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Preliminary Characterization of Fusarium oxysporum f. sp. gladioli Causing Fusarium Corm Rot of Saffron in Italy

Fusarium corm rot of saffron (Crocus sativus L.), incited by Fusarium oxysporum Schlecht. f. sp. gladioli, causes severe stigma yield losses in L'Aquila Province in Central Italy. Primary symptoms during flowering (October through November) include basal stem rot, yellowing and wilting of shoots, and corm rot. The rapid spread of the disease is apparently caused only by movement of contaminated and/or infected corms (2,3). Ten isolates of F. oxysporum f. sp. gladioli, obtained from infected saffron crops located in the principal areas of saffron production in L'Aquila Province (2,3), were characterized by vegetative compatibility tests. The isolates were placed into vegetative compatibility groups (VCGs) using heterokaryon tests with chlorate-resistant nitrate-nonutilizing (nit) mutants. Based on complementation among these isolates and with a representative isolate of VCG 0340 (4), the tested isolates were assigned to VCG 0340. The fact that all isolates examined in this study belong to a single VCG supports the hypothesis that a clonal population of F. oxysporum f. sp. gladioli is spreading in L'Aquila Province in planting stock. In previous studies, only two Italian isolates of the pathogen obtained from Gladiolus were tested for vegetative compatibility, and both were included in VCG 0343 (1,4). Acquisition of further information on a larger number of isolates obtained from other cropping sites and associated with other hosts may result in a better understanding of the origin and spread of the pathogen in Italy, leading to improved strategies for control of Fusarium corm rot of saffron.

References: (1) R. P. Baayen et al. Eur. J. Plant Pathol. 104:887, 1998. (2) C. Cappelli and G. Di Minco. Infitore Fitopatol. 49:27, 1999. (3) C. Cappelli and G. Di Minco. J. Plant Pathol. 80:253, 1998. (4) J. J. Mes et al. Plant Pathol. 43:362, 1994.