The Identification of a Limited Number of Vegetative Compatibility Groups within Isolates of Sclerotinia homoeocarpa Infecting Poa spp. and Agrostis palustris from Temperate Climates

Sclerotinia homoeocarpa is responsible for causing significant damage on a wide variety of different grass species. Because it is an asexual fungus, the study of its population structure can be difficult. Previous research has determined that S. homoeocapra has anywhere from three to 20 vegetative compatibility groups (VCGs) within localized geographic ranges in the United States. However, a survey of a large geographic area has yet to be undertaken. The present study examined 25 isolates of S. homoeocarpa from the United Kingdom, Rhode Island, Massachusetts, Connecticut, Ohio, Illinois and Oregon. Among the 25 isolates, eight VCGs were identified. Other researchers have reported that there are seven VCGs in temperate North America on amenity turfgrasses. It is still unclear how this relates to the pathogen\u27s VCG diversity in subtropical and tropical climates. © 2006 Blackwell Verlag

Anastomosis group and pathogenicity of isolates of Rhizoctonia solani from potato crops in South Australia

Isolates of Rhizoctonia collected from the stems, roots, tuber sclerotia and soil of potato crops in Virginia and Lenswood, South Australia, were identified to anastomosis groups (AG). Of the 301 multinucleate isolates of Rhizoctonia solani tested, 90% were AG-3, 7% were AG-4 and 2% were AG-5; 12 isolates were binucleate Rhizoctonia spp. This is the first report of isolates of AG-4 and AG-5 causing disease in potato crops in South Australia. All AG-3, AG-4 and AG-5 isolates tested caused rhizoctonia disease symptoms on the potato cultivar Coliban in pathogenicity trials conducted under glasshotise conditions. Both AG-3 and AG-5 isolates caused black scurf and stem cankers, although symptoms of black scurf were less severe with AG-5. AG-4 isolates produced the most severe stem and stolon cankers of all isolates tested. The pathogenicity of tuber-borne inoculum was confirmed by growing plants from sclerotia-infested tubers. AG-8 isolates from diseased barley and wheat produced severe root cankers and caused loss of feeder roots on inoculated potato plants. Results suggest that rhizoctonia disease in potato fields in South Australia is caused by a combination of different anastomosis groups and this has important implications for crop rotations.G. R. Balali, S. M. Neate, E. S. Scott, D. L. Whisson, T. J. Wick