Influence of Cultivar Selection On Soil Populations of Verticillium Dahliae and Potential Implications for Cotton (Gossypium hirsutum) Production in West Texas

Verticillium wilt, caused by the soilborne fungus Verticillium dahliae, is an increasingly important disease of cotton in portions of West Texas. The fungus can survive for >20 years as microsclerotia, and disease incidence is related to soil populations. The relationship between disease development in cotton and inoculum production is poorly understood. A microplot study is being conducted starting from January 2008 till now to investigate the effect of variety selection on the population dynamics of V. dahliae over time. Experiments are being conducted in microplots (55cm diameter × 45 cm deep) augmented with field soil infested with V. dahliae. Baseline populations of V. dahliae were determined for each plot using soil dilution plating technique. All possible combinations of the resistant/tolerant variety AFD 5064F and susceptible variety Stoneville 4554B2F are included in a factorial design, arranged in a randomized complete block with seven replications. Disease development was assessed throughout the 2008 and 2009 cropping season, and soil populations were also enumerated to determine changes in microsclerotial populations in soil for each representative treatment. Results from this study would demonstrate the importance of increase in inoculum density over time (temporal population dynamics) in the development of wilt diseases caused by Verticillium dahliae in cotton. In addition, information from these studies may be useful in developing long term management strategies that can be implemented into integrated programs for sustaining the production of cotton in fields infested with Verticillium dahliae.