Two Novel Fungal Symbionts <i>Fusarium kuroshium</i> sp. nov. and <i>Graphium kuroshium</i> sp. nov. of Kuroshio Shot Hole Borer (<i>Euwallacea</i> sp. nr. <i>fornicatus</i>) Cause Fusarium Dieback on Woody Host Species in California

DOI Web Site 4 Citations
  • Francis Na
    Department of Plant Pathology and Microbiology, University of California, Riverside, 92521
  • Joseph D. Carrillo
    Department of Plant Pathology and Microbiology, University of California, Riverside, 92521
  • Joey S. Mayorquin
    Department of Plant Pathology and Microbiology, University of California, Riverside, 92521
  • Cedric Ndinga-Muniania
    Department of Plant Pathology and Microbiology, University of California, Riverside, 92521
  • Jason E. Stajich
    Department of Plant Pathology and Microbiology, University of California, Riverside, 92521
  • Richard Stouthamer
    Department of Entomology, University of California, Riverside, 92521
  • Yin-Tse Huang
    Department of Plant Pathology, National Chung Hsing University, Taichung 402, Taiwan, ROC, and School of Forest Resources and Conservation, Institute of Food and Agricultural Sciences, University of Florida, Gainesville
  • Yu-Ting Lin
    Department of Plant Pathology, National Chung Hsing University, Taichung 402, Taiwan, ROC
  • Chi-Yu Chen
    Department of Plant Pathology, National Chung Hsing University, Taichung 402, Taiwan, ROC
  • Akif Eskalen
    Department of Plant Pathology and Microbiology, University of California, Riverside, 92521

Abstract

<jats:p> Shot hole borer (SHB)-Fusarium dieback (FD) is a new pest-disease complex affecting numerous tree species in California and is vectored by two distinct, but related ambrosia beetles (Euwallacea sp. nr. fornicatus) called polyphagous shot hole borer (PSHB) and Kuroshio shot hole borer (KSHB). These pest-disease complexes cause branch dieback and tree mortality on numerous wildland and landscape tree species, as well as agricultural tree species, primarily avocado. The recent discovery of KSHB in California initiated an investigation of fungal symbionts associated with the KSHB vector. Ten isolates of Fusarium sp. and Graphium sp., respectively, were recovered from the mycangia of adult KSHB females captured in three different locations within San Diego County and compared with the known symbiotic fungi of PSHB. Multigene phylogenetic analyses of the internal transcribed spacer region (ITS), translation elongation factor-1 alpha (TEF1-α), and RNA polymerase II subunit (RPB1, RPB2) regions as well as morphological comparisons revealed that two novel fungal associates Fusarium kuroshium sp. nov. and Graphium kuroshium sp. nov. obtained from KSHB were related to, but distinct from the fungal symbionts F. euwallaceae and G. euwallaceae associated with PSHB in California. Pathogenicity tests on healthy, young avocado plants revealed F. kuroshium and G. kuroshium to be pathogenic. Lesion lengths from inoculation of F. kuroshium were found to be significantly shorter compared with those caused by F. euwallaceae, while no difference in symptom severity was detected between Graphium spp. associated with KSHB and PSHB. These findings highlight the pest disease complexes of KSHB-FD and PSHB-FD as distinct, but collective threats adversely impacting woody hosts throughout California. </jats:p>

Journal

  • Plant Disease

    Plant Disease 102 (6), 1154-1164, 2018-06

    Scientific Societies

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