Effects of temperature, light and incubation period on production, germination and bioactivity of Trichoderma atroviride

Enhanced activity of Trichoderma asperellum introduced in solarized soil and its implications on the integrated control of strawberry-black root rot

An effective method for maintaining the activity and longevity of microorganisms in adverse conditions is microencapsulation. In the present study, synthetic alginate pellets were developed as carriers for the biocontrol agent Trichoderma asperellum. In two field experiments, solarization was applied for three weeks to loamy clay soil that was naturally infested with strawberry-black root rot fungi (Fusarium solani, Rhizoctonia solani and Machrophomina phaseolina). Following solarization, T. asperellum-based alginate pellets or spore suspension were added to the soil. Data reveal that, three weeks solarization of irrigated soil increased its maximum temperature reached by 11-14.2 °C (1-10 cm depth), 11.6-13.1 °C (11-20 cm depth) and 10.1-12.2 °C (21-30 cm depth). In either trial, solarization also successfully lowers the vitality of strawberry-black root rot fungi directly after the solarization phase. When compared to controls, strawberry-black root rot was substantially less common in solarized plots. In two field trials, soil solarization followed by inoculation with alginate pellets based on T. asperellum led to the greatest reductions in black root rot incidence (59.3 and 74.1 %) and severity (72.5 and 75.2 %), as compared to un-solarized control plots. In vivo studies, this treatment dramatically increased the activity of defensive enzymes (peroxidase and chitinase) and strawberry yield (60.5 and 60.0 %, respectively), as compared to non-solarized control plots. In two field studies, the rhizosphere population of native Trichoderma spp. Developed more in solarized soils after the application of alginate pellets based on T. asperellum (86.5 and 83.6 %, respectively), compared to the non-solarized control.

Plant Growth Promotion and Biological Control against Rhizoctonia solani in Thai Local Rice Variety "Chor Khing" Using Trichoderma breve Z2-03

Several strains of Trichoderma are applied in the field to control plant diseases due to their capacity to suppress fungal pathogens and control plant diseases. Some Trichoderma strains also are able to promote plant growth through the production of indole-3-acetic acid (IAA). In southern Thailand, the local rice variety "Chor Khing" is mainly cultivated in the Songkhla province; it is characterized by slow growth and is susceptible to sheath blight caused by Rhizoctonia solani. Therefore, this research aimed to screen Trichoderma species with the ability to promote plant growth in this rice variety and enact biological control against R. solani. A total of 21 Trichoderma isolates were screened for indole compound production using the Salkowski reagent. The Z2-03 isolate reacted positively to the Salkowski reagent, indicating the production of the indole compound. High-performance liquid chromatography (HPCL) confirmed that Z2-03 produced IAA at 35.58 ± 7.60 μg/mL. The cell-free culture filtrate of the potato dextrose broth (CF) of Z2-03 induced rice germination in rice seeds, yielding root and shoot lengths in cell-free CF-treated rice that were significantly higher than those of the control (distilled water and culture broth alone). Furthermore, inoculation with Trichoderma conidia promoted rice growth and induced a defense response against R. solani during the seedling stage. Trichoderma Z2-03 displayed an antifungal capacity against R. solani, achieving 74.17% inhibition (as measured through dual culture assay) and the production of siderophores on the CAS medium. The pot experiment revealed that inoculation with the Trichoderma sp. Z2-03 conidial suspension increased the number of tillers and the plant height in the "Chor Khing" rice variety, and suppressed the percentage of disease incidence (PDI). The Trichoderma isolate Z2-03 was identified, based on the morphology and molecular properties of ITS, translation elongation factor 1-alpha (tef1-α), and RNA polymerase 2 (rpb2), as Trichoderma breve Z2-03. Our results reveal the ability of T. breve Z2-03 to act as a plant growth promoter, enhancing growth and development in the "Chor Khing" rice variety, as well as a biological control agent through its competition and defense induction mechanism in this rice variety.

Identification of a pathogen causing fruiting body rot of Sanghuangporus vaninii

Sanghuangporus vaninii is a medicinal macrofungus that is increasingly cultivated in China. During cultivation, it was found that the fruiting body of S. vaninii was susceptible to pathogenic fungi, resulting in significant economic losses to the industry. The symptoms of the disease occur in the initial stage of fruiting body development. The isolate YZB-1 was obtained from the junction of the diseased and healthy areas of the fruiting body. In order to verify the pathogenicity of YZB-1, its purified spore suspension was inoculated into the exposed area nearby the developing fruiting body of S. vaninii. After 10 days, the same disease symptoms appeared in the inoculated area. Morphological identification and molecular analysis of rDNA ITS region confirmed that the isolate YZB-1 was identified as Trichoderma virens. The temperature stability assay revealed that the mycelia of YZB-1 grew the fastest at 25 °C, with growth slowing down gradually as the temperature increased or decreased. Dual-culture tests of T. virens and S. vaninii showed that the inhibition rate of T. virens on S. vaninii mycelium was the highest (79.01 ± 2.79%) at 25 °C, and more green spores were produced at the intersection of T. virens and S. vaninii.

Light-Induced Changes in Secondary Metabolite Production of Trichoderma atroviride

Many studies aim at maximizing fungal secondary metabolite production but the influence of light during cultivation has often been neglected. Here, we combined an untargeted isotope-assisted liquid chromatography-high-resolution mass spectrometry-based metabolomics approach with standardized cultivation of Trichoderma atroviride under three defined light regimes (darkness (PD), reduced light (RL) exposure, and 12/12 h light/dark cycle (LD)) to systematically determine the effect of light on secondary metabolite production. Comparative analyses revealed a similar metabolite profile upon cultivation in PD and RL, whereas LD treatment had an inhibiting effect on both the number and abundance of metabolites. Additionally, the spatial distribution of the detected metabolites for PD and RL was analyzed. From the more than 500 detected metabolites, only 25 were exclusively produced upon fungal growth in darkness and 85 were significantly more abundant in darkness. The majority were detected under both cultivation conditions and annotation revealed a cluster of substances whose production followed the pattern observed for the well-known T. atroviride metabolite 6-pentyl-alpha-pyrone. We conclude that cultivation of T. atroviride under RL can be used to maximize secondary metabolite production.

Preparation of Trichoderma asperellum Microcapsules and Biocontrol of Cucumber Powdery Mildew

Microencapsulation is an important technique for protecting the viability and activity of microorganisms under adverse environmental conditions. To improve biological control, controlled-release microcapsules of Trichoderma asperellum were prepared and embedded in combinations of the biodegradable wall materials sodium alginate (SA). The microcapsules were evaluated for their ability to control cucumber powdery mildew in the greenhouse. The results showed that the highest encapsulation efficiency of 95% was obtained by applying 1% SA and 4% calcium chloride. The microcapsules provided good, controlled release and UV resistance, and could be stored for a long time. The greenhouse experiment revealed that the T. asperellum microcapsules had a maximal biocontrol efficiency of 76% against cucumber powdery mildew. In summary, embedding T. asperellum in microcapsules is a promising technique to improve the survivability of T. asperellum conidia. The T. asperellum microcapsules exerted significant biocontrol efficiency against cucumber powdery mildew. IMPORTANCE Trichoderma asperellum is widely found in plant roots and soil and has been used for the biocontrol of various plant pathogens; however, the control efficiency of T. asperellum is usually unstable in field trials. To improve the control efficiency of T. asperellum, in the present study, T. asperellum microcapsules were prepared using sodium alginate as wall material to reduce the effects of temperature, UV irradiation, and other environmental factors on its activity, and to significantly improve its biocontrol efficiency on cucumber powdery mildew. Microcapsules can prolong the shelf life of microbial pesticides. This study provides a new way to prepare a biocontrol agent against cucumber powdery mildew with high efficiency.

Solid-State Fermentation of Trichoderma spp.: A New Way to Valorize the Agricultural Digestate and Produce Value-Added Bioproducts

In this study, the agricultural digestate from anaerobic biogas production mixed with food wastes was used as a substrate to grow Trichoderma reesei RUT-C30 and Trichoderma atroviride Ta13 in solid-state fermentation (SSF) and produce high-value bioproducts, such as bioactive molecules to be used as ingredients for biostimulants. The Trichoderma spp. reached their maximum growth after 6 and 3 SSF days, respectively. Both Trichoderma species were able to produce cellulase, esterase, and citric and malic acids, while T. atroviride also produced gibberellins and oxylipins as shown by ultraperformance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) profiling. Experimental evaluation of germination parameters highlighted a significant promotion of tomato seed germination and root elongation induced by T. atroviride crude extracts from SSF. This study suggests an innovative sustainable use of the whole digestate mixed with agro-food waste as a valuable substrate in fungal biorefineries. Here, it has been applied to produce plant growth-promoting fungi and bioactive molecules for sustainable agriculture.

In Vitro Biocontrol Evaluation of Some Selected Trichoderma Strains against the Root Pathogen Fusarium oxysporum of Hot Pepper (Capsicum annum L.) in Bure Woreda, Ethiopia

Capsicum annum L. is a major vegetable crop consumed worldwide as a spice, vegetable, pickle, condiment, and sauce. Each year in Ethiopia, 80% of the yield loss of hot peppers is caused by Fusarium wilt. Controlling this disease using fungicides can pollute the environment and induce genetic resistance in fungal phytopathogens. To solve this serious problem, it is necessary to look for economically safe, long-lasting, and effective biocontrol alternatives. Therefore, the objective of this work was to evaluate antagonistically active Trichoderma strains against F. oxysporumf.sp.capsici using a dual culture assay. The results of this study revealed that out of 32 Trichoderma isolates tested in vitro, only six (T. harzianum (TD1), T. asperellum (TD5), T. viride (TD7), T. hamatum (TD11), T. virens (TD15), and T. longibrachiatum (TD21)) strains showed a varying rate (45.72–93.57%) of biocontrol activity toward the tested pathogen. Of six isolates, three (TD5, TD1, and TD7) strains showed effective antagonists against the root pathogen Fusarium oxysporum f.sp.capsici of hot pepper (C. annum) with a colonization percentage of 89.45%, 90.12%, and 93.57%, respectively. These Trichoderma strains showed higher inhibition efficiency (> 70%) against the mycelial growth of F. oxysporum with good stress tolerance (temperature, pH, salt concentration, and heavy metals) ability. The isolates also produce different hydrolytic enzymes (amylase, protease, cellulase, and chitinase) with mycoparasitism potential against the mycelia growth of F. oxysporum. Therefore, the results of this study concluded that TD1, TD5, and TD7 Trichoderma strains showed potential biocontrol effects with wide stress tolerance ability against the root pathogen F. oxysporum of hot pepper and can thus be recommended as the best alternative for wide greenhouse and field trial evaluations.

Rapid and mass production of biopesticide Trichoderma Brev T069 from cassava peels using newly established solid-state fermentation bioreactor system

Converting agricultural waste into value-added biopesticides to replace chemical pesticides for plant protection is a good alternative for environmental sustainability and resource recycling. In this study, five tropical wastes (cassava peels, banana pseudostem, coconut shell, sugarcane bagasse, and pineapple peels) were screened as substrates for the rapid production of biopesticide Trichoderma Brev T069. Five single tests and a Box-Behnken design (BBD) with response surface methodology were used to optimize the culture conditions to improve the spore yield. The results showed that cassava peel was the optimal solid fermentation substrate, and the optimization enabled a spore yield of 9.31 × 10⁹ spores/g at 3rd day, which was equal to 93.19% of spore yield obtained at 5th day (9.99 × 10⁹ spores/g). A newly packed-bed bioreactor with agitation and ventilation system was developed and used to expand the production that 250 kg of biopesticide (2.89 × 10⁹ spores/g) could be available on the 3rd day. A pot experiment indicated that the biopesticide T. Brev T069 obtained under this production system, when applied at 1 × 10⁷ spores/g of soil had a 64.65% biocontrol efficiency on banana fusarium wilt. This study provides a practical solution for turning a tropical waste into an effective biopesticide which can prevent banana wilt disease, thereby helping to reduce disease management cost and overcome environmental hazards caused by synthetic pesticides.

Temperature Differentially Influences the Capacity of Trichoderma Species to Induce Plant Defense Responses in Tomato Against Insect Pests

Species of the ecological opportunistic, avirulent fungus, Trichoderma are widely used in agriculture for their ability to protect crops from the attack of pathogenic fungi and for plant growth promotion activity. Recently, it has been shown that they may also have complementary properties that enhance plant defense barriers against insects. However, the use of these fungi is somewhat undermined by their variable level of biocontrol activity, which is influenced by environmental conditions. Understanding the source of this variability is essential for its profitable and wide use in plant protection. Here, we focus on the impact of temperature on Trichoderma afroharzianum T22, Trichoderma atroviride P1, and the defense response induced in tomato by insects. The in vitro development of these two strains was differentially influenced by temperature, and the observed pattern was consistent with temperature-dependent levels of resistance induced by them in tomato plants against the aphid, Macrosiphum euphorbiae, and the noctuid moth, Spodoptera littoralis. Tomato plants treated with T. afroharzianum T22 exhibited enhanced resistance toward both insect pests at 25°C, while T. atroviride P1 proved to be more effective at 20°C. The comparison of plant transcriptomic profiles generated by the two Trichoderma species allowed the identification of specific defense genes involved in the observed response, and a selected group was used to assess, by real-time quantitative reverse transcription PCR (qRT-PCR), the differential gene expression in Trichoderma-treated tomato plants subjected to the two temperature regimens that significantly affected fungal biological performance. These results will help pave the way toward a rational selection of the most suitable Trichoderma isolates for field applications, in order to best face the challenges imposed by local environmental conditions and by extreme climatic shifts due to global warming.

Evaluating the impact of turf-care products on soil biological health

Golf courses require extensive use of inputs to meet the needs of playability and aesthetics. The impact of these inputs on soil biological health is largely unknown. Two field trials were conducted at a golf course in Georgia to evaluate short-term effects of wetting agents (Cascade Plus and Duplex [C+D], Revolution [Rev]), plant growth regulators (PrimoMaxx [PM] and Cutless [CL]), and a product called PlantHelper (PH) on soil biological health by measuring microbial abundance and function. Quantitative polymerase chain reaction was used to measure microbial abundance, which included total bacteria, total fungi, and ammonia-oxidizing prokaryotes. Soil respiration and enzyme assays were used as additional indicators of soil health. In bentgrass putting green, total bacteria and ammonia-oxidizing bacteria decreased in abundance in response to the wetting agents and PH, indicating their sensitivity to the products. Whereas C+D stimulated urease activity, Rev and PH caused a short-lived but immediate increase in respiration, indicating that they acted as labile carbon sources. In a bermudagrass fairway, PM was the only product that caused an increase in total bacteria abundance. PrimoMaxx and CL caused a delayed increase in respiration, suggesting that they may have affected the microorganisms indirectly through their impact on root growth and exudate production later. Although CL caused a decrease in urease activity, none of the products significantly affected phosphatase activity. Overall, the products did not seem to have a lasting impact on soil biological health, although long-term studies are needed to confirm these observations.

Evaluation ofTrichoderma atroviride and Trichoderma citrinoviride growth profiles and their potentials as biocontrol agent and biofertilizer

Background

Two Trichoderma species (T. atroviride and T. citrinoviride) were evaluated for their potential to have Trichoderma-based biological control agent and biofertilizer properties.

Materials and Methods

Eight Trichoderma spp. were identified by molecular methods. The mycoparasitic activities against different phytopathogenic fungi and their capacity to produce extracellular lytic enzymes were investigated. Furthermore, indole-3-acetic acid production and phosphate solubilization capabilities of Trichoderma spp. were evaluated together with the effect of some physical parameters and different carbon:nitrogen sources on mycelial growth and conidium production.

Results and Discussion

All strains exhibited lytic enzymes and indole-3 acetic acid production as well as phosphate solubility characteristics. Trichoderma citrinoviride demostrated more mycoparasitic activity against Fusarium oxysporium than T. atroviride whereas T. atroviride was found more effective against Rhizoctonia solani. In particular, at lower temperatures, conidium production of T. atroviride strains were significantly higher than T. citrinoviride strains. Both strains grew well on all carbon sources tested. The effect of organic nitrogen sources on growth were notably higher than inorganic nitrogen sources.

Conclusion

The results provided valuable insight in both the highest mycelial growth and conidia production conditions of these cultures for further similar studies related to development of Trichoderma-based new commercial biological control and biofertilizer formulations in different agro-climatic regions.