Occurrence and Significance of the Temperate Ribotypes of Polymyxa Graminis

A number of subgroups of Polymyxa graminis have been separated on the basis of their rDNA sequence. Isolates of P. graminis found on temperate cereals can similarly be divided into two subgroups known as ribotypes I and II. Nothing is known about the biological significance of these ribotypes with regard to host range and virus transmission. Initial studies have been directed towards testing of P. graminis associated with virus infested soils especially those from an agricultural site in Wiltshire, England known to be infested with Soil borne cereal mosaic virus (SBCMV). A number of wheat cultivars and wild wheat relatives were grown in this soil under controlled environment conditions. Initial results show that both ribotypes of P. graminis are present in this soil but that ribotypes may exhibit host specificity.