Skip to main content
ARS Home » Pacific West Area » Davis, California » Crops Pathology and Genetics Research » Research » Publications at this Location » Publication #271847
Title: Clonal and sexual dispersal of Armillaria mellea in an ornamental landscape.

Author
item TRAVADON, RENAUD - University Of California
item Fujiyoshi, Phillip
item SMITH, MATTHEW - University Of Florida
item DOUHAN, GREG - University Of California
item RIZZO, DAVID - University Of California
item Baumgartner, Kendra

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2011
Publication Date: 6/1/2011
Citation: Travadon, R.R., Fujiyoshi, P.T., Smith, M.E., Douhan, G.W., Rizzo, D.M., Baumgartner, K. 2011. Clonal and sexual dispersal of Armillaria mellea in an ornamental landscape.. Phytopathology. 101:S178.

Interpretive Summary: High densities of planted hosts and frequent irrigation have contributed to severe Armillaria root disease in Golden Gate Park, San Francisco, CA. Our objective was to assess the relative contribution of vegetative growth and basidiospore dispersal to the colonization of the park by Armillaria mellea. We investigated the genetic structure of A. mellea at a fine spatial scale using microsatellite data. Ninety-five unique multilocus genotypes were identified among 166 isolates. Only 28 genotypes (29%) were shared by two or more isolates (clones). The largest two clones, resulting from vegetative growth of one genotype, measured 216 m and 322 m. Spatial autocorrelograms of kinship coefficients, with and without clones, converged at an average distance of 130 m, indicating that this distance constitutes the linear spatial dimension above which clonality does not affect the genetic structure of the population. Up to 100 m, genetic similarity between pairs of isolates decreased linearly with an increase in spatial distance. Beyond 100 m, a random spatial distribution of genotypes was observed, consistent with an establishment from sexual spores from distant sources. The absence of multilocus linkage disequilibrium and the high proportions of genotypes detected only once suggest that most infections in the park resulted from basidiospores. However, 29% of genotypes infected multiple trees as a result of subterranean, vegetative growth.

Technical Abstract: High densities of planted hosts and frequent irrigation have contributed to severe Armillaria root disease in Golden Gate Park, San Francisco, CA. Our objective was to assess the relative contribution of vegetative growth and basidiospore dispersal to the colonization of the park by Armillaria mellea. We investigated the genetic structure of A. mellea at a fine spatial scale using microsatellite data. Ninety-five unique multilocus genotypes were identified among 166 isolates. Only 28 genotypes (29%) were shared by two or more isolates (clones). The largest two clones, resulting from vegetative growth of one genotype, measured 216 m and 322 m. Spatial autocorrelograms of kinship coefficients, with and without clones, converged at an average distance of 130 m, indicating that this distance constitutes the linear spatial dimension above which clonality does not affect the genetic structure of the population. Up to 100 m, genetic similarity between pairs of isolates decreased linearly with an increase in spatial distance. Beyond 100 m, a random spatial distribution of genotypes was observed, consistent with an establishment from sexual spores from distant sources. The absence of multilocus linkage disequilibrium and the high proportions of genotypes detected only once suggest that most infections in the park resulted from basidiospores. However, 29% of genotypes infected multiple trees as a result of subterranean, vegetative growth.