Genetic Mapping of Stigma Exsertion Traits in Rice

Stigma exsertion, the emergence of the female floral organ beyond protective bracts, is a critical determinant of outcrossing potential and hybrid seed yield in rice (Oryza sativa). Genetic mapping has progressed from early quantitative trait locus (QTL) analyses in biparental populations to high-resolution genome-wide association studies (GWAS), fine substitution mapping and targeted gene editing. These efforts have uncovered numerous loci across multiple chromosomes that influence stigma length, style extension and overall exsertion rate. Major QTLs have been refined to sub-megabase intervals and candidate genes involved in cell division, hormone signalling and floral organ morphogenesis have been proposed. The integration of diverse mapping strategies and breeding panels has revealed the polygenic, epistatic and pleiotropic architecture of stigma exsertion, paving the way for marker-assisted selection and molecular design of male-sterile parental lines. Such advances are essential for boosting hybrid rice productivity to address global food security.

Research from Nature Portfolio

Recent studies have employed genome-wide association and high-resolution mapping to chart the genetic basis of stigma exsertion rate. One investigation genotyped over 200 cytoplasmic male-sterile lines with dense SNP arrays and identified clusters of loci associated with stigma exsertion, panicle enclosure and seed-set, revealing tight linkage and allelic directionality conducive to simultaneous trait improvement. Another study dissected a major locus on chromosome 7, delimiting it to under 400 kb, demonstrating its single-gene inheritance and quantifying its effect on single, dual and total stigma exsertion rates; this work provides a clear target for gene isolation and the development of parental lines with enhanced outcrossing efficiency.

Genetic Mapping of Stigma Exsertion Traits in Rice publication trend

The graph below shows the total number of articles in genetic mapping of stigma exsertion traits in rice across all publications each year (not limited to Nature Index journals).

Technical terms

Stigma exsertion rate (SER): Proportion of flowers in which the stigma protrudes beyond the lemma and palea, affecting outcrossing efficiency.

Quantitative trait locus (QTL): Genomic region that contributes to variation in a measurable trait such as SER.

Genome-wide association study (GWAS): Analysis correlating genetic variants across the genome with phenotypic differences in a diverse population.

Marker-assisted selection (MAS): Breeding approach that uses linked molecular markers to track and select for desirable traits.

Single-segment substitution line (SSSL): Genetic line carrying a defined chromosomal segment from a donor parent in the background of a recurrent parent, used for precise locus mapping.

References

1. Grain shape is a factor affecting the stigma exsertion rate in rice. Frontiers in Plant Science (2023).
2. Targeted manipulation of grain shape genes effectively improves outcrossing rate and hybrid seed production in rice. Plant Biotechnology Journal (2022).
3. Genome-wide association study of outcrossing in cytoplasmic male sterile lines of rice. Scientific Reports (2017).
4. Fine mapping a quantitative trait locus, qSER-7, that controls stigma exsertion rate in rice (Oryza sativa L.). Rice (2019).
5. Dissection of closely linked QTLs controlling stigma exsertion rate in rice by substitution mapping. Theoretical and Applied Genetics (2021).