Abstract

The need for the control of plant diseases is being increasingly recognized all over the world and a variety of preventive anc curative methods have been discovered and developed during the las century. The discovery of fungicides in the form of seed steeps, spray fluids and dusts, marks a distinct advance in agricultural science. But suci direct methods of disease control are at best palliatives of a temporary nature that their limitations are sufficiently patent to the farmer as well a: to the student of agriculture. Such methods are, moreover, found to be practicable and economical in so few cases that their successful application is bound to be restricted to a limited number of crop diseases even in the most agriculturally developed countries. Growing demand for disease resistant stock. The utilization of natura resistance as an indirect means of fighting pests and diseases is rapidly gaining popularity in the field of agricultural science. Consequently, plant pathologists all over the world are directing their efforts to exploit this avenue as the surest and, in the long run, the cheapest method of disease control. As instances of the achievements of scientists in producing plants resistant to diseases may be mentioned, blight-resistant potatoes, rust- resistant wheats, wilt-proof cottons, mosaic-free sugarcanes, canker-resis- tant apples, mildew-resistant roses, wilt-free melons, leaf-disease-resistant coffees, etc. These and several other achievements in this line have created an ever-growing demand for breeding crop plants which possess the natural resistance against almost every conceivable kind of disease.

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