Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/1/2007
Publication Date: 1/1/2008
Citation: Devries, R.E., Trigiano, R.N., Windham, M.T., Windham, A.S., Sorochan, J.C., Rinehart, T.A., Vargas, J.M. 2008. Genetic analysis of fungicide resistant Sclerotinia homoeocarpa isolates from Tennessee and Northern Mississippi. Plant Disease. 92:83-90.2008. Interpretive Summary: Sclerotinia homoeocarpa, the causal agent of dollar spot disease, instigates serious problems on golf courses by disrupting the uniformity and aesthetic value of putting greens. The disease is most severe in areas with closely mowed grasses and low nitrogen. Control of S. homoeocarpa is a high priority for golf course managers and several different measures can be utilized to reduce damage from the disease. Dollar spot may be prevented by avoiding conditions of extremely low nitrogen, using resistant cultivars, maintaining proper irrigation and mowing practices, and spreading guttation water accumulations by light weight rolling.The objectives for the current study were as follows: (i) determine if fungicide resistance of these isolates from Tennessee and Mississippi can be associated with specific VCGs, (ii) evaluate genetic diversity between isolates at the nucleotide level by sequencing regions of the conserved genes elongation factor 1-B (EF1-B), B-tubulin, carbomoylphospate synthase (CPS) domain of the CAD complex (CPS, aspartate transcarbamylase (ATC), and dihydroorotase (DHO), respectfully), and internal transcribed spacer region 1 and 2 (ITS 1 and 2), (iii) correlate molecular and VCG differences with fungicide resistance, and (iv) determine if cluster analysis of AFLP molecular markers could be associated with VCG tester group members or fungicide resistance.
Technical Abstract: Sclerotinia homoeocarpa is the causal agent of dollar spot disease that reduces the uniformity and aesthetic value of putting greens around the world. Fungicide resistant isolates of S. homoeocarpa were collected from putting greens at ten locations across Tennessee and northern Mississippi. Genetic diversity between the 60 isolates was investigated using vegetative compatibility, conserved gene sequences, and AFLP (amplified fragment length polymorphism). Six tester strains were paired with Tennessee and northern Mississippi isolates on potato dextrose agar. Some of the 60 isolates were delineated into vegetative compatibility groups. Fungicide resistance could not be associated with a particular vegetative compatibility group. Genetic similarities of isolates at the vegetative compatibility level could be attributed to founder effects. Sequencing of regions of CAD, EF1-B, B-tubulin, and ITS revealed 100% homology between isolates. Capillary gel electrophoresis and analysis of AFLP fragments indicated 86-100% similarity between the isolates. Isolates did not cluster according to fungicide resistance during UPGMA analysis, but did appear to cluster according to vegetative compatibility group and location. Although associations could not be made between molecular markers and fungicide resistance, links between vegetative compatibility and AFLP markers may provide a foundation from which other studies could be performed.