PURIFICATION, CHARACTERIZATION AND BIOLOGICAL ROLE OF A PHEROMONE PRODUCED BY XANTHOMONAS-CAMPESTRIS PV. CAMPESTRIS

Production of a stable, low molecular weight diffusible extracellular factor (DF), by Xanthomonas campestris pv, campestris (Xcc, the causal agent of black rot of crucifers), is essential for xanthomonadin pigm ent and extracellular polysaccharide (EPS) production. DF was produced and purified from liquid cultures by solvent partitioning and ethylac etate extraction. Extract purity was verified via HPLC and bioassays w ith a DF deficient strain of Xcc (A-7). Epiphytic survival and disease development of A-7 was greatly reduced compared to the wild-type Xcc strain, B-24. Application of purified extracts of DF on cauliflower pl ants increased epiphytic survival and subsequent lesion development by strain (A-7) to levels similar to those of B-24. Thus, DF is importan t for epiphytic survival and disease development of X. campestris pv, campestris. (C) 1997 Academic Press Limited.