INFECTIOUS DISEASES OF TROPICAL AND SUBTROPICAL PLANTS IN THE GREENHOUSES OF THE BOTANICAL GARDEN OF PETER THE GREAT – V.L. KOMAROV BOTANICAL INSTITUTE AND DONETSK BOTANICAL GARDEN IN THE AUTUMN-WINTER PERIOD

Microclimatic changes in greenhouses of botanical gardens are stressful for many tropical and subtropical plant species in the autumn-winter period. As a result, their resistance to infections decreases. For three years, lesion degree for introduced plants was studied in two geographically remote botanical gardens – the Botanical Garden of Peter the Great and Donetsk Botanical Garden. In total, 113 tropical and subtropical plant species have been examined, and infectious diseases have been found in 98 species. A group of plants (48 species) has been identified as the most vulnerable to infectious pathologies in the greenhouses of both gardens during the autumn-winter season. Mycoses accounted for more than 70 % of the detected diseases in each botanical garden. In two gardens, 38 pathogenic micromycetes have been identified; their species composition was similar by 39.5 %. 14 species of alien fungi specialized to certain genera and families of tropical and subtropical plants have been found. The proportion of bacterial diseases was higher in Donetsk Botanical Garden (30 %) compared to the Garden of Peter the Great (19 %). The proportion of viroses in both gardens did not exceed 6 %. The most harmful diseases in the greenhouses of the compared gardens were root rot and foot rot, and vascular wilt. They were caused by phytopathogens of the genera Phytophthora, Pythium, Fusarium. The physiological state and decorative qualities of plants were disturbed by spot disease and rot caused by micromycetes of the genera Alternaria, Botrytis, Cladosporium, Colletotrichum, Penicillium, as well as infectious variegation. A distinctive phytosanitary feature of the greenhouses of the Botanical Garden of Peter the Great is a higher incidence of phytophthora rot. To protect greenhouse plants from infectious diseases, a complex of agrotechnical, chemical and biological methods was used.