Two novel Fusarium species that cause canker disease of prickly ash (Zanthoxylum bungeanum) in northern China form a novel clade with Fusarium torreyae

Abstract

Canker disease of prickly ash (Zanthoxylum bungeanum) has caused a decline in the production of this economically important spice in northern China in the past 25 y. To identify the etiological agent, 38 fungal isolates were recovered from symptomatic tissues from trees in five provinces in China. These isolates were identified by conducting BLASTN queries of NCBI GenBank and phylogenetic analyses of DNA sequence data from the nuclear ribosomal internal transcribed spacer region (ITS rDNA), a portion of the translation elongation factor 1-α (TEF1) gene, and genes encoding RNA polymerase II largest (RPB1) and second largest (RPB2) subunits. Results of these analyses suggested that 30/38 isolates belonged to two novel fusaria most closely related to the Florida torreya (Torreya taxifolia Arn.) pathogen, Fusarium torreyae in Florida and Georgia. These three canker-inducing tree pathogens form a novel clade within Fusarium here designated the F. torreyae species complex (FTOSC). BLASTN queries of GenBank also revealed that 5/38 isolates recovered from cankers represented an undescribed phylogenetic species within the F. solani species complex (FSSC) designated FSSC 6. Stem inoculations of three fusaria on Z. bungeanum resulted in consistent canker symptoms from which these three fusaria were recovered. The two novel fusaria, however, induced significantly larger lesions than FSSC 6. Herein, the two novel prickly ash pathogens are formally described as F. zanthoxyli and F. continuum.

• Fusarium continuum
• F. zanthoxyli
• genealogical concordance
• molecular phylogenetics
• morphology
• RPB2
• TEF1

Acknowledgments

This research was supported in part by the National Science-Technology Support Project (No. 2012BAD19B08). The mention of company or trade products does not imply that they are endorsed or recommended by the US Department of Agriculture over other companies or similar products not mentioned. The USDA is an equal opportunity provider and employer. We thank Stacy Sink for assistance with the DNA sequence data and Ning Xie and Jiefei Wang for help collecting specimens.