The biotic factors reducing yields for which resistance or tolerance is developed are parasitic weeds, diseases and pests that attack crops in the field and those that destroy produce after harvest. In the daily agricultural activities, the farmer has to contend with one or more of stress factors which limit crop performance causing serious economic losses to the farmer. The stress conditions are always expensive or sometimes very difficult to alter for profitable farming undertaking since efforts to control or alter the conditions often lead to serious reduction in marginal returns to the farmer.