Quantitative trait locus mapping of ovicidal response in rice (Oryza sativa L.) against whitebacked planthopper (Sogatella furcifera Horvath)

The ovicidal response in rice (Oryza sativa L.) to whitebacked planthopper (WBPH), Sogatella furcifera Horvath, is characterized by the formation of watery lesions which result in the death of WBPH eggs. To determine the genetic mechanism of this ovicidal response, a set of 71 rice recombinant inbred (RI) lines (F₈, F₉, and F₁₀) derived from a cross of japonica cultivar Asominori and indica cultivar IR24, the two parents, and the F₁ were phenotyped for percentage of watery lesions (PWL) and WBPH egg mortality (EM). PWL and EM showed significant positive correlations (P < 0.001) and transgressive segregation was observed for both traits. A total of 10 quantitative trait loci (QTLs) for ovicidal response were detected with 292 RFLP markers in the F₆ and F₇ populations by composite interval mapping (LOD ≥ 1.5). Four of 10 QTLs coincided for PWL and EM and each three QTLs were only detected for PWL and EM. The QTL on chromosome 6 (R1954-L688) was most significantly associated with the ovicidal response and accounted for 69.9% of phenotypic variance for PWL (F₈) and 46.0% of phenotypic variance for EM (F₈). Positive alleles for ovicidal response came from Asominori on chromosomes 1, 3, 6S (short arm), 8, and 12 and from IR24 on chromosomes 2, 6L (long arm), and 10. QTL accumulation from both parents was the genetic basis of the transgressive segregation in the RI population. No epistatic interaction was detected. The Asominori allele on the chromosome 6S QTL was essential to the ovicidal response, and R1954 was found to be a target marker for marker assisted selection.