Acidic soils rapidly retain applied phosphorus fertilizers and consequently present low availability of this nutrient to plants. The use of phosphate-solubilizing microorganisms to help plant phosphorus (P) absorption is a promising sustainable strategy for managing P deficiencies in agricultural soils. Trichoderma strains have been one of the most studied filamentous fungi for improving the production and development of several crop species mainly due to their capability for symbiotic associations and their ability to control soil-borne plant diseases. Thus, this work sought to bioprospect Trichoderma strains from the Amazon rainforest capable of solubilizing/mineralizing soil phosphate and promoting soybean growth. Soybean plants inoculated with selected Trichoderma strains were cultivated in soil under greenhouse conditions and under a gradient of rock phosphate and triple superphosphate. As a result, 19.5% of the isolated Trichoderma strains were able to solubilize phosphate. In addition, those strains produced different organic acids during the solubilization process. Trichoderma spp. strains showed positive responses in the promotion of soybean growth-from 2.1% to 41.1%-as well as in the efficiency of P uptake-up to 141%. These results reveal the potential of Trichoderma spp. from the Amazon biome as promising biofertilizer agents.

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Phosphorus-solubilizing Trichoderma spp. from Amazon soils improve soybean plant growth

Induced resistance to disease in plants

In the present study, the spread of Rhizoctonia solani-induced disease was limited when cucumber plants were pretreated with Trichoderma atroviride TRS25. The systemic disease suppression was related to TRS25-induced resistance (TISR) induction with simultaneous plant growth promotion. Protection of cucumber was related to enhanced activity of defense enzymes, e.g., guaiacol peroxidase (GPX), syringaldazine peroxidase (SPX), phenylalanine ammonia lyase (PAL), and polyphenol oxidase (PPO) as well as phenolic (PC) concentration increases in the conditions of hydrogen peroxide (H2O2) accumulation, resulting in thiobarbituric acid reactive substance (TBARS) decrease. Moreover, the obtained results indicated that TISR might depend on accumulation of salicylic acid derivatives, that is methyl salicylate (MeSA), ethylhexyl salicylate (EHS), salicylic acid glucosylated conjugates (SAGC), and β-cyclocitral as well as volatile organic compounds (VOC) such as Z-3-hexanal, Z-3-hexenol, and E-2-hexenal. The results point to important, not previously documented, roles of these VOC in TISR signaling with up-regulation of PR1 and PR5 gene characteristic of systemic acquired resistance (SAR) and of PR4 gene, marker of induced systemic resistance (ISR). The study established that TRS25 enhanced deposition of callose and lignin in specialized plant cells, which protected vascular system in cucumber shoots and roots as well as assimilation cells and dermal tissues in shoots and leaves. These compounds protected cucumber organs against R. solani influence and made them more flexible and resilient, which contributed to better nutrition and hydration of plants. The growth promotion coupled with systemic mobilization of biochemical and mechanical strengthening might be involved in multilayer protection of cucumber against R. solani activated by TRS25.

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Involvement of metabolic components, volatile compounds, PR proteins, and mechanical strengthening in multilayer protection of cucumber plants against Rhizoctonia solani activated by Trichoderma atroviride TRS25

Tobacco rattle virus (TRV)-mediated virus-induced gene silencing (VIGS) has been frequently used in dicots. Here we show that it can also be used in monocots, by presenting a system involving use of a novel infiltration solution (containing acetosyringone, cysteine and Tween 20) that enables whole-plant level VIGS of (germinated) seeds in wheat and maize. Using the established system, phytoene desaturase (PDS) genes were successfully silenced, resulting in typical photo-bleaching symptoms in the leaves of treated wheat and maize. In addition, three wheat homoeoalleles of MLO, a key gene repressing defense responses to powdery mildew in wheat, were simultaneously silenced in susceptible wheat with this system, resulting in it becoming resistant to powdery mildew. The system has the advantages generally associated with TRV-mediated VIGS systems (e.g., high-efficiency, mild virus infection symptoms, and effectiveness in different organs). However, it also has the following further advantages: (germinated) seed-stage agroinfiltration; greater rapidity and convenience; whole-plant level gene silencing; adequately stable transformation; and suitability for studying functions of genes involved in seed germination and early plant development stages.

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Vacuum and Co-cultivation Agroinfiltration of (Germinated) Seeds Results in Tobacco Rattle Virus (TRV) Mediated Whole-Plant Virus-Induced Gene Silencing (VIGS) in Wheat and Maize.

Fungi of the Trichoderma spp. genus, notably Trichoderma harzianum, are commonly used for biological management of deleterious seed‐ and soil‐borne pathogens. The global biopesticides market is booming with a major share of various commercial formulations of T. harzianum. However, there are some major drawbacks associated with these commercial formulations including short shelf life, low on‐field stability and irregular performance in different agro‐climatic regions. For effectively resolving these issues, new strategies are urgently required for efficient management of pathogens. The present review provides an overview of the use of Trichoderma spp., with special emphasis on T. harzianum, and discusses future trends for biological control. Technologies are described for the microencapsulation of fungi and for the biogenic synthesis of nanoparticles, with the aim of improving the biological control of pathogens and contributing to sustainable agricultural practices. © 2018 Society of Chemical Industry

Trichoderma harzianum‐based novel formulations: potential applications for management of Next‐Gen agricultural challenges

Biocontrol potential of Trichoderma harzianum isolate T-aloe against Sclerotinia sclerotiorum in soybean.

An optimized regeneration and Agrobacterium-mediated transformation protocol based on whole cotyledonary node explants was developed in soybean (Glycine max) cultivar Zhong Huang 13 Adding 6-benzylaminopurine (BAP) in a germinating medium could significantly increase regeneration efficiency; the optimal BAP concentration for shoot formation was 05 mg/L The concentrations of plant growth regulators in a shoot induction medium were optimized by the orthogonal test [L9 (3(3))] The best combination for shoot regeneration was a medium of Murashige & Skoog salts with B5 vitamins (MSB) supplemented with 35 mg/L BAP, 02 mg/L indole-3-butyric acid (IBA), and 02 mg/L kinetin (KT) Under this favorable condition, one node could regenerate 28-30 shoots Soybean whole cotyledonary nodes were transformed by inoculation with A tumefaciens strain EHA105 harboring a vector pBI121 containing a β-glucuronidase gene (gus) GUS assay, polymerase chain reaction, and Southern blot analysis indicated that the gus gene was transformed into soybean plants with 231% transformation efficiency Transgenic plants could be obtained within 5-6 weeks, which was about 4 weeks less than that of a traditional single cotyledonary node method

Honglian Ge

Papers

Biocontrol potential of Trichoderma harzianum isolate T-aloe against Sclerotinia sclerotiorum in soybean.

Efficient soybean regeneration and Agrobacterium-mediated transformation using a whole cotyledonary node as an explant.