21 SNPs and 14 InDels were identified in the promoter regions of TD1, and two SNPs and seven InDels of these sites were found to be significantly associated with KRN (p < 0.05). The results denote that Hap_7 was the favorable haplotype for both KN and KNPR, and Hap_2 was the elite haplotype for KRN. These favorable haplotypes could be utilized in molecular marker-assisted selection (MAS) to improve KN, KNPR, or KRN, and thereby further increase grain yield in maize breeding programs.