Diversity and fungicide resistance of Phytophthora capsici on vegetable crops in Georgia
Jackson, Kimberly Lorraine
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Phytophthora blight caused by Phytophthora capsici has become an increasing concern in vegetable production in Georgia. It is imperative to understand the phenotypic and genotypic diversity and fungicide resistance of the pathogen to design more efficient disease management programs. This study indicated that P. capsici populations in Georgia are diverse. Although isolates from different hosts did not differ morphologically, both mating types were present, and 12 pathotypes were identified based on their aggressiveness on pepper cultivars. All isolates grew at temperatures from 10 to 36oC but not at 38oC. The isolates were divided into five groups based on RAPD analysis, and genetic variations were moderately associated with geographical location and host origin of the isolates. Isolates insensitive to mefenoxam and cyazofamid were identified, but all the isolates were sensitive to fluopicolide and mandipropamid. Field applications of fluopicolide suppressed the disease significantly and could be used as an alternative to mefenoxam.