Identification of Pathogens Causing Alfalfa Fusarium Root Rot in Inner Mongolia, China

Alfalfa Fusarium Root Rot (AFRR) is a serious soil-borne disease with a complex pathogenicity. Diseased samples suspected of AFRR were collected from Hohhot, Ordos, Hulunbeier, Chifeng, and Bayannur in Inner Mongolia, China, leading to 317 isolates. The isolates were identified as Fusarium acuminatum, F. solani, F. equiseti, F. incarnatum, F. oxysporum, F. avenaceum, F. verticillioides, F. proliferatum, F. falciforme, F. tricinctum, F. virguliforme, and F. redolens, and the results of pathogenicity testing showed that 12 Fusarium species could cause alfalfa root rot. Among these, F. verticillioides, F. falciforme, and F. virguliforme have not previously been reported to cause AFRR in China. Although the population structure of the pathogens differed in different regions, the dominant pathogenic species was F. acuminatum. Fungicide toxicity tests showed that seven fungicides inhibited F. acuminatum, of which fludioxonil, kresoxim-methyl, and triadimefon were found to be strongly toxic towards F. acuminatum with EC50 values of 0.09, 2.28, and 16.37 mu g/mL, respectively, suggesting that these could be used as alternative fungicides for the control of AFRR. The results of this study can provide a theoretical basis for exploring the occurrence and epidemiology of alfalfa root rot and strategies for its control.