3. The Relation of Plant Physiology and Chemistry to the Study of Disease Resistance in Plants 1

All phases of crop improvement deal directly or indirectly with the functioning of the plant in its environment. The agronomists, the geneticists, and the plant pathologists in general have been too busy seeking the end point, final yield under local environment, to investigate in detail the processes by which this yield was produced. The next logical step in the crop improvement program, therefore, is combining forces with the plant physiologist and physiological chemist in order that we may study the processes involved and their changes as influenced by environment during the production of this yield. In fact, the agronomists, the geneticists, and the plant pathologists themselves must study the processes of growth, storage of reserves, fruit and seed formation and maturation, the plant metabolism in its entirety, under extremes of environmental conditions. in order scientifically to produce high yielding, satisfactorily combined, disease resistant pedigree strains of field crops. For example, the production of yellows resistant strains of cabbage by Jones (1) 3 and his co-workers in which resistance by selection and hybridization l~as been combined with high yield and good quality in a considerable number of commerciall)r adapted varieties illus-. trates how readily these problems respond to combined cooperative attack. The production of bunt resistant, high-yielding strains of soft winter wheat by Gaines (2) and his associates which meet with the exacting requirements of the northwestern buyers is cited further as a recent example of the many awdlable of cooperative effort and results in crop improvement. Just as agronomy is concerned with the physiology of crop production, so plant pathology is concerned with abnormal plant physiology. In final analysis, each is concerned with cellular physiology and chemistry.