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The aggressiveness of Alternaria dauci isolates was investigated in greenhouse conditions. Twenty-seven isolates were preselected from a large collection to represent high diversity according to geographic or host origins and intergenic spacer (IGS) polymorphism. IGS sequence analysis revealed that isolates were grouped within three different clusters. Eleven isolates were selected and inoculated on a susceptible carrot cultivar. Three criteria (mean lesion number, mean necrotic leaf area and mean disease index) were used to assess the aggressiveness of isolates. Continuous variation in aggressiveness was shown and no clear division into isolate classes was evident. For the host range study, two isolates were inoculated under greenhouse conditions onto nine cultivated Apiaceae species, two wild Daucus species and six cultivated non-Apiaceae species representing six botanical families. Lesions varying in severity were observed on all dicot species (Apiaceae and non-Apiaceae), but no symptoms developed on the two monocots studied (leek and sweetcorn). Plant species were also differentiated on the basis of expanding lesions (cultivated and wild carrot, dill and fennel) or non-expanding lesions (other dicot species). Typical A. dauci conidia were observed after in vitro incubation of leaves with symptoms. Fungal structures were isolated from lesions and A. dauci was confirmed on the basis of conidial morphology and specific conventional PCR results. Genotyping of individual isolates performed with microsatellite markers confirmed the presence of the inoculated isolate. The results clearly showed that, in controlled conditions, the host range of A. dauci is not restricted to carrot.

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Tomato (Lycopersicon esculentum) is one of the most widely grown vegetables in the world. There is a growing concern in recent years, both in developed and developing countries, about the use of hazardous fungicides for controlling plant diseases. The in vitro effect of two fungicides commonly used in Algeria namely Trifidan and Antracol (propineb) on the growth of three pathogenic fungi of tomato, Fusarium oxysporum f.sp. radicis-lycopersici, Fusarium commune and Fusarium redolens was investigated to determine the effectiveness of the fungicides in reducing fungi growth. Each fungicide was assayed at 0, 100, 200, 400 and 500 mg L -1 rate in Potato Dextrose Broth (PDB) and incubated at 28°C for seven days. Data were collected on the mycelia weights of the fungi under each treatment. Mycelia weights of the three fungi were significantly reduced at 100 mg L -1 by the two fungicides under antracol treatment F. redolens and F. commune and a significant reduction was observed at 400 and 500 mgL -1 . Application of Trifidan, significantly decrease in mycelia weight of F. oxysporum f. sp. radicis-lycopersici and F. commune irrespective of the rate applied. F. redolens was completely inhibited by Trifidan, and its inhibition started at 100 mg L -1 .