ABSTRACT
Rhizoctonia solani Kühn [teleomorph: Thanatephorus cucumeris (Frank) Donk.] is an important fungal pathogen widespread in all potato growing areas of the world that causes stem canker and black scurf of potato (Solanum tuberosum L.). The aim of this study was to find a simple and reliable technique for determining the pathogenicity of Rhizoctonia solani isolates. Sixty (60) isolates of R. solani obtained from sclerotia on potato tubers, collected from different market of Agadir and Casablanca regions (Morocco), were studied for their morphology, pathogenicity and molecular characteristics. They were morphologically characterised by the production of sclerotia and moniloïd cells, and by the mycelium growth capacity at 15, 20, 25, 30 and 35°C. This morphological characterisation leads to three groups of isolates. The first group contained P01 and P03 isolates, which were able to develop under 35°C. However, under 25°C, they did not develop sclerotia. The second group, only formed by L17.1 isolate, did not form sclerotia under 25°C and was not able to develop under 35°C. The third group, formed by several isolates, developed sclerotia under 25°C conditions and were not able to grow under 35°C. Also, a positive correlation was consistent between the production of sclerotia and moniloïd cell formation. The anastomosis reaction revealed that P01, P03, L17.1, and L4.1 isolates were identified as AG-4 and for the other isolates as AG-3. The pathogenic characterisation has shown that P01, P03, L4.1, and L17.1 isolates caused important damping off of radish, tomato, beans, zucchini, and melon. However, the other isolates showed only a minor damping off rate. Molecular characterisation confirmed the classical anastomosis grouping of the isolates into AG-3 and AG-4 Anastomosis Groups. The molecular characterisation is the most rapid and reliable technique to determine the anastomosis group of unknown isolates. The three tests including the pathogenicity, the cultural anastomosis grouping, and the molecular method helped to separate the studied isolates to two groups AG-3 and AG-4.
ABSTRACT
The study was conducted to determine fungal communities associated to strawberry plant roots, densities of nematodes in fumigated soil and physico-chemical properties of soil in three commercial strawberry plots (Dlalha, Ouled Aguile and Gnafda) located in Gharb region and visited three times during 2013-2014 season. Under a slight variation of soil temperature and humidity with specific physico-chemical characteristics, a high infestation level of soil by nematodes was marked in the studied farms over the periods of sampling. The lowest number was observed in the first visit attaining 1000 units/g of soil, increased to 5000 units/g of soil in the second sampling period at one site and in the last visit, a significant decrease trend occurs for the big plot which the number of nematodes was reduced to 1500 units/g of soil. The analysis of fungal communities colonizing roots of strawberry plants showed the presence of 13 fungal species. Rhizoctonia solani presented a higher frequencies of isolation from roots of Festival variety reaching respectively 36% and 26.72% in the first and the second visits of Dlalha farms compared to those recorded in the second visit of Ouled Aguile (18%) and Gnafda (13.6%) farms. The Fusarium genus was represented by F. solani, Fusarium sp.1 and Fusarium sp.2 detected at frequencies not exceeding 7.08%. Those of C. gloeosporioides reached 12%, Phytophthora sp. (15.8%). In addition, the appearance of A. alternata, C. herbarum, Aspergillus sp., Circinella sp., Ulocladium sp. and Trichoderma asperellum was more frequent during the three sampling periods.
ABSTRACT
The effect of a composite endomycorrhizal inoculum, native to the rhizosphere of the olive tree, was studied on the growth of leek plants (Allium porrum L.). Inoculation of leek plants was carried out by contacting the root system of leeks with the inoculum endomycorrhizal derived from the olive tree rhizosphere. After five months of inoculation, a significant effect is observed on the growth of the inoculated plants according to witnesses. Indeed, the average values of the aerial weight (11.62 g) and root weight (18.52 g), the diameter (0.5 cm) and the number of leaves (7) of the inoculated plants are higher than those noted in the control plants, respectively 4.42 g, 7.95 g, 0.3 cm, 5.57. Moreover, the frequency and intensity of mycorrhization, respectively 96.66% and 50.33%, the arbuscules contents (44.33%) and vesicles (32.44%) are very important. The roots of control plants are not mycorrhizal. The average number of spores formed in the rhizosphere of the inoculated plants is 160 spores per 100 g of soil. These spores are those of 85 endomycorrhizal species belonging to 16 different genera: Glomus (34 species), Acaulospora (18 species), Gigaspora (5 species), Entrophospora (3 species), Scutellospora (5 species), Pacispora (2 species), Claroideoglomus (2 species), Dentiscutata (1 species), Septoglomus (1 species), Paraglomus (2 species), Rhizoglomus (2 species), Ambispora (3 species), Cetraspora (1 species), Funneliformis (1 species), Diversispora (4 species) and Viscospora (1 species). Statistical analyzes were performed by analysis of variance by the ANOVA test at the 5% level using the STATISTICA software. Leek, is a mycotrophic plant that can be used to multiply an endomycorrhizal inoculum suitable for use in nurseries, and to produce seedlings of different plant species that are vigorous and resistant to pathogens and water stress after transplantation.
ABSTRACT
During a survey on fungi associated with decline symptoms on strawberry plant of Venicia variety, one species belonging to the Botryosphaeriaceae family was isolated. Based on morphological and cultural characteristics, this species identified as Neofusicoccum parvum was reported for the first time in Morocco. To verify the pathogenicity of the fungus, detached leaves of three strawberry varieties were inoculated artificially by depositing over their intact surface mycelia plug or conidial suspension from N. parvum. Severity index was greater on festival leaves reaching 88% compared to 77.73% on Sabrina. In the third treatment, Guariguette showed a low susceptibility with a severity index in order of 25.07%. Conidia concentration on the leaf surface of the Festival and Sabrina strawberry leaves was respectively 1.62 105and 1.2 105 conidia cm-2. Otherwise, in the second treatment, it has been reduced to less than 1.41105 1.16 and 105 conidia.cm-2 on leaves of Festival and Sabrina respectively. After inoculation, the fungus was re-isolated from the lesions to verify Koch’s postulates.
ABSTRACT
The present study is conducted to know the effect of certain cultural practices and the variation of temperature and humidity (bioclimatic stage, slope exposure) on the distribution and importance of the development of tuberculosis disease of olive trees, caused by Pseudomonas savastanoi pv. savastanoi(PSS), in Northwest of Morocco. 1584 trees of oleaster and olive trees (cuttings and grafts) were observed during the period 2013-2014 in several groves in the northwest regions of Morocco. The percentage of infection was calculated by the number of olive trees showing the symptoms of tuberculosis caused by Pseudomonas savastanoi pv. savastanoi. The intensity of the disease in the oleaster and the olive tree was determined by counting the number of knots. The prospection was showed that olive plots are more or less attacked by tuberculosis in the northwest part region of Morocco and more apparent in olive trees in development station in Zoumi and in Boukkara (North and West oriented slopes of 68% and 28% respectively). The percentage of infection was very high in oleaster and graft plants (31% and 28% respectively) in two humid stations (Zoumi and Boukkara). The intensity of the tuberculosis disease showed that oleaster trees are most attacked. The development of olive trees is highly influenced by the symptoms in branches. The fruit size and weight were significantly higher in healthy olive trees than in those showing the symptoms of tuberculosis.