Mapping of quantitative trait loci of ovicidal response to brown planthopper (Nilaparvata lugens Stal) in rice (Oryza sativa L.)

The brown planthopper (BPH), Nilaparvata lugens Stal, is a serious pest of rice (Oryza sativa L.) in Asia. The rice ovicidal response to BPH is charac terized by the formation of watery lesions which result in the death of the eggs. It is one of the factors affecting the suppression of the multiplica tion of BPH. To detect quantitative trait loci (QTLs) for this ovicidal res ponse, a set of 71 rice recombinant inbred lines (F-11) derived from a cros s between a Japonica variety Asominori with ovicidal response and an Indica variety IR24 without ovicidal response were phenotyped for grade of watery lesions (GWL) and egg mortality (EM) of BPH, GWL and EM showed a significa nt positive correlation (P < 0.001) and transgressive segregation was obser ved for EM. In composite interval mapping for GWL and EM with 293 RFLP mark er loci, two QTLs each on the long arm of chromosome 1 (1L) and the short a rm of chromosome 6 (6S) were detected for both GWL and EM. The 6S QTL expla ined 72.1% and 85.1% of the phenotypic variations for GWL and EM, respectiv ely, The QTL on 1L explained 19.8% and 17.8% of the phenotypic variations f or GWL and EM, respectively. Both alleles from Asominori increased GWL and EM. The Asominori allele at the 6S QTL was essential for the ovicidal respo nse to BPH and the Asominori allele at the 1L QTL could increase the EM of BPH in the presence of the Asominori allele at the 6S QTL. It is concluded that the two RFLP loci, R1954 linked to 6S QTL and C112 linked to 1L QTL ca n be used for marker-assisted selection.