In years 2-3, the UAF performed extensive phenotyping of ~390 diverse rice accessions (USDA Rice Mini-core Collection-URMC and Japonica Diversity Panel-JDP) for the identification of candidate genes by genome-wide association studies (GWAS), which could determine the seed set and grain quality under stress. An additional bi- parental (Cypress and LaGrue US rice cultivars) mapping population of 200 lines with molecular markers (LSU) is being currently used to validate results from the diverse panels analyzed.
In year 3, a diverse subset of the heat-tolerant and heat-sensitive rice accessions representing by medium and long-grain types were analyzed for their HNT response using transcriptomics of mRNA (UAF) and miRNA (OSU), and metabolomics (UALR). The comparative metabolomics analysis proved that sugar and carbon metabolism were differentially regulated in HNT-tolerant rice cultivars compared to HNT-sensitive cultivars. These pathways were also differentially regulated in transcriptomes of these genotypes.
Finally, to assess methods and develop the biotechnology tools for functional validation of candidate genes, gene-editing methods were developed for selected heat-tolerant and heat-sensitive genotypes (UAF), using the Chalk5 gene as a target for engineering and visualization of the chalky phenotype.
The Year 3 activities led to important insights into the mechanisms of the perturbation of rice grain quality traits under HNT conditions, pointing to the crucial role of carbohydrate metabolism pathways in determining grain quality and yield during HNT. This hypothesis is being supported by molecular and phenotypic data obtained on rice cultivars showing contrasting HNT phenotypes.
For research overview, please visit https://rice-hnt-stress.uark.edu/research-overview/