Search

Abstract Isolates of Colletotrichum acutatum , C. fragariae and C. gloeosporioides pathogenic to strawberry plants were examined by sequence analysis of the 5.8S-ITS region. Phylogenetic relationships among isolates of Colletotrichum are, for the most part, congruent with the molecular groups established in earlier works. 5.8S-ITS sequence analysis showed a high level of genetic divergence within C. acutatum. Isolates of this species clustered into two very distinct clusters with further subdivision. The divergences between C. fragariae and C. gloeosporioides were too low to distinguish them as separate species. On the basis of the sequence data, specific primers were designed both to identify isolates belonging to the genus Colletotrichum , and to distinguish isolates of the species C. acutatum . The specificity of these primers was validated by testing a wide range of strawberry isolates of Colletotrichum , non-strawberry isolates of Colletotrichum and other fungi used as controls. Although the 5.8S-ITS sequences were not polymorphic enough to allow the construction of C. gloeosporioides -specific primers, specific PCR amplification followed by an Mvn I digestion provides a tool to specifically identify strawberry isolates of C. gloeosporioides . [ABSTRACT FROM AUTHOR]

Abstract Strains of Colletotrichum species isolated from diseased strawberry plants from different countries were studied by random amplified polymorphic DNA (RAPD). Grouping and variability shown by RAPD supported the results of previous molecular studies made of Colletotrichum species. The variability was larger with C. acutatum , in which 15 different RAPD patterns were observed. Cluster analysis (UPGMA) was used to divide the C. acutatum strains into two major groups that correlated with other molecular markers previously used. Strains belonging to the first group showed a high level of similarity despite their diverse geographical origins, which probably correspond to a clonal population that resulted from a rapid and wide expansion of the strawberry trade. On the contrary, strains belonging to the second group showed a high level of genetic diversity that could indicate that they belong to lineages of older origins and/or to sexual reproducing lines. Within C. fragariae and C. gloeosporioides , two morphologically indistinguishable species, less genetic variability was observed, but both species were differentiated by RAPD patterns. A C. fragariae associated RAPD band was cloned, sequenced and used to design specific primers for this species. A PCR product of 580 bp was obtained only when DNA from C. fragariae strains was used, and this is proposed as a method for quickly and easily identifying C. fragariae strains. [ABSTRACT FROM AUTHOR]