Infection of Soybean In Vivo with the Fungi Diaporthe eres

Studies were carried out to assess the pathogenicity of the Diaporthe eres species in relation to soybeans using artificial infection methods to clarify the phylogenetic specialization of Diaporthe fungi. The work was carried out in 2021–2023 in Amur oblast under conditions of pot experiment. The objects were soybean plants of the early ripening variety Sentyabrinka and midripening Kitrossa as well as two strains of microscopic fungi Diaporthe eres. Identification of Diaporthe fungi was carried out by molecular genetic methods and according to cultural and morphological characteristics. Infection of soybean was carried out at different stages development, agar blocks with inoculum were placed on artificially created mechanical damage on the stems. To confirm the penetration of D. eres through natural routes, soybean leaves were inoculated of the studied strains’ spore suspension. The appearance of disease symptoms and repeated isolation of D. eres from the tissue of an infected plant indicate the manifestation of pathogenicity of the species towards the soybean. Two studied strains of D. eres, previously isolated from apricot shoots, exhibit low aggressiveness towards soybean (the infection rate did not exceed 10%) as compared with a strain of Diaporthe sp. isolated from a soybean plant (the infection rate was 100%). The D. eres MF-Pm‑4a strain turned out to be more aggressive than D. eres MF-Pm‑5a since the frequency of its repeated isolation from inoculation sites was 20% higher, and it was isolated from noninoculation sites in 10% of cases. Younger soybean plants in the R‑1 development phase turned out to be more resistant, they had a longer incubation period, and no visible symptoms of the disease were noted on day 40 after inoculation. Soybean infection in the R‑3 development phase is characterized by a very short incubation period: 15 days. The midripening soybean variety Kitrossa was found to be more resistant than the early ripening variety Sentyabrinka.