Open AccessBiological and Phylogenetic Characterization of Fusarium oxysporum Complex, Which Causes Yellows on Brassica spp., and Proposal of F. oxysporum f. sp. rapae, a Novel Forma Specialis Pathogenic on B. rapa in Japan
Author(s) -
Junichiro Enya,
Masayuki Togawa,
Tōru Takeuchi,
Shinichiro Yoshida,
Seiya Tsushima,
Tsutomu Arie,
Takahiro Sakai
Publication year - 2008
Publication title -
phytopathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.264
H-Index - 131
eISSN - 1943-7684
pISSN - 0031-949X
DOI - 10.1094/phyto-98-4-0475
Subject(s) - biology , brassica rapa , fusarium oxysporum , phylogenetic tree , botany , brassica oleracea , subspecies , phylogenetics , gene , brassica , genetics , zoology
Although the causal agent of yellows of Brassica rapa (turnip, pak choi, and narinosa) in Japan was reported in 1996 to be Fusarium oxysporum f. sp. conglutinans, this classification has remained inconclusive because of a lack of detailed genetic and pathogenic studies. Therefore, we analyzed the taxonomic position of this organism using Japanese isolates of F. oxysporum complex obtained from diseased individuals of various B. rapa subspecies. Phylogenetic analyses using partial sequences of the rDNA intergenic spacer region and the mating-type gene (MAT1-1-1α-box) showed that B. rapa and cabbage isolates belong to different monophyletic clades that separated at early evolutionary stages. Additionally, correlations were observed between the molecular phylogeny and the vegetative compatibility groups. Isolates from turnip, komatsuna, and narinosa (B. rapa group) did not show pathogenicity against cabbage or broccoli (B. oleracea group), although they caused severe symptoms on their original host species. In contrast, cabbage isolates had significantly higher (P = 0.05) virulence on B. oleracea than on B. rapa crops. Our results indicate that F. oxysporum complex isolates from B. rapa and B. oleracea are not only phylogenetically distinct but also differ in host specificity. Therefore, we propose a novel forma specialis, F. oxysporum f. sp. rapae, which causes yellows on B. rapa, including turnip, komatsuna, pak choi, and narinosa.