Mapping of quantitative trait loci associated with resistance to brown planthopper in rice by means of a doubled haploid population

The brown planthopper (BPH), Nilaparvata lugens (Stil) (Homoptera: Delphacidae), is one of the major insect pests of rice (Oryza sativa L.). Many major genes are now available to manage this pest through host-plant resistance. In this study, we mapped quantitative trait loci (QTLs) associated with resistance to BPH using a doubled haploid (DH) population derived from the cross IR64/Azucena. We evaluated a set of 94 DH lines using a series of phenotypic tests that cover seedling resistance and resistance mechanisms: antixenosis, antibiosis, and tolerance. QTL analysis detected six QTLs on chromosomes 1, 2,6, and 7 associated with resistance to BPH in this mapping population. The QTLs on chromosome 7 (Est9-RZ337B) and 2 (RG157-RZ318) showed their association with seedling resistance and antibiosis, respectively. Four QTLs on chromosomes 1 (RG146-RG345), 6 (RG213-Est2; Pgi2-pRD10B), and 7 (RG773-Est2) showed their association with tolerance. The phenotypic contribution of the QTLs ranged from 10.4 to 17.6%. The study confirmed the presence of QTLs on chromosomes 1, 2, and 6 that have been previously reported for resistance to BPH populations of the Philippines. In addition, two additional QTLs were detected on chromosome 7 (Est7-RZ337B and RG773-CDO59) in the same mapping population. The results showed that detailed phenotypic analyses of plant resistance would help in improving the efficiency of QTL detection and in understanding the quantitative resistance to insect pests in crop plants.