Fine Mapping of Major qTAC8c for Tiller Angle in Oryza rufipogon

Tiller angle plays an essential role in determining plant architecture and yield in rice. In this study, we identified qTAC8c, a major quantitative trait locus (QTL) for tiller angle, through introduced introgression of a segment from Oryza rufipogon BJ-5 into indica ZH8015. The qTAC8c was mapped to a 1469.55-kb region on chromosome 8 with the basis on 8 K chip analysis and map-based cloning, and was further narrowed down to a 76.75-kb region containing eleven open reading frames (ORFs). Sequencing and expression analyzing indicated ORF1 (LOC_Os08g33530) is the causal gene for qTAC8c. A total of ten single nucleotide polymorphism (SNPs) and one insertion were detected in the 4792-bp genome in ORF1 between ZH8015 and NIL-85. ORF1 encodes a TCP family of transcription factors. Meanwhile, two SNPs (SNP5 and SNP6) in the coding region of ORF1 resulted in two amino acid changes (L125F and L180S). Interestingly, SNP1 to SNP7 affected grain traits, especially grain width. Besides, a functional marker S3 was designed to detect promoters of qTAC8c in rice varieties, which could be a useful application for marker-assisted selection (MAS) breeding of plant architecture in rice. This study provides genetic resources for plant architecture and grain size improvement in rice.