The occurrence of barley root diseases in different agri-ecological zones of Syria

Abstract

A survey was conducted to determine the occurrence of root diseases and the identity of causal agents on barley grown in northern agricultural areas of Syria in 1992 and 1993. In 1992, 20 plants with at least 1 cm long subcrown internodes were randomly selected from each of 53 fields when plants were between flowering and maturity. In 1993, 50 plants were selected from each of 72 fields. In addtion, four wheat fields were sampled in 1993. Plants were visually rated for disease severity on the subcrown internode. Fungal cultures were isolated from root tissues by plating on selective and general media. Isolates were tested for pathogenicity using a seedling bioassay, and representative pathogens were identified to the species level. Root rot was more severe in the drier agricultural zones and disease severity increased with crop maturity. There was a weak negative association between disease severity and the number of tillers per plant. The most prevalent pathogens in both years were Microdochium nivale (average of 43%), Cochliobolus sativus (35%), red-pigmented Fusaria (13%), and Microdochium bolleyi (8%). More than 80% of the C. sativus and M. nivale isolates, and less than 20% of the Fusarium spp. and M. bolleyi isolates, were pathogenic. Cochliobolus sativus was most common in the drier areas, whereas M. nivale was most common in the wetter areas, particularly from the northwest region. This paper is the first report of M. nivale and M. bolleyi on barley and Gaeumannomyces graminis var. tritici on wheat in Syria. Other root disorders (pests) found included cyst-forming nematodes and Porphyrophora tritici.