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This research aimed to study diversity among a collection of Rhizoctonia solani strains, isolated from many crops in Morocco, based on radial mycelial growth on potato dextrose agar (PDA) at different pH and temperature levels. The in vitro antifungal efficacy of essential oils (EOs) derived from aromatic and medicinal plants of Thymus vulgaris, Origanum compactum, Rosmarinus officinalis, Eucalyptus sp., Salvia sp., Cistus ladanifer and Lavandula stoechas was also evaluated by measuring the mycelial growth of this plant pathogenic fungus after placing active mycelial plugs of each strain on Petri dishes using a disc diffusion method of EOs. The Minimum Inhibitory Concentration (MIC) of each EO was also determined. The growth rates observed under different temperatures and pH levels varied among isolates and did not show similar responses for the same levels of the two growth parameters. However, the maximum mycelial growth of the majority of isolates was reached between 20 and 30°C as well as at pH 7. Among the EOs tested, the results revealed that EO of Thymus vulgaris and Origanum compactum were very effective on controlling R. solani strain RS1 with growth inhibition rate of 75,9% and 60,6%, respectively. The MIC of these EOs was at 0.03%. According to the gas chromatography analysis, Carvacrol (61.8%) and thymol (47.8%) are the major constituents of O. compactum and T. vulgaris EOs, respectively, suggesting that these natural compounds have important potential to control R. solani and could be useful for developing effective organic fungicides.

Olive knot disease caused by Pseudomonas savastanoi pv. savastanoi (PSS) is considered as the main bacterial disease of olive tree in Morocco. However, sole prophylactic measures are available. The main aim of this work was to evaluate the effects of eighteen antagonistic bacteria, as an alternative approach, to control in vitro and in planta the pathogens strains previously isolated from olive trees in Morocco. In vitro experiments revealed that many bacterial strains such as Rahnella aquatilis, Enterobacter ludwiqii, Paenibacillus brasiliensis, and Bacillus subtilis selected from collection of Regional Center of Agronomic Research, were efficient on solid media against pathogen strains. Their inhibition zones ranged from 8 to 23 mm with a higher inhibition rates found by B. subtilis strains. Enzymatic activities of antagonistic strains were assessed (cellulase, protease and amylase) as well as some plant growth promotion traits (phosphorus solubilisation and indole acetic acid production) for performance screening. B. subtilis 2515-1 was selected for pots experiment using olive trees (cv. Arbequina). This bacterium significantly reduced number and weight of knots against two pathogens strains (PSS 2064-8 and PSS 2102-4). The most reduction rates of weight and knot number were respectively 95.60% and 50%. This study suggested an alternative approach to assess the efficiency of selected bacterium in field conditions.