Pythium spp. – rosnący problem w uprawie ogórka pod osłonami

Abstract

In 2022 and 2023, a record number of cucumber samples came to the Plant Diseases Clinic in Institute of Plant Protection – National Research Institute in Poznan. The dominant problem (more than 90% of the samples) was the sudden wilting of healthy-looking plants, despite adequate water availability. The yield decreased drastically, and the plants in the entire rows dried up and died prematurely. Until 2019, similar symptoms appeared sporadically on cucumbers delivered to the Clinic. On the basis of microscopic observation, confirmed by isolation on artificial substrates from fragments of infected cucumber, the cause of the disease was identified – fungus-like organisms (Oomycetes) of the genus Pythium. In soilless cultivation systems, they cause soft rot of the roots and the shoot base of cucumber and the so-called sudden wilting of a cucumber. Typical symptoms of infection are stunted plant growth, brown discoloration of the root tips and wilting of the plant during the warmer times of the day (they regain turgor during the night). Infected plants turn yellow and die. Infection can occur all year round. In summer, thermophilic species are the most serious problem, while in winter and early spring, spe¬cies preferring lower temperatures. The samples delivered to the Clinic were dominated by the species Globisporangium ultimum (Trow) Uzuhashi, Tojo & Kakish commonly known as Pythium ultimum Trow. The importance of Pythium spp. in the cultivation of cucumber under cover increases year by year, taking into account the frequency of occurrence in the samples delivered to the Clinic.