PHENOTYPIC SCREENING AND SINGLE MARKER ANALYSIS FOR BROWN PLANTHOPPER RESISTANCE IN RICE (Oryza sativa L.)

Abstract

Brown planthopper (BPH), Nilaparvata lugens (Stål) is a destructive pest that poses a threat to the food security of rice producing countries. In order to breed rice varieties with resistance to the brown planthopper, it is necessary to identify highly resistant germplasm sources. Seventy-three genotypes were evaluated using standard seed box screening technique over a period of two seasons that have shown varied levels of response reactions to the planthopper. Simultaneously, fifty-three microsatellite markers linked to BPH resistance were employed to find their association with BPH resistance. This association was estimated using regression based Single Marker Analysis (SMA) in Microsoft Excel. The significant marker trait associations (MTAs) were indicated by a P-value (< 0.05) along with corresponding R2 for each marker explaining the total phenotypic variation for BPH resistance accounted by markers. Statistically significant marker-trait associations were observed for five of the 39 polymorphic markers viz, RM335, RM510, RM589, RM8213 and RM494 indicating the possibility of significant putative genetic loci associated with BPH resistance on chromosomes 4, 6 and 10. The percentage of the total phenotypic variation as explained by the significant markers ranged from 1.0% to 24.4% suggesting the reliability of these genetic markers for further improvement of breeding for BPH resistance. Since these markers are linked with Bph3, Bph17(t), QBph6 and QBph10 genes/QTLs respectively, the presence of these genes in the resistant germplasm lines found in the study could be exploited through marker-assisted breeding programs for the development of BPH resistant cultivars.