Showing papers on "Trichoderma harzianum published in 2001"
TL;DR: It is shown that the improvement of plant nutritional level may be directly related to a general beneficial growth effect of the root system following T. harzianum inoculation and this phenomenon was evident from 5 days post-inoculation throughout the rest of the growth period, resulting in biomass accumulation in both roots and shoots.
Abstract: The potential of the biocontrol agent Trichoderma harzianum strain T-203 to induce a growth response in cucumber plants was studied in soil and under axenic hydroponic growth conditions. When soil was amended with T. harzianum propagules, a 30% increase in seedling emergence was observed up to 8 days after sowing. On day 28, these plants exhibited a 95 and 75% increase in root area and cumulative root length, respectively, and a significant increase in dry weight (80%), shoot length (45%) and leaf area (80%). Similarly, an increase of 90 and 30% in P and Fe concentration respectively, was observed in T. harzianum inoculated plants. To better characterize the effect of T. harzianum during the early stages of root colonization, experiments were carried out in a gnotobiotic hydroponic system. An increased growth response was apparent as early as 5 days post-inoculation with T. harzianum, resulting in an increase of 25 and 40% in the dry weight of roots and shoots, respectively. Similarly a significant increase in the concentration of Cu, P, Fe, Zn, Mn and Na was observed in inoculated roots. In the shoots of these plants, the concentration of Zn, P and Mn increased by 25, 30 and 70%, respectively. Using the axenic hydroponic system, we showed that the improvement of plant nutritional level may be directly related to a general beneficial growth effect of the root system following T. harzianum inoculation. This phenomenon was evident from 5 days post-inoculation throughout the rest of the growth period, resulting in biomass accumulation in both roots and shoots.
506 citations
TL;DR: It is suggested that improved proteolytic activity of the antagonist may be important for the biological control of the nematodes.
Abstract: The fungal biocontrol agent, Trichoderma harzianum, was evaluated for its potential to control the root-knot nematode Meloidogyne javanica. In greenhouse experiments, root galling was reduced and top fresh weight increased in nematode-infected tomatoes following soil pretreatment with Trichoderma peat-bran preparations. The use of a proteinase Prb1-transformed line (P-2) that contains multiple copies of this gene improved biocontrol activity in the greenhouse experiments compared with the nontransformed wild-type strain (WT). All the Trichoderma strains showed the ability to colonize M. javanica-separated eggs and second-stage juveniles (J2) in sterile in vitro assays, whereas P-2 also penetrated the egg masses. This protease-transformed line presented the same nematicidal and overall proteolytic activity as the WT in in vitro tests in which concentrated soil extracts from Trichoderma-treated soils immobilized the infective J2. However, the J2 immobilization and proteolytic activities of both P-2...
417 citations
TL;DR: Of 24 Trichoderma isolates, T. harzianum Rifai (T24) showed a potential for control of the phytopathogenic basidiomycete Sclerotium rolfsii when T24 was grown on different carbon sources, growth inhibition by the T24 culture filtrate correlated with the activity of extracellular chitinase and β-1,3-glucanase.
Abstract: Of 24 Trichoderma isolates, T. harzianum Rifai (T24) showed a potential for control of the phytopathogenic basidiomycete Sclerotium rolfsii. When T24 was grown on different carbon sources, growth inhibition of S. rolfsii by the T24 culture filtrate correlated with the activity of extracellular chitinase and β-1,3-glucanase. The 43-kilodalton (kDa) chitinase and the 74-kDa β-1,3-glucanase were purified from the T24 culture filtrate in two and three steps, respectively, using ammonium sulphate precipitation followed by hydrophobic interaction chromatography (phenyl-Sepharose) and gel filtration (β-1,3-glucanase). Km and Kcat were 3.8 g l–1 and 0.71 s–1 for the chitinase (chitin) and 1.1 g l–1 and 52 s–1 for the β-1,3-glucanase (laminarin). The chitinase showed higher activity on chitin than on less-acetylated substrate analogues (chitosan), while the β-1,3-glucanase was specific for β-1,3-linkages in polysaccharides. Both enzymes were stable at 30°C, while at 60°C the chitinase and the β-1,3-glucanase were rapidly inactivated, showing half-lives of 15 and 20 min, respectively. The enzymes inhibited growth of S. rolfsii in an additive manner showing a promising ED50 (50% effective dose) value of 2.7 µg/ml.
190 citations
TL;DR: Examination of MVOCs from indoor air samples may become an important method in indoor air hygiene for the detection of type and intensity of masked contamination by moulds.
183 citations
TL;DR: Northern and Western analyses indicated that AGN13.1 is induced by conditions that simulated antagonism of T. harzianum, and it is proposed that this enzyme contributes to the antagonistic response of the fungus.
Abstract: Trichoderma harzianum secretes α-1,3-glucanases when it is grown on polysaccharides, fungal cell walls, or autoclaved mycelium as a carbon source (simulated antagonistic conditions). We have purified and characterized one of these enzymes, named AGN13.1. The enzyme was monomeric and slightly basic. AGN13.1 was an exo-type α-1,3-glucanase and showed lytic and antifungal activity against fungal plant pathogens. Northern and Western analyses indicated that AGN13.1 is induced by conditions that simulated antagonism. We propose that AGN13.1 contributes to the antagonistic response of T. harzianum.
148 citations
TL;DR: A novel 36-kDa endochitinase named chit36 has been isolated and characterized from Trichoderma harzianum Rifai TM and completely inhibited the germination of Botrytis cinerea conidia.
Abstract: A novel 36-kDa endochitinase named chit36 has been isolated and characterized from Trichoderma harzianum Rifai TM. Partial amino acid sequences from the purified protein were used to clone the fungal cDNA, based on polymerase chain reaction with degenerate primers. The complete open reading frame encodes a 344-amino acid protein which shows 84% similarity to a putative chitinase from Streptomyces coelicolor. Chit36 was overexpressed under the pki1 constitutive promoter from Trichoderma reesei via biolistic transformation of T. harzianum TM. Stable transformants showed expression and endochitinase activity of chit36 in glucose-rich medium. Culture filtrates containing secreted CHIT36 as the sole chitinolytic enzyme completely inhibited the germination of Botrytis cinerea conidia. Growth of Fusarium oxysporum f. sp. melonis and Sclerotium rolfsii were significantly inhibited on agar plates on which the Trichoderma transformants had previously been grown.
141 citations
TL;DR: Data show that Chit33 is an enzyme involved in mycoparasitism; and its formation is controlled by induction, by either carbon or nitrogen starvation and, to a low degree, also under conditions of temperature stress.
Abstract: We investigated the regulation of chit33 expression in Trichoderma harzianum CECT 2413. This gene encodes the Chit33 endochitinase, which is a major component of the fungus' chitinolytic enzyme system and is important for biocontrol. To this end, both Northern analysis and reporter gene fusions of a 1.4-kb fragment of the 5'-upstream sequences of chit33 to the Aspergillus niger goxA gene (encoding glucose oxidase) and the Aquorea victoria green fluorescent protein were used. Northern analysis and data obtained with the reporter systems were compatible, thus showing that the 1.4-kb fragment bears all necessary information for the regulation of chit33 gene expression. chit33 is weakly expressed during growth on chitin and Rhizoctonia solani cell walls. The addition of N-acetylglucosamine transiently induced chit33 expression in resting cells of the fungus. The addition of either glucose or glycerol prevented induction of chit33 gene expression by chitin or cell walls. Incubation of T. harzianum in the presence of low concentrations (0.1%, w/v) of glucose and high concentrations (38 mM) of ammonium sulfate, or in the presence of high concentrations (1%, w/v) of glucose and low concentrations (0.38 mM) of ammonium sulfate also stimulated chit33-mRNA accumulation, although to a lower degree than induction by N-acetylglucosamine. Transfer of T. harzianum cultures to either 40 degrees C or 4 degrees C initiated a very rapid expression of chit33 in the absence of an inducer, yet only at very low levels (5%) of the induced control. Confrontation experiments, using the gfp gene as a reporter and R. solani as a host, showed that chit33 is expressed only during but not before the stage of overgrowth on R. solani. These data show that Chit33 is an enzyme involved in mycoparasitism; and its formation is controlled by induction, by either carbon or nitrogen starvation and, to a low degree, also under conditions of temperature stress.
106 citations
TL;DR: This paper presents a meta-analyses of the determinants of antibody resistance to EJB and shows clear patterns of action that can be attributed to cell reprograming and “cell reprogramming”.
102 citations
TL;DR: Toxic-metabolite-emitting microbes were isolated from the indoor environment of a building where the occupant was suffering serious building-related ill-health symptoms and dissipated the mitochondrial membrane potential of boar spermatozoa.
Abstract: Toxic-metabolite-emitting microbes were isolated from the indoor environment of a building where the occupant was suffering serious building-related ill-health symptoms. Toxic substances soluble in methanol and inhibitory to spermatozoa at <10 μg (dry weight) ml−1 were found from six bacterial isolates and one fungus. The substances from isolates of Bacillus simplex and from isolates belonging to the actinobacterial genera Streptomyces and Nocardiopsis were mitochondriotoxic. These substances dissipated the mitochondrial membrane potential (Δψ) of boar spermatozoa. The substances from the Streptomyces isolates also swelled the mitochondria. The substances from isolates of Trichoderma harzianum Rifai and Bacillus pumilus damaged the cell membrane barrier function of sperm cells.
89 citations
TL;DR: Extracellular xylanase production by selected isolates of the current study was characterized during their growth on xylan as a sole carbon source on solid medium and the results revealed that 93.3% of the isolates tested could degrade xylan and the highest activity against xylan was showed by members of Aspergillus, Fusarium, Penicillium and Trichoderma.
89 citations
TL;DR: Transgenic broccoli plants expressing a Trichoderma harzianum endochitinase gene were obtained by Agrobacterium tumefaciens-mediated transformation and PCR and Southern blot analysis confirmed the presence of the gene in plants initially selected via resistance to kanamycin.
Abstract: Transgenic broccoli plants expressing a Trichoderma harzianum endochitinase gene were obtained by Agrobacterium tumefaciens-mediated transformation. PCR and Southern blot analysis confirmed the presence of the gene in plants initially selected via resistance to kanamycin. Primary transformants (T0) and selfed progeny (T1) were examined for expression of the endochitinase gene using a fluorometric assay and for their resistance to the fungal pathogens Alternaria brassicicola and Sclerotinia sclerotiorum. All transgenic plants with elevated endochitinase activity had the expected 42 kDa endochitinase band in western blot analysis, whereas no such band was detected in the non-transgenic control. Leaves of most mature T0 plants had 14–37 times higher endochitinase activity than controls; mature T1 plants had higher endochitinase activity (100–200 times that in controls), in part because of lower control values. T0 plantlets in vitro or young plants in soil had higher absolute and relative endochitinase activity. When detached leaves of T0 plants were inoculated with A. brassicicola, lesion size showed a significant negative correlation with endochitinase levels. After inoculation of two-month old T0 plants with A. brassicicola, all 15 transgenic lines tested showed significantly less severe disease symptoms than controls. In contrast, lesion size on petioles of T0 and T1 plants inoculated with S. sclerotiorum was not statistically different from controls.
TL;DR: Field experiments showed that Trichoderma harzianum , nonpathogenic Rhizoctonia (np-R) and cattle manure compost amendment (CMC-H) applied in furrow could reduce black scurf incidence in organically grown potatoes.
TL;DR: Chitinase Chit42 from Trichoderma harzianum CECT 2413 is considered to play an important role in the biocontrol activity of this fungus against plant pathogens as well as on high molecular mass insoluble substrates such as ground chitin or chit in-rich fungal cell walls.
Abstract: Chitinase Chit42 from Trichoderma harzianum CECT 2413 is considered to play an important role in the biocontrol activity of this fungus against plant pathogens. Chit42 lacks a chitin-binding domain (ChBD). We have produced hybrid chitinases with stronger chitin-binding capacity by fusing to Chit42 a ChBD from Nicotiana tabacum ChiA chitinase and the cellulose-binding domain from cellobiohydrolase II of Trichoderma reesei. The chimeric chitinases had similar activities towards soluble substrate but higher hydrolytic activity than the native chitinase on high molecular mass insoluble substrates such as ground chitin or chitin-rich fungal cell walls.
TL;DR: This mutant performed better than the wild type during in vitro experiments, overgrowing and sporulating on Rhizoctonia solani earlier, killing this pathogen faster and exerting better protection on grapes against Botrytis cinerea.
Abstract: Trichoderma harzianum is a well-known biological control agent against fungal plant diseases. In order to select improved biocontrol strains from Trichoderma harzianum CECT 2413, a mutant has been isolated for its ability to produce wider haloes than the wild type, when hydrolysing pustulan, a polymer of β-1,6-glucan. The mutant possesses between two and four times more chitinase, β-1,3- and β-1,6-glucanase activities than the wild type, produces about three times more extracellular proteins and secretes higher amounts of a yellow pigment (α-pyrone). This mutant performed better than the wild type during in vitro experiments, overgrowing and sporulating on Rhizoctonia solani earlier, killing this pathogen faster and exerting better protection on grapes against Botrytis cinerea.
TL;DR: Cowpea seeds treated with three Trichoderma spp.
Abstract: Cowpea seeds treated with three Trichoderma spp. at four inoculum doses, and at four exposure times in three different formulations were planted in soils amended with Macrophomina phaseolin a, and assessed for stand establishment and post-emergence damping off. The highest percentage plant stands at 21 days after planting were 66% for T. koningii and T. harzianum , and 51% for Trichoderma sp., at 6.8 2 10 7 , 2.0 2 10 10 , and 1.0 2 10 7 colony forming units (CFUs) ml -1 , respectively. Across sampling dates and irrespective of time of exposure to the formulations, the T. harzianum and T. koningii formulations resulted in significantly greater percentage plant stands than the seeds treated with a Trichoderma sp. and the controls. Seed treatment formulations with Trichoderma spp. were derived from propagule suspensions at the most effective inoculum dose in Tween 80, in suspension with cooked cassava starch as an adhesive, or in a slurry with uncooked cassava starch. At 21 days, the suspensions wi...
TL;DR: An antagonistic mechanism based on initiation of germination in sufficiently concentrated inocula suggests that at suboptimal temperatures the efficacy of Trichoderma antagonists might be improved by conidia activation prior to application.
Abstract: The effect of preliminary nutrient activation on the ability of conidia of the antagonist Trichoderma harzianum (atroviride) P1 to suppress Botrytis cinerea was investigated in laboratory, greenhouse, and field trials. Preliminary nutrient activation at 21 degrees C accelerated subsequent germination of the antagonist at temperatures from 9 to 21 degrees C; at >/=18 degrees C, the germination time of preactivated T. harzianum P1 conidia did not differ significantly from that of B. cinerea. When coinoculated with B. cinerea, concentrated inocula of preactivated but ungerminated T. harzianum P1 conidia reduced in vitro germination of the pathogen by >/=87% at 12 to 25 degrees C; initially quiescent conidia achieved this level of suppression only at 25 degrees C. Application of quiescent T. harzianum P1 conidia to detached strawberry flowers in moist chambers reduced infection by B. cinerea by >/=85% at 24 degrees C, but only by 35% at 12 degrees C. Preactivated conidia reduced infection by >/=60% at 12 degrees C. Both quiescent and preactivated conidia significantly reduced latent infection in greenhouse-grown strawberries at a mean temperature of 19 degrees C, whereas only preactivated conidia were effective in the field at a mean temperature of 14 degrees C on the day of treatment application. An antagonistic mechanism based on initiation of germination in sufficiently concentrated inocula suggests that at suboptimal temperatures the efficacy of Trichoderma antagonists might be improved by conidia activation prior to application.
TL;DR: Type C-4 strain of Trichoderma harzianum was isolated as a microorganism with high cellulolytic activity and β-Glucosidase, involved in the last step of cellulose saccharification by degrading cellobiose to glucose, plays an important role in the cellulase enzyme system with a synergic action with endoglucanase and cellobio-hydrolase for cellulose degradation.
Abstract: Type C-4 strain of Trichoderma harzianum was isolated as a microorganism with high cellulolytic activity. β-Glucosidase is involved in the last step of cellulose saccharification by degrading cellobiose to glucose, and plays an important role in the cellulase enzyme system with a synergic action with endoglucanase and cellobio-hydrolase for cellulose degradation. β-Glucosidase from T. harzianum type C-4 was purified to homogeneity through Sephacryl S-300, DEAE-Sephadex A-50, and Mono P column chromatographies. It was a single polypeptide with the molecular mass of 75,000 by SDS-PAGE. The enzyme was very active at pH 5.0 and 45 °C. No significant inhibition was observed in the presence of metal ions, thiol reagents, or EDTA. The enzyme was stable in the presence of 5% ox gall and digestive enzymes. p-Nitrophenyl-β-D-cellobioside worked as a substrate for the enzyme as much as p-nitrophenyl-β-glucopyranoside. Glucose and gluconolactone showed competitive inhibition with a Ki of 1 mM and 1.8 μM, respectively...
01 Jan 2001
TL;DR: Applications of bioproducts of Chaetomium, Penicillium and Trichoderma significantly reduced the disease incidence on leaves, twigs and fruits of grape in all varieties as compared to the chemical control.
Abstract: Anthracnose of the grape varieties Bigblack, Nanpha, Blackopal, Loose perlette and White malaca are caused by Colletotrichum gloeosporioides. All isolates obtained from grape anthracnose were shown to be pathogenic; isolate WMF01 was the most virulent on all tested varieties of grape. Assays using crude extracts from Chaetomium cupreum CC, C. globosum CG, Trichoderma harzianum PC01, T. hamatum PC02, Penicillium chrysogenum KMITL44 and antibiotic substances Rotiorinol, Chaetoglobosin-C and Trichotoxin A50 were carried out to test bioactivity. All extracts and compounds inhibited the growth of C. gloeosporioides strain WMF01, with average ED50 values between 1 to 50 ppm. Applications of bioproducts of Chaetomium, Penicillium and Trichoderma, and a mixture of those bioproducts in a powder formulation and a chemical control were conducted in the field to control anthracnose disease of 5-varieties of grape. All bioproducts significantly reduced the disease incidence on leaves, twigs and fruits of grape in all varieties as compared to the chemical control.
TL;DR: The results indicate the potential of Trichoderma treatments in grapevine nurseries for the production of stronger vines with lower Phaeomoniella/Phaeoacremonium and Cylindrocarpon infection levels.
Abstract: The growth-stimulating attributes of Trichoderma treatments (dips, soil amendments and drenches with
Trichoderma products containing propagules of selected strains of Trichoderma harzianum) in grapevine nurseries,
and their effect on the occurrence of fungi in roots and rootstocks of nursery grapevines, in particular fungi causing
Petri disease (Phaeomoniella chlamydospora and Phaeoacremonium spp.) and black foot rot (Cylindrocarpon spp.),
were compared with quintozene/procymidone treated (standard) vines. Early shoot growth of Trichoderma treated
vines was visibly better than that of the control vines. Eight months after planting, at uprooting, percentage take and
shoot mass of Trichoderma and standard treated vines were similar, but total root mass was significantly higher for
Trichoderma treated vines. Low percentages of Cylindrocarpon spp. were isolated from the rootstocks of treated and
untreated vines, while less Petri disease fungi were isolated from rootstocks of Trichoderma treated vines. Markedly
fewer fungi were also isolated from the roots of Trichoderma treated vines. Incidences of Petri disease fungi in roots
of Trichoderma and standard treated vines were similar, but fewer Cylindrocarpon spp. were isolated from Trichoderma
treated vines. These results indicate the potential of Trichoderma treatments in grapevine nurseries for the production
of stronger vines with lower Phaeomoniella/Phaeoacremonium and Cylindrocarpon infection levels.
TL;DR: The biotype Th2 from white button mushroom compost was the stronger antagonist and could be a source of problems in solid state fermentations with different white rot basidiomycetes if it contaminates them.
Abstract: Antagonisms between Trichoderma spp. and white-rot fungi are of interest for lignocellulose degradation and mushroom cultivation. Production of emergent hyphae, formation of pigmented barrag- es and production of laccases were followed and com- pared during confrontations between mycelia of two T harzianum isolates with seven wood-rotting and seven leaf litter-rotting basidiomycetes. No specific defense pattern associated with each group of basid- iomycete was identified but the number of species forming barrages with pigmented zones was higher in the group of wood decayers. Trichoderma harzian- um induced increases in extracellular laccase activi- ties only with some basidiomycete species. The two T harzianum had been isolated as mushroom antag- onists from two different media. Differences in their aggressiveness resulted in differences in the time giv- en to the basidiomycetes for developing their resis- tance mechanisms. The biotype Th2 from white but- ton mushroom compost was the stronger antagonist and could be a source of problems in solid state fer- mentations with different white rot basidiomycetes if it contaminates them.
TL;DR: Capacities of T. harzianum, biotype Th2, to colonise mushroom compost are not due to a specific ability to produce enzymes necessary for compost degradation but to their tolerance to the inhibitory effect of bacteria present in compost.
TL;DR: It is concluded that the secondary metabolite profile contains sufficient information for classification and species identification of Trichoderma strains from water-damaged building materials or indoor dust.
Abstract: Forty-four Trichoderma strains from water-damaged building materials or indoor dust were classified with chromatographic image analysis on full chromatographic matrices obtained by high performance liquid chromatography with UV detection of culture extracts. The classes were compared with morphological identification and rDNA sequence data, and for each class all strains were of the same identity. With all three techniques each strain – except one – was identified as the same species. These strains belonged to Trichoderma atroviride (nine strains), Trichoderma viride (three strains), Trichoderma harzianum (10 strains), Trichoderma citrinoviride (12 strains), and Trichoderma longibrachiatum (nine strains). The odd strain was identified as Trichoderma hamatum by morphology and rDNA sequencing, but not by image analysis as no reference strains of this species were included. It is concluded that the secondary metabolite profile contains sufficient information for classification and species identification.
TL;DR: Results suggest that fungivorous nematodes may be a significant biotic constraint on activity of biocontrol fungi in the field.
Abstract: A fungivorous nematode, Aphelenchoides sp., was isolated from field soil by baiting with mycelium of the biocontrol fungus Trichoderma harzianum ThzID1, and subsequently was maintained on agar cultures of the fungus. Interactions between the nematode and the green fluorescent protein-producing transformant, T. harzianum ThzID1-M3, were investigated in both heat-treated (80°C, 30 min) and untreated field soil. ThzID1-M3 was identified in soil by epifluorescence microscopy. When ThzID1-M3 was added to soil as an alginate pellet formulation, addition of the nematode (10 per gram of soil) significantly reduced radial growth and recoverable populations of the fungus, and the effect was greater in heat-treated soil than in untreated soil. Addition of ThzID1-M3 to soil pretreated with the nematode (10 per gram of soil) stimulated nematode population growth for approximately 10 to 20 days, whereas nematode populations decreased in the absence of added Trichoderma sp. When sclerotia of Sclerotinia sclerot...
TL;DR: Research indicates that in furrow applications of T. harzianum, this biocontrol agent would be compatible with a captan and/or benomyl seed treatment for control of other seedling diseases.
Abstract: Trichoderma harzianum C52 is an effective biocontrol agent of the onion white rot pathogen Sclerotium cepivorum. For this biocontrol agent to be integrated into an existing disease management programme, it must be compatible with the fungicides commonly used on onions. The sensitivity of T. harzianum spores to the field rate of eight fungicides commonly applied to onions was determined in an in vitro assay. Results indicate that T. harzianum was least sensitive to procymidone and captan and most sensitive to mancozeb, tebuconazole and thiram. A glasshouse pot trial confirmed that T. harzianum was sensitive to mancozeb but tolerant of captan. This research indicates that in furrow applications of T. harzianum would be compatible with a captan and/or benomyl seed treatment for control of other seedling diseases.
TL;DR: This work evaluated the feasibility of the use of aqueous-two phase systems (ATPS), as in situ extraction systems, in order to overcome the toxic effects of 6PP and to improve culture productivity.
Journal Article•
TL;DR: Postharvest decay of onion bulbs was examined, and onion bulbs with 1st quality grade were rotten most severely by 51%, followed by 32% for 2nd and 21% for 3rd grades, indicating that larger bulbs had higher incidences of bulb rots.
Abstract: Postharvest decay of onion bulbs was examined by inspecting the commercial packages in the market or in storage. Bulb rot incidence was unexpectedly high, and onion bulbs with 1st quality grade were rotten most severely by 51%, followed by 32% for 2nd and 21% for 3rd grades. This indicates that larger bulbs had higher incidences of bulb rots. Major pathogens associated with basal and neck rots were Fusarium oxysporum and Aspergillus sp. or Botrytis allii, respectively, of which basal rot was most prevalent and damaging during storage. Among the epiphytic microorgani는 from onion plants, several Bacillus and Paenibacillus spp. and previously selected Pseudomonas putida and Trichoderma harzianum had inhibitory efficacy against bulb rot pathogens. Among these B. amyloliquefaciens BL-3, Paenibacillus polymyxa BL-4, and P. putida Cha 94 were highly inhibitory to conidial germination of F. oxysporum and B. allii. P. putida Cha 94, B. amyloliquefaciens BL-3, P. polymyxa BL-4, and T. harzianum TM were applied in the rhizoplane of onion at transplanting. Initially antagonist populations decreased rapidly during the first one month. However, among these antagonists, rhizoplane population densities of BL-3, Cha 94, and TM were consistently high thereafter, maintaining about 10-10 cells or spores per gram of onion root up to harvest time. The other bacterial antagonist BL-4 survived only for two months. TM was the most effective biocontrol agent against basal rot, with the number of rotten bulbs recorded at 4%, while that of the control was 16%. Cha 94 was effective for the first 20 days, but basal rot increased thereafter and had about the same control efficacy as that of BL-3 and BL-4. When the antagonists were applied to the topping areas of onion bulbs at harvest, TM was the most effective in protecting the stored onion bulbs from neck rotting. The second effective antagonist was BL-3. TM and BL-3 completely suppressed the neck rot in another test, suggesting that biocontrol of postharvest decay of onion using these microorganisms either at the time of transplanting or at harvesting may be promising.
01 Jan 2001
TL;DR: Michel-Aceves, A.C., Rebolledo-Dominguez, O., Lezama-Gutierrez, R., Ochoa-Moreno, M.E., Mesima-Escamilla, J.C. as mentioned in this paper, ySamuels, G.J.
Abstract: Resumen es: Michel-Aceves, A.C., Rebolledo-Dominguez, O., Lezama-Gutierrez, R., Ochoa-Moreno, M.E., Mesima-Escamilla, J.C., ySamuels, G.J. 2001. Especies de Trichode...
Journal Article•
TL;DR: Seed and seedling rot complex of soybean caused predominantly by Rhizoctonia solani Kuhn, Sclerotium rolfsii Sacc.
Abstract: Seed and seedling rot complex of soybean caused predominantly by Rhizoctonia solani Kuhn, Sclerotium rolfsii Sacc., Macrophomina pliaseolina ( Tassi) Goid and Fusarium spp. is a major obstacle in increasing soybean production in many countries. It is very difficult to manage these pathogens as their nature of survival is both through the formation of sclerotia chlamydospores and saprophytic phase on soil organic matter. Biological control has emerged as an alternative and promising means for management of such type of diseases.Biocontrol agents like Gliocladium virens and Trichoderma harzianum antagonise pathogens by antibiosis, competition, mycoparasitism or other form of direct exploitation.
TL;DR: It is suggested that the biocontrol ability of T. harzianum involves competition with the pathogen for substrates including the seed coat, and wounded or infected root tissue, including those caused by infecting pathogens.
Abstract: The activity of Trichoderma harzianum in the spermosphere and rhizosphere of different plant species was studied by use of a β-glucuronidase (GUS) transformant (strain T3a). Hereby, direct observation of micro-habitats supporting metabolic activity of T. harzianum is reported. Germination of conidia and mycelial growth were not supported by exudates from healthy roots of various ages. Instead, growth and activity of T. harzianum depended on access to dead organic substrates such as seed coats, decaying roots, and wounds, including those caused by infecting pathogens. A correlation between the GUS activity of T. harzianum and the biomass of Pythium ultimum in infected roots was established. On the basis of our observations, we suggest that the biocontrol ability of T. harzianum involves competition with the pathogen for substrates including the seed coat, and wounded or infected root tissue.
TL;DR: Comparison of the expected additive and observed effects revealed no synergism between endochitinase and Bayleton, and some transgenic lines sprayed with fungicide at doses higher than ED50 showed resistance similar to the non-sprayed transgenic Lines, again suggesting no synergistic effect.
Abstract: Progeny from transgenic broccoli (cv. Green Comet) expressing a Trichoderma harzianum endochitinase gene were used to assess the interaction between endochitinase and the fungicide Bayleton in the control of Alternaria brassicicola. In vitro assays have shown synergistic effects of endochitinase and fungicides on fungal pathogens. Our study examined the in planta effects of endochitinase and Bayleton, individually and in combination. Two month old transgenic and non-transgenic plants were sprayed with ED50 levels of Bayleton and/or inoculated with an A. brassicicola spore suspension. Disease levels in non-sprayed transgenic plants were not statistically different from sprayed transgenic plants nor from sprayed non-transgenic controls. Thus endochitinase-transgenic plants alone provided a significant reduction of disease severity, comparable to the protection by fungicide on non-transgenic plants. Comparison of the expected additive and observed effects revealed no synergism between endochitinase and Bayleton (at ED50 level), and usually less than an additive effect. Some transgenic lines sprayed with fungicide at doses higher than ED50 showed resistance similar to the non-sprayed transgenic lines, again suggesting no synergistic effect. Lack of synergism may be due to incomplete digestion of the cell wall by endochitinase, so that the effect of Bayleton at the cell membrane is not enhanced.