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1.
World Journal of Microbiology and Biotechnology - Industrialisation, directly or indirectly, exposes humans to various xenobiotics. The increased magnitude of chemical pesticides and toxic heavy...  相似文献   

2.
The objective of this research was to evaluate Trichoderma harzianum strain T22 as a biocontrol agent of collar and root rot caused by different Calonectria pauciramosa isolates. Thus, the microsclerotia-forming ability and virulence of twenty C. pauciramosa isolates were assessed. Microsclerotia production varied partially among the isolates and dual culture with T22 on carnation leaf agar revealed isolates with both high and low microsclerotia-forming ability. Inoculation tests on red clover (Triflolium pratense) demonstrated its susceptibility to the pathogen. On red clover, the degree of virulence and T22 effects in controlling infections were highly variable among the isolates tested. A nursery trial performed on Feijoa sellowiana seedlings confirmed previous results, clearly indicating virulence variability among C. pauciramosa isolates. For three isolates tested in nursery trial, T22 effectiveness in controlling infection was inversely related to their degree of virulence. Overall, T. harzianum strain T22 showed good antagonist activity in reducing microsclerotia production on carnation leaf and the incidence and severity of collar and root rot on both selected hosts. This data could be crucial in developing integrated pest management strategies in ornamental plant nurseries.  相似文献   

3.
To ensure proper use of Trichoderma harzianum in agriculture, accurate data must be obtained in population monitoring. The effectiveness of qRT-PCR to quantify T. harzianum in different growing media was compared to the commonly used techniques of colony counting and qPCR. Results showed that plate counting and qPCR offered similar T. harzianum quantification patterns of an initial rapid increase in fungal population that decreased over time. However, data from qRT-PCR showed a population curve of active T. harzianum with a delayed onset of initial growth which then increased throughout the experiment. Results demonstrated that T. harzianum can successfully grow in these media and that qRT-PCR can offer a more distinct representation of active T. harzianum populations. Additionally, compost amended with T. harzianum exhibited a lower Fusarium oxysporum infection rate (67%) and lower percentage of fresh weight loss (11%) in comparison to amended peat (90% infection rate, 23% fresh weight loss).  相似文献   

4.
Four isolates of Trichoderma harzianum (ThN3, Th11, Th12 and Th16) were selected for their ability to control the in vitro development of the tomato root pathogen Pyrenochaeta lycopersici. Analysis of the mechanisms involved in biocontrol showed that the formation of non-volatile metabolites appears to be one of those involved in biocontrol of P. lycopersici by all T. harzianum isolates tested. Nevertheless, the higher secretion of chitinases, both in number of isoenzymes and activity by the Th11 strain, correlated well with its higher ability to control this agent in laboratory and greenhouse experiments as compared to the other T. harzianum isolates tested. The secretion of beta-1,3-endoglucanases and/or proteases appeared to have less significance than endochitinases in the biological control of P. lycopersici.  相似文献   

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6.
The purpose of this study was to investigate the effects of isolates T22, T9 and T6 of Trichoderma harzianum on isolate F42 of Fusarium oxysporum f. sp. radicis-cucumerinum. The effect of T. harzianum isolates on controlling disease was examined under greenhouse conditions. Results showed that these three isolates, respectively, had the high effect on inhibition of pathogen growth. In examining the severity of disease in the greenhouse, it was found that isolate T22 had the greatest effect on controlling the pathogen. The results of volatile compounds showed that these isolates, respectively, were effective in reducing mycelial growth of isolate F42. The highest peroxidase activity was observed on the fourth day in isolate T6 and the highest phenylalanine ammonia lyase enzyme activity was observed on the fifth day in isolate T22. Based on the results, isolate of T22 showed the greatest effect on the induction of resistance against F42 and may be a successful agent for biological control of root and stem rot of cucumber.  相似文献   

7.
Three Trichoderma harzianum isolates viz., Th-Sks, Th-Ke and Th-Ar collected from respective states of India viz., Rajasthan, Kerala and Andhra Pradesh were evaluated for the management of six fungal diseases namely damping off, Fusarium wilt, Rhizoctonia wilt, early leaf spot, late blight and Septoria leaf spot in tomato. During in vitro analysis, T. harzianum isolates inhibited the pathogens’ growth. Isolate Th-Sks was the most virulent antagonist against all the test pathogens and exhibited maximum of 79.47% growth inhibition of Phytophthora infestans. Isolate Th-Sks proved most effective at suppression efficacy in the range of 95–100% and 91–100% against all diseases under glasshouse and in the field conditions, respectively. Tomato seeds treatment with isolate Th-Sks also promoted plant height (78.23 cm) and fruits yield (290 g/plant) during field trial and data were found to be not-significantly different from other isolates. Thus, it is concluded that isolate Th-Sks can be utilised as a biocontrol agent for management of fungal diseases in tomato.  相似文献   

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9.
The scarcity of fresh water in the Mediterranean region necessitates the search for halotolerant agents of biological control of plant diseases that can be applied in arid-zone agriculture irrigated with saline water. Among 29 Trichoderma strains previously isolated from Mediterranean Psammocinia sp. sponges, the greatest number of isolates belong to the Trichoderma longibrachiatum-Hypocrea orientalis species pair (9), H. atroviridis/T. atroviride (9), and T. harzianum species complex (7), all of which are known for high mycoparasitic potential. In addition, one isolate of T. asperelloides and two putative new species, Trichoderma sp. O.Y. 14707 and O.Y. 2407, from Longibrachiatum and Strictipilosa clades, respectively, have been identified. In vitro salinity assays showed that the ability to tolerate increasing osmotic pressure (halotolerance) is a strain- or clade-specific property rather than a feature of a species. Only a few isolates were found to be sensitive to increased salinity, while others either were halotolerant or even demonstrated improved growth in increasingly saline conditions. In vitro antibiosis assays revealed strong antagonistic activity toward phytopathogens due to the production of both soluble and volatile metabolites. Two marine-derived Trichoderma isolates, identified as T. atroviride and T. asperelloides, respectively, effectively reduced Rhizoctonia solani damping-off disease on beans and also induced defense responses in cucumber seedlings against Pseudomonas syringae pv. lachrimans. This is the first inclusive evaluation of marine fungi as potential biocontrol agents.  相似文献   

10.
Spores of the biocontrol agent Trichoderma harzianum P1 produced in liquid media and harvested in the stationary sporulation stage SSS (after 60?h), had higher viability after slow (>4×) and fast drying (>12×) than their counterparts harvested in the exponential sporulation stage, ESS (after 30?h). The trehalose content of SSS spores was almost 20× higher than that of ESS spores (0.16 vs. 3.4?mg/100?mg, respectively). Heat shock (40?°C?×?90?min) effectively increased the trehalose content 2.5× with respect to untreated SSS spores. The trehalose content achieved in heat-treated SSS spores was almost 60% higher than the maximum reached by holding the spores under water-stress at 97% relative humidity prior to drying.  相似文献   

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12.
The mycoparasite Trichoderma harzianum has been extensively used in the biocontrol of a wide range of phytopathogenic fungi. Hydrolytic enzymes secreted by the parasite have been directly implicated in the lysis of the host. Dual cultures of Trichoderma and a host, with and without contact, were used as means to study the mycoparasitic response in Trichoderma. Northern analysis showed high-level expression of genes encoding a proteinase (prb1) and an endochitinase (ech42) in dual cultures even if contact with the host was prevented by using cellophane membranes. Neither gene was induced during the interaction of Trichoderma with lectin-coated nylon fibres, which are known to induce hyphal coiling and appressorium formation. Thus, the signal involved in triggering the production of these hydrolytic enzymes by T. harzianum during the parasitic response is independent of the recognition mediated by this lectin-carbohydrate interaction. The results showed that induction of prb1 and ech42 is contact-independent, and a diffusible molecule produced by the host is the signal that triggers expression of both genes in vivo. Furthermore, a molecule that is resistant to heat and protease treatment, obtained from Rhizoctonia solani cell walls induces expression of both genes. Thus, this molecule is involved in the regulation of the expression of hydrolytic enzymes during mycoparasitism by T. harzianum.  相似文献   

13.
In order to identify a specific marker for T. harzianum AS12-2, a strain capable of controlling rice sheath blight caused by Rhizoctonia solani, UP-PCR was performed using five universal primers (UP) both separately and in pairwise combinations. The application of two UP primers resulted in the amplification of unique fragments from the genomic DNA of T. harzianum AS12-2, clearly distinguishing it from other Trichoderma strains. The unique fragments had no significant sequence homology with any other known sequence available in databases. Based on the sequences of the unique fragments, 14 oligonucleotide primers were designed. Two primer sets amplified a fragment of expected size from the DNA of strain T. harzianum AS12-2 but not from any other examined strains belonging to T. harzianum, to other Trichoderma species assayed, or to other common fungi present in paddy fields of Mazandaran province, Iran. In conclusion, SCAR (sequence characterized amplified regions) markers were successfully identified and rapid, reliable tools were provided for the detection of an effective biocontrol Trichoderma strain, which can facilitate studies of its population dynamics and establishment after release into the natural environment.  相似文献   

14.
Trichoderma harzianum is a soil-borne filamentous fungus that exhibits biological control properties because it parasitizes a large variety of phytopathogenic fungi. In this study the SOD gene was successfully transferred into the bio-control fungus Trichoderma harzianum with an efficiency of 60–110 transformants per 107 spores by using Agrobacterium tumefaciens-mediated transformation. Putative transformants were analyzed to test the transformation by the southern blot. Antifungal activities of the transformants were examined under abiotic stresses. The transformants were exposed to 40°C for three days and 2 mol/l NaCl at 27°C for 5–10 days to assay antifungal activities with Sclerotinia sclerotiorum. The inhibition rates of the transformants, comparing to Trichoderma harzianum with no SOD gene transferred, were respectively 83.96% after 40°C and 60.13% after 2 mol/l NaCl. The results showed that the SOD transformants had significantly higher resistance to heat and salt stress.  相似文献   

15.
The influence of pH, carbon:nitrogen (C:N) ratio, carbon content and harvesting time on spore attributes of the biocontrol agent Trichoderma harzianum was evaluated. The effect of these culture parameters on viability, shelf-life and ultrastucture was also assessed. pH was a key parameter to manipulate for both growth and sporulation, while carbon concentration and C:N ratio strongly affected spore production time. At fixed pH, the C:N ratio had a limited influence on production yield, but was critical for spore shelf-life. The highest spore longevity was found in a medium with a C:N ratio of 14 and a pH of 7.0, when most resulting spores were still alive after 45 d storage. These spores also remained viable during storage under a broad range of relative humidities, indicating that they would be more sustainable in the field.  相似文献   

16.
Two biological control agents, Pythium nunn and Trichoderma harzianum isolate T-95, were combined to reduce Pythium damping-off of cucumber in greenhouse experiments lasting 3–4 weeks. T. harzianum T-95, a rhizosphere competent mutant, was applied to seeds and P. nunn was applied to pasteurized and raw soils naturally and artificially infested with Pythium ultimum. Some treatments were also amended with bean leaves to enhance the activity of P. nunn. The biological control of Pythium damping-off was evaluated in a Colorado soil (Nunn sandy loam) and an Oregon soil mix, which were replanted twice after 2 and 3 months. Interactions between P. nunn and T-95 were detected in the Colorado but not the Oregon soil. No consistent evidence of antagonism between P. nunn and T. harzianum was seen, and significant interactions were detected in the Colorado, but not the Oregon soil. In the first planting of some treatments, the combination of P. nunn and T. harzianum gave greater control of damping-off than either applied alone. P. nunn was most effective in soils that were pasteurized or amended with bean leaves. T. harzianum controlled Pythium damping-off in the Colorado, but not the Oregon soil. In both soils, disease declined over time in treatments amended with bean leaves but without P. nunn or T. harzianum added. This suppression was greater in the Colorado soil, which contained an indigenous population of P. nunn. This work demonstrates that two compatible biological control agents can be combined to give additional control of a soil-borne plant pathogen.  相似文献   

17.
Trichoderma harzianum, isolate T 01-22, was cultured on either sorghum grains, ground mesocarp fibre of oil-palm or oil-palm shell, both amended with urea fertilizer (100:1, w/w). T. harzianum cultured on ground mesocarp fibre was then used to coat seeds of Chinese kale (Brassica alboglabra Bailey) to control damping-off of seedlings caused by Pythium aphanidermatum. Biomass of T. harzianum cultured on ground mesocarp fibre of oil-palm was more effective than Captan and Benomyl, but less effective than Metalaxyl, in controlling damping-off of Chinese kale seedlings. Viability of T. harzianum growing on sorghum grains was reduced significantly during 7 months storage, followed by that of T. harzianum cultured on ground mesocarp fibre and oil-palm shell, both amended with urea fertilizer (46-0-0) at 100:1 (w/w).  相似文献   

18.
Filamentous fungi are very promising organisms in both the control and the reduction of the amount of heavy metal released by human and industrial activities. In particular, Trichoderma harzianum demonstrated to be tolerant towards different heavy metals, such as mercury and cadmium, even though the mechanism underlying this tolerance is not fully understood. By using a particular strategy of the suppression subtractive hybridization technique, we were able to identify in the strain IMI 393899 of T. harzianum eight different genes up-regulated in the presence of mercury II with respect to cadmium. Among the genes identified, a possible role in the tolerance mechanism could be envisaged for hydrophobin, due to its ability to dissolve hydrophobic molecules into aqueous media. We also show that IMI 393899 grows at the same rate of control culture in the presence of mercury I and that all eight genes isolated were also up-regulated in this condition.  相似文献   

19.
Trichoderma harzianum is a soil-borne filamentous fungus that exhibits biological control properties because it parasitizes a large variety of phytopathogenic fungi. The production of hydrolytic enzymes appears to be a key element in the parasitic process. Among the enzymes released by Trichoderma, the aspartic proteases play a major role. A gene (SA76) encoding an aspartic protease was cloned by 3' rapid amplification of cDNA ends from T. harzianum T88. The coding region of the gene is 1,593 bp long, encoding a polypeptide of 530 amino acids with a predicted molecular mass 55 kDa and a pI of 4.5. The catalytic aspartic residues characteristic of aspartic proteases are conserved with an active-site motif (DSG); however, the DSG in the N-terminal lobe is unusual in that Ser replaced Thr. Northern blot analysis indicated that SA76 was induced in response to different fungal cell walls. Aspartic protease SA76 was expressed in Saccharomyces cerevisiae under control of the GAL1 promoter. The enzyme activity culminates (10.5 U mL(-1)) 72 h after induction with galactose. The temperature optimum of the enzyme was 45 degrees C and its pH optimum was 3.5. The culture supernatant of the S. cerevisiae strain that expressed the aspartic protease SA76 was able to inhibit the growth of five phytopathogenic fungi. The inhibition of mycelial growth varied between 7% and 38%.  相似文献   

20.
Chocolate spot disease is the most prevalent and important disease in the major faba bean growing regions in the world. Different concentrations of the abiotic inducer (0.3 and 0.5 mM benzothiadiazole) and the biotic inducer (1 × 107 and 2 × 107 spore/ml Trichoderma harzianum) were used alone or in combination to study their efficiency against faba bean chocolate spot disease caused by Botrytis fabae and Botrytis cinerea and their effect on some chemical analyses (phenylalanine ammonia lyase activity, total flavonoids and peroxidase isozymes, pectin and lignin content and total chlorophyll content). Application of the tested inducers as foliar treatment significantly reduced the severity of chocolate spot disease as compared with untreated infected plants. The reduction in disease severity was associated with a gradual increase in phenylalanine ammonia lyase activity. Maximum increase was recorded at 72 h after inoculation with B. fabae and B. cinerea. In addition, the levels of flavonoids in induced infected leaves recorded a sharp increase at 24 h after inoculation with B. fabae or B. cinerea. Also, pectin and lignin contents in the cell wall of induced infected plants were significantly increased as compared with untreated infected plants. Beside the induction of resistance, the tested inducers markedly increased total chlorophyll content in treated infected plants as compared with untreated infected plants. Isozymes analysis revealed that new peroxidase bands were induced only in treated faba bean leaves in response to infection with B. fabae or B. cinerea.  相似文献   

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