Screening And Antimicrobial Efficacy Of Secondary Metabolites From Trichoderma Species Against Plant Pathogenic Fungus,Bacteria And Nematode

Phytopathogens(bacteria,fungi and nematode)cause huge losses to agricultural crops each year,thereby posing threats to food security throughout the world.It is an urgent need of time to explore novel strategies for the management of plant pathogens.Use of biological control agents and their products such as their antimicrobial metabolites can be utilized as an effective,eco-friendly and economical tool for managing plant pathogens.As the genus Trichoderma is a rich source of antimicrobial secondary metabolites,there is a great opportunity to explore more and more antimicrobial compounds from Trichoderma spp.In this study,the experiment 1 was performed to study the thirty Trichoderma spp.and five different growth media(solid wheat,STP,MOF,MMK2 and Su M)for the production of antimicrobial metabolites against plant pathogenic fungi,Fusarium oxysporum causing wilting in many crops.Results showed that metabolites from only 15 Trichoderma spp.showed antifungal activity against F.oxysporum.The maximum antifungal activity was shown by metabolites of Trichoderma citrinoviride(T130)followed by T.afroharzianum(T52)and T.virens(T2013)metabolites.Among the five growth media tested for metabolites productions,the fungal metabolites obtained on solid wheat media were best in term of antifungal activity followed by MOF and STP media.Metabolites from T.longibrachiatum obtained on wheat media that gave maximum antifungal activity,were further separated into different fractions for the analysis of antifungal compound.Experiment 2 was conducted to study fungal metabolites from fifty Trichoderma spp.obtained on 5 growth media(solid wheat,STP,MOF,MMK2 and Su M)for their antibacterial activity against two devastating plant pathogenic bacteria Ralstonia solanacearum and Xanthomonas campestris.Scanning electron microscopy(SEM)was also conducted to observe the effect of fungal metabolites on bacterial cell morphology.It was shown that metabolites of different Trichoderma spp.obtained on different growth media were differ in the degree of their bioactivity.Metabolites of T.pseudoharzianum(T113)obtained on solid wheat media were more effective followed by metabolites from T.asperelloides(T136),T.pseudoharzianum(T129)and T.pseudoharzianum(T160).Metabolites from other strains either showed a very little activity or no activity against the studied bacteria.As evident from the SEM,fungal metabolites produced severe morphological changes,such as rupturing of the bacterial cell walls,disintegration of cell membrane and cell content leaked out.Different growth media used for obtaining metabolites from Trichoderma spp.were also seen to have different results in term of bioactivity against R.solanacearum and X.compestris.Usually fungal metabolites obtained on solid wheat media showed highest antibacterial activity followed by those obtained on STP and MOF media.Fungal metabolites from Su M and MMK2 media gave least activity as compared to others.Experiment 3 was carried out to investigate the metabolites from thirty Trichoderma spp.obtained on 5 growth media(solid wheat,STP,MOF,MMK2 and Su M)for their nematicidal activity against a destructive and broad host range nematode Meloidogyne incognita.The morphological alterations under the influence of fungal metabolites were also analyzed.Among all Trichoderma spp.metabolites from T.viridae obtained on STP and solid wheat media showed highest percent J2 s mortality and inhibition in egg hatching of M.incognita.Among the five media tested for the production of nematicidal metabolites,STP media was superior regarding the production of metabolites for egg hatch inhibition followed by solid wheat media.Microscopic observation indicated that most effective fungal extract(T.viridae on STP and soild media)probably infected and destroyed internal organs,resulting in straightened and stiffened body shape.The results of this experiment suggested that T.viridae could be selected as effective candidate for antimicrobial metabolite source against notorious plant parasitic nematode M.incognita.Overall,it is concluded that the genus Trichoderma possess a strong capacity to produce most diverse secondary metabolites.These antimicrobial metabolites can be used effectively in organic agriculture for the management of plant pathogens,thereby the use of harmful synthetic chemicals can be minimized in plant protection.As evident from this study,the production of antimicrobial metabolites is highly dependent on growth media,it is therefore recommended to investigate more growth media for the effective production of specific antimicrobial metabolites.