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

937 M. H. PEI and C. RUIZ IACR-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol BS41 9AF, UK. E-mail : ming.pei!bbsrc.ac.uk. Received 6 August 1999 ; accepted 23 November 1999. Amplified fragment length polymorphism (AFLP) was used to examine genetic variation in two forms of Melampsora rust on Salix viminalis, the ‘ stem-infecting 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. Eleven SIF and 26 LET isolates from the UK were tested using two primer combinations. Of the 215 AFLP markers scored, 93% were polymorphic. AFLP profiles were distinct between SIF and LET (Nei Li’s similarity coefficients between SIF and LET isolatesˉ 22–35%). Within SIF, AFLP patterns were very similar (similarity 98±9%), indicating that SIF is an asexual population and may have a clonal lineage. Within LET, similarities were 69%. LET isolates 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 from AFLP were in good agreement (Spearman’s rank correlationˉ 0±85) with that of RAPD when both SIF and LET isolates were included, but the correlation was less obvious (ˉ 0±49) when only LET isolates were included. Identical banding patterns were obtained when AFLP was performed using either a Perkin–Elmer 480 or a Perkin–Elmer 9700 Thermocyclers, each programmed with a different PCR profile. INTRODUCTION Recently, amplified fragment length polymorphism (AFLP) has increasingly been used for various organisms, including bacteria, fungi, plants and animals. The AFLP approach is based on selective PCR amplification from a total digest of genomic DNA and, like many other PCR-based methods, fingerprints are produced without prior knowledge of sequences (Vos et al. 1995). AFLP has proven to be a powerful DNA fingerprinting technique and has also been show