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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #379011

Research Project: Healthy, Sustainable Pecan Nut Production

Location: Fruit and Tree Nut Research

Title: First report of Macrophomina phaseolina, Fusarium brachygibbosum, and Lasiodiplodia theobromae causing fungal watermelon vine decline in Southwest and West-Central Florida

Author
item Pisani, Cristina
item Adkins, Scott
item Turechek, William
item Patel, Pragna
item Rosskopf, Erin

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Wilt and vine decline symptoms were observed on watermelon plants in Glades and Hardee Counties in Florida in spring 2017 that resembled viral watermelon vine decline caused by squash vein yellowing virus (SqVYV). When no SqVYV was detected, greenhouse studies and morphological and molecular analyses revealed three new fungal pathogens, Macrophomina phaseolina, Fusarium brachygibbosum, and Lasiodiplodia theobromae that were not previously reported on watermelon in Florida. A previously reported oomycete, Pythium spinosum was also detected, but was determined not to be a causal agent for this disease complex. This would be the first report of these three pathogens on Florida watermelon.

Technical Abstract: Wilt and vine decline symptoms were observed on watermelon plants in Glades and Hardee Counties in Florida in spring 2017 that resembled viral watermelon vine decline caused by squash vein yellowing virus (SqVYV). When no SqVYV was detected, greenhouse studies and morphological and molecular analyses revealed three fungal pathogens, Macrophomina phaseolina, Fusarium brachygibbosum, and Lasiodiplodia theobromae, that were not previously reported on watermelon in Florida. A previously reported oomycete, Pythium spinosum, was also detected but when applied alone, resulted in disease incidence that was comparable to the untreated check, ruling it out as a primary causal agent of the symptoms observed in the field. In one of three experiments, seedlings inoculated with a combination of Macrophomina phaseolina, Fusarium brachygibbosum, and Pythium spinosum suffered the highest disease severity based on AUDPC values. In another experiment, seedlings inoculated with F. brachygibbosum exhibited the most severe symptoms and rapid disease development following inoculation. When seeds were inoculated with either single or combinations of fungi, seeds inoculated with L. theobromae resulted in seedlings with the greatest disease severity. This is the first report of these three fungal pathogens on Florida watermelon.