Molecular identification and pathogenicity of Fusarium and Alternaria species associated with root rot disease of wolfberry in Gansu and Ningxia provinces, China

Wolfberry (Lycium barbarum) ranks in the top 10 best-selling medicinal plants in China and it has been used for centuries as a medicine and a food supplement. It is suggested to have benefits on human health due to the rich content of polysaccharides, carotenoids, flavonoids, and alkaloids contained in its fruits, leaves, and root bark. Recently, severe root rot diseases have been causing plant losses in major growing areas. Here, we report fungi causing root rot disease in Chinese wolfberry plants. The analysis of nucleotide sequences of the internal transcribed spacer (ITS) region revealed a total of 92 isolates isolated from both soil and plant material samples.Fusariumspp. were the most abundant (58%), followed byPenicilliumspp. (9%), andAlternariaspp. (5%).Fusariumspp. includedF.oxysporum(36%),F.solani(30%),F.chlamydosporum(9%),F.nematophilum(9%), andF.tricinctum(8%). Sequences from the translation elongation factor 1-alpha gene (TEF-1 alpha) were used to confirm the identity ofFusariumspp. and showed the predominance ofF.oxysporumandF.solani. To confirm the pathogenicity of isolates, four isolates belonging toFusariumspp. and one isolate belonging toAlternariaspp., isolated from wolfberry root tissues with root rot symptoms, were tested in outdoor and laboratory conditions. Results revealed that the five tested isolates were pathogenic with varying degrees of aggressiveness and ability to induce symptoms of root rot in wolfberry seedlings. The five isolates were recovered from inoculated seedlings, completing Koch's postulates. This is the first report on causative agents of root rot in Chinese wolfberry.