Evaluation of the Temporal and Spatial Occurrence of Fusarium Oxysporum F. Sp. Vasinfectum Races As Influenced By Selected Cotton Genotypes in the National Cotton Fusarium Wilt Evaluation Field in Alabama

Fusarium oxysporum f. sp. vasinfectum (FOV) is pathogenic to cotton not only in the United States but also in all major cotton growing regions around the world.  Many different biotypes known as races have been documented infecting cotton and inducing symptoms of wilting, stunting, chlorosis and necrosis of leaves, vascular discoloration, and even plant death.  This pathogen also interacts with nematodes such Meloidogyne incognita, the root-knot nematode (RKN) to cause even more damage to cotton. Many races of the FOV pathogen have been found to be present in a single field.  It has been observed that some races are more commonly found at certain times of the cotton season, such as race 4 in the western part of the country commonly infecting and causing stand reductions in the early part of the season.  This study was initiated to 1) Determine the in-season temporal variability of FOV races on selected Upland, Pima, and Acala cotton cultivars with known tolerance or resistance to RKN and certain FOV races. 2) Map the spatial variability of FOV races across a naturally infested field.  Test included Field plots consisting of 5 Upland, 2 Pima, and 1 Acala cotton varieties that have resistance or susceptibility to either FOV, RKN, or both were established in 2018.  Plants exhibiting symptoms of FOV infection were collected from the field for fungal isolation at weekly intervals for the first six weeks and bi-weekly for the remainder of the season.  Portions of the Translation elongation factor (EF-1α), β-tubulin (Bt) and the Phosphate:H⁺ symporter (PHO) were used to identify the race designation for each isolate of FOV collected to determine the temporal and spatial distribution of the pathogen.