Characterizing Beltrania pseudorhombica the causal agent of pistachio leaf and fruit spot in Arizona
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In 2016 and 2017, we have constantly recovered a fungus with typical biconical (diamond shaped) conidia from pistachio fruit (cv. Kerman) received from Cochise County, Arizona, United States. Morphological and molecular characterization identified the isolates as Beltrania pseudorhombica, a member of the Beltraniaceae family that is an uncommon plant pathogen. In in-vitro tests, B. pseudorhombica showed temperatures of 26.9 °C and 31.1 °C as the optimal for the mycelial growth and conidial germination, respectively. Pathogenicity tests demonstrated the isolate capacity to cause lesion in leaflets (Kerman > Lost Hills > Golden Hills > Kalehghouchi) and fruits (Lost Hills > Kalehghouchi > Golden Hills > Kerman). The preventive fungicide application with sole formulation of demethylation inhibitor and mixed formulation of succinate dehydrogenase inhibitors and quinone outside inhibitors offered the greatest lesion control, when compared with the sole formulation of quinone outside inhibitors. This short communication provides important epidemiological information that can be useful to avoid the dissemination of new pathogens in new pistachio production areas in the United States.
KeywordsBeltraniaceae Fungicide efficacy Pathogenicity Pistacia vera
The authors thank the California Pistachio Research Board for financial support, the AZ pistachio growers for allowing us to collect field samples, and to Dr. Pedro Crous for useful discussions.
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