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item ABAD, P.
item PEREZ, A.
item MARQUES, M.C.
item VICENTE, M.J.
item Bruton, Benny

Submitted to: European Plant Protection Organization Bulletin
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Vine decline is a broad term used to describe a disease syndrome in cucurbits in which the vines begin to collapse and die as the fruit approach maturity. In Spain, one of the most important diseases of muskmelon is referred to as vine decline, collapse, or sudden wilt. Two fungi involved in vine declines are Acremonium cucurbitacearum and Plectosporium tabacinum. Because these two fungi occur in Spain and the United States, research was initiated to determine if the fungi possessed similar genetic background assessed by vegetative compatibility grouping (VCG). It was determined that A. cucurbitacearum isolates from California and Texas shared VCGs with isolates from Spain with VCGs 2 and 3 being most prominent. Consequently, isolates from Spain and the United States appear to be very similar genetically. In contrast, few isolates of P. tabacinum share the same VCG and those that did were from the same geographic region. This suggests that P. tabacinum isolates posses great genetic diversity in nature.

Technical Abstract: One of the most important diseases of muskmelon in Spain has been referred to as collapse, sudden wilt, or vine decline. Different soilborne plant- pathogens cause syndromes very similar in their symptomathology, which is characterized by a sudden collapse of the plant when fruits are ripening. Acremonium cucurbitaceaum and Plectosporium tabacinum are two of the fungi implicated in this disease. Genetic diversity among populations of these two plant-pathogens has been approached by the assessment of vegetative compatibility using nitrate non-utilizing auxotrophs. In A. cucurbitacearum, with a host range limited to Cucurbitaceae and found in Spain, California and Texas, ten vegetative compatibility groups (VCGs) have been identified. P. tabacinum, anamorph of Plectosphaerella cucumerina, has worldwide distribution and wide plant host range. From a collection of P. tabacinum isolates with different plant and geographical origins, only four pairs have developed complementary heterokaryons when pairings of phenotypically distinct nit mutants (nitl x NitM) were conducted. Each of the four VCGs consist of two members with close geographical origin and all the isolates were from diseased melon plants. From the remaining P. tabacinum isolates, two did not produce nit mutants, two were self-incompatible and the others vegetatively incompatible between them, suggesting that this fungal species may have wide genetic diversity in nature.