Identification of root rot pathogens isolated on spring grain crops in Republic of Mordovia

The root rot caused by fungi of Fusarium and Bipolaris genera has damaged both winter and spring cereals. The specific rang of the disease agents is characteristic to certain ecological and geographical areas. Root Rot symptoms on wheat ( Triticum L.), rye ( Secale cereale L.), oats ( Avena L.) and barley ( Hordeum L.) plants are similar. The soil is the basic source of the infection. Also mass infection has been transferred by seeds in the years of abundant precipitations. Pathogenic properties of the root rot agents is due to their ability to develop hydrolytic enzymes and toxins, such as helminthosporol, helminthosporal, victoxin in B. sorokiniana strains, isomarticin, zearalenone, diacetoxyscirpenol, nivalenol in Fusarium spp., etc. The Fusarium and Bipolaris species are facultative parasites. In the paper the study of fungal species causing root rot and leaf spot of cereals in the Republic Mordovia territory, and also pathogenic properties of widespread and infrequent Fusarium spp. has been represented. Damaged plants of spring wheat, barley and oats (a total of 38 cultivars) in heading stage were sampled. The infected leaves and roots were cut into fragments, aseptically sterilized and placed in Petri dishes on 2 % potato-glucose agar. During growth, the mycelia slices were transferred on a new nutrient medium. As a result, the pure cultures were isolated and the morphology of their colonies were studied. For the evaluation of morphology uniformity of strains, we isolated not less than 20 single spore cultures of fungi using serial cultivations of spore suspensions. Pathogenic and toxic properties of Fusarium spp. and Bipolaris sp. strains were studied in biotest on seeds of susceptible wheat cultivar Mironovskaya 808. Finally, there were a total of 457 isolates of pathogenic and saprophytic fungi. No clear specialization of fungi species to cereals was shown. The several species of genera Fusarium ( F. heterosporum, F. sporotrichioides, F. oxysporum ) and Bipolaris ( В. sorokiniana ) prevailed on roots of wheat, barley and oat plants. Isolates of F. redolens, F. verticillioides, F. tricinctum were few. There were many accompanying saprophytic isolates allocated together with pathogenic fungi, such as Alternaria alternatа, Mortierella elongatа var. elongatа, Papulaspora appendicularis, Clonostachys rosea f. catenulatа, Acremonium strictum, Trichoderma hamatum, etc. As a result of monosporous selections, 24 strains of Fusarium spp. and Bipolaris sp. with stable morphology have been isolated. The wide rang of plant-hosts was found out for F. heterosporum, F. sporotrichioides, F. oxysporum and Bipolaris sorokiniana. The widespread species of fungi had various pathogenic and toxic properties, indicating their strong intraspecific variability. Rare fungal species possessed toxicity to test-plant seedlings, but were not pathogenic. This fact possibly explains their low frequency in the root rot mycobiota. В. sorokiniana strains were highly pathogenic and toxic to tests plants.