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Aims: This study investigated the efficiency of six fungicides against Fusarium spp. associated to peach seedling decline in Tunisian nurseries.

Rhizoctonia root rot of pepper (Capsicum annuum L.) is becoming serious in Tunisia. Comparative pathogenicity tests performed for Rhizoctonia solani isolates recovered from pepper and potato showed that Rhiz.7 and Rhiz.4 were the most aggressive. They reduced by 53.5%-91.4% the aerial part fresh weight of inoculated cv. Baklouti plants relative to control. Rhiz.7 decreased by 81%-88% the root fresh weight on cvs. Beldi and Baklouti. Various fungal and bacterial agents were tested against R. solani. Dual culture trials showed that Trichoderma harzianum, T. viride and Glicladium virens grew and sporulated profusely over R. solani colonies and altered its hyphae. Pseudomonas huttiensis 69, P. aureofaciens 31 and Burkholderia glathei 35 reduced pathogen growth by 9.71-12.87%. These bio-agents were tested for their effects on rhizoctonia root rot disease and pepper growth. On cv. Beldi, pre-emergence damping-off, noted after 15 days, was suppressed by 55 (for G. virens), 45 (for T. viride) and 50% (for T. harzianum). This inhibition reached 57.14% using Bacillus pumilus 420 and P. putida 227. Tested on pepper cv. Altar, all tested fungi decreased by 40% post-emergence damping-off, and significantly increased the plant height of R. solani-inoculated and treated plants by 21.13 (for T. viride) to 36.34% (for T. harzianum) relative to control. P. aureofaciens 314 and P. putida 227 completely suppressed R. solani post-emergence expression. Treatments with P. aureofaciens 314, P. aureofaciens 31, Bacillus pumilus 420, P. fluorescens Pf and P. putida 227 induced a significant increase in their height compared to control. An improvement of the aerial part fresh weight by 54.54, 48.09 and 47.74%, as compared to control, was induced by P. aureofaciens 314, B. glathei 35 and P. huttiensis 69, respectively. Indeed, strains of B. thuringensis were found to be efficient for the biocontrol of R. solani of chili pepper based on in vitro assays [20]. Moreover, B. cepacia was shown able to reduce the severity of Rhizoctonia diseases associated to pepper and tomato [19]. Antibiosis seems to be their principal mode of action [21].Pseudomonas species were shown capable of markedly inhibiting the growth of R. solani in vitro and in vivo. Indeed, tomato plants were also highly protected against R. solani infestations using this bacterium suspended in water [19]. Moreover, fluorescent Pseudomonas species were found to induce systemic resistance in plants as a result of root colonization [18].Recently, several rhizobacterial isolates and mainly B. thuringiensis B2 (KU158884), B. subtilis B10 (KT921327) and Enterobacter cloacae B16 (KT921429) were found to be efficient for the suppression of R. solani radial growth and disease severity and for the enhancement of tomato growth [10].In Tunisia, R. solani is still being a destructive pathogen of pepper and investigations for its biocontrol are lacking. Therefore, the objectives of the current study were: (i) to evaluate the aggressiveness of different R. solani isolates involved in dam...

Citrus black spot (CBS), caused by the fungus Phyllosticta citricarpa, is associated with serious yield and quality losses. The climate suitability of the Mediterranean Basin for CBS development has been long debated. However, CBS has been described in Tunisia. In this study, a generic model was used to simulate potential infections by ascospores and pycnidiospores together with a degree-day model to predict the onset of ascospore release. High-resolution climatic data were retrieved from the ERA5-Land dataset for the citrus-growing regions in the Mediterranean Basin and other locations where CBS is present. In general, the onset of ascospore release was predicted to occur late in spring, but there is no agreement on the adequacy of this empirical model for extrapolation to the Mediterranean Basin. The generic model indicated that infections by ascospores and pycnidiospores would be concentrated mainly in autumn, as well as in spring for pycnidiospores. In contrast to previous studies, the percentage of hours suitable for infection was higher for pycnidiospores than for ascospores. The values obtained with the generic infection model for Tunisia and several CBS-affected locations worldwide were similar to those for other citrus-growing regions in Europe and Northern Africa. These results support previous work indicating that the climate of the Mediterranean Basin is suitable for CBS development.

Background The effect of Aspergillus spp. and Trichoderma harzianum isolates was evaluated against the growth of Fusarium oxysporum, F. solani, Pythium ultimum and Phytophthora citrophthora affecting peach seedlings. Results The in vitro results revealed the ability of these antagonistic in reducing the radial growth of these pathogens. The most important mycelial growth reduction was of 85.82%, recorded for F. oxysporum in confrontation with A5 of Aspergillus candidus. Aspergillus flavus A4 and A. niger A10 were the most effective against F. solani with an inhibition percent more than 60%. For P. citrophthora, A. flavus A4, A. candidus A5, A. terreus A9 and A. niger A10 inhibited the mycelia growth by more than 60%. Aspergillus nidulans A1 was the most effective against Pythium ultimum (72.07%). Trichoderma harzianum isolates T9 and T10, are the most effective with a high inhibition percent of mycelial growth. The inhibition induced after 4 days of incubation, against F. oxysporum, F. solani, P. citrophthora and Pythium ultimum by these 2 antagonists exceeded 70, 60, 70 and 80%, respectively. The in planta test showed the efficacy of antagonists tested solo against some pathogens. In fact, Bacillus subtilis improved the health status by 62.55% compared to the control inoculated with P. ultimum. Trichoderma harzianum T9 significantly reduced the root rot index by 87.5% than the control inoculated with F. solani. In the same sense, B. subtilis significantly reduced this parameter by 62.55 and 88.89% than the control inoculated with P. ultimum and P. citrophthora, respectively. Furthermore, B. subtilis (B) and Aspergillus niger A10 improved plants height than the control inoculated with Pythium ultimum by 31.52 and 40.49%, respectively. However, the combinations of antagonists (T9 + T10; A5 + A10 and B + T10) did not improve their efficacy. Conclusions The isolates T. harzianum (T9 and T10), A. candidus A5 and A. niger A10 were the most effective in vitro against Fusarium, Pythium and Phytophthora species associated with peach seedling decline. The in vivo assay showed the effectiveness of B. subtilis against P. ultimum and P. citrophthora and the potential effect of T. harzianum T9 against F. solani. Their combinations revealed to be ineffective.