Analysis of a doubled-haploid rice population derived from a cross between ‘IR64’ and ‘Azucena’ showed that quantitative trait loci (QTLs) that contributed to the BPH resistance of IR64 also existed on chromosome 1, 2, 3, 4, 6 and 8, in addition to a major gene on chromosome 12 controlling BPH resistance in this population (Huang et al. 1997; Alam and Cohen
1998)