Bacterial blight of cotton: has it reemerged as a problem because of changes in the bacterial population?
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This applied, research-led project addresses the resurgence of bacterial blight of cotton. Bacterial blight, caused by Xanthomonas citri subsp. malvacearum (Xcm), is a yield limiting disease of cotton and also survives and spreads in seed. It must be controlled for sustainable production of cotton. The project proposes to collect a diverse set of Xcm from Georgia, Mississippi, and Texas. Xcm injects type 3 effector proteins (T3Es) into plants to promote susceptibility in cultivars. Most pathogenic Xanthomonads deploy 10-30 distinct T3E proteins during infection, and on a population level, these T3E repertoires are variable. The Xcm isolates collected in this project will be characterized for T3Es. In addition, Xcm isolates from Texas will be tested on cotton cultivars differing in their disease response to race 18 of Xcm. These tests should provide evidence if a race shift is occurring. There is an additional hypothesis, that the resurgence of the disease is due to an interaction between Xcm and another bacteria. Tests will be conducted in the greenhouse on varieties that should be resistant and susceptible to bacterial blight, using other bacteria that are isolated in close proximity to Xcm.Extension specialists in Georgia, Mississippi and Texas will develop material for producers to manage this disease using IPM principles including current cultivars and their susceptibility to the disease, importance of plowing in infected plant material, and planting seed that is clean of the bacteria. Changes in production practices, particularly regarding cultivar choice, will be monitored by the extension specialists via surveys as well as general state-wide bacterial blight problems. If a new race of Xcm is found, it will be made available to cotton breeding programs.