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Stem rot of jewel orchids caused by a new forma specialis, F usarium oxysporum f. sp. anoectochili in T aiwan
Author(s) -
Huang L.W.,
Wang C.J.,
Lin Y.S.,
Chung W.C.,
Chung W.H.
Publication year - 2014
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1111/ppa.12133
Subject(s) - biology , stem rot , fusarium oxysporum , pathogenicity , intergenic region , pathogen , fusarium , botany , internal transcribed spacer , phylogenetic tree , microbiology and biotechnology , gene , genetics , genome
Stem rot of A noectochilus formosanus (Af) caused by Fusarium oxysporum (Fo) is a major limiting factor to jewel orchid production in Taiwan. Fo causes discoloration in vascular tissues. However, some newly collected Fo isolates from Af stem rot do not cause vascular discoloration, suggesting changes may have occurred in the pathogen. Among recent Fo isolates from A f there are two colony types, the cottony alba ( CA ) and the sporodochial ( S ). In order to confirm that both colony types cause A f stem rot, 200 isolates were obtained from diseased stems in N antou C ounty and characterized by colony type and whether or not the infected plants had vascular discoloration. Isolates of both the CA and S types caused stem rot of A f; some isolates in each colony type caused vascular discoloration whilst others did not. Pathogenicity tests with 22 isolates resulted in stem rot disease severity ratings on A f of 3·1–4·0 and 2·1–4·0 with CA and S type colonies, respectively. The same isolates failed to cause disease on C attleya , D endrobium or P halaenopsis plants. Phylogenetic analysis of partial intergenic spacer sequences showed that these isolates were distinguishable from other formae speciales of F o and could be separated into two groups correlated with the CA or S type colonies with high bootstrap. Based on pathogenic, morphological and molecular characterizations, the F o that causes stem rot of A f is proposed to be a new forma specialis, F . oxysporum f. sp. anoectochili , with different pathotypes.