ARS | Publication request: Genetic Diversity of Phoma sclerotioides Isolates from Minnesota

Submitted to: North American Alfalfa Improvement Conference
Publication Type: Abstract Only
Publication Acceptance Date: July 27, 2010
Publication Date: July 27, 2010
Citation: Castell-Miller, C.V., Dornbusch, M.R., Samac, D.A. 2010. Genetic Diversity of Phoma sclerotioides Isolates from Minnesota [abstract]. 42nd North American Alfalfa Improvement Conference & 21st Trifolium Conference, July 27-30, 2010, Boise, Idaho.

Technical Abstract: Phoma sclerotioides causes brown root rot in alfalfa (Medicago sativa) and root rot of several other legumes and winter wheat. The disease is widespread in the northern tier States of the U.S. and southern Provinces of Canada where it contributes to winter injury and stand loss. Previously, a multilocus phylogenetic analysis suggested that at least three subtypes of P. sclerotioides are present in North America. We used molecular population genetic tools to understand the relationships and the population structure of P. sclerotioides isolates of the Central subtype recovered from two production fields in Minnesota in 2007. Portions of 3 genes of 18 isolates, the internal transcribed spacers of the rDNA (ITS; 497 bp), chitin synthase (CHS; 300 bp), and glyceraldehyde-3-phosphate dehydrogenase (G3PD; 526 bp), were analyzed. Within a location distinct haplotypes were recovered, but overall diversity is low to intermediate. AMOVA test indicates that there is not population differentiation by collection site using sequences of the genes individually (ITS FST=0.05 P-value=0.28; G-3-DP FST=0.00 P-value=0.65; CHS FST=0.00 P-value=0.57). Preliminary results using a parsimony analysis support separation of isolates from Minnesota from the Western and Eastern subtypes. This may indicate limited gene flow among regions. These results indicate that disease resistance breeding and disease management efforts need to consider regional difference in the pathogen population.