Etude des myco-pathogènes de Lens culinaris et évaluation de l’effet de deux souches de Trichoderma harzianum

Abstract

In order to evaluate the bio protector effect of two strains of Trichoderma harzianum on two Cylindrosporium sp and Fusarium solani phytopatogens, a pathosystem using the model legume Lens culinaris has been chosen. The isolation of mycetes allowed us to obtain 197 fungal isolates of the different samples taken from BARAOUIA and AIN SEMARA sites, in the region of Constantine. In fact, 87 fungal isolates were obtained from different soil depths, with a fungal dominance in the depths 5 and 10. The rest of isolates (110) were obtained from different levels of plants, with a homogeneous distribution in terms of the number of isolates between the air and the underground surface. The macroscopic and microscopic identification of the set of isolates allowed for trying them into 25 genus, whose 55.34% of trains taken from BARAOUIA site and 46.30% of AIN SEMARA site are phytopatogens. Two fungal isolates with an antagonist activity were preselected after having developed important zones of inhibition on the PDA medium. The preliminary and molecular identification of these isolates has shown that they belong to Trichoderma harzianum 127a and Trichoderma harzianum 127b. The conducted tests In vitro antagonism against both pathogens Lens culinaris, namely Cylindrosporium sp and Fusarium solani; have revealed that the inhibition rate by the volatile metabolites is 62.70% in average, and those by diffusible metabolites is 86.34% in average. The evaluation of the rate competition exerted by T-T-127b and 127a, revealed that our Trichoderma strains have the ability to reduce from 70 to 83% growth C.SP and from 67 to 82% F of growth .solani.From these results, it seems that the efficiency of the strains of Trichoderma is more important when gathering all the ways of action (the use of spores). The optimisation of the fermentation medium (FL) has revaluated that the optimal conditions of the biomass production of T-127a and T-127b are: pH 5, temperature of 30°C and a culture medium on a malt extract (M2). The cultivation of biomass T- 127a and T-127b on wheat bran (FMS) has achieved a smooth greenish powder, whose concentration before purification is 3.27 109C/mL for T-127a and 3.33 109C/mL for T-127b. Moreover, the application of these spores on lentil plants, has revaluated that, in case of no treatment with antagonist strains, the inoculated plants with one of the pathogens (C. sp or F. solani) receive a hydric deficit leading to rise in the prolin content, a decrease in the chlorophyll content, in the concentration of the total sugars and in the growth. However, the plants stimulated by the strains of Trichoderma, had a stable content of prolin, a high content of chlorophyll and sugars as well as a rapid growth. The other treatments were able to conserve values of sugars, chlorophyll, prolin and a growth similar to the samples. In conclusion, our strains of Trichoderma harzianum prodycing at the laboratory level have important antifungal activities, which allow them of being exploited and the industrial level.