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A near-isogenic Fusarium oxysporum f.sp. lycopersici strain with a novel combination of avirulence characteristics

Teunissen, H.A.S., Boer, Y., Verkooijen, J., Cornelissen, B.J.C., Haring, M.A.
Phytopathology 2003 v.93 no.11 pp. 1360-1367
Solanum lycopersicum var. lycopersicum, Solanum pimpinellifolium, Solanum pennellii var. pennellii, tomatoes, Fusarium oxysporum f. sp. lycopersici, plant pathogenic fungi, pathogenicity, virulence, disease resistance, pathotypes, nonpathogenic strains, isogenic lines, genetic variation, genes, chromosome mapping, genetic markers, amplified fragment length polymorphism
A novel Fusarium oxysporum f. sp. lycopersici strain (F1-27) was obtained from protoplast fusions between race 1 Fol004 (putative avirulence genotype A1a2a3) and race 2 Fol007 (a1A2A3). Bioassays using different tomato cultivars revealed new virulence characteristics for F1-27 that were mitotically stable. The corresponding avirulence genotype for F1-27 was assigned a1A2a3. Despite their distinction in avirulence genotype, molecular analysis revealed that parent Fol007 and F1-27 were near-isogenic strains. The electrophoretic karyotype of F1-27 was identical to that observed for Fol007. Foxy-amplified fragment length polymorphism (AFLP) marker analysis showed that all Fol007-specific bands were present in F1-27. In addition, 11 new F1-27-specific Foxy insertions were identified. Segregation of both virulence and these new Foxy-AFLP markers was observed in a backcross between F1-27 and its parent Fol007. One marker was found to cosegregate with the a3 allele. The nature of the genetic change in this strain is discussed.