Assessing the effectiveness of Byssochlamys nivea and Scopulariopsis brumptii in pentachlorophenol removal and biological control of two Phytophthora species.

Bioremediation and biological-control by fungi have made tremendous strides in numerous biotechnology applications. The aim of this study was to test Byssochlamys nivea and Scopulariopsis brumptii in sensitivity and degradation to pentachlorophenol (PCP) and in biological-control of Phytophthora cinnamomi and Phytophthora cambivora. B. nivea and S. brumptii were tested in PCP sensitivity and degradation in microbiological media while the experiments of biological-control were carried out in microbiological media and soil. The fungal strains showed low PCP sensitivity at 12.5 and 25 mg PCP L(-1) although the hyphal size, fungal mat, patulin, and spore production decreased with increasing PCP concentrations. B. nivea and S. brumptii depleted completely 12.5 and 25 mg PCP L(-1) in liquid culture after 28 d of incubation at 28 °C. Electrolyte leakage assays showed that both fungi have low sensitivity to 25 mg PCP L(-1) and produced no toxic compounds for the plant. B. nivea and S. brumptii were able to inhibit the growth of the two plant pathogens in laboratory studies and reduce the mortality of chestnut plants caused by two Phytophthorae in greenhouse experiments. The two fungal strains did not produce volatile organic compounds able to reduce the growth of two plant pathogens tested.

Multiple roles and effects of a novel Trichoderma hydrophobin.

Fungi belonging to the genus Trichoderma are among the most active and ecologically successful microbes found in natural environments, because they are able to use a variety of substrates and affect the growth of other microbes and virtually any plant species. We isolated and characterized a novel type II hydrophobin secreted by the biocontrol strain MK1 of Trichoderma longibrachiatum. The corresponding gene (Hytlo1) has a multiple role in the Trichoderma-plant-pathogen three-way interaction, while the purified protein displayed a direct antifungal as well as a microbe-associated molecular pattern and a plant growth promotion (PGP) activity. Leaf infiltration with the hydrophobin systemically increased resistance to pathogens and activated defense-related responses involving reactive oxygen species, superoxide dismutase, oxylipin, phytoalexin, and pathogenesis-related protein formation or activity. The hydrophobin was found to enhance development of a variety of plants when applied at very low doses. It particularly stimulated root formation and growth, as demonstrated also by transient expression of the encoding gene in tobacco and tomato. Targeted knock-out of Hytlo1 significantly reduced both antagonistic and PGP effect of the wild-type strain. We conclude that this protein represents a clear example of a molecular factor developed by Trichoderma spp. to establish a mutually beneficial interaction with the colonized plant.

A novel fungal metabolite with beneficial properties for agricultural applications.

Trichoderma are ubiquitous soil fungi that include species widely used as biocontrol agents in agriculture. Many isolates are known to secrete several secondary metabolites with different biological activities towards plants and other microbes. Harzianic acid (HA) is a T. harzianum metabolite able to promote plant growth and strongly bind iron. In this work, we isolated from the culture filtrate of a T. harzianum strain a new metabolite, named isoharzianic acid (iso-HA), a stereoisomer of HA. The structure and absolute configuration of this compound has been determined by spectroscopic methods, including UV-Vis, MS, 1D and 2D NMR analyses. In vitro applications of iso-HA inhibited the mycelium radial growth of Sclerotinia sclerotiorum and Rhizoctonia solani. Moreover, iso HA improved the germination of tomato seeds and induced disease resistance. HPLC-DAD experiments showed that the production of HA and iso HA was affected by the presence of plant tissue in the liquid medium. In particular, tomato tissue elicited the production of HA but negatively modulated the biosynthesis of its analogue iso-HA, suggesting that different forms of the same Trichoderma secondary metabolite have specific roles in the molecular mechanism regulating the Trichoderma plant interaction.

Harzianic acid: a novel siderophore from Trichoderma harzianum.

Agriculture-relevant microorganisms are considered to produce secondary metabolites during processes of competition with other micro- and macro-organisms, symbiosis, parasitism or pathogenesis. Many different strains of the genus Trichoderma, in addition to a direct activity against phytopathogens, are well-known producers of secondary metabolites and compounds that substantially affect the metabolism of the host plant. Harzianic acid is a Trichoderma secondary metabolite, showing antifungal and plant growth promotion activities. This report demonstrates the ability of this tetramic acid to bind with a good affinity essential metals such as Fe(3+) , which may represent a mechanism of iron solubilisation that significantly alters nutrient availability in the soil environment for other microorganisms and the host plant.