Trichoderma Harzianum Isolate Research Articles

Comparison of the Efficacy of Trichoderma and Bacillus Strains and Commercial Biocontrol Products against Grapevine Botryosphaeria Dieback Pathogens

Grapevine trunk diseases (GTDs) cause significant yield losses worldwide and limit the lifespan of vineyards. In the last few years, using biological control agents (BCAs) for pruning wound protection has become a promising management strategy for the control of these pathologies. This study aimed to compare the antifungal activities of a grapevine-native Trichoderma harzianum isolate and a high-potential Bacillus velezensis strain against two pathogenic Botryosphaeriaceae species in artificially inoculated, potted, grafted plants under controlled greenhouse conditions, taking three commercial biocontrol products (based on T. atroviride I-1237, T. harzianum T-22, and Bacillus subtilis BS03 strains) as a reference. To reproduce certain field conditions more realistically, inoculation of the protective agents and the pathogens was conducted simultaneously immediately after pruning instead of allowing the BCAs to colonize the wounds before pathogen inoculation. Significant differences in necrosis lengths were detected for both Neofusicoccum parvum- and Diplodia seriata-infected plants, and a remarkable protective effect of Bacillus velezensis BUZ-14 was observed in all cases. Trichoderma-based treatments showed different efficacies against the two pathogenic fungi. While the three tested BCAs resulted in significant reductions in vascular necrosis caused by N. parvum, they did not significantly reduce D. seriata infection compared to the untreated inoculated control. The B. subtilis strain was not effective. The reported results provide support for the potential Bacillus velezensis may have for pruning wound protection against Botryosphaeriaceae fungi, encouraging its evaluation under natural field conditions.

Genetic Diversity of Trichoderma harzianum Isolates in Sunflower Rhizosphere: The Application of the URP Molecular Marker

The genetic diversity of 77 Trichoderma harzianum isolates collected from sunflower rhizosphere soils in Urmia, Khoy, and Salmas in West Azerbaijan province, Iran, was evaluated by using the Universal Rice Primer (URP) molecular marker. The DNA band pattern of the isolates was developed using seven primers of this marker. These primers produced 186 gene loci, out of which 182 loci were polymorphic. Accordingly, the genetic diversity of the isolates was calculated, and their kinship relations were determined by cluster analysis using the NTSYS software package. URP-6R had the highest marker index among the studied primers, followed by URP-1F, URP-4R, and URP-25F, implying their higher efficiency in discriminating between the isolates. The results showed that the URP marker could discriminate between isolates using macroscopic morphological characteristics, such as color and colony type, potential of pigment production in the culture medium, and colony growth rate. Furthermore, there was no significant relationship between the geographical distribution of the isolates and the band patterns generated by the primers except for a few cases. The results generally revealed that the URP marker was an efficient tool for determining the genetic diversity of T. harzianum.

Potency of two Trichoderma harzianum isolates in liquid and solid organic formula for controlling bacterial wilt on tomato in the field

This research aimed to determine the potency of two Trichoderma harzianum isolates in solid and liquid organic formulas to control bacterial wilt and on growth and yield of tomato in the field. This research was carried out at the Laboratory of Plant Protection and the tomato field at Banteran Village, Sumbang Sub-District, Banyumas Regency at altitude of 600 m above sea level for four months. A randomized block design was used with five replicates. The treatments were control, T. harzianum T10, T. harzianum T215, combination of T. harzianum T10 + T. harzianum T215, and bactericide (a.i. 20% streptomycin sulfate). Variables observed were pathosystem components (incubation period, infection rate, disease intensity, and late populations of the antagonists), growth components (plant height, plant fresh and dry weight, and root fresh and dry weight), yield components (number of fruits, fruit weight), and phenolic compounds analysis qualitatively. The results showed that T. harzianum T10 + T. harzianum T215 was effective to suppress the disease as 58.61%. The treatment of T. harzianum T10 + T. harzianum T215 was effective to increase crop height, fresh weight of plants, dry weight of plants, fresh weight of roots, dry weight of roots, number of fruits and fruit weight as 38.86, 35.37, 51.67, 24.78, 37.41, 40.61, and 53.22%, respectively. All treatments could increase phenolic compound content qualitatively.

Efficacy of T harzianum isolates in plant growth promotion and BLB management in rice

Rice crop is highly vulnerable at all stages of growth to different pathogens that affect the quality and quantity of its yield. Among the different diseases, Bacterial blight of rice (Xanthomonas oryzae pv. oryzae), a deadly bacterial disease is among the most destructive affliction of cultivated rice (Oryza sativa and O. glaberrima). In severe epidemics, crop loss may be as high as 75 percent, and millions of hectares of rice are infected annually. Biological control based on antagonism is a potential, non-chemical and eco-friendly approach for managing plant diseases. Biocontrol agents like Trichoderma spp. are acclaimed as effective, eco-friendly and cheap, nullifying the ill effects of chemicals. The present study involved five different isolates of Trichoderma harzianum viz. IRRI-2, IRRI-3, IRRI-4, IRRI-5, IRRI-6 obtained from International Rice Research Institute. Variations were observed while comparing the efficacy of different Trichoderma harzianum isolates, IRRI-5 and IRRI-2 isolates exhibited superior anti-bacterial activities in vitro. Rice crop was raised from Trichoderma treated seeds and further challenge inoculates with Xoo to induce disease in plants. All the T. harzianum treated plants had lower incidence of diseases and higher yield than the untreated plant. Yield attributing characters like plant height, days of active tillering, panicle initiation and maturity, total number of grains per panicle, number of filled grains per panicle was positively influenced by Trichoderma harzianum application. However, there were variations among the treatment, isolate IRRI-5 was found most effective followed by IRRI-2, IRRI-4, IRRI-3 and IRRI-6 respectively.

In vitro and in planta potential effect of some indigenous antagonists against Fusarium and pythiaceous species associated with peach seedlings decline

BackgroundThe effect of Aspergillus spp. and Trichoderma harzianum isolates was evaluated against the growth of Fusarium oxysporum, F. solani, Pythium ultimum and Phytophthora citrophthora affecting peach seedlings.ResultsThe in vitro results revealed the ability of these antagonistic in reducing the radial growth of these pathogens. The most important mycelial growth reduction was of 85.82%, recorded for F. oxysporum in confrontation with A5 of Aspergillus candidus. Aspergillus flavus A4 and A. niger A10 were the most effective against F. solani with an inhibition percent more than 60%. For P. citrophthora, A. flavus A4, A. candidus A5, A. terreus A9 and A. niger A10 inhibited the mycelia growth by more than 60%. Aspergillus nidulans A1 was the most effective against Pythium ultimum (72.07%). Trichoderma harzianum isolates T9 and T10, are the most effective with a high inhibition percent of mycelial growth. The inhibition induced after 4 days of incubation, against F. oxysporum, F. solani, P. citrophthora and Pythium ultimum by these 2 antagonists exceeded 70, 60, 70 and 80%, respectively. The in planta test showed the efficacy of antagonists tested solo against some pathogens. In fact, Bacillus subtilis improved the health status by 62.55% compared to the control inoculated with P. ultimum. Trichoderma harzianum T9 significantly reduced the root rot index by 87.5% than the control inoculated with F. solani. In the same sense, B. subtilis significantly reduced this parameter by 62.55 and 88.89% than the control inoculated with P. ultimum and P. citrophthora, respectively. Furthermore, B. subtilis (B) and Aspergillus niger A10 improved plants height than the control inoculated with Pythium ultimum by 31.52 and 40.49%, respectively. However, the combinations of antagonists (T9 + T10; A5 + A10 and B + T10) did not improve their efficacy.ConclusionsThe isolates T. harzianum (T9 and T10), A. candidus A5 and A. niger A10 were the most effective in vitro against Fusarium, Pythium and Phytophthora species associated with peach seedling decline. The in vivo assay showed the effectiveness of B. subtilis against P. ultimum and P. citrophthora and the potential effect of T. harzianum T9 against F. solani. Their combinations revealed to be ineffective.

Effect of Four Liquid Organic Wastes on The Growth of Four Trichoderma harzianum Isolates and Their Effect on Cucumber Growth and Yield

The aim of this research was to determine the effect of fourliquid organic substrates on the growth of four Trichoderma harzianum isolates and their effect on cucumber growth and yield. Randomized block design was used with 20 treatments and 3 replicates. The treatments consisted of control, tofu liquid waste, rice washing water, coconut water, and tapioca waste substrates each combined with four T. harzianum isolates. Variables observed were conidia density during decomposition, conidia late density, crop height, root length, root fresh and dry weight, crop fresh and dry weight, the first flowering, number of fruits per plant, and fruit weight. Result of the research showed that in the tapioca waste substrate, only T16 isolates was able to grow well with a maximum density of 6,70x107 conidia/mL. In the rice washing water substrate, conidia growth of the isolate was better than coconut water substrate with a maximum density of 6,25x107 conidia/mL. The best liquid organic substrate for growing media of T. harzianum was tofu liquid waste. On the 4th day with the tofu waste substrate, T16 isolate could achieve conidia density of 1,12x108 conidia/mL. The liquid organic substrate resulted from T. harzianum decomposition was not different on cucumber yield.

Identification and Characterization of Triple Action Bioagents (TAB) and Their Potency against Fusarium Wilt of Lentil

Fusarium wilt is a severe disease that plays a significant role in reducing the yield of lentil. Under favorable conditions for disease growth, the disease can cause complete crop failure and can be a crucial limiting issue for lentil cultivation in specific geographical zones. The current work focused on isolating potentialbio-agents exhibiting copper oxychloride resistance and evaluating their efficacy in seed treatment for ecologically sustainable management of Fusarium wilt of lentil. Seventy biocontrol agent isolates were isolated and tested for resistance by growing them on Potato Dextrose Agar medium (PDA) amended with copper oxychloride at the rate of 2500 ppm. Isolate-H10 and isolate-C9 showed more excellent compatibility with copper oxychloride fungicide with 69 mm and 65 mm radial growths, respectively. The isolates H10 and C9 had the highest inhibitory percentages of 84.30% and 83.94% against Fusarium oxysporum f. sp. lentis, respectively, and the highest phosphorus solubilization index (PSI). Primers (ITS 1 and ITS 4) identified these putative bioagents as Trichoderma harzianum isolate skua-tab-1 and Penicillium crysogenum strain Tab2. Sequences were submitted to the NCBI and assigned the accession numbers MK414603 and MK418066. In pot culture, these isolates also demonstrated their superiority in reducing the disease incidence and severity if seeds were treated with H10 and C9 alone or in combination with copper oxychloride fungicide. The two isolated bioagents exhibit three fundamental properties: compatibility with copper oxychloride, antagonistic activity toward the pathogen fall armyworm, and the ability to dissolve phosphorus minerals.

Assessment the ability of Trichoderma harzianum Fungi in Bioremediation of some of Heavy Metals in Waste Water

The study included the use of Trichoderma harzianum for biodegradation heavy metals in a wastewater treatment plant and their ability to decompose these minerals through a series of tests. The first test involved the use of two Trichoderma harzianum isolates for biodegradation through a filtration action. In the second test, the comparison was used in pre and post-treatment in Petri dishes, The result showed a clear green growth of fungi and their use of heavy metals as an energy source. Scanning Electronic Microscope SEM) was used to compare the vegetative growth of fungi before and after treatment on P.D.A media, which showed clear and normal growth with a short growth period of the Petri dish after treatment and compared it to the control of the Petri dish with different magnification powers (6738x, 5988x, 2713x, 2509x)., 6453x, 5708x, 2598x, 2400x). A third test used a Atomic Absorption technique to quantify heavy metals for the site 2 after 28 days of bioremediation. The results showed the highest removal rate of Cd was 98.63% and Mn was94.35% for (T.h1) and the lowest biodegradation of Zn and Fe (39.77% and 47.43%,) respectively. The nutrient had the highest removal rate of PO4 was 69.87% and the lowest percentage of NO3 was 8.91%.The results also showed the highest removal rate for (T.h2) Mn and Cd with rates of 86.41% and 81.73%, the lowest percentage of decomposition of Zn was 52.27%, and the highest percentage of decomposition of PO4 was 70.74% Lowest removal rate of NO3 was 36.49%. A Atomic Absorption technique was used to quantify heavy metals after 28 days of biological treatment for the site1. The results showed the highest biodegradation percentage (T.h1) for manganese and Pb 83.27% and 84.50%, respectively, and the lowest biodegradation percentage was Zn and Fe (33.67%, 38.09%,) respectively, and the nutrient removal rate was the highest, NO3 was 85.27 %, The lowest rate is 27.74% of SO4. The results showed the highest removal rate (T.h2) for the elemental fungus Mn (87.32%) and Pb (84.01%) and the lowest percentage for Fe was (36.90%).The results of the experiment showed that the fungi largest biomass are the most efficient in the bioremediation process and the removal of pollutants from wastewater.

Biocontrol of Fusarium wilt of tomato by nano-extract of Trichoderma harzianum

Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici is an important disease of tomato worldwide. The pathogen was isolated and purified from infected plants in tomato-growing greenhouses in southwest Iran during 2017. The impact of colony’s extract of four Trichoderma harzianum isolates were tested on colony growth of the pathogen in-vitro. Premium isolate colony's extract of T. harzianum was converted to nano-product by mixing with silver-nitrate. The formation of nano-particles in this product was evaluated by dynamic light scattering, and scanning electron microscopy. The impact of nano-product was tested on colony growth of the pathogen and its EC50 was determined. Then the impact of this product and silver-nitrate was tested on the disease severity in two tomato varieties in-vivo. Colony’s extract of all four isolates of T. harzianum reduced the colony growth of the pathogen, but the effect of an isolate’s extract of T.harzianum 39 was more. Produced nano-extract had EC50441.9ppm for the pathogen. It also caused a significant reduction of the disease severity in-vivo, and its effect was more than silvernitrate alone. Potential of T. harzianum nano-extract for biological control of the disease is being reported for the first time as per our knowledge.

The Effect of Salinity on Growth, Antagonistic Potential, Protease Activity, and Proline Content of Trichoderma harzianum

Salinity is one of the major limiting factors for sustainable crop production and the growth of beneficial microorganisms. Screening of biocontrol agent Trichoderma harzianum isolates under saline conditions could be necessary to select more efficient strains to alleviate salt stress through biopriming in plants. The present study aimed to investigate the antagonistic capacity of 14 T. harzianum isolates against Macrophomina phaseolina as well as the growth, protease activity, and proline content under different concentrations of salt. All isolates except Th15 and Th18 exhibited an over 85% inhibition against M. phaseolina at 0 mM NaCl in c and showed a noticeable decline in their antagonistic capacity as salt concentration increased. Colony growth decreased with increasing salt concentrations in all isolates tested. The growth of all isolates at 0 mM was significantly higher than the other NaCl treatments except at 70 mM NaCl. Protease activity also declined with the increased level of salt. Isolates displayed a wide range of protease expression patterns even at the same salinity as in the case of proline content. Unlike protease enzyme, proline content significantly increased at 240 mM NaCl. Salinity played a significant role in T. harzianum isolates with regards to the growth, antagonistic capacity, protease activity, and proline content.

Biological effects of two Trichoderma harzianum isolates and mint oil on some postharvest fungal pathogens of sugar beet

Abstract Sugarbeet (Beta vulgaris L.) stored in outdoor piles prior to processing, during this storage period the crop is subject to multiple postharvest rots. Some fungal pathogens (A. niger, A. flavus, Fusarium sp. and Rhizopus sp.) were isolated and identified from rotted sugarbeet. Pathogenicity test of the isolated fungi had different pathogenicity rates using different concentrations of spore suspension at different incubation periods. A. flavus showed little number of lesions and negative effect on sugarbeet when tested for pathogenicity. Two antagonists of Trichoderma harzianum were tested for their effectiveness on sugarbeet rot fungal pathogens and compared with mint oil. In dual culture, size of clear zone is not correlated with the occurrence of pathogen overgrowth by antagonists. The antagonistic action of the two tested isolates of T. harzianum against the isolated phytopathogens indicated different degrees of antagonism. The non-volatile and gaseous volatile organic compounds by the antagonists inhibited growth of phytopathogens on agar plates, and no inhibition was investigated for Rhizopus sp. and Fusarium spp. by the tested volatile and non-volatile compounds, respectively. Moreover, mint oil showed inhibition degrees as well as volatile compounds of antagonists for all of the tested pathogens except against Rhizopus. Sugarbeet treated with mint oil as well as culture filtrate of T. harzianum suppressed pathogen spore germination on the surface of sugarbeet root resulted in decreasing rot incidence. This work provides strong evidence that T. harzianum and mint oil are competitors to control sugarbeet rot.

Effect of Ectomycorrhizal Fungi and Trichoderma harzianum on the Clove (Syzygium aromaticum L.) Seedlings Performances

This study aims to find out the interaction effect of application combination of ectomycorrhizal fungi and Tc-Jjr-02 Trichoderma harzianum isolate on initial growth of clove seed (Syzygium aromaticum L.). The experiment was arranged factorially by using Completely Randomized Design; first factor: application of ectomycorrhizal fungi (without and with ectomycorrhiza), while the second factor: the application of Trichoderma fungi (without and with T. harzianum), the experiment was repeated 4 times. The variables observed were: number of leaves, leaf area, stem diameter, root length, root weight, wet weight and dried straw, and intensity of mycorrhiza infection. Data analysis using 5% ANNOVA continued with HSD test. The results showed that there was a significant interaction effect between the combination of ectomycorrhizal fungi and Trichoderma application on the number and extent of leaf and the intensity of root infection of clove seedlings. The combination of ectomycorrhizal fungi and T. harzianum isolates can be used for the production of healthy clove seedlings.

Response surface methodology based optimization of keratinase production from Trichoderma harzianum isolate HZN12 using chicken feather waste and its application in dehairing of hide

Keratin proteins are a major constituent of feathers which largely contribute to environmental pollution. The present study reports a potent feather degrading fungi isolated from soil and molecularly characterized (18S rDNA gene sequencing) and identified as Trichoderma harzianum isolate HZN12 (KP235366). Assessment of keratinase production from the isolate revealed better production under solid state fermentation (SSF) conditions (1320 U/g) over submerged (185 U) using chicken feathers. The effect and contribution of independent process variables were studied by Plackett–Burman design. Additionally, statistical modeling by central composite design of response surface methodology was applied to optimize the culture conditions for keratinase production under SSF. Maximum keratinase production (10,150 U/g) was validated with a 7.7 fold increase under the optimized conditions (chicken feather meal 3 g/20 ml, yeast extract 0.2%, glucose 0.9%, pH 8.5 and temperature of 37 °C) with a correlation coefficient (R2) = 95.56%. Keratinase was employed for dehairing of goat hide and assessed based on different organoleptic properties. The keratinase dehaired skin exhibited superior properties in comparison to the chemical treatment. Furthermore, keratinase also showed good stability and compatibility with the tested commercial detergents making it suitable for industrial applications such as, leather and detergent industries. The results suggest an ecofriendly approach for biodegradation of chicken feather waste.

Efektivitas Beberapa Isolat Trichoderma Sp. Terhadap Keterjadian Penyakit Bulai yang Disebabkan oleh Peronosclerospora maydis dan Pertumbuhan Tanaman Jagung (Zea mays)

Corn (Zea mays) is one of the important cereals crops as the source of food, animals feed or energy. The corn produces has decreased by year to year. One of the factors that decreased the corn produces is downy mildew. Downy mildew desease caused by Peronosclerospora maydis fungi that decreased the production until 90%. Application of antagonistic fungi is one of the alternative control. Trichoderma spp. is one of the antagonistic fungi that can suppress growth of another fungus. Trichoderma spp. is saprofit soil microorganism that naturally attacks pathogen fungi and has benefits for plant growth. This research was aimed to know the effect of some isolates of Trichoderma spp. for diseases of downy mildew and the effect for the plant growth. Treatments were prepared with Randomized Complete Block (RCB) with 7 treatments and 4 repetitions. The treatments consist are P0 (control), P1 (application Trichoderma viride isolate GDR), P2 (application Trichoderma harzianum isolate TRJ), P3 (application Trichoderma harzianum isolate TGN), P4 (application Trichoderma viride isolate NTF), P5 (application Trichoderma longibrachiatum isolate GRP) and P6 (application Trichoderma viride isolate KLN). The results of this research were Trichoderma viride isolate GDR, Trichoderma harzianum isolate TGN, Trichoderma viride isolate NTF and Trichoderma viride isolate KLN can be suppressed the disease incidence of downy mildew, but unaffected for the plants growth.

Evaluation of Some Trichoderma harzianum Isolates for the Management of Soilborne Diseases of Brinjal and Okra

Present study investigated the efficacy of 6 Trichoderma harzianum isolates against damping off and wilt diseases of brinjal and okra caused by Fusarium oxysporium (FO) and Pythium aphanidermatum (PA), respectively in order to get more effective isolates for disease management. Isolated pathogens from brinjal were named as Fob and Pab and from okra Foo and Pao for F. oxysporum and P. aphanidermatum, respectively. In vitro analysis revealed that T. harzianum isolates inhibited the radial growth of both pathogens and isolate Th-Sks was most effective with 78.44 and 74.16% growth inhibition of Fob and Pab, and 78.19 and 78.11% of Foo and Pao, respectively. Production of volatile and non-volatile metabolites by isolate Th-Sks was more aggressive in mycelial growth inhibition of all test pathogens than that of other isolates. Isolate Th-Sks had highest suppression efficacy i.e. 95.92 and 98.93% for Fob and Pab, 96.43 and 93.33% for Foo and Pao under glasshouse conditions, 96.18 and 95.73% for Fob and Pab, and 94.66 and 96.18% for Foo and Pao in the field conditions, respectively. Additionally, seed treatment of brinjal and okra with isolate Th-Sks gave a significant stimulatory effect on plant height (brinjal 52.9 cm; okra 110.5 cm) and increased fruit yield (brinjal 328.3 g; okra 294.6 g) in comparison to other isolates and control sets during field trials. Thus, it is concluded that isolate Th-Sks can be used as biocontrol agent for management of wilt and damping off diseases of okra and brinjal after multilocation trials.

Screening of native Trichoderma harzianum isolates for their ability to control Verticillium wilt of strawberry

Screening of native Trichoderma harzianum isolates for their ability to control Verticillium wilt of strawberry

Biological spectrum of Trichoderma harzianum Rifai isolates to control fungal diseases of tomato (Solanum lycopersicon L.)

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.

Vineyard Compost Supplemented with Trichoderma Harzianum T78 Improve Saline Soil Quality

AbstractUnderstanding soil degradation is especially important in the Mediterranean Region where desertification is a serious problem, and soil salinization is one of the causes. Salinity reduces soil quality, limits crop productivity and brings on long term soil degradation. Therefore the restoration of degraded soils is necessary to reduce land degradation, improve soil fertility and achieve a sustainable food production. The addition of compost supplemented with the beneficial microorganism Trichoderma harzianum isolate T78 to saline soils (NaCl) was studied to determine the impact on soil microbiology, which is the key to restore and rehabilitate degraded soils. The selected Trichoderma harzianum isolate T78 showed high salt tolerance despite the low osmotolerance of the genus Trichoderma. Increasing salt concentration reduced Trichoderma sp colony‐forming units (CFU) from natural soil and adversely affected soil microbial biomass C as well as dehydrogenase, β‐glucosidase, phosphatase and urease activities. Simultaneous amendment of the saline soil with compost and inoculation with T. harzianum T78 improved the soil microbiological quality; the number of T. harzianum T78 CFU did not decrease as NaCl increased. As T. harzianum strain T78 is salt tolerant, increasing the relative abundance of this specific strain would contribute to the rehabilitation of saline soils. Vineyard composts supplemented with T. harzianum T78 represent a promising approach for the treatment and improvement of saline soil properties. Copyright © 2016 John Wiley & Sons, Ltd.

Influence of exogenous cholesterol in Pythiaceae resistance to inhibition by Trichoderma antibiosis

The purpose of this study was to determine if exogenous cholesterol availability influenced Pythiaceae resistance to antibiosis. Characterisation of an isolate of Phytophthora erythroseptica and Pythium ultimum for tolerance to antibacterial compounds found that 0.05 g.l−1 chloramphenicol inhibited mycelial growth by 96.6 % and 23.5 % respectively. However, the addition of cholesterol (0.01 g l−1) to potato dextrose agar (PDA) containing 0.05 g l−1 chloramphenicol was found to increase mycelial growth of P. erythroseptica, indicating a role for cholesterol in tolerance to inhibitory antibacterial compounds. To determine if this property extended to suppressive effects of a potential biocontrol agent, P. erythroseptica and P. ultimum were then tested against a cell-free filtrate of diffusible metabolites produced by a suppressive Trichoderma harzianum isolate in the presence and absence of cholesterol in PDA. In the absence of cholesterol, diffusible metabolites of the T. harzianum isolate were found to inhibit mycelial growth of P. erythroseptica and P. ultimum on PDA by 98 % and 63.6 % respectively (P < 0.0001). However, the inhibitory effect of the metabolites was mitigated when 0.005 g l−1 of cholesterol was present in PDA, with mycelial growth of P. ultimum and P. erythroseptica reduced by only 60.4 % and 41.8 %, respectively (P < 0.0001), much less inhibition than was observed in the absence of cholesterol. These results demonstrated that access to exogenous cholesterol can influence the sensitivity of Pythiaceae species to antibiosis by positively influencing mycelial growth.

Biological control of Fusarium wilt on common beans by in-furrow application of Trichoderma harzianum

Two field trials were conducted during the summer and winter seasons of 2010 to evaluate the effect of biocontrol agents against Fusarium wilt of common bean. Treatments included six Trichoderma harzianum isolates applied in planting furrows at 1.2 × 1012 conidia/ha, and one seed treatment with carboxin + thiram. Non-treated and infested plots served as control. Three T. harzianum isolates, CEN287, CEN290 and CEN316, reduced Fusarium wilt incidence and disease severity in the summer trial; incidence averaged 43.9 and 82.4 % in effective treatments and infested control plots, respectively. During the winter season, four isolates, CEN290, 1306, CEN316 and CEN287, reduced wilt incidence by 22.4, 26.7, 41.2 and 51.3 %, respectively, compared to the infested control (92.8 %) and fungicide-treated seeds (85.8 %). In general, ranking of treatments were similar whether incidence or severity was evaluated. However, CEN287 and CEN316 were ranked as the most effective isolates in both seasons. Crop yield-related variables were not affected by the treatments. Fusarium oxysporum population in soil was positively associated with disease incidence and severity, and negatively associated with grain number per pod and 100-grain mass in the summer experiment. In the winter trial, increasing densities of Trichoderma spp. in soil were correlated with increased 100-grain mass and number of grains per pod. The results highlight the value of in furrow applications of biocontrol agents for managing Fusarium wilt of common bean.