GENETIC DIVERSITY OF FUSARIUM-MONILIFORME DETECTED BY VEGETATIVE COMPATIBILITY GROUPS AND RANDOM AMPLIFIED POLYMORPHIC DNA MARKERS

Genetic diversity among Fusarium moniliforme isolates was analysed usi ng vegetative compatibility group (VCG) and random amplified polymorph ic DNA (RAPD) techniques. In the first experiment, RAPD was used to an alyse a set of 43 isolates collected from different corn growing areas in Israel and the US. The isolates were assigned to 27 different VCGs . Thirty-two RAPD haplotypes were also detected by analysing 48 polymo rphic bands. RAPD could differentiate all the VCGs, except in two case s where two VCGs were assigned a single RAPD haplotype. In six cases, however, molecular variation was detected among isolates belonging to the same VCG. Cluster analysis of the RAPD data showed a very good agr eement with the VCG grouping, e.g. isolates of the same VCG were alway s closely clustered by the molecular data. In a second experiment, 63 isolates of Fusarium moniliforme were collected from six corn lines gr owing in a single corn field. Extensive genetic variation was observed among the isolates: 42 different VCGs and 37 RAPD haplotypes were ide ntified. Once again, RAPD patterns could differentiate nearly all the VCGs. However, in four cases, two different VCGs were grouped into a s ingle RAPD haplotype, while in another three cases, isolates of the sa me VCG could be differentiated by distinct molecular haplotypes. The v ariation data was used to gain insight on the population structure and the patterns of genetic variation among geographical locations and wi thin a single field. Hierarchical gene diversity analysis of the RAPD data indicated that most of the genetic variability (81%) was distribu ted within corn lines in the same field, suggesting that RAPD haplotyp e, or VCG frequencies, were not significantly affected by the plant ge notypes grown in this experiment. Most of the RAPD band combinations d id not display significant gametic phase disequilibrium, suggesting th at active recombination might be occurring in the field. Our results i ndicate that by using a small number of primers, similar resolution wa s obtained by RAPD and VCG analysis, respectively. RAPD analysis is ho wever, simpler to perform and its sensitivity in genotyping individual s within Fusarium moniliforme can be increased by analysing more prime rs, enabling a more detailed population genetic analysis of this impor tant pathogen.