Genetic Analysis and Fine Mapping of QTLs for Stigma Exsertion Rate in Rice

Area of Science:

• Plant Genetics and Breeding
• Agricultural Science
• Molecular Biology

Background:

• Stigma exsertion rate (SER) is vital for hybrid rice seed production, influencing the outcrossing ability of male sterile lines (MSLs).
• The underlying molecular genetic mechanisms of SER are not well understood, hindering targeted breeding efforts.

Purpose of the Study:

• To identify and characterize quantitative trait loci (QTLs) controlling stigma exsertion rate (SER) in rice.
• To understand the genetic basis of SER for improving hybrid rice seed production through male sterile line (MSL) enhancement.

Main Methods:

• Utilized a recombinant inbred line (RIL) population derived from two rice lines (B805D and Hua6S) to identify QTLs.
• Validated major QTLs (qSE1 and qSE9) in a residual heterozygous line (RHL) background.
• Fine-mapped QTLs and employed sequencing, expression, and haplotype analysis to identify candidate genes, including OsBOP1.

Main Results:

• Identified 14 QTLs for SER, with two major QTLs, qSE1 and qSE9, significantly increasing stigma exsertion rates (dual, single, and total).
• The Hua6S allele of qSE1 and the B805D allele of qSE9 were shown to increase pistil size, contributing to improved SER.
• Fine-mapping localized qSE1 and qSE9, and a single nucleotide variation in OsBOP1 was identified as the likely functional variation for qSE1.

Conclusions:

• This study provides a foundation for cloning genes responsible for SER in rice.
• The identified alleles of qSE1 and qSE9 offer valuable genetic resources for improving SER in male sterile lines (MSLs).
• These findings can significantly contribute to the genetic improvement of hybrid rice seed production.