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. 2019 Jul 18;14(7):e0219821.
doi: 10.1371/journal.pone.0219821. eCollection 2019.

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

Aparna Petkar  1 , Karen Harris-Shultz  2 , Hongliang Wang  2 , Marin Talbot Brewer  3 , Leilani Sumabat  3 , Pingsheng Ji  1
Affiliations

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

Aparna Petkar et al. PLoS One. .

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 genetic diversity of the pathogen, FON isolates were collected from symptomatic watermelon plants in commercial fields in Georgia and Florida, USA, and identified based on morphological characteristics and PCR analysis using FON-specific primers. Discriminant analysis of principal components (DAPC) of 99 isolates genotyped with 15 simple sequence repeat (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 (ФPT) 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, respectively. 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.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Principal coordinate analysis of four populations of Fusarium oxysporum f. sp. niveum isolates collected from watermelon fields in southeastern United States.
Sampling locations include Berrien County, Georgia (GA1), Cook County, Georgia (GA2), Tift County, Georgia (GA3), and Florida (FL). PC1 (80.08%) and PC2 (5.57%) refer to the first and the second coordinate.
Fig 2
Fig 2. Discriminant analysis of principal components for Fusarium oxysporum f. sp. niveum (FON) from the southeastern United States showing scatterplot of the 8 assigned clusters based on Bayesian information criterion.
The four populations include: Berrien County, Georgia (GA1), Cook County, Georgia (GA2), Tift County, Georgia (GA3), and Florida (FL).
Fig 3
Fig 3. Discriminant analysis of principal components for Fusarium oxysporum f. sp. niveum (FON) from the southeastern United States showing a histogram of assignment probability of 99 FON isolates from 4 field populations into eight genetic clusters.
The four populations include: Berrien County, Georgia (GA1), Cook County, Georgia (GA2), Tift County, Georgia (GA3), and Florida (FL).
See this image and copyright information in PMC

References

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