Phenotype Modification in Cotton for Control of Verticillium Wilt Through Dense Plant Population Culture. Stephen Wilhelm, Professor, Department of Plant Pathology, University of California, Berkeley 94720. James E. Sagen, Staff Research Associate, and Helga Tietz, Associate Specialist, Department of Plant Pathology, University of California, Berkeley 94720. Plant Dis. 69:283-288. Accepted for publication 17 September 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-283.

The continuous threat to the cotton industry of California’s San Joaquin Valley by Verticillium wilt is ultimately traceable to the long-practiced varietal monoculture of Acala cotton. A remedy is seen in genetic diversification of cultivars grown; this can be achieved by rotation with early-maturing, genetically distinct varieties that possess the highest possible wilt resistance and are adaptable to high-density planting. Two new cotton breeding lines developed for the San Joaquin Valley that meet these requirements are described. With their wilt resistance derived from Gossypium barbadense or a wild race of G. hirsutum, or both, their genetic backgrounds differ from that of the currently grown Acala SJ varieties. Their wilt resistance is optimized by their adaptability to high-density planting. Their early maturity and suitability for once-over harvesting by either stripper or spindle picker permit early shredding of stalks and early plow-down, factors favorable to containment of Verticillium. Yields and fiber qualities of the two breeding lines are competitive with those of current varieties.

Keyword(s): Acala Cal-120, Acala Cal-150, earliness, Hopi cotton, immunity, One-Variety Cotton Law.