Resistance of Japanese plum cultivars to biotic stress in the Middle Amur Region, Russia

Abstract

The study evaluated a collection of plum cultivars and hybrid forms at the Far Eastern Agricultural Research Institute (FEARI), Russia, to identify genotypes with high resistance to major fungal diseases. The objective was to select sources of resistance to brown rot (moniliosis), red leaf spot (polystigmosis), and shot-hole disease (clasterosporiosis) for use in breeding programs to develop new environmentally adapted cultivars. The article presents the results of resistance evaluation in plum genotypes to key biotic stresses. Fungal diseases cause substantial damage to plum orchards in the Middle Amur region, with brown rot, red leaf spot, and shot-hole disease being the most harmful. Their development is promoted by unfavorable weather conditions during the growing season, particularly high humidity during flowering and prolonged rainfall at the onset of fruiting. Research was conducted in 2023–2025 using 27 cultivars and hybrid forms of Japanese plum (Prunus salicina Lindl.) of diverse geographic origin held in the fruit-crop collection of the FEARI. The degree of fungal infection was found to depend on cultivar-specific traits and the meteorological conditions of the year. Several cultivars and hybrid forms exhibiting stable resistance to the most damaging diseases of the Middle Amur region, namely brown rot, shot-hole disease, and red leaf spot, were identified. These resistant genotypes can be used in hybridization to obtain new breeding material.