Association Studies Unravel a Link Between Yield Components and Disease Resistance of Rice

Rice blast disease is one of the major constraints of stable rice production; however, a link between blast disease resistance and specific yield components of rice has not been established. In the present study, a subset of the USDA rice core collection consisting of 151 Oryza sativa was selected using the specific Pi-ta gene marker and 126 of them were verified to contain functional Pi-ta genes. These were then genotyped with 156 polymorphic SSR markers distributed among the 12 chromosomes. Twelve common US blast races were used to evaluate disease reactions of the accessions, and yield components, including heading date, plant height, brown and paddy seed weight, were determined in two environments. The links between disease reaction, yield components, and DNA profile were established using genome wide association analysis. A total of 44 blast resistant loci were identified among all rice chromosomes. Most of the loci were in close proximity to either cloned or finely mapped R genes, except for 6 loci on chromosome 3. A total of 42 SSR markers were associated with seed weight, heading date and plant height. To name a few, on chromosome 1, the resistant alleles of RM431 and RM1339 were associated with reduced plant height and the resistant allele of RM490 was associated with later heading date. In contrast, all 126 rice germplasm with Pi-ta were correlated with lower seed weights. These findings revealed a sophisticated epistatic interaction between rice yield components and disease resistance, and further progress will be presented.