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Poster: Diseases of Plants: New & Emerging Diseases


Cytospora leucostoma is the most virulent and prevalent causal agent of Cytospora Canker on peaches on the Western Slope of Colorado
J. Stewart (1), K. Otto (1), I. Minas (2), S. Miller (1) (1) Bioagricultural Sciences and Pest Management, Colorado State University, U.S.A.; (2) Department of Horticulture and Landscape Architecture; Western Colorado Research Center Colorado State Univer

Cytospora canker on peaches (Prunus persica (L.) Batsch) is known to be caused by three species, Cytospora cinctum, C. leucostoma, and C. paraleucostoma within growing areas of the United States. In Colorado, recent surveys show that over 90% of the trees on the Western Slope are infected with Cytospora canker, causing significant economic impacts to peach growers. Understanding how these species differ phenotypically and in disease cycle and progression is important for disease management. The objectives of this study were to identify Cytospora isolates collected from high and low elevation sites, examine population structure and recombination, and assess each species/population for phenotypic characters such as virulence, temperature growth and culture morphology. The ITS region was sequenced to identify 106 isolates. Both C. leucostoma and C. paraleucostoma were recovered, although Cytospora leucostoma was the most prevalent. Additional sequencing of 4 genetic loci (ca. 1950 bps), suggested that C. leucostoma and C. paraleucostoma recombine and that well-supported clades do not exist for 3 of the 5 loci. Phenotypic characterization indicates overlapping variation in temperature, growth, culture morphology, and virulence. These data suggest that isolates are genetically distinct populations of C. leucostoma rather than cryptic species.