<Emphasis Type="Italic">Trichoderma harzianum</Emphasis>: a biocontrol agent against <Emphasis Type="Italic">Bipolaris oryzae</Emphasis>

Rice brown spot, caused by Bipolaris oryzae, can be a serious disease causing a considerable yield loss. Trichoderma harzianum is an effective biocontrol agent for a number of plant fungal diseases. Thus, this research was carried out to investigate the mechanisms of action by which T. harzianum antagonizes Bipolaris oryzae in vitro, and the efficacy of spray application of a spore suspension of T. harzianum for control of rice brown spot disease under field conditions. In vitro, the antagonistic behavior of T. harzianum resulted in the overgrowth of B. oryzae by T. harzianum, while the␣antifungal metabolites of T.␣harzianum completely prevented the linear growth of B. oryzae. Light and scanning electron microscope (SEM) observations showed no evidence that mycoparasitism contributed to the aggressive nature of the tested isolate of T. harzianum against B. oryzae. Under field conditions, spraying of a spore suspension of T. harzianum at 10⁸ spore ml⁻¹ significantly reduced the disease severity (DS) and disease incidence (DI) on the plant leaves, and also significantly increased the grain yield, total grain carbohydrate, and protein, and led to a significant increase in the total photosynthetic pigments (chlorophyll a and b and carotenoids) in rice leaves.     

<Emphasis Type="Italic">Trichoderma harzianum</Emphasis>: occurrence in the air and clinical significance

Trichoderma harzianum, a filamentous fungus, is being widely used as a potential biopesticide. The potential of this fungus in causing skin sensitization, however, was poorly investigated as yet. The objective of this study was to monitor the occurrence of T. harzianum in the air and to explore its skin sensitizing potential. Seasonal periodicity of T. harzianum was studied for the years 2002–2004 by an Andersen air sampler. The skin sensitizing potential of T. harzianum extract was studied in 389 patients with suspected respiratory allergy by skin prick test (SPT) and specific IgE level was determined by ELISA. SDS–PAGE and immunoblotting were also performed. T. harzianum colony count varied from 3.69 to 134.88 CFU m⁻³ with the peak achieved in February. Relative humidity was found to be a significant (P < 0.05) factor predicting the occurrence of T. harzianum in the air. Positive skin reaction (wheal diameter ≥ 3 mm) was observed in 105 patients (26.99%). T. harzianum crude extract was resolved in 18 protein bands (12–72 kDa) on SDS–PAGE (12% gel) including two IgE-binding protein bands (21 and 32 kDa). T. harzianum can be considered an important inhalant allergen.     

<Emphasis Type="Italic">Trichoderma harzianum</Emphasis> Rifai 1295-22 Mediates Growth Promotion of Crack Willow (<Emphasis Type="Italic">Salix fragilis</Emphasis>) Saplings in Both Clean and Metal-Contaminated Soil

We investigated if the plant growth promoting fungus Trichoderma harzianum Rifai 1295-22 (also known as “T22”) could be used to enhance the establishment and growth of crack willow (Salix fragilis) in a soil containing no organic or metal pollutants and in a metal-contaminated soil by comparing this fungus with noninoculated controls and an ectomycorrhizal formulation commercially used to enhance the establishment of tree saplings. Crack willow saplings were grown in a temperature-controlled growth room over a period of 5 weeks’ in a garden center topsoil and over 12 weeks in a soil which had been used for disposal of building materials and sewage sludge containing elevated levels of heavy metals including cadmium (30 mg kg⁻¹), lead (350 mg kg⁻¹), manganese (210 mg kg⁻¹), nickel (210 mg kg⁻¹), and zinc (1,100 mg kg⁻¹). After 5 weeks’ growth in clean soil, saplings grown with T. harzianum T22 produced shoots and roots that were 40% longer than those of the controls and shoots that were 20% longer than those of saplings grown with ectomycorrhiza (ECM). T. harzianum T22 saplings produced more than double the dry biomass of controls and more than 50% extra biomass than the ECM-treated saplings. After 12 weeks’ growth, saplings grown with T. harzianum T22 in the metal-contaminated soil produced 39% more dry weight biomass and were 16% taller than the noninoculated controls. This is the first report of tree growth stimulation by application of Trichoderma to roots, and is especially important as willow is a major source of wood fuel in the quest for renewable energy. These results also suggest willow trees inoculated with T. harzianum T22 could be used to increase the rate of revegetation and phytostabilization of metal-contaminated sites, a property of the fungus never previously demonstrated.     

Exposure to airborne microorganisms,hyphal fragments,and pollen in a field of organically grown strawberries

Many working environments are predisposed for larger than average amounts of fungi and other microorganisms often due to organic material being handled. From 2003 to 2007, the area used for strawberry production in Denmark increased by 62%. The purpose of this study was to determine the levels of exposure to microorganisms, endotoxin, (1→3)-β-d-glucan (β-glucan), and pollen in a field of strawberries. The study was carried out in eastern Denmark from the middle of June to the beginning of August 2008. The strawberries were grown organically, and microbiological pest control agents (MPCAs) were applied during this and former growth seasons. In order to measure exposure to inhalable bioaerosol components, we used stationary filter samplers. Bioaerosol sampling was performed during 4 working days, and a total of 57 samplings were performed. The filters were analysed for contents of fungi, MPCAs, endotoxin, β-glucan, and pollen. The mean exposure was 6,154 CFU Cladosporium sp. m⁻³, 1.0 × 10⁵ fungal spores m⁻³, 4.1 × 10⁴ hyphal fragments m⁻³, 5.8 × 10³ pollen m⁻³, 57.3 ng β-glucan m⁻³, and 8.9 endotoxin units (EU) m⁻³. A significant and positive correlation was found between β-glucan and fungal spores and between CFU of Cladosporium sp. and CFU of fungi. We selected specifically for Metarhizium anisopliae, Beauveria bassiana, and the applied MPCAs Trichoderma harzianum, T. polysporum, and Bacillus thuringiensis but found none of these species. In conclusion, our study shows that berry pickers in this organic strawberry field were potentially subjected to higher levels of fungal spores, Cladosporium sp., hyphal fragments, pollen, and thus also β-glucan than is usually seen in outdoor air. Exposure to MPCAs was not seen. The exposure to endotoxin was only slightly higher than e.g. in a town.     

Production,formulation and antagonistic activity of the biocontrol like-yeast <Emphasis Type="Italic">Aureobasidium pullulans</Emphasis> against <Emphasis Type="Italic">Penicillium expansum</Emphasis>

Aureobasidium pullulans (de Bary) Arnaud (Ach 1-1) was grown in a glucose fed-batch fermentor to 106 g dry wt l⁻¹ in 48 h. The cells were dried in a fluidized bed dryer with a final viability of 62%. After 7 months at 4°C, the viability was 28% of the initial value (= 2.3 × 10¹⁰ c.f.u. g⁻¹ dry matter). A protection level of 89% was achieved with the biomass preparation at 1 × 10⁸ c.f.u. ml⁻¹ after 28 and 7 days for apples stored respectively at 5 and 25°C against Penicillium expansum. Our process is suitable to produce large quantities of the strain Ach 1-1 as biological control agent for apple preservation.     

Antagonistic interactions between fungal pathogens and phylloplane fungi of guava

Dominant phylloplane fungi of guava (Psidium guajava L.) were screened for their antagonistic activities against the two pathogens,Colletotrichum gloeosporioides andPestalotia psidii, bothin vitro andin vivo. Culture filtrates ofAspergillus niger, Fusarium oxysporum andPenicillium citrinum caused more than 50% growth inhibition ofC. gloeosporioides. Filtrates ofCephalosporium roseo-griseum andF. oxysporum were most effective in reducing the growth ofP. psidii. Volatiles produced from the cultures ofA. niger, F. oxysporum, P. citrinum andP. oxalicum inhibited the growth ofC. gloeosporioides, whereas volatiles fromC. roseo-griseum, F. oxysporum andTrichoderma harzianum inhibited the growth ofP. psidii. The inhibitory effect of volatiles decreased with increase in incubation time. In general, the maximum effect of volatiles was noticed after 48 h incubation. Different grades of colony interactions in dual cultures were recognised between the two pathogens and the phylloplane fungi examined. Maximum inhibition ofC. gloeosporioides was caused byAureobasidium pullulans, Cladosporium cladosporioides, epicoccum purpurascens, F. oxysporum andMyrothecium roridum, whereasAspergillus terreus, C. roseo-griseum andP. oxalicum significantly reduced the growth ofP. psidii. Application of a spore suspension of each test fungus inhibited lesion development of guava leaves caused by the test pathogensin vitro. Inhibition was more pronounced when the spore concentration was increased.A. pullulans, C. cladosporioides, E. purpurascens, F. oxysporum, andT. harzianum were found to be strongly antagonistic toC. gloeosporioides. A. niger, A. terreus, C. roseo-grisem andT. harzianum were strongly antagonistic toP. psidii.     

Biological control ofRhizoctonia solani in strawberry fields byTrichoderma harzianum

Summary Trichoderma harzianum preparations was used in two successive field experiments in commercial strawberry nurseries and fruiting fields. Disease severity ofRhizoctonia solani in daughter plants was reduced by 18–46 % in the treated nursery plots. Infestation of nursery soil with the pathogen, as tested by planting beans in soil samples was reduced by the Trichoderma treatment by up to 92% as compared to the untreated control. A rapid decline of the disease was observed in soil fromT. harzianum treated plots, successively planted with bean seedlings. More isolates ofTrichoderma sp. antagonistic toR. solani, were found in the infested field as compared to the non infested one.Trichoderma harzianum treated plants, transferred to the commercial field gave a 21–37% increase in early yield of strawberries. A combined treatment in the nursery and in the fruiting field resulted in a 20% yield increase as compared to control plots.     

Effect of Abiotic Stress on Phosphate Solubilization by Biocontrol Fungus <Emphasis Type="Italic">Trichoderma</Emphasis> sp.

This study was undertaken to explore the role of Trichoderma sp. in phosphate (P) solubilization and antagonism against fungal phytopathogens. All fungal isolates (SE₆, KT₆, KT₂₈, and BRT₁₁) and a standard culture of T. harzianum (Th-std) were able to antagonize two fungal phytopathogens (Sclerotium rolfsii and Rhizoctonia solani) of chickpea (Cicer arietinum L.) wilt complex. Transmission electron microscopic studies (TEM) further confirmed ultra-cytological changes in the sclerotia of S. rolfsii parasitized by Trichoderma sp. All fungal cultures exhibited production of NH₃ and siderophore, but only BRT₁₁, SE₆, and Th-std could produce HCN. Among all the cultures tested, isolate KT₆ was found to be most effective for solubilization of ferric phosphate releasing 398.4 μg ml⁻¹ phosphate while isolates BRT₁₁ and SE₆ showed more potential for tricalcium phosphate (TCP) solubilization releasing 449.05 and 412.64 μg ml⁻¹ phosphate, respectively, in their culture filtrates. Part of this study focused on the influence of abiotic stress conditions such as pH, temperature, and heavy metal (cadmium) on phosphate (TCP) solubilizing efficiency. Two selected cultures KT₆ and T. harzianum retained their P solubilizing potential at varying concentrations of cadmium (0–1000 μg ml⁻¹). Isolate KT₆ and standard culture of T. harzianum released 278.4 and 287.6 μg ml⁻¹ phosphate, respectively, at 1000 μg ml⁻¹cadmium. Maximum solubilization of TCP was obtained at alkaline pH and at 28°C temperature. Isolate BRT₁₁ was found most alkalo-tolerant releasing 448.0 μg ml⁻¹ phosphate at pH 9.     

Biological control of onion neck rot (Botrytis aclada): Protection of wounds made by leaf topping

The efficacy of fungal antagonists in protecting onions from neck rot caused by Botrytis aclada was investigated. Leaf wounds made by topping of onions during harvest, which are considered as important entrance sites for B. aclada, were treated with conidial suspensions (5 × 10⁷ conidia ml^‐1) of antagonists. In field experiments with artificial inoculation with conidia of B. aclada, applications of Trichoderma viride during harvest reduced the incidence of neck rot, assessed after three months’ storage of the onions at 9° C, from 35% to 24% in 1989 and from 28% to 18% in 1990, when onions initially had been stored under favourable conditions for fungal development. Comparable results were obtained with T. hamatum and Gliocladium roseum. A bioassay based on wound treatment of detached onion leaves was developed to select further antagonists. From 40 candidate antagonists tested, 20 strains gave similar or better control than the strain of T. viride applied in the field experiments. Effective antagonists could be found amongst strains of Trichoderma spp. Gliocladium spp. and Penicillium spp. as well as amongst fungi such as Aureobasidium pullulans and yeasts isolated from green leaves of onion or rye.     

Effect of fungal species involved in the olive fruit rot on the qualitative properties of olive oil

Olive oil is the most important product of olive fruits with worldwide consumption, particularly in Mediterranean countries. Olive oil is generally extracted mechanically from the olive fruits. Some biotic and abiotic factors may affect the quality of oil extracted from olive fruit. Contamination with fungi during growth period in the garden or during the conservation of the harvested crop under storage condition may leave negative effects on the quality of olive oil. However, there is no data available on the effects of fungal infections on qualitative properties of olive oil in Iran. In the present study effects of several fungal groups previously isolated from rotten olive fruit in olive orchards including Alternaria alternata, Fusarium nygamai, Aspergillus ochraceus, Arthrinium phaeospermum, Cladosporium cladosporioides, Aureobasidium pullulans, Epicoccum nigrum, Penicillium expansum, Truncatella angustata, Trichothecium roseum and Trichoderma harzianum were evaluated on some qualitative properties of olive oil, under laboratory condition on two olive cultivars (Zard & Roghani). For this purpose fresh and healthy fruits of olive, were surface sterilisation with 96% ethanol and rinsed with sterile water and then inoculated with each of the fungal groups separately using spore suspension (10^6?ml^?1). The experiment was carried out in two replicates for each treatment (fungal isolates). The results of this study revealed that fungal infection caused significant increase in the extracted oil acidity and peroxide values. However, there was no significant difference in the acidity and peroxide values among different treatments (fungal isolates).     

Effects of Thymus kotschyanus var. glabrescens Boiss. extract on mitomycin-C induced chromosomal aberrations and sister chromatid exchanges in human lymphocytes

In this investigation, clastogenic effects of Thymus kotschyanus var. glabrescens Boiss. extract (TE) and anticlastogenic effects of this extract against Mitomycin C (MMC) induced chromosome damage have been evaluated in human peripheral blood lymphocytes in vitro. Two series of experiments were conducted. In the first, only 10⁻⁵, 10⁻⁴, 10⁻³ and 10⁻² μl ml⁻¹ concentrations of TE were used for 48 h to detect potential clastogenicity. In the second, MMC (0.38 μg ml⁻¹) plus 10⁻⁵, 10⁻⁴, 10⁻³ and 10⁻² μl ml⁻¹ concentrations of TE were used for 48 h to determine anticlastogenic effects. TE did not increase sister chromatid exchanges (SCEs) (except 10⁻² μl ml concentration) and chromosome aberrations (CAs) significantly compared with negative and solvent controls. However, it decreased the frequency of MMC induced chromosome aberrations. Decreasing was significant at 10⁻⁴, 10⁻³ and 10⁻² μl ml⁻¹ concentrations. On the other hand, TE significantly increased MMC-induced SCEs for all treatment groups compared with positive control.     

Pullulan production from deproteinized whey by Aureobasidium pullulans

Aureobasidium pullulans P56 was investigated using an adaptation technique and a mixed culture system. The adaptation of A. pullulans and the mixed cultures of A. pullulans and/or Lactobacillus brevisX20, Debaryomyces hansenii 194 and Aspergillus niger did not increase the production of polysaccharide. Enzymic hydrolysis of lactose in deproteinized whey gave a higher polysaccharide concentration and polysaccharide yield than acidic hydrolysed lactose. Maximum polysaccharide concentration (11.0 ± 0.5 g L⁻¹), biomass dry weight (10.5 ± 0.4 g L⁻¹), polysaccharide yield (47.2 ± 1.8%) and sugar utilization (93.2 ± 2.8%) were achieved using enzyme-hydrolysed whey (pH 6.5) containing 25 g L⁻¹ lactose and supplemented with K₂HPO₄ 0.5%, L-glutamic acid 1%, olive oil 2.5%, and Tween 80 0.5%. In this case the pullulan content of the crude polysaccharide was 40%. Received 16 December 1997/ Accepted in revised form 12 March 1999     

The Role of Sucrose in Regulation of Trunk Tissue Development in Betula pendula Roth

Comparative ultrastructural analysis of the conducting and non-conducting phloem cells in the common straight-grained silver birch (Betula pendula var. pendula) and the Karelian birch (B. pendula var. carelica) with abnormal patterned wood was carried out, leading to the conclusion that there is an elevated sucrose content in the conducting phloem of the Karelian birch. A connection between sucrose levels and formation of abnormalities in the development of conducting tissues in the Karelian birch trunk was surmised. Experiments in which exogenous sucrose was applied to the silver birch trunk tissues have demonstrated the effects of different sucrose concentrations (0 g L⁻¹, 10 g L⁻¹, 25 g L⁻¹, 50 g L⁻¹, 100 g L⁻¹) on the formation of xylem and phloem structural elements, and they yielded the types of tissue development that correspond to the abnormal tissue development in the Karelian birch trunk.     

Effect of antimicrobial activity of Melaleuca alternifolia essential oil on antagonistic potential of Pleurotus species against Trichoderma harzianum in dual culture

Melaleuca alternifolia (tea tree) essential oil was investigated for its “in vitro” ability to control Trichoderma harzianum, a fungal contaminant that causes extensive losses in the cultivation of Pleurotus species. The antifungal activity of M. alternifolia essential oil and antagonist activities between Pleurotus species against three T. harzianum strains were studied in dual-culture experiments on an agar-based medium in which different concentrations of essential oil were incorporated. M. alternifolia essential oil at a concentration of 0.625 μL/mL, inhibited T. harzianum mycelial growth by 5.9–9.0%, depending on the strain. At the same concentrations P. ferulae and P. nebrodensis stimulated mycelial growth by 5.2–8.1%. All strains of T. harzianum were antagonistic to the Pleurotus species in the control. When essential oil was added to the substrate cultural, the antagonistic activity of T. harzianum against the Pleurotus species was weak (0.0625 μL of essential oil) or non-existent (0.125 μL of essential oil). M. alternifolia essential oil could be an alternative to the synthetic chemicals that are currently used to prevent and control T. harzianum in mushroom cultivation.     

The performance of fungal xylan-degrading enzyme preparations in elemental chlorine-free bleaching for Eucalyptus pulp

Cellulase-free xylan-degrading enzyme preparations from Acrophialophora nainiana, Humicola grisea var. thermoidea and two Trichoderma harzianum strains were used as bleaching agents for Eucalyptus kraft pulp, prior to a chlorine dioxide and alkaline bleaching sequence. In comparison to the control sequence (performed without xylanase pretreatment), the sequence incorporating enzyme treatment was more effective. Removal of residual lignin was indicated by a reduction in kappa number. Overall, enzyme preparations from T. harzianum were marginally more effective in reducing pulp viscosity and chlorine chemical consumption and improving the brightness of the kraft pulp. However, the highest reduction in pulp viscosity was mediated by the xylanase preparation from A. nainiana. Xylanase pretreatment compares very favorably with that of chemical pulping. Journal of Industrial Microbiology & Biotechnology (2002) 28, 204–206 DOI: 10.1038/sj/jim/7000227 Received 27 April 2001/ Accepted in revised form 03 November 2001     

Fungicides and some biological controller agents effects on the growth of fusarium oxysporum causing paprika wilt: Wirkung von fungiziden und einigen biologischen kontrollwirkstoffen auf das wachstum des paprikawelke verursachenden fusarium oxysporum

Soil samples from both healthy and diseased paprika roots were tested to identify their mycoflora. Thirty-one species belonging to 16 genera were collected from rhizosphere and rhizoplane samples. The most frequently isolated fungi were Aspergillus flavus, A. niger, A. terreus, Fusarium oxysporum, Penicillium jensenii and Trichoderma harzianum. Fusarium oxysporum was the most common Fusarium species in the rhizoplane samples of diseased roots and identification was confirmed by RAPD-PCR technique. Trichoderma harzianum, T. pseudokoningii and Glioclaium roseum were chosen to study their biological control efficiency against Fusarium oxysporum. These fungal species reduced the percentage of seedling infection to 25, 40 and 50%, respectively. With the increasing of fungicide (Folicur and Ridomil) doses the dry weight of F. oxysporum decreased. Also, the increasing of fungicide dose lead to a slight decrease in the dry weight of T. harzianum, T. pseudokoningii and Glioclaium roseum.     

Biotransformation of steriodal saponins in Dioscorea zingiberensis C. H. Wright to diosgenin by Trichoderma harzianum

Diosgenin is an important starting material in the steroidal hormone industry. Traditionally, diosgenin is mainly produced by acid hydrolysis of Dioscorea zingiberensis C. H. Wright (DZW) tubers. This method yields numerous byproducts that can cause serious pollution. In this study, diosgenin was obtained by biotransformation of steroidal saponins in DZW afforded by Trichoderma harzianum CGMCC 2979. The medium was optimized for maximum diosgenin production. The addition of phosphate buffer, surfactant Tween-85, and Fe²⁺ increased the yield of diosgenin by 50.28%, 33.35%, and 22.07%, respectively. The optimum medium obtained by response surface methodology was composed of 60 mmol l⁻¹ phosphate buffer, 0.07% (w/v) Tween-85, and 0.93 mmol l⁻¹ Fe²⁺. Under these conditions, a maximum diosgenin yield of 30.05 ± 0.59 mg g⁻¹ was achieved, which was slightly higher than that obtained from traditional acid hydrolysis. By hydrolyzing the un-transformed steroidal saponins after biotransformation, the total diosgenin yield increased by 35% compared to traditional method. Moreover, chemical oxygen demand and residual reduced sugar in the wastewater produced by this integrated process were only 3.72% and 0.3%, respectively, that of the traditional acid hydrolysis method.     

Effects of Progesterone, β-Estradiol,and Androsterone on the Changes of Inorganic Element Content in Barley Leaves

The present study was performed to determine the changes in inorganic element content in barley leaves of mammalian sex hormones (MSH). Barley leaves were sprayed with 10⁻⁴, 10⁻⁶, 10⁻⁹, 10⁻¹², 10⁻¹⁵ M concentrations of progesterone, β-estradiol, and androsterone at 7th day after sowing. The plants were harvested at the end of 18 days after treatment with MSH solutions. The inorganic element concentrations were determined using wavelength dispersive X-ray fluorescence spectroscopy technique. Although the all MSH concentrations significantly (p < 0.05) increased the concentrations of calcium, magnesium, phosphorus, sulfur, copper, manganese, aluminum, zinc, iron, potassium, and chlorine, it decreased those of sodium concentration in barley leaves. The maximum changes in the element concentrations were obtained at 10⁻⁹ M for plant leaves treated with progesterone, 10⁻⁶ M for plant leaves treated with β-estradiol and androsterone. The present study elucidated that MSH significantly (p < 0.05) affected the inorganic element concentrations in barley leaves.     

Fungal Biodegradation and Detoxification of Cork Boiling Wastewaters

The ability of several fungal strains to degrade and to detoxify cork boiling wastewaters was investigated. The fungal strains used in this work were Sporothrix sp., Trichoderma koningii, Chrysonilia sitophila and Penicillium glabrum isolated from cork bark as well as Fusarium flocciferum and Phanerochaete chrysosporium. The results obtained in the degradation experiments carried out with each fungus showed that all fungi display similar abilities, with a chemical oxygen demand reduction of 54.2 % (± 4.7 %) attained within five days of incubation. F. flocciferum presented the highest value for the reduction of chemical oxygen demand of 62 %. In addition, a rise in pH values of around 3 units was detected with all the strains, except for Penicillium glabrum. Toxicity tests performed on Vibrio fischeri revealed that fungal treatment of the wastewaters causes the complete loss of toxicity in the cases of Sporothrix sp., T. koningii, P. chrysosporium and F. flocciferum. The other two tested strains were also able to detoxify the raw wastewaters, causing a ten‐fold decrease in toxicity. The results obtained in sequential biodegradation experiments with different pairs of fungi showed that although the increment in the COD reduction did not exceed 10 %, an important reduction in toxicity and a pH rise were attained.     

Determination of the growth and solubilization capabilities of <Emphasis Type="Italic">Trichoderma harzianum</Emphasis> T1

The growth capability of Trichoderma harzianum Rifaii Tl was tested on Malt Extract and Czapeks Dox agar containing different concentrations of Cu²⁺, Zn²⁺, Mn²⁺, Fe²⁺ and Ca²⁺. The T. harzianum Tl isolate was observed to produce mycelia and spores in various mineral-containing media. It showed the lowest tolerance to Ca²⁺ and the highest tolerance to Fe²⁺. Solubilization capability of T. harzianum Tl for some insoluble minerals via acidification of medium has been tested on MnO₂, CuO, Fe₂O₃ and metallic Zn. T. harzianum Tl was able to solubilize MnO₂ and metallic Zn in a liquid medium.