Intensity of infection of tomato by Phytophthora infestans in central Ukraine in relation to varietal resistance

Abstract

Phytophthora infestans is widespread in the central part of Ukraine, infecting tomatoes everywhere but not to the same extent in different years. The disease can completely destroy the crop in epiphytotic years. We have studied commercial cultivars and hybrids of tomato with different degrees of resistance to P. infestans. The degree of disease development and the date of its appearance were found to depend on the resistance group of the genotype investigated. In weakly resistant tomato cultivars and hybrids, first disease symptoms were noticed 3–4 days earlier than in more resistant ones. The degree of disease development reached 40–80% on weakly resistant genotypes at the end of the growing season, but only 5–40% on resistant ones (depending on the suitability of conditions for development of P. infestans). The development of P. infestans on fruits also depended on the degree of resistance. Differences between moderately and weakly resistant tomatoes in the degree of disease development and the date of its appearance were not significant. The data was corroborated in the laboratory conditions in the way of artificial inoculation.