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Genetic and pathogenic characterization of verticillium dahliae infecting artichokes in the Valencia region of Eastern Spain

Olivares-García, C., Collado-Romero, M., Mercado-Blanco, J., Pérez-Artés, E., Giménez-Jaime, A., Armengol, J., Gárcia-Jiménez, J., Jiménez-Diaz, R.M.
Acta horticulturae 2004 no.660 pp. 491-495
Verticillium dahliae, artichokes, conidia, cotton, fungi, heterokaryon, hybrids, mutants, pathotypes, polymerase chain reaction, virulence, Spain
Verticillium dahliae isolates from artichokes in Alicante (45), Castellón (19) and Valencia (32) provinces at eastern-central Spain were characterized by means of vegetative compatibility grouping (VCG) analysis and duplex, specific polymerase chain reaction (PCR) assays. Isolates were assigned to VCGs through complementation tests of nitrate-nonutilizing (nit) mutants with reference nit testers of VCGs1A, 2A, 2B, 3, 4A and 4B. Duplex PCR assays were carried out using two sets of primer pairs that produce either specific markers for V. dahliae or for the cotton-defoliating (D) and nondefoliating (ND) pathotypes of the fungus. In addition, 18 V. dahliae isolates representative of the VCGs and geographic origins were tested for virulence to artichokes hybrid cvs. Nun. 6374 and Nun. 9444 by root-dip inoculation in a 10(6) conidia ml-1 suspension. Of the 96 tested isolates, 29.2% belonged to VCG2A, 64.6% to VCG2B and 3.1% to VCG4B. One isolate was assigned to VCG1A and two (2.1%) were heterokaryon self-incompatible (HIS). VCG2B isolates occurred in the three provinces with a frequency ranging from 27.4 to 42.0%. Of the VCG2A isolates, 92.8% were from Alicante and 7.2% from Valencia. V. dahliae isolates from Valencia showed the greatest VCG diversity, while all the isolates from Castellón were of VCG2B. PCR markers of the D and ND cotton pathotypes were not reliable for characterizing isolates from artichokes; rather, some 55% of VCG2B isolates and the HSI isolates shared a marker with the VCG1A D-isolate. All tested isolates were pathogenic to artichokes but virulence to cvs. 6374 and 9444 varied among VCGs.