Identification of Major Brown Planthopper Resistance Genes in Indigenous Thai Upland Rice Germplasm Using Molecular Markers

Brown planthopper (BPH) is the most problematic insect in rice cultivation, as it decreases crop yields. In this study, 143 upland rice varieties were genotyped for five essential Bph resistance genes: bph2, Bph3, Bph14, Bph15, and Bph17. The gene frequencies of the five Bph resistance genes varied from 33.57% to 61.54%. The 139 varieties contained one to five Bph resistance genes. Polymorphism information content values ranged from 0.4460 to 0.4984 with an average of 0.4744. Cluster analysis supported the subpopulations identified by STRUCTURE. An analysis of molecular variance analysis identified 7% variance among and 92% variance within subpopulations, indicating a significant gene exchange between the two subpopulations. The evaluation of BPH resistance using the SEM system by IRRI showed that 2 varieties were resistant to BPH, 29 varieties were moderately resistant, and 112 varieties were susceptible. The Bph3, Bph14, and Bph15 genes and BPH resistance showed significant correlation. These findings provide important information regarding BPH-resistant varieties for future use in rice breeding programs.

Automated summary

This study investigated the genotyping of five BPH resistance genes in 143 upland rice varieties, revealing varying gene frequencies and the presence of one to five resistance genes in 139 of the varieties. Cluster analysis and molecular variance analysis indicated gene exchange between two subpopulations. The evaluation of resistance using the SEM system found a limited number of resistant varieties, moderate resistance in several varieties, and susceptibility in the majority. Significant correlations were found between the Bph3, Bph14, and Bph15 genes and BPH resistance.