Identification of seed-borne pathogens in rice and evaluation of the natural attack

Rice is a main food crop being a host to various pests and diseases that pose a threat to production. Its seeds represent a rich substrate for the development of a number of fungal pathogens. During the period 2023 – 2024, research was conducted on the territory of Maritsa Vegetable Crops Research Institute – Plovdiv, in order to isolate and identify seed-borne phytopathogens causing rice diseases, as well as to establish the degree of natural attack on Bulgarian and introduced varieties and lines. As a result, it was found that rice seeds collected from different samples in the Plovdiv region were infected with fungal pathogens of 5 genera: Alternaria spp., Cladosporium spp., Fusarium spp., Drechslera spp. and Sclerophthora spp. Six types of fungi were identified, among which Fusarium culmorum and Alternaria alternata were predominant. The species were identified in both years of the study, which was a confirmation for the economic importance and the widespread distribution of the phytopathogens. The current state of resistance to seed-borne pathogens under the conditions of a natural infectious background was determined. Differences in variety susceptibility were established. 23.3% of the studied samples had high and stable field resistance. The lowest attack index is reported for Bogdan and Avalya varieties and line 131 originating in Bulgaria. Pamety Tychina and Fujisaka varieties stand out as the most sensitive when grown in the Plovdiv region. The most variable reaction and unstable resistance were established in Deneb and TR 1759 Turkish varieties.