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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Subtropical Plant Pathology Research » Research » Publications at this Location » Publication #414392
Research Project: Mitigation of Domestic, Exotic, and Emerging Diseases of Subtropical and Temperate Horticultural Crops

Location: Subtropical Plant Pathology Research

Title: Factors affecting development of pseudothecia produced by Venturia effusa in vitro

Author
item CHARLTON, NIKKI - Noble Research Institute
item Bock, Clive
item Boykin, Deborah
item YOUNG, CAROLYN - North Carolina State University

Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2024
Publication Date: 10/3/2024
Citation: Charlton, N.D., Bock, C.H., Boykin, D.L., Young, C.A. Factors affecting development of pseudothecia produced by Venturia effusa in vitro. Plant Pathology. 74:180-195. 2024. https://doi.org/10.1111/ppa.14008.
DOI: https://doi.org/10.1111/ppa.14008

Interpretive Summary: Scab is a destructive disease of pecan caused by the plant pathogenic fungus Venturia effusa. The disease occurs in the southeastern US. The fungus was assumed to perpetuate solely through asexually produced spores, but the sexual stage was recently identified. To investigate factors influencing the development of the sexual stage (called a pseudothecium) different mating types of the fungus were crossed pairwise on agar. Production and maturation of pseudothecia was assessed at 4, 8, 12, 16, 22 C, with incubation periods of 2, 3, or 4 months, either with or without light (0 or 12 h photoperiod) during maturation. Temperature, month, and paired cross affected production of pseudothecia. Similar numbers of pseudothecia were produced at 4, 8, 12, and 16 C, but fewer at 22 C. The isolate and mating type cross affected the number of pseudothecia. Light had no effect on maturation of pseudothecia in this study. The results indicate the likely temperatures and durations required to produce the sexual stage in the field, which has ramifications for production of the sexually produced spores.

Technical Abstract: Pecan scab, caused by Venturia effusa, is the most destructive disease of pecan in the southeastern US. The fungus was assumed to perpetuate solely through asexually produced conidia. Yet the identification of heterothallic mating type idiomorphs has led to successful crosses producing pseudothecia in vitro. To investigate factors influencing the development of pseudothecia, three isolates of each mating type (MAT1-1 × MAT1-2) were crossed pairwise on oatmeal agar. Pseudothecial production and maturation was assessed at 4, 8, 12, 16, 22 C, with incubation periods of 2, 3, or 4 months, either with or without light (0 or 12 h photoperiod) during maturation. There were significant effects of temperature, month, and cross on production of pseudothecia. Similar numbers of pseudothecia were produced at 4, 8, 12, and 16 C (2.3-1.8 pseudothecia), but significantly fewer at 22 C (0.1 pseudothecia). Pseudothecia remained immature at 22 C suggesting a cold period is required for ascospore maturation. The isolate and mating type cross affected the number of pseudothecia, with both MAT1-1 and MAT1-2 contributing to the number produced, which interacted with time. MAT1-1 had the greatest effect on the number of pseudothecia produced, but this was modulated by MAT2-2. At the highest temperature there were no differences among mating type crosses. Light had no effect on maturation of pseudothecia in this study. The results indicate the likely temperatures and durations required to produce pseudothecia in the field; ascospores may play a role as primary inoculum in the disease cycle of pecan scab.