Ecological management of tropical sugar beet (TSB) root rot (Sclerotium rolfsii (Sacc.) by rhizosphere Trichoderma species

Trichoderma species are collected from different location of sugarbeet growing areas of Tamil Nadu and it is effective against Sclerotium rolfsii pathogen caused by sugarbeet ecosystems. Out of thirty-one isolates of Trichoderma viride and four isolates of Trichoderma harzianum collected and tested for their antagonistic activity against S. rolfsii by dual culture technique, one isolate was found to be effective T. viride (TVB1) that recorded the maximum (73.03%) inhibition on the mycelial growth recording only 2.40 cm growth as against 8.90 cm in the control. The isolates of T. harzianum THB-1 recorded 71.19% mycelial growth reduction over control. The colonisation behaviour of T. viride (TVB1) revealed that it completely over grew on pathogen within 48 h after interaction with the pathogen, and speed of growth on pathogen was also high and it possesses a higher level of competitive saprophytic ability. The best four isolates of TVB1, TVB-2, TVB-3 and TVB31 and two isolates of T. harzianum THB-1 and THB-2 were compared with other species of Trichoderma longibrachiatum, Trichoderma reesei, Trichoderma koningii and Chaetomium globosum and tested under in vitro condition. BA of neem cake at 150 kg ha^?1 + T. viride isolate (TVB1) at 2.5 kg/ha recorded least root rot disease incidence of 17.05% which accounted for 75.37% disease reduction over control and highest recorded maximum root yield 65.73 t ha^?1 and increasing sugar content.     

Use of Trichoderma harzianum and Gliocladium vitens for the Biological Control of Post-emergence Damping-off and Root Rot of Cucumbers Caused by Pythium ultimum

The antagonist strains Gliocladium virens G2 and Trichoderma harzianum T3 originally isolated from Pythium suppressive peat, and two benomyl-resistant strains of T. harzianum, T12B and T95, were evaluated as biological control agents of damping-off and root rot of cucumbers in sphagnum peat caused by Pythium ultimum. All strains were equally effective when applied as 1 % peat-bran preparations, whereas the effectiveness of disease control was reduced at higher concentrations of the antagonists. The two wild-type strains were also found to be effective when applied as conidial suspensions, and in this case no reduction in disease control was seen at higher concentrations. G. virens G2 and T. harzianum T12B showed antibiotic activity against P. ultimum in in vitro tests; however there were no signs of mycoparasitism of P. ultimum by any of the antagonist strains.     

Studies on the Biological Control of Phytophthora cryptogea Pethybr. et Laff. II. Effectiveness of Trichoderma and Gliocladium spp. in the Control of Phytophthora Foot Rot of Gerbera

Bip T containing about 10⁹ spores of Trichoderma viride, applied to peat 10 days before inoculation of substrate with Phytophthora cryptogea, effectively controlled Phytophthora foot rot of gerbera. The biocide in dosage of 300 and 600 g/m³ inhibited the development of the pathogen in substrate. The other potential antagonists T. hamatum and T. viride applied into peat at a dosage of 600 g/m³, decreased Phytophthora foot rot development.     

Evaluation of seed dressing and soil application formulations of Trichoderma species for integrated management of dry root rot of chickpea

The efficacy of the newly developed seed dressing and soil application formulations of Trichoderma viride, T. virens and T. harzianum were evaluated individually and in combinations under pot and field experiments for the management of dry root rot (Rhizoctonia bataticola) of chickpea (Cicer arientinum). In pot experiments, T. harzianum based seed dressing formulation, Pusa 5SD, and soil application formulations, Pusa Biogranule 5 (PBG 5) and Pusa Biopellet 10G (PBP 10G), were found to be effective in reducing dry root rot incidence in chickpea and increasing the seed germination, shoot and root lengths of the crop. Under field experiments, a combination of soil application of T. harzianum based PBP 10G and seed treatment with Pusa 5SD+carboxin was found to be the best by providing the highest seed germination, shoot and root lengths and grain yield and the lowest dry root rot incidence in chickpea.     

Mycolytic effect of extracellular enzymes of antagonistic microbes to Colletotrichum falcatum,red rot pathogen of sugarcane

Strains of selected bacteria and Trichoderma harzianum isolated from sugarcane rhizosphere and endosphere regions were tested for the production of chitinolytic enzymes and their involvement in the suppression of Colletotrichum falcatum, red rot pathogen of sugarcane. Among several strains tested for chitinolytic activity, 12 strains showed a clearing zone on chitin-amended agar medium. Among these, bacterial strains AFG2, AFG 4, AFG 10, FP7 and VPT4 and all the tested T. harzianum strains produced clearing zones of a size larger than 10 mm. The antifungal activity of these strains increased when chitin was incorporated into the medium. Trichoderma harzianum strain T5 showed increased levels of activity of N-acetylglucosaminidase and -1,3-glucanase when grown on minimal medium containing chitin or cell wall of the pathogen. Lytic enzymes of bacterial strains AFG2, AFG4, VPT4 and FP7 and T. harzianum T5 inhibited conidial germination and mycelial growth of the pathogen. Enzymes from T. harzianum T5 were found to be the most effective in inhibiting the fungus. When mycelial discs of the pathogen were treated with the enzymes, electrolytes were released from fungal mycelia. The results indicated that antagonistic T. harzianum T5 caused a higher level of lysis of the pathogen mycelium, and the inhibitory effect was more pronounced when the lytic enzymes were produced using chitin or cell wall of the pathogen as carbon source.     

Biocontrol of onion white rot by application of Trichoderma species formulated on wheat bran powder

In vitro, Trichoderma album, Trichoderma harzianum, Trichoderma koningii, Trichoderma viride and Trichoderma virens showed antagonistic effect against the most pathogenic isolate (Sc2) of Sclerotium cepivorum, the cause of onion white rot disease. Five Trichoderma preparations of each Trichoderma sp. were prepared on wheat bran powder to be used for controlling white rot disease of onion. Greenhouse and field experiments followed the same trend where T. harzianum and T. koningii were the most effective in reducing the incidence and severity of white rot disease compared with the control. Trichoderma species preparations caused promotion to vegetative parameters of onion plants in pots and increase bulb productivity in filed. In this regard, T. harzianum and T. koningii were the most effective. A positive correlation was found between the biocontrol activity of Trichoderma species preparations and enhancement of peroxidase, polyphenoloxidase and chitinase enzymes in onion plants to resist infection with S. cepivorum.     

Nutritional constraints on displacement of Fusarium pseudograminearum from cereal straw by antagonists

Displacement of the fungus Fusarium pseudograminearum from stubble by antagonists is a potential means of biocontrol of crown rot in cereals. The role of carbon and nitrogen nutrition in interactions between the pathogen and the antagonists Fusarium equiseti, Fusarium nygamai, Trichoderma harzianum and the non-antagonistic straw fungus Alternaria infectoria was investigated. Sole carbon source utilization patterns on Biolog plates were similar among the three Fusarium species, suggesting a possible role for competition. However, carbon niche overlap was unlikely to be important in antagonism by T. harzianum. Straw medium supplemented with sugars generally reduced the inhibitory effect of antagonists on growth of F. pseudograminearum in dual culture, indicating that availability of simple carbon sources does not limit antagonism. Adding nitrogen as urea, nitrate or ammonium to straw medium had little effect on antagonism by F. equiseti and F. nygamai, but ammonium addition removed the inhibitory effect of T. harzianum on growth of F. pseudograminearum. Displacement of F. pseudograminearum from straw by all fungi in a Petri dish assay was greater when urea or nitrate was used as a nitrogen source than with ammonium. All forms of nitrogen significantly increased displacement of F. pseudograminearum from straw under simulated field conditions when straws were either inoculated with T. harzianum or exposed to resident soil microbes. However, in 2 out of 3 experiments urea and nitrate were more effective than ammonium. The results suggest that availability of nitrogen, but not carbon, is limiting the activities of antagonists of F. pseudograminearum in straw, and the way nitrogen is applied can influence the rate of displacement and mortality of the pathogen in host residues.     

Mixed PGPR consortium: an effective modulator of antioxidant network for management of collar rot in cauliflower

Abstract

Sclerotinia sclerotiorum is a cosmopolitan fungal pathogen causing stem and collar watery soft rot of cauliflower. Previous management of this disease with chemical pesticides caused hazardous results which lead to use of more eco-friendly microbial approaches. In the present study, consortia of Trichoderma harzianum TNHU27 and Pseudomonas aeruginosa PJHU15 were assessed for their ability in controlling Sclerotinia rot in cauliflower. The seedlings of cauliflower were challenged singly and in consortium with these two compatible microbes. The plants were evaluated upon challenge inoculation with S. sclerotiorum for changes in total phenolic content, the activity of defense and antioxidative enzymes. The microbial consortium comprising of T. harzianum and P. aeruginosa significantly enhanced the defense responses of the plant in comparison to pathogen challenged and unchallenged control. The study elucidates that plant beneficial microbes in the consortium may provide superior protection by induction of faster and enhanced defense responses in comparison to unchallenged and single microbe challenged plants under pathogen challenged conditions.     

An integrated approach to managing Rhizoctonia solani on maize in marginal soils: field studies

Abstract

A study was conducted over two seasons in a marginal soil with an acid saturation of 54%. A plant growth promoting rhizobacterium, Bacillus megaterium, a commercial biocontrol agent, Trichoderma harzianum Strain kd (Eco-T^®), and soluble potassium silicate were used in this study. The objective was to control maize yield reduction caused by Rhizoctonia solani AG2 root rot isolated from infected maize. R. solani reduced maize yields significantly by 34% in the first season. However, the losses decreased in the second season from 34% to 10%. In the first season, combination of T. harzianum, B. megaterium and potassium silicate increased maize yields by 130%. The highest yield in the presence of R. solani was treatments with T. harzianum (216%) followed by T. harzianum plus potassium silicate (214%) and lastly T. harzianum plus B. megaterium (178%). However, in the second season, T. harzianum plus potassium silicate treatment resulted in the highest yields.     

Trichoderma species on Agaricus bisporus farms in Serbia and their biocontrol

Twenty Trichoderma isolates were collected on 13 Serbian Agaricus bisporus farms and one in Bosnia and Herzegovina during 2006–2010. Twelve isolates were classified into five species by standard mycological studies and ITS1/ITS4 sequence analyses, namely Trichoderma atroviride, Trichoderma koningii, Trichoderma virens, Trichoderma aggressivum f. europaeum and Trichoderma harzianum. Eight isolates were not identified to the species level but were shown to be related to T. harzianum. The isolates of T. harzianum exhibited the highest virulence to the harvested A. bisporus pilei and T. virens and T. aggressivum f. europaeum the lowest. Antifungal activity of two biofungicides based on Bacillus subtilis and tea tree oil and the fungicide prochloraz manganese were tested in vitro to all Trichoderma isolates. Prochloraz manganese and B. subtilis were highly toxic to all tested Trichoderma isolates, their ED₅₀ values were below 0.3 and 1.3 mg L^?1, respectively. Tea tree oil did not exhibit a significant antifungal activity (ED₅₀ = 11.9–370.8 mg L^?1). The effectiveness of biofungicides was evaluated against T. harzianum in a mushroom growing room, and they were applied alone or in combination with the fungicide at a respective proportion of 20:80%. Prochloraz manganese showed higher effectiveness than both tested biofungicides or their respective mixtures. The biofungicide based on B. subtilis demonstrated greater effectiveness in preventing disease symptoms than tea tree oil. B. subtilis combined with the fungicide revealed less antagonism in effectiveness against pathogen than tea tree oil.     

The volatile-producing Flavobacterium johnsoniae strain GSE09 shows biocontrol activity against Phytophthora capsici in pepper

Aims: Previously, we selected a bacterial strain (GSE09) antagonistic to Phytophthora capsici on pepper, which produced a volatile compound (2,4‐di‐tert‐butylphenol), inhibiting the pathogen. In this study, we identified strain GSE09 and characterized some of the biological traits of this strain in relation to its antagonistic properties against P. capsici. In addition, we examined bacterial colonization on the root surface or in rhizosphere soil and the effect of various concentrations of the volatile compound and strain GSE09 on pathogen development and radicle infection as well as radicle growth. Methods and Results: Strain GSE09 was identified as Flavobacterium johnsoniae, which forms biofilms and produces indolic compounds and biosurfactant but not hydrogen cyanide (HCN) with little or low levels of antifungal activity and swimming and swarming activities. Fl. johnsoniae GSE09 effectively colonized on pepper root, rhizosphere, and bulk (pot) soil, which reduced the pathogen colonization in the roots and disease severity in the plants. Various concentrations of 2,4‐di‐tert‐butylphenol or strain GSE09 inhibited pathogen development (mycelial growth, sporulation, and zoospore germination) in I‐plate (a plastic plate containing a center partition). In addition, germinated seeds treated with the compound (1–100 μg ml^?1) or the strain (10²–10¹⁰ cells ml^?1) significantly reduced radicle infection by P. capsici without radicle growth inhibition. Conclusions: These results indicate that colonization of pepper root and rhizosphere by the Fl. johnsoniae strain GSE09, which can form biofilms and produce indolic compounds, biosurfactant, and 2,4‐di‐tert‐butylphenol, might provide effective biocontrol activity against P. capsici. Significance and Impact of the Study: To our knowledge, this is the first study demonstrating that the Fl. johnsoniae strain GSE09, as a potential biocontrol agent, can effectively protect pepper plants against P. capsici infection by colonizing the roots.     

Isolation of Trichoderma and Evaluation of their Antagonistic Potential against Alternaria porri

Nine isolates of Trichoderma were collected from Assiut Governorate, Egypt, as leaf surface and endophytic fungi associated with onion flora stalks. Four isolates were identified as Trichoderma harzianum, while five isolates were belonging to Trichoderma longibrachiatum. The antagonistic activity of these isolates against onion purple blotch pathogen Alternaria porri was studied in vitro using dual culture assay. All tested Trichoderma isolates showed mycoparasitic activity and competitive capability against the mycelial growth of A. porri. Mycoparastic activity of Trichoderma was manifested morphologically by the overgrowth upon the mycelial growth of the pathogen and microscopically by production of coiling hyphae around pathogen hyphae. Isolates of T. harzianum exhibited high ability to compete on potato dextrose agar (PDA) medium causing the maximum rate of pathogen inhibition (73.12%), while isolates of T. longibrachiatum showed inhibition rate equalling 70.3%. Chitinase activity of Trichoderma was assayed, and T. harzianum Th‐3013 showed the maximum value contributing 2.69 U/min. Application of T. harzianum Th‐3013 to control purple blotch disease in vivo under greenhouse conditions caused disease reduction up to 52.3 and 79.9% before and after 48 h of pathogen inoculation, respectively, while the fungicide Ridomil Gold Plus caused disease reduction comprising 56.5 and 71.7%, respectively. This study proved that T. harzianum Th‐3013 as a biocontrol agent showed significant reduction in onion purple blotch disease compared with the tested fungicide.     

Biological inductions of systemic resistance to collar rot of peppermint caused by Sclerotium rolfsii

The efficacy of eight fungal and eight bacterial isolates was tested for their ability to inhibit the growth of Sclerotium rolfsii, the causal agent of collar rot of peppermint. In vitro studies revealed that Trichoderma harzianum (THA) and Pseudomonas fluorescens (PFM) showed the highest inhibition of mycelial growth (68.28; 74.25 %) of S. rolfsii. The antagonists T. harzianum and P. fluorescens were compatible with each other and they were tested alone and together in in vivo for the control of S. rolfsii. Besides, the induction of defense-related enzymes such as peroxidase, polyphenoloxidase, phenylalanine ammonia-lyase, and the accumulation of phenolics in peppermint plants due to the application of bioagents were also studied. Combined application of talc-based formulation of bioagents and challenge inoculation with S. rolfsii recorded maximum induction of defense-related enzymes, and accumulation of phenolics as compared with individual application. This study suggests that the increased induction of defense-related enzymes (two- to threefold) and phenolic content (threefold) due to the combination treatment of bioagents might be involved in the reduction of collar rot incidence.     

Influence of beneficial microorganisms during in vivo acclimatization of in vitro-derived tea (<Emphasis Type="Italic">Camellia sinensis</Emphasis>) plants

The effects of native isolates of Pseudomonas fluorescens, Azospirillum brasilense, and Trichoderma harzianum on rooting and acclimatization of in vitro-grown shoots and plantlets of tea were evaluated. In vitro bacterization of P. fluorescens failed to establish, while both T. harzianum and A. brasilense retarded shoot growth, eventually overtaking shoot cultures in in vitro rooting. Acclimatization of rooted plantlets in soil amended with bioinoculants, either individually or in various combinations, promoted plantlet survival. Moreover, efficiency of nutrient uptake of plantlets was higher in the presence of microorganisms. Root rot or wilting of tissue culture-derived plants was not observed in bioinoculant-treated plants, as they possessed relatively higher activities of defense enzymes, including peroxidase and phenylalanine ammonia lyase.     

Biocontrol potential of Trichoderma species against mango malformation pathogens

Malformation disease of Mango (Mangifera indica L.) caused by Fusarium moniliforme var. subglutinans is one of the most destructive diseases, which is a major production constraint in the mango-growing regions of India. In this study, The bioagents Trichoderma viride (Tr1), Trichoderma virens (Tr2) and Trichoderma harzianum (Tr3) were evaluated in culture with the pathogens to monitor the antagonistic effect and their volatile compound and culture filtrates (non-volatile compound). It was found that all the three isolates of bioagents significantly checked the growth of F. moniliforme var. subglutinans. In dual culture, the best result was obtained with T. harzianum followed by T. virens and T. viride. A similar result was also observed in the case of culture filtrates ofTrichoderma spp. The results clearly showed that inhibition of the growth of the fusaria isolates by T. harzianum was significantly superior to T. viride andT.virens. In case of antifungal activity of volatile compounds released by Trichoderma isolates, it was also observed that T. virens was more superior to T.harzianum and T. viride.     

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

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

Ultrastructure of Mycoparasitism of Trichoderma, Gliocladium and Laetisaria Species on Botryodiplodia theobromae

Mycoparasitic activities of various isolates of Trichoderma viride, T. harzianum, T. hamatum, T. longibrachiatum, T. koningii, T. pseudokoningii, Gliocladium virens and Laetisaria arvalis were studied against a serious plant pathogen, Botryodiplodia theobromae by scanning electron microscopy (SEM). Macroscopic observations of fungal growth in dual-cultures revealed that most of the isolates made hyphal contact with the pathogen within 2 days after inoculation, leading to the inhibition in pathogen growth. However, T. viride Tv-4, T. hamatum and T. pseudokoningii inhibited pathogen growth before hyphal contact and exhibited an inhibition zone between the colonies of both fungi. SEM investigations demonstrated that in case of hyphal interaction, the firm binding of antagonists (T. viride Tv-1 & Tv-3, T. harzianum Th-1 & Th-2, T. longibrachiatum and L. arvalis) to B. theobromae hyphae established either by coiling around its hyphae, or by penetrating its hyphal cells by forming hooks, haustoria and appressoria-like structures which invariably led to cell disruption. Although T. koningii and G. virens Gv-2 & Gv-3 did not interact physically by way of coiling and penetration, they produced wall lytic enzymes or antifungal substances after coming in contact with B. theobromae which caused wrinkling, bursting and collapsing of pathogen mycelium. It is, therefore, suggested that the outcome of the interaction of antagonist and pathogen was most likely determined by initial hyphal contact that triggered a series of events in pathogen degradation.     

Influence of bio-inoculants on the control of root rot and wilt disease of pyrethrum caused by Rhizoctonia solani

The effect of four bio-inoculants namely, Glomus aggregatum, Streptomyces sp., Bacillus subtilis and Trichoderma harzianum and a fungicide, Ridomil-mancozeb was evaluated on the biomass production and control of root rot and wilt disease under glasshouse conditions. Results showed that 21-day- prior inoculation with G. aggregatum was most effective where none of the treated plants produced disease symptoms and interestingly their growth was increased by 39.4%. The colonisation by G. aggregatum (>80%) also increased P concentration in shoot. While, similar treatment with Streptomyces sp., B. subtilis, T. harzianum and Ridomil-mancozeb individually failed to produce any significant effect over Rhizoctonia solani inoculated control, where all inoculated plant died, prematurely. The simultaneous and 3-day-post treatments of G. aggregatum were non-effective but simultaneous treatment with Streptomyces sp. produced 70% disease control, while B. subtilis and T. harzianum individually provided 50% control. Their effects were either better or at par when compared with the simultaneous treatment of Ridomil-mancozeb. In 3-day-post treatment, Streptomyces, B. subtilis and Ridomil-mancozeb individually provided 50% disease control, whereas T. harzianum was least effective as it could protect only 25% plants against infection. The results reveals that 15 days prior treatment of G. aggregatum can significantly controls the root rot and wilt disease of pyrethrum. Further, treatment of Streptomyces can also serve the next effective post infection control method.     

Potential bio-control agent for management of post-flowering stalk rot complex and maize plant health

The of aim of this study was to evaluate the potentiality of the native isolate of Trichoderma harzianum from IARI farm for the management of post-flowering stalk rot of maize and improvement of plant health. The treatment was tried as a seed treatment with the potent commercial formulation Kalisena SD (Aspergillus niger), neem kernel powder and effective fungicides (Thiram, Carbendazim, Captan) for comparison of its efficacy. The minimum disease was recorded in plots treated with native isolate both due to Fusarium moniliforme and Macrophomina phaseolina. The fungicides Carbendazim and Thiram ranked second in controlling the disease due to F. moniliforme and M. phaseolina, respectively. Plant health with respect to vigour and plant stand were found to be better than those of all the other treatments. It is concluded that the native isolate of T. harzianum may be used for maintaining good plant health and managing post-flowering stalk rot of maize.     

Inhibitory activity of plant growth regulators on Phytophthora palmivora causing cassava tuber rot

Auxins and cytokinins are implicated in a wide variety of developmental and physiological processes in plants. Phytophthora palmivora causes tuber rot in cassava growing regions of Tamil Nadu and Kerala, South India. The in vitro effect of cytokinin, benzyl amino purine (BAP) and auxins, naphthalene acetic acid (NAA) and indole acetic acid (IAA) on P. palmivora mycelium growth was investigated. The inhibitory activity varied among the growth regulators and complete inhibition of the pathogen was observed at 50, 2000 and 2500 ppm by the BAP, IAA and NAA, respectively. The effective growth regulator, BAP was also analysed on tubers before and after the invasion of the pathogen to observe its effect in tuber. Further, it was also checked against the bio-control agent Trichoderma harzianum. The study indicates that the use of BAP could be an important approach in controlling tuber rot pathogen, P. palmivora.