PHENOTYPIC SCREENING AND SINGLE MARKER ANALYSIS FOR BROWN PLANTHOPPER RESISTANCE IN RICE (Oryza sativa L.)
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Brown planthopper (BPH), Nilaparvata lugens (StÃ¥l) is a destructive pest that poses a threat to the food security of riceÂ producing countries. In order to breed rice varieties with resistance to the brown planthopper, it is necessary to identify highlyÂ resistant germplasm sources. Seventy-three genotypes were evaluated using standard seed box screening technique over aÂ period of two seasons that have shown varied levels of response reactions to the planthopper. Simultaneously, fifty-threeÂ microsatellite markers linked to BPH resistance were employed to find their association with BPH resistance. This association wasÂ estimated using regression based Single Marker Analysis (SMA) in Microsoft Excel. The significant marker trait associationsÂ (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 39Â polymorphic markers viz, RM335, RM510, RM589, RM8213 and RM494 indicating the possibility of significant putative genetic lociÂ associated with BPH resistance on chromosomes 4, 6 and 10. The percentage of the total phenotypic variation as explained byÂ the significant markers ranged from 1.0% to 24.4% suggesting the reliability of these genetic markers for further improvement ofÂ breeding for BPH resistance. Since these markers are linked with Bph3, Bph17(t), QBph6 and QBph10 genes/QTLs respectively,Â the presence of these genes in the resistant germplasm lines found in the study could be exploited through marker-assistedÂ breeding programs for the development of BPH resistant cultivars.