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ARS Home » Research » Publications at this Location » Publication #88626
Title: VEGETATIVE COMPATIBILITY GROUPS IN ACREMONIUM CUCURBITACEARUM

Author
item ABAD, P - UNIVERSIDAD POLITECNICA
item HACK, T - UNIVERSIDAD POLITECNICA
item VICENTE, M - UNIVERSIDAD POLITECNICA
item Bruton, Benny
item GARCIA-JIMENEZ, J - UNIVERSIDAD POLITECNICA

Submitted to: Kluwer Academic Publishers Netherlands
Publication Type: Proceedings
Publication Acceptance Date: 6/6/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Vine decline is a general term used to describe a disease syndrome in cucurbits in which the vines begin to collapse and die as the fruit approach maturity. Acremonium cucurbitacearum is a newly described fungus that has caused severe losses to muskmelon in Spain over the last fifteen years. More recently, the fungus was found associated with vine declines of muskmelon in California and Texas. The fungus is suspected of causing economic losses in muskmelon in northern California, however, it does not appear to cause detectable losses in the Rio Grande Valley of Texas. The purpose of this study was to determine the genetic diversity between the fungus from Spain, California, and Texas. Vegetative compatibility groupings (VCG) analysis has been shown to be a useful technique for examining the genetic diversity among populations of plant pathogenic fungi. Two physiologically distinct individuals of the same species belong gto the same VCG if they can fuse asexually, forming a stable heterokaryon. Results demonstrated that at least some isolates from Spain, California, and Texas fell within the same VCG indicating little genetic diversity among isolates of the fungus. Consequently, differences in disease incidence and severity between Spain, California, and Texas are probably due to environmental interactions and not necessarily differences in the fungus.

Technical Abstract: Economic losses in melon (Cucumis melo L.) production have occurred in many Spanish agricultural areas during the last fifteen years. The disease has been called acremonium melon collapse, caused by Acremonium cucurbitacearum. The same disease has been recently observed in melon production areas of California and Texas (USA). Typical symptoms of the disease are root corking and a sudden collapse of the plant during fruit ripening. Vegetative compatibility analysis is a useful tool for examining genetic diversity among populations of plant pathogenic fungi. Field isolates of A. cucurbitacearum from different areas of Spain, Sacramento and San Joaquin Valleys in California, and south Texas have been analyzed for vegetative compatibility using standard procedures. PDA and MM (minimal medium) containing KC10**3 were used to generate nit mutants. The nit mutant testers from all isolates were paired in all combinations to determine vegetative compatibility. The formation of dense aerial myceliu typical of wild-type isolate where two phenotypically distinct nit mutants came in contact indicated that the isolates were vegetatively compatible and belong to the same VCG. Eight distinct VCGs were identified among 29 Spanish A. cucurbitacearum isolates examined. Of these, 62% fell within VCG-1, VCG-2 or VCG-3. Two "bridge" isolates were vegetatively compatible with more than one of these VCGs, suggesting that these VCGs may be closely related. The California and Texas isolates fell within the same VCGs as some of the Spanish isolates, however, they were in distinctly different groups from each other.