Identification and Characterization of Fusarium Species Associated with Wilt of Eleocharis dulcis (Chinese water chestnut) in China.

Fusarium wilt is one of the most important diseases of Eleocharis dulcis (Chinese water chestnut) in China. In order to characterize the pathogens responsible, 69 Fusarium isolates were collected from diseased plants in E. dulcis production areas of the Chinese provinces Anhui, Fujian, Hubei, Hunan, Jiangsu, and Zhejiang. These were then identified based on morphological and molecular characteristics. F. commune was the most common species (92.8%) and was widely distributed in the six provinces. A novel species within the Gibberella fujikuroi species complex (GFSC) was found in Hubei and Zhejiang provinces (5.8%), and an unidentified Fusarium sp. was found only in Hubei province (1.4%). Thirty F. commune isolates from different provinces and four GFSC isolates were selected for sequence analyses of the translation elongation factor 1-α (EF-1α), the mitochondrial small subunit (mtSSU) ribosomal DNA, and the nuclear ribosomal intergenic spacer region (IGS). Maximum parsimony and Bayesian analyses of the multilocus sequence data of these two species plus other taxa showed that the two species formed two distinct, well-supported clades among the three individual and combined gene genealogies. Isolates from different locations were scattered, with no evidence of geographic specialization. Pathogenicity assays showed that the two Fusarium spp., including the unidentified Fusarium sp., were pathogenic to E. dulcis 'Tuanfeng seven'. There was no relationship between the source of isolates and their pathogenicity. This is the first description of F. commune, a novel species within the GFSC, and an unidentified Fusarium sp. as causal agents of Fusarium wilt of E. dulcis in China.