ABSTRACT
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.
ABSTRACT
ABSTRACT The effects of reduced doses of methyl bromide (MB) or metham sodium, heating, short solarization, and soil microbial activity, alone or in combination, on survival of soilborne fungal pathogens were tested in a controlled-environment system and field plots. Sublethal doses of heating or MB delayed germination of Sclerotium rolfsii sclerotia. Combining MB and heating treatments was more effective than either treatment alone in controlling S. rolfsii and Fusarium oxysporum f. sp. basilici. The application heating followed by fumigation with MB, was significantly more effective in delaying and reducing germination of S. rolfsii sclerotia and in controlling F. oxysporum f. sp. basilici than the opposite sequence. Further, incubation in soil and exposure to microbial activity of previously heated or MB-treated sclerotia increased the mortality rate, indicating a weakening effect. Similarly, incubation of chlamydospores of F. oxysporum f. sp. melonis and F. oxysporum f. sp. radicis-lycopersici in soil in the field after fumigation further reduced their survival, confirming the laboratory results. In field tests, combining MB or metham sodium at reduced doses with short solarization was more effective in controlling fungal pathogens than either treatment alone. Treatment sequence significantly affected pathogen control in the field, similar to its effect under controlled conditions. This study demonstrates a frequent synergistic effect of combining soil treatments and its potential for improving pathogen control and reducing pesticide dose, especially when an appropriate sequence was followed.
