Cultural Diversity of Clasterosporium Pathogen Isolates in Plum (Prunus domestica) Orchards in Southern Russia

Among fungal pathogens aff ecting stone fruit crops in Russia and worldwide, Wilsonomyces carpophilus (Lév.) Adask., J. M. Ogawa & E. E. Butler (Clasterosporium carpophilum (Lev.) Aderh., anamorph) lead to the most severe commercial consequences. This pathogen causes clasterosporiosis, also known as shot hole disease of stone fruits. Study ing the intraspecifi c variability of the pathogen in a particular region allows researchers to track changes occurring within populations, including assessing their ecological adaptability. The aim of this study was to evaluate the cultural diversity of monospore isolates of W. carpophilus obtained from domesticated plum (Prunus domestica L.) commercial orchards. Monospore isolates of the pathogen were collected from infected dormant shoots of the Kabardinskaya Rannyaya plum cultivar in commercial orchards located in the central subzone of the Prikubanskaya horticultural region of Krasnodar Krai. The isolates were cultivated on potato-glucose agar (PGA) and analyzed by such cultural characteristics as colony size, shape, profi le, aerial mycelium structure, colony edge features, coloration, and sporulation patterns. Each morpho type was identifi ed based on a unique combination of cultural traits. The growth rate of the isolates was measured on days 2, 3, 4, 5, 11, 12, and 30 after inoculation. Analysis of 17 W. carpophilus isolates revealed high variability in their cultural characteristics. On the 12th day of cultivation at room temperature, colony size on PGA ranged from 36.0 to 45.0 mm, with growth rates varying from 1.3 to 3.5 mm/day. However, signifi cant diff erences in growth rates among individual isolates were not observed. Cultural characteristics of the isolates on days 12 and 30 diff ered substantially, with colony size and coloration changing signifi cantly over time. Older cultures exhibited darker shades of aerial mycelium compared to younger colonies. The cultural analysis identifi ed fi ve distinct morphotypes of the pathogen. The most frequently ob served morphotypes were 1, 2, and 3, accounting for approximately 80 % of the total sample. The study demonstrates a high level of intrapopulation diversity in W. carpophilus.