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POSTERS: Abiotic interactions

Physiological changes in conidia of the fungal pathogen Neofusicoccum mediterraneum when exposed to desiccation
John Lake - California State University, Fresno. Margaret Ellis- California State University Fresno, Themis Michailides- University of California Davis, Kearney Agricultural Research & Extension Center

Neofusicoccum mediterraneum is an important Botryosphaeriaceae fungal pathogen that impacts pistachio production in California, with crop losses reported from 40-100%. When conidia of N. mediterraneum are not continuously exposed to moisture, their germination process is interrupted, and the one-cell hyaline conidia become brownish black, develop thickened cell walls and septa within the cell. It is hypothesized that these physiological changes in the conidia allows the fungus to adapt to and survive adverse climatic conditions making them solar and drought tolerant. The objective of this research was to determine if this physical alteration of the conidia is induced by desiccation. Fungal colonies were grown on low nutrient pistachio leaf agar medium for two to three weeks. A 1x105/ml conidial suspension was placed onto a semi permeable cellophane sheet in a glass petri dish and exposed to air from a laminar flow hood for 20 minutes. The conidia were then exposed to desiccation periods of 1, 2, and 3 hours. After the desiccation period, the cellophane sheets were placed on water agar and allowed to rest for 24 hours before conidial transformations were observed. There was a significant difference among treatments (P < 0.05), where 55, 77 and 87% of the conidia were converted as above at 1, 2, and 3 hours, respectively. These results suggest that desiccation can induce changes in N. mediterraneum conidia making them tolerant and able to survive adverse conditions.