Advances in breeding for resistance to hoppers in rice

Abstract

Rice productivity is hampered by a number of diseases and insects. Among the insects, hoppers including planthoppers and leafhoppers are typical phloem-sap feeders, which are very serious and damaging insect pests of rice in Asia. Many chemicals have been recommended for the control of planthoppers, but due to their feeding habit at the base of the plant, the farmers are unable to notice and effectively control these pests. Exploiting host plant resistance to hoppers and incorporating resistant genes in commercial cultivars are an alternative, economical and environment-friendly approach. To date, approximately 70 resistance genes against hoppers have been identified, and most of these genes have been tagged with molecular markers. Recently six genes for resistance to brown planthopper (BPH) in different lines have been cloned using map-based cloning. Based on molecular analysis of cloned genes, it appears that there is considerable similarity in the plant response to BPH infestation and fungal/bacterial pathogen attack. Marker-assisted selection (MAS) and pyramiding of genes for resistance to BPH and green rice leafhopper (GRH) have shown higher level and wide spectrum of resistance than their monogenic lines. In addition, transgenic approaches including RNAi have targeted various plant lectins and volatile compounds to generate resistance to hoppers. In context of changing climate, the major challenge for plant breeders is to breed varieties while taking care of changing populations of planthoppers and biotype development. Future research priorities should concentrate on high-throughput screening of germplasm for field resistance to planthoppers, identifying and transferring new genes for resistance from different sources to broaden the gene pool of rice and identifying durable combination of genes for marker-assisted pyramiding.