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Development of Crop Resistance to Diseases and Nematodes¹

ABSTRACT

Attention is given to the scope of the problem involved in breeding for disease resistance, past accomplishments, and problems and challenges of the future.

The scope of the problem is outlined in terms of the number of crop species, the number of crop diseases, and the vast acreage devoted to crops. All crop species are assumed to have a minimum of one disease that must be controlled by resistant varieties or by chemicals.

Past accomplishments are illustrated with data demonstrating that chemicals are used to control diseases on only a small percentage of the high-acreage field crops. Varieties resistant to important diseases are responsible for the limited use of chemicals on these crops. The extensive use of chemicals to control diseases of fruits and vegetables, and the possible consequences in man's food chain, are noted.

Problems identified as needing increased attention in the 1970's include the allocation of resources, cooperative approaches to disease control, generalized sources of resistance, genetic diversity and non-nuclear inheritance, diseases caused by deficiencies or excesses of minerals, and biological control of seedling diseases.

¹ Paper presented Dec. 28–29, 1970, in Chicago, Ill., at the American Association for the Advancement of Science Section "O" Agriculture Symposium on "Agriculture and the Quality of the Environment in the Seventies."

² Professor and Head, Department of Agronomy and Plant Genetics, Univ. of Minnesota, St. Paul 55101.