Multi-Locus Phylogeny and Taxonomy of the Fungal Complex Associated With Rusty Root Rot of Panax ginseng in China

Abstract

Panax ginseng rusty root rot caused by the Ilyonectria species complex is a devastating disease, and it is one of the main factors contributing to the difficulty in continual cropping. Rusty root rot occurs in all ginseng fields, but little is known about the taxonomy of the fungal pathogen complex, especially Ilyonectria and Ilyonectria-like species. Rusty root rot samples were collected from commercial ginseng cultivation areas of China, and the pathogens were isolated and purified as single spores. Based on the combination analysis of multiple loci (rDNA-ITS, TUB, HIS3, TEF, ACT, LSU, RPB1, RPB2, and SSU) and morphological characteristics, the pathogens causing ginseng rusty root rot were determined. Fungal isolates were obtained from infected roots in 56 locations within main cultivation areas in China. A total of 766 strains were identified as Ilyonectria, Ilyonectria-like and Rhexocercosporidium species, including I. robusta (55.0%), I. communis (21.7%), I. mors-panacis (10.9%), I. pseudodestructans (2.0%), I. changbaiensis (1.3%), I. qitaiheensis (1.3%), Neonectria obtusispora (2.0%), Dactylonectria torresensis (0.5%), D. sp. (0.5%), and R. panacis (1.5%), and four novel species, Thelonectria ginsengicola (1.0%), T. jixiensis (1.0%), T. mulanensis (0.8%) and T. fusongensis (0.5%), with a total of 14 species. As the pathogen present in the highest proportion, I. robusta was the most prevalent and damaging species, unlike the pathogens reported previously. All of the examined strains were proven to cause ginseng rusty root rot. Our results indicate that the taxonomy of the fungal complex associated with ginseng rusty root rot includes Ilyonectria, Ilyonectria-like genera (Dactylonectria, Neonectria, and Thelonectria) and Rhexocercosporidium.

Genetic Diversity and Population Structure of Cylindrocarpon-like Fungi Infecting Ginseng Roots in Northeast China

“…We provided a whole picture of the pathogen complex of CLF populations associated with ginseng root diseases in Northeast China by analyzing 169 isolates. Among the CLF species, I. robusta , I. communis and I. mors-panacis are the top three most frequently isolated species causing ginseng root diseases in Northeast China, which was also supported by previous studies [ 1 , 2 ]. Although I. robusta and I. communis were more frequently isolated than I. mors-panacis , they were less virulent than I. mors-panacis .…”

“…In addition, seven species of CLF anamorphs, such as Ilyonectria species, take account for two-thirds of the total population. Similar to red-skin root of Asian ginseng, rusty root rot is another devastating disease and is also mostly caused by species with CLF anamorphs [ 2 ].…”

Occurrence and Distribution of Fusarium Communities in the Root Zone in a Post-Bog Permanent Meadow in Relation to Mineral Fertilization and Growing Seasons

“…Given the finding reported by Geiser et al [ 73 ], i.e., “We see no benefit in splitting Fusarium in favor of competing names that are largely tied to rarely observed sexual” and the equivalence of the Fusarium and Gibberella names indicated by Lombard et al [ 74 ] and Crous et al [ 75 ], the identified species Gibberella avenacea and Gibberella pulicaris were assigned to FTSC and FSAMSC, respectively. The other strains were classified into genera related to Fusarium , i.e., the Ilyonectria radicicola complex according to Guan et al [ 76 ] and the Cylindrocarpon and Fusicolla groups according to O’Donnell et al [ 68 ].…”