Asperellum Strain Research Articles

Characterization of Three Different Chitinase Genes from Trichoderma asperellum Strain Ta13

Trichoderma asperellum is well-known for the biocontrol activity against diverse plant pathogens. Various cell wall degrading enzymes viz. chitinases, glucanases and proteases are produced by T. asperellum against plant pathogens. Chitinases are the main class of enzyme that operate against fungal pathogen cell wall. In the present study, a total of three different chitinase genes viz. Chit42, Chit2 and ChitB were cloned and characterized from T. asperellum strain Ta13. The phylogenetic analysis of three different chitinase gene sequences formed separate cluster among themselves. Sequence similarity analysis of the nucleotide and amino acid sequences showed the uniqueness and distinct nature of the amplified chitinase genes. Maximum chitinase activity (93.5 mg/ml NAGA concentration) revealed that Ta13 is an efficient chitinase producer which acts against agriculturally important pathogens.

Characterization of volatile secondary metabolites from Trichoderma asperellum

Many Trichoderma isolates are known to secrete several secondary metabolites with different biological activities towards plants and other microbes. The production of such compounds varies according to the strain. In the present study, volatile secondary metabolites from the culture filtrate of Trichoderma asperellum strain were characterized using Gas chromatography-Mass spectrometry (GC-MS). Results of GC-MS detected 43 secondary metabolites in the T. asperellum strain including many important volatile secondary metabolites such as 1,2-Benzenedicarboxylic acid, 2-butoxy-2-oxoethyl butyl ester (peak area-3.59%), 1,2-Benzenedicarboxylic acid dibutyl ester (peak area-2.02 %), 2H-Pyran-2-one (peak area-66.63 %), palmitic acid (peak area-2.86 %), several phenolic isomers, methyl cyclohexane etc., all reportedly having effective pesticidal activity. The results indicated that these secondary metabolites could be useful for biological control applications of T. asperellum strain against diverse plant pathogens.

Increased rhizosphere populations of Trichoderma asperellum strain T34 caused by secretion pattern of root exudates in tomato plants inoculated with Botrytis cinerea

Root exudates secreted from plants can modify rhizosphere microbiota by enhancing or inhibiting the growth of biological control agents (BCAs) and/or pathogens. Similarly, microorganisms can modify the secretion of plant root exudates. The aim of this study was to analyse the effect of a Botrytis cinerea leaf infection on the secretion of tomato root exudates and on the populations of the BCA Trichoderma asperellum strain T34 (T34). This study found that the secretion pattern of root exudates in tomato plants was influenced by B. cinerea infection in plant leaves. An increase in the levels of gluconic acid was observed, while levels of sucrose and inositol decreased. A decrease in the severity of B. cinerea by the induction of systemic resistance triggered by T34 was also observed. Tomato plants infected with B. cinerea maintained the populations of T34 in the roots, while populations of T34 decreased in plants not inoculated with the pathogen. Samples exposed to media containing gluconic acid (as the only carbon source or at the same concentration found in roots exudates) saw an increase in the in vitro growth of T34 compared to media without gluconic acid. In conclusion, a change in the secretion pattern of root exudates caused by B. cinerea, together with the enhanced growth of T34 in the presence of gluconic acid, indicates the existence of leaf to root communication. The result of this is enhanced populations of T34, and in turn induced disease resistance and a consequential reduction in disease severity.

Trichoderma asperellum strains confer tomato protection and induce its defense-related genes against the Fusarium wilt pathogen

Fusarium wilt of tomato (FW) caused by Fusarium oxysporum f. sp. lycopersici (FOL) is a major challenge for tomato production worldwide. For sustainable management of FW, the potential of five strains of Trichoderma asperellum was evaluated under greenhouse conditions. The results indicated that FOL infected plants treated with T. asperellum strains significantly reduced disease incidence and severity compared with FOL-only infected plants. The reduction of wilt disease on plants treated with T. asperellum strains was accompanied by a significant reduction in FOL populations in tomato stems and rhizosphere. Moreover, the application of T. asperellum promoted tomato plant growth irrespective of the presence or absence of FOL. Two strains of T. asperellum (TS-12 and TS-39) that showed the best performance in minimizing disease development and increases in plant growth parameters were selected for elucidating their ability in triggering tomato defense mechanisms. The expression levels of defense-related genes, chitinase (SlChi3), β-1,3-glucanase (SlGluA) and PR-1 (SlPR-1a) were significantly increased in the stems and roots of Trichoderma treated, FOL infected plants, compared with FOL-only infected ones. These results indicate that the application of T. asperellum strains TS-12 and TS-39 can be used as an alternative strategy to manage FW through their antagonistic activities and abilities to induce systemic resistance.

Trichoderma asperellum is effective for biocontrol of Verticillium wilt in olive caused by the defoliating pathotype of Verticillium dahliae

Verticillium wilt caused by a highly virulent, defoliating (D) pathotype of Verticillium dahliae is threatening olive production in Spain and other Mediterranean countries. This disease must be managed by an integrated strategy, in which biocontrol agents can play an important role. We have investigated the potential of Trichoderma asperellum strains for antagonism against V. dahliae and suppression of Verticillium wilt of olive caused by the D pathotype. First, we tested the antagonistic potential of T. asperellum strains Bt2, Bt3 and T25 against six V. dahliae isolates, four of the D and two of the nondefoliating (ND) pathotypes, in different in vitro assays. All T. asperellum strains overgrew the colonies of all V. dahliae isolates to a similar extent. However, extracellular compounds from strains Bt3 and T25 showed higher anti-V. dahliae activities than those of Bt2 in membrane assays. Also, growth of Bt2 was reduced by ND V. dahliae whereas that of Bt3 and T25 was not affected by V. dahliae-secreted compounds. In planta assays using strains Bt3 and T25, and ’Picual’ olive plants, showed that the two T. asperellum strains significantly reduced the severity of symptoms and the standardized area under the disease progress curve caused by highly virulent D V. dahliae, but not the final disease incidence. Strain T25 significantly increased growth of ‘Picual’ plants and displayed higher ability for colonizing the olive rhizosphere and establishing endophytic infection in olive roots than Bt3.

Antagonistic and Biocontrol Potential of Trichoderma asperellum ZJSX5003 Against the Maize Stalk Rot Pathogen Fusarium graminearum

The efficacy of seven strains of Trichoderma asperellum collected from the fields in Southern China was assessed against Fusarium graminearum (FG) the causal agent of corn stalk rot of maize were in vitro for their antagonistic properties followed by statistical model of principal compound analysis to identify the beneficial antagonist T. asperellum strain. The key factors of antagonist activity were attributed to a total of 13 factors including cell wall degrading enzymes (chitnase, protease and β-glucanases), secondary metabolites and peptaibols and these were analyzed from eight strains of Trichoderma. A linear regression model demonstrated that interaction of enzymes and secondary metabolites of T. asperellum strain ZJSX5003 enhanced the antagonist activity against FG. Further, this strain displayed a disease reduction of 71% in maize plants inoculated with FG compared to negative control. Pointing out that the T. asperellum strain ZJSX5003 is a potential source for the development of a biocontrol agent against corn stalk rot.

Compost from forest cleaning green waste and Trichoderma asperellum strain T34 reduced incidence of Fusarium circinatum in Pinus radiata seedlings

Fusarium circinatum is a quarantine pathogen in numerous countries that causes important economic losses in forest nurseries and mature pine trees. Alternatives to chemical control of plant diseases such as suppressive composts and the use of biological control agents in growth media can reduce the incidence and spread of disease. In this work, four gorse composts obtained from forest cleaning green wastes and reference compost prepared from the organic fraction of solid urban waste were studied as environmentally sustainable peat substitutes. Their ability to suppress the effects of mating types M1 and M2 of the pathogen F. circinatum on Pinus radiata was evaluated in the presence or absence of the biocontrol agent Trichoderma asperellum strain T34. One of the gorse composts was more suppressive than the reference compost (15% and 55% of disease incidence, respectively). The former had a low EC, moderate amounts of P, Ca, Mg and K, and high levels of NH4+, as well as moderate levels of Ca, B and oligotrophic actinomycetes, the highest levels of total fungi, moderate levels of Trichoderma spp. and the lowest levels of Fusarium spp. Adding T34 to the moderately suppressive and non-suppressive composts decreased pre- and post-emergence incidence of the disease by up to 50%.In conclusion, one gorse compost decreased the incidence of F. circinatum disease when used as a growth medium for P. radiata seedlings. T. asperellum strain T34 further reduced the incidence of disease and improved the health of pine seedlings grown in moderately non-suppressive composts.

Peptaibols from Trichoderma asperellum TR356 strain isolated from Brazilian soil.

The Trichoderma genus consists of a group of free-living filamentous fungi, including species able to act as biological control agents (BCAs) against pathogenic fungi. It is believed that this ability is due to synergy between several mechanisms, including the production of a wide variety of secondary metabolites by these organisms. Among these, we highlight the production of peptaibols, an antibiotic peptide group characterized by the presence of non-proteinogenic amino acids such as α-aminoisobutyrate (Aib), as well as by N-terminal modifications and amino alcohols in the C-terminal region. This study aimed to outline a profile of peptaibol production and to identify secreted peptaibols from the Trichoderma asperellum TR356 strain, described as an efficient BCA against S. sclerotiorum. The fungus was grown on TLE 0.3% glucose medium for 5 days, with agitation at 120 rpm in the dark. Liquid medium filtrate was used as the metabolite source. These extracts were subjected to high performance liquid chromatography (HPLC) and subsequent analysis by matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF). The results indicate the production of two classes of peptaibols for this T. asperellum strain. Primary structures of two asperelines (A and E) and five trichotoxins (T5D2, T5E, T5F, T5G and 1717A) have been elucidated. Most of these peptaibols had been previously described in T. viride and T. asperellum marine strains. This is the first report of some of these compounds being produced by a T. asperellum strain from soil. Future analyses will be necessary to elucidate the three-dimensional structures and their activities against pathogens.

Physiological effects of the induction of resistance by compost or Trichoderma asperellum strain T34 against Botrytis cinerea in tomato

Certain types of compost used as growth media can induce resistance to foliar pathogens in above-ground parts of a plant. The induction of resistance can sometimes be associated with growth impairment and yield reduction. The objective of this study was to establish whether plants grown in olive marc compost had enhanced resistance against Botrytis cinerea at the cost of growth or physiological performance.Tomato plants grown in mature olive marc compost had approximately 60% less disease severity than plants grown in perlite. As a reference, plants grown in perlite enriched with the known inducer of resistance Trichoderma asperellum strain T34 (T34) had 35% less disease severity than plants grown in perlite. The salicylic acid (SA) pathway/abscisic acid (ABA) is involved in compost induced systemic resistance. Instead, perlite enriched with T34 is not linked to SA pathway/ABA. Physiological measures of water status, root/shoot ratio, stable isotopes of C and chlorophyll fluorescence showed that the plants grown in compost were close to a stress situation. However, growth measured as biomass and plant height of plants grown in compost was higher than in plants grown in perlite suggesting that plants in compost were not grown in a stress situation, but in a eustress. Tomato plants grown in perlite enriched with T34 had better growth, measured as total leaf area, biomass, height and nutrient uptake, than plants grown in perlite. Physiological measures showed that plants grown either in perlite or perlite enriched with T34 did not show any abiotic stress situation.

Effectiveness of biological control of Phytophthora capsici in pepper by Trichoderma asperellum strain T34

Pepper ( Capsicum annuum L.), one of the most widely grown vegetables worldwide, is susceptible to root rot caused by Phytophthora capsici . Many biocides have recently been banned in Europe because of human health and environmental concerns. Integrated pest management is a European priority, where biological control together with other agronomic practices should replace pesticide management of plant diseases in the future. Application of different concentrations of the fungus Trichoderma asperellum strain T34 (the in T34 Biocontrol®) on incidence of disease caused by P. capsici in pepper was studied. Different methods of application of the microbial control agent and inoculation of the pathogen were examined. T34 and etridiazole (Terrazole®) were compared for their ability to suppress P. capsici . T34 reduced disease in most of the assayed situations (up to 71% disease reduction), while etridiazole was effective only when applied at the same time as the pathogen. The results obtained are discussed on the basis of the different modes of action of T34 and etridiazole. T34 is a useful biological alternative to chemicals for the control of P. capsici in pepper.

Production of a feed additive based on selenium-containing mycelium of fungi of the genus Trichoderma

The process of selenium accumulation and increase of biomass on media containing various selenium concentrations in four species of the genus Trichoderma is studied. It is shown that the mycelium of T. asperellum strain TH-5 with selenium is not toxic and can be used as a selenium-containing feed additive.

Trichoderma asperellum: A potential biocontrol agent for Pythium myriotylum, causal agent of cocoyam (Xanthosoma sagittifolium) root rot disease in Cameroon

Root rot disease caused by Pythium myriotylum is a major threat to cocoyam cultivation in Cameroon. Control methods based on agricultural practices and chemical treatments have limitations. Since biocontrol is an interesting alternative, this study assessed the potential of four Trichoderma asperellum strains to control P. myriotylum. The antagonistic and mycoparasitic potential of the T. asperellum strains was evaluated in vitro through dual culture and interaction tests. Subsequently, the ability of T. asperellum to protect cocoyam plants from P. myriotylum infection was tested in vivo. Our results showed that all four T. asperellum strains were antagonistic to P. myriotylum, although differences were found among the strains. The growth of P. myriotylum was inhibited by more than 60%. Furthermore, the four T. asperellum strains were aggressive mycoparasites of P. myriotylum. In in vivo trials, pretreatment of cocoyam plants with the strains PR10 and PR11 of T. asperellum could reduce P. myriotylum infection by 50%. Both PR10 and PR11 strains of T. asperellum present promising biocontrol potential against P. myriotylum.

Trichoderma asperellum Chi42 Genes Encode Chitinase

Four Trichoderma strains (CH2, SH16, PQ34, and TN42) were isolated from soil samples collected from Quang Tri and Thua Thien Hue provinces in Vietnam. The strains exhibited high chitinolytic secretion. Strain PQ34 formed the largest zone of chitinase-mediated clearance (> 4 cm in diameter) in agar containing 1% (w/v) colloidal chitin. Analysis of the internal transcribed spacer regions of these strains indicated that they were Trichoderma asperellum. The molecular weights of the chitinases were approximately 42 kDa. Chitinase genes (chi42) of T. asperellum strains TN42, CH2, SH16, and PQ34 were 98~99% homologous to the ech42 gene of T. harzianum CB-Pin-01 (accession No. DQ166036). The deduced amino acid sequences of both T. asperellum strains SH16 and TN42 shared 100% similarity.

Control of Postharvest Rots of Banana Fruits by Conidia and Culture Filtrates of Trichoderma Asperellum

Banana fruits are highly perishable and prone to microbial infection that cause significant damage. Fungicides and pesti- cides that are used to control this infection are toxic to man and animals, hence there is the need for environmentally friendly control measures of fruit rot pathogens. Simultaneous inoculation of fruits with Trichoderma species and rot pathogens resulted in rot on the fingers, but rot produced by T. asperellum NG-T161 alone or in combination with the pathogens was reduced, compared to rot produced by the pathogens alone. Treatment of fruits with conidia and culture filtrates of T. asperellum NG-T161 for 30 min prior to in- oculation with the pathogens provided a better control than their simultaneous application. Only Trichoderma species were recovered on plated portions of rotted tissues from inoculations with the pathogens and the antagonists on the fruits. At 50% (v/v) the filtrates inhibited the mycelial growth of Fusarium oxysporum and Colletotrichum musae by 49.7 and 60.3% respectively but Lasiodiplodia theobro- mae was not inhibited. T. asperellum strains were found to be mycoparasitic on banana fruit rot pathogens. Conidia and culture filtrates of T. asperellum NG-T161 controlled the rot on banana fruits. It could be developed into a biopesticide for the control of postharvest banana fruit rot pathogens.

Biodegradation of aliphatic hydrocarbon by indigenous fungi isolated from used motor oil contaminated sites

Eighteen indigenous fungal isolates has been successfully isolated from samples of used motor oil, top five centimetres of soil and drainage water contaminated with used motor oil. All of the pure fungal isolates obtained were identified, characterized and subjected to preliminary screening by evaluating the average growth rate of each fungal isolates on minimal media containing 1% (v/v) used motor oil. Trichoderma asperellum strain TUB F-1067 (SA4), Trichoderma asperellum strain Tr48 (SA5), Trichoderma asperellum strain TUB F-756 (SA6), Penicillium species (P1), and Aspergillus species (P9) were further selected for their hydrocarbon biodegradation potential. Among these five fungal isolates selected, P1 strain presented a significant degree of degradation by degrading almost all of the n-alkanes (n-C-15 to n-C-23 range) present in the used motor oil, thus of greater potential in degrading the aliphatic hydrocarbon compounds of used motor oil.

Response surface methodology study of the combined effects of temperature, pH, andawon the growth rate ofTrichoderma asperellum

To evaluate the influence of environmental parameters (water activity aw, temperature, and pH) on the radial growth rate of Trichoderma asperellum (strains PR10, PR11, PR12, and 659-7), an antagonist of Phytophthora megakarya, the causal agent of cocoa black pod disease. The radial growth of four strains of T. asperellum was monitored for 30 days on modified PDA medium. Six levels of aw (0.995, 0.980, 0.960, 0.930, 0.910, and 0.880) were combined with three values of pH (4.5, 6.5, and 8.5) and three incubation temperatures (20, 25, and 30 degrees C). Whatever the strain, mycelial growth rate was optimal at aw between 0.995 and 0.980, independently of the temperature and pH. Each strain appeared to be very sensitive to aw reduction. In addition, all four strains were able to grow at all temperatures and pH values (4.5-8.5) tested, highest growth rate being observed at 30 degrees C and at pH 4.5-6.5. The use of response surface methodology to model the combined effects of aw, temperature, and pH on the radial growth rate of the T. asperellum strains confirmed the observed results. In our model, growth of the T. asperellum strains showed a greater dependence on aw than on temperature or pH under in vitro conditions. aw is a crucial environmental factor. Low aw can prevent growth of T. asperellum strains under some conditions. The observed and predicted radial growth rate of strain PR11 showed its greater capacity to support low aw (0.93) as compared with other tested strains at 20 degrees C. This is in agreement with its better protective level when applied in medium-scale trials on cocoa plantations. This study should contribute towards improving the biocontrol efficacy of T. asperellum strains used against P. megakarya. Integrated into a broader study of the impact of environmental factors on the biocontrol agent-pathogen system, this work should help to build a more rational control strategy, possibly involving the use of a compatible adjuvant protecting T. asperellum against desiccation.

Composts from agricultural waste and the Trichoderma asperellum strain T-34 suppress Rhizoctonia solani in cucumber seedlings

Abstract Using composts in agriculture to minimize organic wastes and to reduce the addition of fertilizers and fungicides in crop production is highly effective. Our results show that among those tested composts aged 0.5–1 year, cork compost reduced diseases caused by Rhizoctonia solani in cucumber plants (53% of diseased plants) in comparison to peat (up to 89%). However, all composts aged 1.5–3 years (comprised of cork, grape marc, olive marc and spent mushroom) highly suppressed Rhizoctonia disease, measuring 3, 11, 27 and 29% of diseased plants, respectively. Plant growth media enriched with the biological control agent Trichoderma asperellum (strain T-34) reduced the incidence of R. solani disease when amended at 10 3 cfu ml −1 . In composts aged 0.5–1 year, T-34 was only efficient when added to spent mushroom and cork compost, although it remained well established in all of them. The fact that T-34 rendered all composts aged 1.5–3 years highly suppressive is attributed to the low levels of easily biodegradable substances. Rhizoctonia damping-off in cucumber plants can be reduced by using composts and/or the biological control agent T. asperellum strain T-34. In addition, the extent to which composts suppress this disease depends on the nature of the composted materials, increasing with the composts’ maturity level.