PHYSIOLOGICAL SPECIALIZATION AND PATHOTYPE DISTRIBUTION OF PUCCINIA-RECONDITA IN WESTERN-EUROPE, 1995

A pathogenicity survey of Puccinia recondita f.sp. tritici (Prt) was c onducted in western Europe in 1995. Random urediospore isolates (850) of Put were collected from the air by means of a jet spore sampler in wheat-growing regions of Austria, Belgium, France, Germany, northern I taly, Switzerland and the UK. Pathogenicity of the isolates was determ ined in tests of detached primary leaf segments maintained on water ag ar supplemented with benzimidazole (35 p.p.m.). The differential genot ypes used were Thatcher, 20 near-isogenic Thatcher lines each with a s ingle leaf rust resistance gene, and five cultivars/lines with additio nal resistance genes. All isolates were avirulent for the genes Lr9, L r19, Lr21, Lr24, Lr25 and Lr29, and both virulence and avirulence were detected for the remaining 19 genes. Fifty-three pathotypes were iden tified, four of which predominated (64% of isolates) and were widespre ad throughout western Europe. Three of the four predominant pathotypes were also identified in collections of wheat leaf rust collected in P oland, Hungary, Estonia and Finland. One pathotype, which comprised 35 % of isolates in the south of France, was not detected in any other re gion. This pathotype was indistinguishable from several isolates obtai ned from Morocco, which suggested that it may have originated from nor thern Africa. Comparisons with previously published data suggested tha t the four predominant pathotypes were very similar and possibly the s ame as pathotypes present in the former Czechoslovakia for up to 20 ye ars. The results obtained provide evidence of migration of Prt over co nsiderable distances in western Europe, stressing the need for a co-or dinated approach for genetical control of the disease in this region.