An attempt to identify genetic variation in salivary protein sequences of the green rice leafhopper (Nephotettix cincticeps) that is associated with virulency against resistant rice varieties

The green rice leafhopper (GRH: Nephotettix cincticeps) is a major insect pest of rice in Japan. Field-collected GRHs normally do not survive on resistant rice varieties because they fail to feed on the phloem sap of these varieties. However, after rearing them on the resistant, we succeeded to find for virulent GRHs that were capable of feeding on the resistant varieties and established biotypes. Any virulence of the GRH biotypes examined was found to be dominated by a single dominant or recessive gene. Based on the possibility that the virulency is associated with mutations in some salivary components, we compared the gene sequences of salivary proteins among different GRH biotypes. As a result, several variations were observed in different proteins of different GBH biotypes, such as 1 base pair (bp) substitution with amino acid alterations, 1 bp deletion with the frame shift, and a 3 bp insertion. To determine whether these genetic variations were associated with the virulency of the individuals, we started linkage analysis in the segregating F₂ generation of crosses between virulent and avirulent GBH biotypes.