Sclerotic productivity, mycelial compatibility, and pathogenicity of the isolates of the fungus Sclerotinia sclerotiorum (Lib.) de Bary
The study aimed to determine the variability of S. sclerotiorum populations from different soil and ecological conditions of Ukraine. Using phytopathological and mycological methods, 42 isolates of S. sclerotiorum, the causative agent of white mold, were obtained from infected soybean, sunflower, dahlia, winter rape and pea plants and stored on potato-glucose agar (PGA). To study sclerotic productivity, isolates were cultured on PGA in Petri dishes. To identify groups of mycelial compatibility, isolates were grown in pairs in all possible combinations. To study the pathogenicity of S. sclerotiorum isolates, leaves of winter rape were inoculated with 5 mm disks of mycelial culture from a five-day-old fungus, and surface areas of lesions on the leaf blade were measured. According to the results of the study, intensive production of sclerotia is exhibited by isolates of S. sclerotiorum from the population G. The smallest mass of sclerotia was produced by Bn28 (0.15 g), D21 (0.17 g), and D25 (0.19 g) isolates. Han10 and Han 40 (0.43 g), D26 (0.44 g), and Han 39 (0.46 g) isolates were the most productive. Mass sclerotia produced by all other investigated isolates of S. sclerotiorum ranged from 0.21 g to 0.37 g. Variability in mycelial compatibility of different combinations of S. sclerotiorum isolates was also revealed. Isolates obtained from soybean plants (population A) were characterized by the lowest level of mycelial compatibility-14%. In population C (sunflower), the proportion of isolate pairs characterized by mycelial compatibility was the largest-67%. All studied S. sclerotiorum isolates obtained from various host plants caused pathological processes on leaves of winter rape. Han42, Ps37, D21, and Han38 isolates had the lowest levels of pathogenicity. Han8, Han12, Han17, Han16, Gm6, Bn28, and Ps33 isolates were characterized by moderate pathogenicity. Strong pathogenicity was shown by Han18, D24, Gm2, Ha13, D22, D27, Han14, Ps35, Ps35, Han9, Han11, D23, D26, Han39, Gm5, Han20, and Bn32 isolates. Han40, Han10, Gm3, Gm7, Han19, Han41, D25, Bn31, Gm1, Ps34, Gm4, Bn29, and Bn30 isolates had a very high degree of pathogenicity. The study results revealed that the fraction of compatible pairs of isolates in different populations ranged from 14 to 67%.