IDENTIFICATION AND ORIGIN OF RACES OF PSEUDOMONAS-SYRINGAE PV PHASEOLICOLA FROM AFRICA AND OTHER BEAN GROWING AREAS

Isolates of Pseudomonas syringae pv. phaseolicola from Africa and othe r bean growing areas were categorized into nine races on the basis of their reactions to eight differential cultivars following artificial i noculation. Eight hundred and ninety-three isolates representing 303 d isease occurrences were initially identified as P.s. pv. phaseolicola by their pathogenicity to bean, cultural and serological characteristi cs and phage sensitivity. These tests also served to distinguish P.s. pv, phaseolicola from the closely related pathovars P.s. pv. glycinea and P.s. pv. syringae. Detailed race determinations were carried out o n 175 selected isolates of p.s. pv. phaseolicola representative of the different geographical regions and hosts in which the pathogen was fo und and nine races were identified. A number of races (1,2,5,6 and 7) were distributed worldwide with race 6 predominant. Other races were f ound mainly in Africa; races 3 and 4 in East/Central Africa and races 8 and 9 in Southern Africa. Most isolates were obtained from the major host, Phaseolus vulgaris. Alternative natural hosts included 10 legum e species representative of seven different genera (Cajanus cajan, Des modium sp., Lablab purpureus, Macroptilium atropurpureum, Neonotonia w ightii, Phaseolus acutifolius, P. coccineus, P. lunatus, Vigna angular is is and V. radiata). Of these, Desmodium sp. constitutes a new host record.