ANALYSIS OF DIVERSE ISOLATES OF COLLETOTRICHUM-LINDEMUTHIANUM INFECTING COMMON BEAN USING MOLECULAR MARKERS

Colletrotrichum lindemuthianum is the major pathogen of common bean (P haseolus vulgaris) in tropical regions. This fungus exhibits diverse p hysiological races, based on pathogenicity tests conducted on a differ ential range of bean cultivars. Molecular markers were used to assess the genetic basis of such variability in this fungus which lacks a sex ual stage. Random amplification of polymorphic DNA (RAPD), Restriction fragment length polymorphism (RFLP) of the ribosomal genes and RFLP o f PCR-amplified internal transcribed spacers of ribosomal DNA were use d. A selection of 12 isolates originating from diverse countries or lo cations was chosen from a collection and analysed for molecular variab ility and for pathogenicity. Two separate molecular groups were identi fied. Regarding DNA polymorphism and pathogenicity, a correlation was established within group II since all of the isolates in this group ex hibited the same avirulence spectrum, even though they originated from three different continents. Such a correlation could not, however, be established for group I, in which isolates exhibited four different a virulence spectra. Consideration of DNA polymorphism groupings and the geographical origins of isolates suggests that no correlation can be established, as isolates from Latin America are spread throughout both groups.