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ARS Home » Southeast Area » Tifton, Georgia » Crop Genetics and Breeding Research » Research » Publications at this Location » Publication #359860

Title: Genetic and phenotypic diversity of Fusarium oxysporum f. sp. niveum populations from watermelon in the southeastern United States

item PETKAR, APARNA - University Of Georgia
item Harris-Shultz, Karen
item Wang, Hongliang
item BREWER, MARIN - University Of Georgia
item SUMABAT, LEILANI - University Of Georgia
item JI, PINGSHENG - University Of Georgia

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2019
Publication Date: 7/18/2019
Citation: Petkar, A., Harris-Shultz, K.R., Wang, H., Brewer, M.T., Sumabat, L., Ji, P. 2019. Genetic and phenotypic diversity of Fusarium oxysporum f. sp. niveum populations from watermelon in the southeastern United States. PLoS ONE. 14(7):e0219821.

Interpretive Summary: Watermelon is an economically important vegetable commodity in Georgia and Florida. The warm, humid environments of these states favor foliar disease development. Fusarium wilt is a soilborne disease caused by the fungal pathogen Fusarium oxysporum f. sp. niveum (FON). Spores of FON can live in the soil without a host plant for 15 years or more. Currently there are four races of FON described in the U.S. and each race is more aggressive than the last. Race 2 is widespread and aggressive to seedless watermelon cultivars. Race 3 was first identified in 2010 from Maryland and has recently been found in Florida. In this study the genetic and race diversity was examined from FON samples collected in Georgia and Florida. From the marker data, two main groups were identified. One group was composed of mainly samples from Florida whereas the other group contained most of the isolates from Georgia. Overall, 5%, 39%, and 56% of the isolates were identified as race 0, race 2, and race 3, respectively (no race 1 was identified). This study identified that the most aggressive races are prevalent in Georgia and Florida. As genetic resistance is currently unavailable in seedless watermelon, management strategies must be utilized to combat this disease.

Technical Abstract: Fusarium wilt of watermelon, caused by Fusarium oxysporum f. sp. niveum (FON) occurs worldwide and is responsible for substantial yield losses in watermelon-producing areas of the southeastern United States. Management of this disease largely relies on the use of integrated pest management (i.e., fungicides, resistant cultivars, crop rotation, etc.). Knowledge about race structure and genetic diversity of FON in the southeastern US is limited. To determine the genetic diversity of FON, simple sequence repeat (SSR) markers were used. Discriminant analysis of principal components (DAPC) of 99 isolates genotyped with 15 SSR markers grouped the isolates in eight distinct clusters with two prominent clusters (clusters 1 and 8). Cluster 1 consisted of a total of 14 isolates, out of which 85.7% of the isolates were collected in Florida. However, most of the isolates (92.4%) in cluster 8 were collected in Georgia. Both DAPC and pairwise population differentiation analysis ('PT) revealed that the genetic groups were closely associated with geographical locations of pathogen collection. Three races of FON (races 0, 2 and 3) were identified in the phenotypic analysis; with race 3 identified for the first time in Georgia. Overall, 5.1%, 38.9% and 55.9% of the isolates were identified as race 0, race 2 and race 3. The majority of the isolates in cluster 1 and cluster 8 belonged to either race 2 (35.6%) or race 3 (45.8%). Additionally, no relationship between genetic cluster assignment and races of the isolates was observed. The information obtained on genotypic and phenotypic diversity of FON in the southeastern US will help in development of effective disease management programs to combat Fusarium wilt.