GENETIC-VARIATION AMONG VEGETATIVE COMPATIBILITY GROUPS OF FUSARIUM-OXYSPORUM F-SP CUBENSE ANALYZED BY DNA-FINGERPRINTING

Genetic variation within a worldwide collection of 208 isolates of Fus arium oxysporum f. sp. cubense, representing physiological races 1, 2, 3, and 4 and the 20 reported vegetative compatibility groups (VCGs), was analyzed using modified DNA amplification fingerprinting. Also cha racterized were 133 isolates that did not belong to any of the reporte d VCGs of F. oxysporum f. sp. cubense including race 3 isolates from a Heliconia species and isolates from a symptomatic wild banana species growing in the jungle in peninsular Malaysia. The DNA fingerprint pat terns were generally VCG specific, irrespective of geographic or host origin. A total of 33 different genotypes were identified within F: ox ysporum f. sp. cubense; 19 genotypes were distinguished among the isol ates that belonged to the 20 reported VCGs, and 14 new genotypes were identified among the isolates that did not belong to any of the existi ng VCGs. DNA fingerprinting analysis also allowed differentiation of n ine clonal lineages within F. oxysporum f. sp. cubense. Five of these lineages each contained numerous closely related VCGs and genotypes, a nd the remaining four lineages each contained a single genotype. The g enetic diversity and geographic distribution of several of these linea ges of F. oxysporum f. sp. cubense suggests that they have coevolved w ith edible bananas and their wild diploid progenitors in Asia. DNA fin gerprinting analysis of isolates from the wild pathosystem provides fu rther evidence for the coevolution hypothesis. The genetic isolation a nd limited geographic distribution of four of the lineages of F. oxysp orum f. sp. cubense suggests that the pathogen has also arisen indepen dently, both within and outside of the center of origin of the host.