Population Structure of Puccinia recondita in Western Europe During 1995, as Assessed by Variability in Pathogenicity and Molecular Markers

The population structure of Puccinia recondita f[ sp[ tritici "Prt# in western Europe was examined by assessing varia! bility in pathogenicity and in randomly ampli_ed poly! morphic DNA "RAPD# among 50 single uredinial isolates[ The isolates were chosen to represent pathotypes detected in a previous survey of pathogenic variability in the fungus in western Europe in 0884[ Thirty!_ve patho! types were identi_ed by assessing infection types pro! duced by the 50 isolates on 13 di}erential lines\ each with a single gene for resistance to Prt[ In contrast\ only 07 RAPD phenotypes were identi_ed by scoring 08 poly! morphic RAPD bands generated with eight RAPD primers[ When analysed by cluster and bootstrap analy! ses\ the pathogenicity and RAPD results revealed little evidence for robust distinct clusters among the isolates[ Multiple isolates of several pathotypes collected from widely separated locations such as Belgium\ GermanyFrance\ Italy and Switzerland had the same RAPD phenotype\ providing evidence of clonal migration over considerable distances in western Europe[ Some varia! bility "one or two band di}erences# was observed in RAPD phenotype within several pathotypes\ indicating the possible occurrence of genetic changes independent of pathogenicity\ and:or the independent development of pathotypes with di}erent genetic backgrounds[ Two groups of isolates identi_ed in the 0884 survey\ di}er! entiated by pathogenicity for genes Lr2a\ Lr2bg\ Lr2ka and Lr29\ were not distinguished by RAPD phenotypeindicating that the groups probably do not constitute separate lineages within the pathogen population[ Little correlation was apparent between the polymorphisms observed in pathogenicity and RAPD phenotypes[ The similarity in the genetic backgrounds of the isolates\ as assessed by RAPD markers\ suggest that the observed di}erences in pathogenicity may have arisen by selection U[ S[ Copyright Clearance Center Code Statement] 9820 0674:1999:3792 9058 , 04[99:9 for speci_c virulences corresponding to genes for resist! ance in wheat cultivars grown in the region[ Three isolates of pathotype 2\ restricted in its distribution to southern France during 0884\ were distinct from all other isolates in RAPD phenotype[ Circumstantial evidence suggests that this pathotype originated from northern Africa\ and that it belongs to a group of leaf rust pathogens spe! cialized to durum wheats[