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Title: Identification, occurrence and pathogenicity of Rhizopycnis vagum on muskmelon in Spain

Author
item ARMENGOL, J. - U. POL. DE VALENCIA SPAIN
item VINCENT, A. - U. POL. DE VALENCIA SPAIN
item MARTINEZ-CULEBRAS, P. - U. POL. DE VALENCIA SPAIN
item Bruton, Benny
item GARCIA-JIMENEZ, J. - U. POL. DE VALENCIA SPAIN

Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2002
Publication Date: 1/13/2003
Citation: Armengol, J., Vincent, A., Martinez-Culebras, P., Bruton, B.D., Garcia-Jimenez, J. 2003. Identification, occurrence and pathogenicity of Rhizopycnis vagum on muskmelon in Spain. Plant Pathology. 52:68-73.

Interpretive Summary: Numerous fungi have been suspected or shown to cause vine decline diseases of cucurbits. Intensive cultivation of these crops with inadequate rotation has resulted in an increase in both the number and severity of diseases involved in the vine decline complex and consequently has accounted for significant economic losses worldwide. The fungus, Rhizopycnis vagum, is a recently described pathogen of cucurbits in the United States and Central America. In a disease survey of melon fields in the major production areas of Spain, the fungus was isolated from approximately 30% of the fields exhibiting symptoms of vine decline. This research also showed that watermelon, Cucurbita hybrids used as rootstocks for watermelon production, Amaranthus sp., and grapevine are additional hosts for R. vagum. Studies demonstrated that the fungus was pathogenic to melons causing slight to moderate damage to the roots. Although the fungus is not highly aggressive, it no doubt contributes to the disease complex known as vine decline in cucurbits.

Technical Abstract: Rhizopycnis vagum is a recently described coleomycetous fungus that contributes to vine decline of muskmelons in Honduras, Guatemala, Texas and California. This fungus has been associated with roots of muskmelon plants affected by vine decline in different Spanish muskmelon production areas. The identification of isolates collected from 1996 to 2000 has been supported by cultural and morphological studies as well as sequencing of the ITS region of the rDNA and phylogenetic analysis. Additionally, a small number of isolates from muskmelon with growth characteristics similar to R. vagum were identified as Phoma terrestris. This study also shows that watermelon, Cucurbita hybrids used as rootstcks for watermelon production, Amaranthus sp., and grapevine are additional hosts for R. vagum. Based on disease reaction in muskmelon roots, the pathogenicity of ten isolates of R. vagum from different hosts and geographical origins was demonstrated. The fungus caused discoloration, lesions and eventually the presence of pink coloration on the roots. The contribution of R. vagum and P. terrestris to the vine decline complex of muskmelon in Spain is discussed