Mlo gene in barley and wheat. The product of Mlo gene helps powdery mildew infection on barley and wheat. Knockout/or mutation of native Mlo would create resistant crop, which is being used in Europe for decades on barley, and now begin with wheat recently. 

Activation of the brassinosteroid and abscisid acid pathway (if not over-activated!) can promote rice susceptibility to different root nematodes.

Ethylene production genes are potential candidates.... Please kindly refer to attached paper