The Past and Current Impact of Fusarium Oxysporum f. Sp. Vasinfectum Race 4 on Cotton Production in California

Fusarium oxysporum f. sp. vasinfectum (Fov) race 4 is an extremely virulent wilt pathogen to susceptible cotton varieties. Within the United States, Fov race 4 currently is geographically limited, first identified in California in 2001 and Texas in 2017. Since the introduction of Fov race 4 in California, it has been a recurring and expanding threat to California’s cotton production. Work done in California with Fov race 4 by various researchers during the past decade has produced evidence that cultural and chemical control methods (seed or in-furrow chemical or biological treatments, altered planting dates, crop rotations) typically have not adequately controlled infestations of Fov race 4 or adequately limited crop losses when growing Fov race 4 susceptible or moderately susceptible cultivars. Recommended strategies for improving crop survival and limiting economic damages have focused on identification of and growing more Fov race 4 tolerant cultivars, and growers to a large extent have taken this approach. More recently, in California, we have identified that our Fov populations in production fields are more diverse than previously reported. Our current research is focused on a survey of the cotton production fields in CA, and to molecularly characterize the Fov isolates collected during the survey. This current work will be important for the continued breeding efforts to develop superior cotton cultivars with high levels of resistance to Fov race 4.