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United States Department of Agriculture

Agricultural Research Service

Title: Natural Infection of An Herbaceous Host by Armillaria: a Case Study on Hemerocallis

Authors
item Blaedow, Karen -
item Baumgartner, Kendra
item Cox, Kerik - CORNELL UNIVERSITY
item Schnabel, Guido - CLEMSON UNIVERISTY

Submitted to: Canadian Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 2009
Publication Date: January 1, 2010
Citation: Blaedow, K.E., Baumgartner, K., Cox, K.D., Schnabel, G. 2010. NATURAL INFECTION OF AN HERBACEOUS HOST BY ARMILLARIA: A CASE STUDY ON HEMEROCALLIS. Canadian Journal of Plant Pathology. 32:351-360.

Interpretive Summary: Our objective was to determine the species identity of Armillaria isolates cultured from a new herbaceous host, Hemerocallis (daylily). To address the fact that no one technique can distinguish all North American Armillaria species, we utilized all available tests for identification, including both traditional (mating tests, basidiocarp morphology) and molecular (DNA sequence analsis of the rDNA internal transcribed spacer, ITS, and intergenic spacer I, IGS-I). Analysis of IGS-I revealed similarity between our daylily isolates and those of three species (A. cepistipes, A. gallica, A. sinapina). Mushroom morphology and analysis of ITS narrowed the identity to two species (A. calvescens, A. gallica). Identity was further narrowed to A. gallica, based primarily on spore size and, in part, on the results of mating tests between our daylily isolates and tester isolates of A. gallica. The presence of rhizomorphs in the topsoil of daylily beds and on the roots of symptomatic daylilies, coupled with our finding of identical ITS among daylily isolates and a dogwood isolate, suggest that rhizomorphs from A. gallica spread from resident hosts to infect the daylilies. Our consistent findings among isolates from multiple sources (basidiospores, mycelial fans, and rhizomorphs) and hosts (daylily and dogwood) suggest that species of Armillaria previously reported in South Carolina, A. mellea and A. tabescens, were not responsible. Our finding of A. gallica in South Carolina further extends the southern distribution of this species in North America.

Technical Abstract: Our objective was to determine the identity of Armillaria isolates cultured from a new herbaceous host, Hemerocallis (daylily). To address the fact that no one technique can distinguish all North American Armillaria species, we utilized all available tests for identification, including both traditional (mating tests, basidiocarp morphology) and molecular (phylogenetic analyses of rDNA internal transcribed spacer, ITS, and intergenic spacer I, IGS-I). Phylogenetic analyses of IGS-I sequences revealed similarity between our daylily isolates and A. cepistipes, A. gallica, and A. sinapina. Basidiocarp morphology and parsimony analysis of ITS sequences narrowed the identity of our daylily isolates to A. calvescens or A. gallica. Identity was further narrowed to A. gallica, based primarily on basidiospore size and, in part, on diploidization of haploid isolates in mating tests with A. gallica testers. The presence of rhizomorphs in the topsoil of daylily beds and on the roots of symptomatic daylilies, coupled with our finding of identical ITS sequences among daylily isolates and a dogwood isolate, suggest that rhizomorphs from A. gallica spread from resident hosts to infect the daylilies. Our consistent findings among isolates from multiple sources (basidiospores, mycelial fans, and rhizomorphs) and hosts (daylily and dogwood) suggest that species of Armillaria previously reported in South Carolina, A. mellea and A. tabescens, were not responsible. Our finding of A. gallica in South Carolina further extends the southern distribution of this species in North America.

Last Modified: 10/25/2014
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