Invasive Species Compendium

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Abstract

Comparison of cultural and morphological characters and ITS sequences in anamorphs of Botryosphaeria and related taxa.

Abstract

Anamorphs of 22 strains of botryosphaeriaceous fungi including Fusicoccum spp., Diplodia spp., Sphaeropsis spp., and Lasiodiplodia theobromae [Botryosphaeria theobromae] were compared using conidial characters, cultural morphology, growth rates and nucleotide sequences of the nuclear rDNA internal transcribed spacers ITS 1 and ITS 2. The ITS data shared consensus with morphological and cultural characters in separating 7 of the 22 strains. The 7 strains were placed into 1 of 3 groups that corresponded with the morphological species B. theobromae, S. sapinea [Diplodia pinea], and F. luteum. Only partial consensus was achieved with the remaining 15 strains, as ITS sometimes grouped together strains with uniform morphological and cultural characters and other times it did not. The 10 Fusicoccum strains, identified as anamorphs of B. dothidea or B. ribis, were divided into 2 ITS groups and up to 5 groups based on traditional characters. The 2 putative B. ribis strains were consistently grouped together and appeared to represent a stable variant of B. dothidea. Two morphologically indistinguishable Sphaeropsis sp. strains, identified as anamorphs of B. obtusa, were separated into 2 ITS groups, one containing all S. sapinea strains and the other containing D. mutila (B. stevensii) and D. quercina. Conidial colour, wall texture, septa number, size and shape, as well as mycelial growth under different temperatures were consistent characters within some presumed morphological species, and within some ITS groups, but none of the characters were universally informative. Moreover, conidial pleomorphy and plasticity of some morphological and cultural characters caused problems for differentiating strains using traditional characters, particularly with Sphaeropsis and Diplodia form-genera. The possibility that the ITS region is not informative at the species level for some of the taxa evaluated is considered.