Various experiments were carried out to promote biological control under semi-arid ecological conditions. In vitro assay, Aspergillus flavus seemed to be the most effective bioagent against Fusarium oxysporum f. sp. niveum and Fusarium solani f. sp. cucurbitae with mycelial inhibition rate above 50%. Aspergillus flavus, Aspergillus niger, and Aspergillus terreus exhibited an exceptional hyperparasitism against F. oxysporum f. sp. melonis. The mycelial growth of five Macrophomina phaseolina isolates decreased in the presence of Trichoderma harzianum (44.42%). In greenhouse experiments, both A. flavus and A. fumigatus used preventively of melon inoculated with FOM generated the highest damage reduction rate of top and root dry weights (40–42 and 51–52%, respectively) and the lowest disease severity index (DSI). A. flavus was also effective in improving the plant development with the highest shoot (SDW) and root (RDW) dry weight values. Penicillium digitatum, Trichoderma harzianum, and Trichoderma viride treated preventively on watermelon and melon plants inoculated with M. phaseolina decreased the damage of SDW and RDW and DSI. The development rate revealed the growth improvement potential of T. harzianum (watermelon, 15%) and A. flavus (melon, 12%). Watermelon plants inoculated with F. solani f. sp. cucurbitae and treated curatively with Trichoderma erinaceum, T. viride, and A. flavus and other inoculated by F. oxysporum f. sp. niveum and treated by Trichoderma helicum recorded the highest values of growth parameters, similarly for T. erinaceum on melon plants inoculated by F. solani f. sp. cucurbitae. Among all treatments for plants inoculated by F. oxysporum f. sp. melonis, those three bioagents T. viride, T. erinaceum, and A. flavus revealed efficiency in plant growth. Trichoderma harzianum is the best bioagents against cucurbit soil-borne pathogens. Preventive treatment represents an effective strategy. Dipping roots with bioagent fungi suspension improve a good interaction pathogen antagonist.

Citrus blast and black pit that became increasingly important bacterial diseases are caused by Pseudomonas syringae pv. syringae. This study aimed to evaluate the antibacterial potential of Bacillus species strains and garlic extracts against two P. syringae isolates (BAT13 and DAPP-PG115). The Bacillus species strains were isolated from symptomless citrus leaves. Under in vitro conditions, 21 Bacillus species strains and garlic extract displayed antibacterial activity against the pathogen. Under greenhouse conditions, antagonistic bacteria, garlic extract, and copper sulfate confirmed their antimicrobial effect on P. syringae and reduced significantly the extend of stem necrosis 10 weeks after inoculation by BAT13 up to 60.55, 56.11, and 45.83%, and by DAPP-PG115 up to 70.83, 62.5, and 46.52%, in respect to relevant treatments. Garlic extract was the most effective treatment in our hands, and it suggests that Allium sativum extract could be used to control and prevent infection by the pathogen.

A survey was conducted, during 2012/2013, to identify the causal agents of citrus gummosis in Tunisia. The obtained isolates were identified by molecular and pathological criteria. Three species of Pythium (P. aphanidermatum, P. ultimum and P. dissotocum) and two species of Phytopythium (P. vexans and P. mercuriale) were recovered. Pathogenic tests, using twigs inoculation method for five citrus varieties under laboratory conditions, showed necrotic lesions similar to those observed in natural infected citrus trees by gummosis. In greenhouse experiments, the pathogenicity of the species to citrus was demonstrated by soil and trunk inoculations. Results showed necrotic lesions in the trunk of the variety “Clementine”. P. ultimum is the most virulent, while P. mercuriale was the least virulent in trunk inoculation. Symptom of necrotic roots has been also observed. This is the first report of Pythium and Phytopythium species within the citrus area in Tunisia.

This investigation included the chemical analysis of Peganum harmala (P. harmala) seed oil and its antifungal properties against 10 fungal species. Seed oils of six populations were analyzed using high performance liquid chromatography (HPLC) and gas chromatograph/mass spectrometry (GC-MS). The HPLC analysis indicated that P. harmala seed oil exhibited a very high level of tocopherol contents, with values in the range of 2385.66–2722.68 mg/100 g. The most abundant tocopherol isomer was δ-tocopherol (90.39%), followed by γ-tocopherol (8.08%) and α-tocopherol (1.14%). We discovered for the first time the presence of tocotrenols in P. harmala seed oils of the six populations studied. The GC-MS analyses revealed that linoleic acid was the main fatty acid (65.17%), followed by oleic acid (23.12%), palmitic acid (5.36%) and stearic acid (3.08%). We also studied the antifungal activity of seed oil of the Medenine (MD) population on ten fungal pathogens. The antifungal effects differed among pathogens and depended on oil concentrations. Seed oil of the MD population caused a significant decrease in mycelial growth of all fungi tested, with values ranging 31.50–82.11%, except for Alternaria sp., which showed no inhibition. The antifungal activity against the 10 selected fungi can be explained by the richness in tocols of the extracted oil and make P. harmala a promising crop for biological control. Furthermore, the importance of fatty acids and the wide geographic spread in Tunisia of this species make this crop a potential source of renewable energy.

Aims: To survey nurseries and diagnosis of the young peach seedlings decline, to investigate the Fusarium species associated with the decline of peach in Tunisian nurseries using morphological and molecular tools and determine the pathogenicity of the most predominant species on peach seedlings. Place and Duration of Study: Tunisian peach nurseries and Department of Biological Sciences and Plant Protection, Higher Institute of Agronomy of Chott Mariem, 4042, Sousse, Tunisia, between November 2012 and July 2014. Methodology: The surveys were conducted in peach nurseries. Five root samples were taken from each vigor of each peach variety. The isolation and the morphological identification were done on PDA medium. The molecular identification was done using ITS1 and ITS4. Pathogenicity tests were made for the dominant species which are F. oxysporum (25 isolates) and F. solani (8 isolates). Results: The isolation was done on PDA medium and morphological and molecular identification (using ITS1 and ITS4) revealed the presence of 62 isolates of Fusarium oxysporum, 32 isolates of F. solani, 7 isolates of F. equiseti, 4 isolates of F. proliferatum and 2 isolates of F. chlamydosporum. F. oxysporum and F. solani were isolated from roots from all surveyed nurseries. F. equiseti were isolated from roots from nurseries in Chebika, Zaghouan and Monastir. F. proliferatum was recovered from roots from nurseries in the Chebika and Zaghouan regions. F. chlamydosporum were recovered only from roots in nurseries at Monastir region. Pathogenicity of Fusarium oxysporum and Fusarium solani was evaluated by using two varieties of peach, Carnival and Royal Glory grafted onto the Garnem rootstock (Prunus dulcis x hybrid clonal of Prunus persica) planted in inoculated soil Symptoms of peach decline namely browning of the apical vegetative part, height reduction and collar rot. These two Fusarium species were more virulent on Carnival than Royal Glory. Fusarium solani induced root and collar rot symptoms whereas F. oxysporum induced necrotic roots symptom, browning and height reduction. Conclusion: This finding showed that Fusarium oxysporum and F. solani were the most dominant species. They were virulent to peach seedlings.