This project addresses the number one priority issue from the 2018 Arizona Iceberg Lettuce Research Council (AILRC) survey: Disease Control and Management. The Yuma Center of Excellence for Desert Agriculture (YCEDA) was established to be responsive to the critical needs of the production agriculture industry.  Fusarium wilt of lettuce is one of the challenges prioritized by YCEDA stakeholders, and we are working on several fronts to investigate strategies to control this disease.

Fusarium wilt of lettuce, caused by the soil-residing fungus Fusarium oxysporum f.sp. lactucae (Fol), has increasingly become a problem in Arizona, causing significant losses in lettuce crops. Historically growers in Arizona experience Fusarium wilt of lettuce problems on iceberg lettuce planted in September and a lower level of disease in the spring plantings, but that is changing as growers have been reporting significant losses in lettuce planted in October when the weather is not as conducive for disease development. To properly manage the new disease pressure that growers are experiencing, we need to understand how several variables influence disease development. If the increased disease pressure is the result of a change in the genetic makeup of the population of Fol, this will significantly shift efforts to breed for Fusarium wilt resistance. 

The goal of this project is to determine if there is significant variability in the Fol population in Yuma that will influence lettuce breeding efforts and growers' management decisions. Results from this study will determine if breeding programs need to shift to breeding from resistance to multiple Fol races or genotypes. This study may also indicate the importance of evaluating lettuce cultivars in the greenhouse against highly virulent Fol isolates and in multiple field locations.