A novel pathogen Fusarium cuneirostrum causing common bean (Phaseolus vulgaris) root rot in China

Several fungal pathogens cause root rot of common bean, among which Fusarium spp. are the most common pathogens causing Fusarium root rot (FRR) worldwide. FRR has been becoming an increasingly severe disease of common bean in China, but the species of Fusarium spp. have remained unclear. Thus, this study was performed to identify the pathogen causing common bean root rot in Liangcheng County, Inner Mongolia, China. Nineteen Fusarium-like isolates were obtained after pathogen isolation and purification. The pathogenicity test indicated that eight isolates caused severe disease symptoms on common bean, while 11 other isolates were not pathogenic. The eight pathogenic isolates, FCL1-FCL8, were identified as Fusarium cuneirostrum by morphological characterization and phylogenetic analysis using partial sequences of EF-1 alpha, ITS, 28S, and IGS regions. Host range test showed that the representative F. cuneirostrum isolate FCL3 was also pathogenic to mung bean, while not pathogenic to adzuki bean, chickpea, cowpea, faba bean, pea, and soybean. Moreover, 50 common bean and 50 mung bean cultivars were screened for resistance to FRR, and seven highly resistant or resistant cultivars of common bean were identified, while no resistant cultivars of mung bean were screened. This study revealed that F. cuneirostrum was one of common bean FRR pathogens in Inner Mongolia and it could induce mung bean root rot as well. To our knowledge, this is the first report of F. cuneirostrum causing FRR of common bean in China.