Abstract:

Plant pathogens can spread over time and in space via seeds. The aims of this study were to determine whether the main alfalfa varieties currently grown in China harbor pathogens causing destructive diseases， for example， Verticillium alfalfae， and to provide data to support the safe introduction， transportation， and disease control of alfalfa. We collected seeds of 32 alfalfa varieties from Chinese alfalfa breeders and importers. The fungi were isolated by the potato dextrose agar plate method and then identified. The pathogenicity of the fungal strains isolated from Zhongmu No.3 against seeds and seedlings was determined. Fungi in 19 genera， including 20 species of V. alfalfae and other quarantine pathogens， were detected from the tested seeds. The main fungi on alfalfa seeds were Alternaria spp.， Penicillium spp.， and Aspergillus spp.， which are common in the environment. There were significant differences in the frequency of seed-borne fungi among different alfalfa varieties. The percentage of seeds harboring pathogenic fungi was 26.18%-67.54% without disinfection， and disinfection decreased the average percentage of fungi by 25.10%. In pathogenicity tests against seeds， the seed germination percentage was significantly decreased by Cladosporium sp.， Epicoccus nigrum， Acremonium sp. and Alternaria alternata. In pathogenicity tests against seedlings， Talaromyces sp.， Chaetomium globosum，Aspergillus flavus， Stenophyllium solani， and other fungi significantly inhibited the shoot and root growth of seedlings， causing them to wither and rot.

Key words: alfalfa, seed-borne fungi, germination, seedling growth