Dissecting brown planthopper resistance genes in Oryza and its wild relatives: A review

Rice is cultivated and consumed worldwide. It belongs to genus ‘ Oryza ’ with about 21 wild relatives and eight identified genomes which makes it accessible to the huge pool of genetic resources. The rice crop can be distressed by various biotic and abiotic stressors that affect its productivity. Brown planthoppers (BPH) are major pests of different persistent biotypes in different regions. Several major and minor genes and quantitative trait loci (QTLs) regulate BPH resistance, a composite character. These genes/QTLs employ different resistance mechanisms and may be specific to each biotype. 22 of the 44 BPH genes are found in the wild cousins of rice. Several genes have been discovered, cloned, functionally assessed, and introduced into various lines. Most of the identified genes have not been functionally studied rendering their mechanisms to remain unknown. With the discovery that BPH-1 could not provide protection against Biotype 2, there were concerns about a major plant hopper outbreak. To avoid such a scenario, genes from various sources and different resistance mechanisms are being explored.