Abstract
Losses in crops caused by plant pathogenic bacteria and parasitic nematode are increasing because of a decrease in efficacy of traditional management measures. There is an urgent need to develop nonchemical and ecofriendly based management to control plant diseases. A potential approach of controlling plant disease in the crops is the use of biocontrol agents and their secondary metabolites (SMs). Luckily fungi and especially the genus Trichoderma comprise a great number of fungal strains that are the potential producer of bioactive secondary metabolites. In this study secondary metabolites from ten Trichoderma spp. were evaluated for their antibacterial and nematicidal potential against phytopathogenic bacteria Ralstonia solanacearum, Xanthomonas compestris and plant parasitic nematode Meloidogyne incognita. Five different growth media were evaluated for the production of SMs. It was shown that SMs of different Trichoderma spp. obtained on different growth media were different in the degree of their bioactivity. Comparison of five growth media showed that SMs produced on solid wheat and STP media gave higher antibacterial activity. SMs of T. pseudoharzianum (T113) obtained on solid wheat media were more effective against the studied bacteria followed by SMs from T. asperelloides (T136), T. pseudoharzianum (T129) and T. pseudoharzianum (T160). Scanning electron microscopy (SEM) was further conducted to observe the effect of SMs on bacterial cell morphology. As evident from the SEM, SMs produced severe morphological changes, such as rupturing of the bacterial cell walls, disintegration of cell membrane and cell content leaking out. SMs from T. viridae obtained on liquid STP and solid wheat media showed the highest percent of M. incognita juveniles (J2s) mortality and inhibition in egg hatching of M. incognita. The results of our study suggest that T. pseudoharzianum (T113) and T. viridae could be selected as an effective candidate for SMs source against phytopathogenic bacteria and M. incognita respectively.
Highlights
Both biotic and abiotic agents cause diseases in plants and pose a problem in agriculture by significantly affecting plant growth and crop yield at a global scale [1,2]
Pre-identified and −80 ◦C-preserved pure cultures of ten Trichoderma strains including T. pseudoharzianum (T113), T. koningiopsis (T84), T. asperelloides (T136), T. pseudoharzianum (T129), T. pseudoharzianum (T160), T. afroharzianum (32233), T. acitrinoviride (T130), T. longibrachiatum (T161), T. afroharzianum (T52), T. viridescens (T196) and phytopathogenic bacteria R. solanacearum and X. compestris were obtained from the Agricultural Culture Collection of China (ACCC) and the Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences (Beijing, China)
After control, SMs from T. pseudoharzianum (T113) exhibited maximum antibacterial activity compared to other strains, followed by T. asperelloides (T136), T. pseudoharzianum (T129) and T. pseudoharzianum (T160) (Tables 1 and 2)
Summary
Both biotic and abiotic agents cause diseases in plants and pose a problem in agriculture by significantly affecting plant growth and crop yield at a global scale [1,2]. The main plant pathogens are viruses, oomycetes, fungi, bacteria and nematodes Among the latter, there are more than 200 phytopathogenic bacterial species [4], the most important of which are Agrobacterium, Pseudomonas, Pectobacterium, Xylella, Erwinia, Ralstonia, Dickeya and Xanthomonas [5]. A species of the genus Ralstonia, is a gram-negative bacterium and is considered to be one of the most devastating plant pathogens It has a global distribution and has a significant economic impact worldwide [6]. Another bacterium Xathomonas campestres, a member of genus Xanthomonas, is the pathogen of tomato and pepper bacterial spots, which reportedly cause 50% yield losses for tomatoes in many countries around the world [7,8]. RKNs cause the formation of giant cells in the roots of plants, prevent the absorption of water and nutrients and promote the infection of pathogenic microorganisms [11]
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