DEVELOPMENT OF PCR FOR THE DETECTION OF POLYMYXA-BETAE IN SUGAR-BEET ROOTS AND ITS APPLICATION IN-FIELD STUDIES

A previously cloned 1.8 kb PCR Polymyxa betae DNA fragment has been fu lly sequenced and used to design PCR primers for the specific detectio n of P. betae in sugar beet seedling roots. The primers did not amplif y sequences from fungi closely related to P. betae, or from sugar beet or other microorganisms commonly associated wit h sugar beet roots. P rotocols which combine PCR with Southern/dot blot analysis of products were developed to detect P. betae in sugar beet roots. A nested PCR p rotocol was also developed and shown to provide levels of sensitivity that allow more rapid screening for P. betae infection. Subsequently, PCR was used to detect P. betae in a survey of infection incidence in 65 sugar beet Fields, Seventy one percent of fields and 33% of plants sampled were infected by late June, with a lower incidence on peat as compared to mineral soils. (C) 1995 Academic Press Limited