Host-induced gene silencing of the acetolactate synthases VdILV2 and VdILV6 confers resistance to Verticillium wilt in cotton (Gossypium hirsutum L.).

Cotton Verticillium wilt caused by Verticillium dahliae (V. dahliae) is one of the most destructive fungal diseases and is difficult to control. However, resistant germplasm resources are scarce in cotton. Many studies have shown that host-induced gene silencing (HIGS) is a practical and effective technology in crop disease prevention by silencing virulence genes of pathogens. Acetolactate synthase (ALS) contains a catalytic subunit ILV2 and a regulatory subunit ILV6, which catalyzes the first common step reaction in branched-chain amino acid (BCAA) biosynthesis. We identified two acetolactate synthases, VdILV2 and VdILV6, which are homologs of ILV2 and ILV6, respectively, in Magnaporthe oryzae. To characterize the function of VdILV2 and VdILV6 in V. dahliae, we suppressed their expression in the strong pathogenic isolate Vd991 by using HIGS technology. VdILV2- or VdILV6-silenced V. dahliae had a dramatic reduction in pathogenicity. The results indicated that VdILV2 and VdILV6 are involved in the pathogenicity of V. dahliae. HIGS of VdILV2 or VdILV6 provides a novel fungicide target and an effective control to resist Verticillium wilt caused by V. dahliae.