Genetic Basis for Higher Resistance to the Brown Planthopper in japonica Rice Cultivar ‘Akiharuka’

The brown planthopper (BPH), Nilaparvata lugens Stål, is a major insect pest of rice and causes serious yield reduction. Our research group developed and released the japonica rice cultivar ‘Akiharuka’ which exhibitshigh BPH resistance. Here, to identify the chromosomal regions controlling this resistance, we performed DNA marker analysis using breeding and progeny lines of ‘Akiharuka’. We evaluated BPH resistance under laboratory and field conditions. Four quantitative trait loci (QTLs) were identified in these lines (one on each of chromosomes 1, 3, 4 and 5) based on damage scores obtained in a standard seedbox screening test. The ‘Akiharuka’ alleles at all QTLs decreased the damage scores. The effects of two QTLs, one QTL on the long arm of chromosome 3 (qBPH3-1) and one on the long arm of chromosome 4 (qBPH4-1) were likely additive and contributed to the high BPH resistance of ‘Akiharuka’. The ‘Akiharuka’ allele at qBPH3-1 reduced the survival rate of BPH and the number of BPH insects infesting plants under field conditions. qBPH3-1 and qBPH4-1 appear to be major genetic factors underlying the high BPH resistance of ‘Akiharuka’ and would be useful for the marker-assisted breeding of cultivars resistant to BPH.