Особливості біології гриба Phomopsis helianthi М. та патогенезу фомопсису соняшника

Abstract

One of the main issues of successful annual sunflower growing is resistance against the necrothrophic fungus Phomopsis helianthi Munt, which is capable to destroy the entire crop of sunflower. The aim of research was studying cycle of development fungus Phomopsis helianthi M. and the features of sunflower plants defeat. The investigations were carried out in the field in Genicheskiy district of Kherson region and in Kherson regional phytosanitary laboratory. In a long period of time, the disease is in latent form in seed. The first symptoms is pycnidia and clarification of affected seminal skin tissue appear during seeds germination. On the seeds of P. helianthi was discovered complete mushroom stage Diaporthe helianthi Munt Cv, et al. The obtained results indicate possibility of transmitting the disease by seminal material in other regions where this disease is absent. The stage of the D. helianthi mushroom in the teleomorph form in the field, we found at the end of May on stems of sunflower, which were wintered after harvesting. On the remains of plants, where pycnides of the phomaxis pathogen were formed, we commit the formation of the D. helianthi strain with 1-5 peritheces. The departure of ascospore began in the beginning of second decade of May. In third decade of June, a mass exit from the ascospores of peritations was noted. The first symptoms of illness on sunflower plants in Henichesk district of Kherson region were recorded at the beginning of second decade of July in 10 days after irrigation. On the stems of sunflower between 4-7 pairs of leaves formed dark gray stains. Over time, necrosis extends along the length of stem from the place of its initial manifestation. The stains size affected by pathogen stalks ranged from 2.5-3 cmto 12.7-14.0 cm. On affected by phomopsis plants of sunflower, disease pathogens formed a flattened ellipsoid-shaped pycnidia with an aperture. They were located dotted along the leading vessels and were characterized by the following sizes: 290-520 × 265-410 microns. In the ripening phase, pycnides were seen on surface side of stem. During rain or irrigation, they broke through stem epidermis and on its surface in form of strips out a mass of pycnospores. Thus, after latent pathogenesis phase, the pathogen actively begins to form a pycnidial stage. During sunflower growing season, the pathogenesis of phomopsis occurs in all overground organs of plants. The presence of Diaporthe helianthi strain with peritheces and ascospores on seed has been established, indicating possibility of spreading the disease with seeds. The latter are found on unprotected plant remains. During vegetation, pathogen forms an anamorphic stage, and teleomorphic in the end. Phomopsis helianthi causes damage to overground part of sunflower plants in form of necrotic stains, damage to stem tissue, loss of turgor, burns of leaves and under-harvest. Key words: annual sunflower, Phomopsis helianthi M., Diaporthe helianthi Munt Cv, et al., biology of development, distribution.