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  • Author or Editor: H. Boureghda x
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Study and comparison of efficiency of the antagonist species Trichoderma atroviride, T. harzianum and T. longibrachiatum against Fusarium wilt were carried out using in vitro and in vivo based bioassay. Significant decrease of both growth and conidia production of the pathogen are obtained compared to the control. Thus, the highest percentages of diameter colony reduction and conidial production were obtained with the T. atroviride isolate (Ta.13), causing 65.64% reduction in colony diameter (direct confrontation), 48.71% reduction in colony diameter (indirect confrontation), and a complete inhibition of conidial production. Once more in direct confrontation, T. atroviride overgrowth the pathogen colony and sporulate above. The seed treatment by Trichoderma spp. isolates before sowing in a soil already infested by the pathogen led to a significant decrease of disease severity compared to the untreated control. The weakest index of disease severity is obtained with the T. atroviride isolates (Ta.13), which cause 83.92% reduction compared to the control. The most effective isolates in protection chickpea seedlings against the disease were the three strains of T. atroviride species (Ta.3, Ta.7 and Ta.13) as well as the isolate T. harzianum (Th.16). Reduction of disease severity obtained was associated with an increase of the vegetal growth including the stem height as well as the plant fresh and dry weight.

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Fourteen strains of Trichoderma spp. were isolated from Algerian desert soils and assessed for their antagonistic activity against Fusarium crown and root rot of wheat. Biocontrol efficiency of Trichoderma spp. was studied by in vitro and in vivo based bioassay against three pathogenic species: F. culmorum, F. graminearum and F. verticillioides. In vitro based bioassay (dual culture) results obtained with all Trichoderma spp. isolates showed significant decrease in colony diameter of Fusarium species compared to the control. The highest percentages of reduction in colony diameter were obtained with T. harzianum Thr.4 causing a growth reduction of 70.68%, 67.05 and 70.57% against F. culmorum, F. graminearum and F. verticillioides, respectively. All Trichoderma spp. isolates were able to overgrow and sporulate above F. culmorum colonies but no overgrowth was observed with F. graminearum and F. verticilliodes. The seed treatment by Trichoderma spp. isolates before sowing in a soil already infested by the pathogens led to a significant decrease of disease severity compared to the untreated control. The highest disease index decrease (>70%) was obtained with two isolates of T. harzianum (Thr.4 and Thr.10) and T. viride Tv.6 against the three fungal pathogens. Lytic enzymes production by Trichoderma spp. isolates was tested in liquid cultures containing fungal cell walls of each pathogen as sole carbon source. Higher levels of protease and chitinase activities were induced by hyphal cell walls of F. graminearum than cell walls of F. verticillioides and F. culmorum. T. harzianum Thr.4 exhibited the highest enzyme activities with hyphal cell walls of F. graminearum and F. culmorum. However, in the medium amended with cell wall of F. verticillioides, maximal lytic activities were recorded for T. viride Tv.6.

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Root-knot nematode Meloidogyne spp. is one of the most dangerous pests on vegetable crops in Algeria. Actually, research of alternative methods against these enemies is necessary. Culture filtrates of three species of filamentous fungi, Trichoderma harzianum, T. atroviride, T. longibrachiatum, tested against Meloidogyne incognita showed a nematicide effect on larval mortality of the second stage and also inhibited the potential of hatching nematode whose effectiveness varies with species, time of exposition and concentration. Finally, the use of some of these species of fungi can be an alternative method in the management of this bioagressor.

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