AFLP evidence of the distinctive patterns of life-cycle in two forms of Melampsora rust on Salix viminalis

Amplified fragment length polymorphism (AFLP) was used to examine genetic v ariation in two forms of Metampsora rust on Salix viminalis, the 'stem-infe cting form' (SIF) and the f. sp. larici-epitea typica (LET) of M. epitea. A simple two-tube method was used to obtain genomic DNA suitable for AFLP. E leven SIF and 26 LET isolates from the UK were tested using two primer comb inations. Of the 215 AFLP markers scored, 93% were polymorphic. AFLP profil es were distinct between SIF and LET (Nei & Li's similarity coefficients be tween SIF and LET isolates = 22-35%). Within SIF, AFLP patterns were Very s imilar (similarity >98.9%), indicating that SIF is an asexual population an d may have a clonal lineage. Within LET, similarities were > 69%. LET isola tes collected from a site at Long Ashton in 1991-1993 were closely related and, therefore, may have come from the same local source. Similarity data f rom AFLP were in good agreement (Spearman's rank correlation = 0.85) with t hat of RAPD when both SIF and LET isolates were included, but the correlati on was less obvious (= 0.49) when only LET isolates were included. Identica l banding patterns were obtained when AFLP was performed using either a Per kin-Elmer 480 or a Perkin-Elmer 9700 Thermocyclers, each programmed with a different PCR profile.