Soilborne fungal pathogens of small grain cereal crops in Bulgaria: species composition and distribution

Ivo Yanashkov, Zhelyu Avramov, Tzenko Vatchev

Abstract: Small grain cereal crops including wheat, barley, rye, oats, triticale, einkorn etc. are subject to attacks of various soil inhabiting plant pathogenic fungi and fungus-like organisms. All growth stages of cereal crops are susceptible to infections. Attacks lead to pre-emergence decay of seeds, post-emergence dаmping-off of cereal seedlings, root and lower stem rot in later growth stages of the infected cereals. In individual cases, infection proceeds without obvious symptoms until favourable conditions arise or disease remains latent to the end of growing season and harvesting. Results of the present study show that fungi of genus Fusarium are the most frequent soilborne pathogens isolated from cereal crops in the country. Predominating species include F. oxysporum, F. graminearum and F. culmorum, constituting respectively 32%, 22% and 12% of the total number of pathogenic isolates obtained from the roots and lower stems of cereal plants. Other Fusarium species, such as F. sporotrichiella and F. equiseti, occur sporadically in a few fields grown with cereals. Other soil inhabiting pathogens, associated with root rot and stem base necrotic lesions on cereal crops are Drechslera sorokiniana and Rhizoctonia solani, constituting respectively 11% and 8% of the total number of isolated fungi. Fungus-like isolates of genus Pythium, P. ultimum in particular, and some currently unidentified Pythium spp., represent 10% of isolated fungi. The representatives of this genus are among the most prevalent pathogens, attacking root system of cereal plants, cultivated in waterlogged and cool soils. These species can infect cereal plants either individually or in combinations of two and more pathogens. Mixed infections with Fusarium spp., Pythium spp. and Rhizoctonia solani occur in some of the surveyed cereal fields in the country. Economic losses caused by soilborne diseases of cereal crops in various grain-producing areas vary over the years and depend on the host species, soil, climatic and agronomical conditions of growing.

Keywords: community structure; distribution; pathogenic soil inhabiting fungi; small grain cereal crops

Date published: 2017-07-25