Molecular Plant-Microbe Interactions (2002) 15, 840-846

Deanna L. Funnell and Hans D. VanEtten (2002)
Pisatin demethylase genes are on dispensable chromosomes while genes for pathogenicity on carrot and ripe tomato are on other chromosomes in Nectria haematococca
Molecular Plant-Microbe Interactions 15 (8), 840-846
Abstract: Studies on the wide-host-range fungus Nectria haematococca MP VI have shown a linkage between virulence on pea and five of nine PDA genes that encode the ability to detoxify the pea phytoalexin, pisatin. Most of the PDA genes are on chromosomes of approximately 1.6 megabases (Mb) and two of these genes, PDA1-2 and PDA6-1, have been demonstrated to reside on approximately 1.6-Mb chromosomes that can be lost during meiosis. Prior studies also have shown that the dispensable chromosome carrying PDA6-1 contains a gene (MAK1) necessary for maximum virulence on chickpea. The present study evaluated whether the other approximately 1.6-Mb chromosomes that carry PDA genes also are dispensable, their relationship to each other, and whether they contain genes for pathogenicity on hosts other than pea or chickpea. DNA from the PDA1-1 chromosome (associated with virulence on pea) and the PDA6-1 chromosome (associated with virulence on chickpea) were used to probe blots of contour-clamped homogeneous electric field (CHEF) gels of isolates carrying different PDA genes and genetically related Pda^- isolates. All of the approximately 1.6-Mb PDA-bearing chromosomes hybridized with both probes, indicating that they share significant similarity. Genetically related Pda^- progeny lacked chromosomes of approximately 1.6 Mb and there was no significant hybridization of any chromosomes to the PDA1-1 and PDA6-1 chromosome probes. When isolates carrying different PDA genes and related Pda^- isolates were tested for virulence on carrot and ripe tomato, there was no significant difference in lesion sizes produced by Pda⁺ and Pda^- isolates, indicating that genes for pathogenicity on these hosts are not on the PDA-containing chromosomes. These results support the hypothesis that the chromosomes carrying PDA genes are dispensable and carry host-specific virulence genes while genes for pathogenicity on other hosts are carried on other chromosomes.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Deanna L. Funnell-Harris

Research topic(s) for pests/diseases/weeds:
molecular biology - genes

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Neocosmospora haematococca	Carrot (Daucus carota)
	Neocosmospora haematococca	Tomato (Solanum lycopersicum)