Major genes contributes disease resistance in the form of

Major genes contribute to disease resistance in the form of Vertical resistance.
A plant variety that exhibits a high degree of resistance to a single race, or strain, of a pathogen is said to be vertically resistant; this ability usually is controlled by one or a few plant genes.
One or a few major role genes that could be sufficient to make a plant resistant to a pathogen is referred to as R-gene, monogenic, oligogenic, or vertical resistance.