Recent shift in trends of agricultural practices from application of synthetic fertilizers and pesticides to organic farming has brought into focus the use of microorganisms that carryout analogous function. Trichoderma spp. is one of the most popular genera of fungi commercially available as a plant growth promoting fungus (PGPF) and biological control agent. Exploitation of the diverse nature of secondary metabolites produced by different species of Trichoderma augments their extensive utility in agriculture and related industries. As a result, Trichoderma has achieved significant success as a powerful biocontrol agent at global level. The endorsement of Trichoderma spp. by scientific community is based on the understanding of its mechanisms of action against a large set of fungal, bacterial and in certain cases viral infections. However, it is still an agnostic view that there could be any single major mode of operation, although it is argued that all mechanisms operate simultaneously in a synchronized fashion. The central idea behind this review article is to emphasize the potentiality of applications of target specific secondary metabolites of Trichoderma for controlling phytopathogens as a substitute of commercially available whole organism formulations. With the aim to this point, we have compiled an inclusive list of secondary metabolites produced by different species of Trichoderma and their applications in diverse areas with the major emphasis on agriculture. Outlining the importance and diverse activities of secondary metabolites of Trichoderma besides its relevance to agriculture would generate greater understanding of their other important and beneficial applications apart from target specific biopesticides.

The present study is focused on the extracellular synthesis of silver nanoparticles (AgNPs) using culture supernatant of an agriculturally important bacterium, Serratia sp. BHU-S4 and demonstrates its effective application for the management of spot blotch disease in wheat. The biosynthesis of AgNPs by Serratia sp. BHU-S4 (denoted as bsAgNPs) was monitored by UV–visible spectrum that showed the surface plasmon resonance (SPR) peak at 410 nm, an important characteristic of AgNPs. Furthermore, the structural, morphological, elemental, functional and thermal characterization of bsAgNPs was carried out using the X-ray diffraction (XRD), electron and atomic microscopies, energy dispersive X-ray (EDAX) spectrometer, FTIR spectroscopy and thermogravimetric analyzer (TGA), respectively. The bsAgNPs were spherical in shape with size range of ∼10 to 20 nm. The XRD and EDAX analysis confirmed successful biosynthesis and crystalline nature of AgNPs. The bsAgNPs exhibited strong antifungal activity against Bipolaris sorokiniana, the spot blotch pathogen of wheat. Interestingly, 2, 4 and 10 µg/ml concentrations of bsAgNPs accounted for complete inhibition of conidial germination, whereas in the absence of bsAgNPs, conidial germination was 100%. A detached leaf bioassay revealed prominent conidial germination on wheat leaves infected with B. sorokiniana conidial suspension alone, while the germination of conidia was totally inhibited when the leaves were treated with bsAgNPs. The results were further authenticated under green house conditions, where application of bsAgNPs significantly reduced B. sorokiniana infection in wheat plants. Histochemical staining revealed a significant role of bsAgNPs treatment in inducing lignin deposition in vascular bundles. In summary, our findings represent the efficient application of bsAgNPs in plant disease management, indicating the exciting possibilities of nanofungicide employing agriculturally important bacteria.

The beneficial use of silver nanoparticles (AgNPs) in agroecosystems is not fully explored with partial information available, of which most of the studies are limited to laboratory conditions and only few involve natural ecosystems. AgNPs, being the most popular metallic nanoparticles exhibiting antimicrobial property, are predominantly used for plant disease management. Owing to the ill hazards of chemically synthesized AgNPs, their biosynthesis using environment-friendly biomolecules is gaining noteworthy attention. In addition, considering the advantages of nanoformulations over biopesticides, there is no doubt that biosynthesized AgNP-based biopesticides could revolutionize the agricultural sector in the future. Though enhanced commercial use of AgNPs has generated biosafety issues in modern scenario but expecting their significant contribution towards agricultural sector, it is too early to predict the risk factor associated with their usage. To unveil the toxicity factor of AgNPs, we need to focus and understand the major interactions of AgNPs in agroecosytems. Hence, the present review highlights (i) the potential application of AgNPs in the agricultural sector particularly for plant disease management, (ii) significance of biosynthesized AgNPs using microbes and plants over their chemical synthesis, (iii) major interactions of AgNPs in agroecosystems (with soil, soil biota, and plants) with emphasis to deal with toxicity-determining factors, and (iv) identifying future research work holding promising applications of biosynthesized AgNPs in agroecosystems.

Nanotechnology representing a new frontier in modern agriculture is anticipated to become a major thrust in near future by offering potential applications. This integrating approach, i.e., agri-nanotechnology has great potential to cope with global challenges of food production/security, sustainability and climate change. However, despite the potential benefits of nanotechnology in agriculture so far, their relevance has not reached up to the field conditions. The elevating concerns about fate, transport, bioavailability, nanoparticles toxicity and inappropriateness of regulatory framework limit the complete acceptance and inclination to adopt nanotechnologies in agricultural sector. Moreover, the current research trends lack realistic approach that fail to attain comprehensive knowledge of risk assessment factors and further toxicity of nanoparticles toward agroecosystem components viz. plant, soil, soil microbiomes after their release into the environment. Hence in the present review we attempt to suggest certain key points to be addressed in the current and future agri-nanotechnology researches on the basis of recognized knowledge gaps with strong recommendation of incorporating biosynthesized nanoparticles to carry out analogous functions. In this perspective, the major points are as follows: (i) Mitigating risk assessment factors (responsible for fate, transport, behavior, bioavailability and toxicity) for alleviating the subsequent toxicity of nanoparticles. (ii) Optimizing permissible level of nanoparticles dose within the safety limits by performing dose dependent studies. (iii) Adopting realistic approach by designing the experiments in natural habitat and avoiding in vitro assays for accurate interpretation. (iv) Most importantly, translating environmental friendly and non-toxic biosynthesized nanoparticles from laboratory to field conditions for agricultural benefits.

Seeds are the crucial input in agriculture as most of the world food crops are grown from seeds and they are circulated at large scale in international trade. However, many plant pathogens can be seed transmitted, and seed distribution is an extremely capable way of introducing plant pathogens into fresh areas as well as a means of endurance of the pathogen between growing seasons. In past decades, chemicals are widely used for seed treatment as a potent approach towards disease control; however, rising concern about their negative impact on the environment and human health minimizes their use and promotes biological control for plant pathogens. Biopriming is a currently popular approach of seed treatment which includes inoculation of seed with beneficial microorganisms (biological aspect) and seed hydration (physiological aspect) to protect the seed from various seed-and soilborne diseases. Biopriming treatment is able to incite changes in plant characteristics and facilitate uniform seed germination and growth associated with microorganism inoculation. Seed priming and osmo-priming are commonly being used in many horticultural crops to amplify the growth and uniformity of germination. However, it may be used alone or in combination with biocontrol agents to advance the rate of seed emergence and minimize soilborne diseases. On the other hand, some biocontrol agents are used as seed dressers and are able to colonize the rhizosphere, helping seeds to resist various abiotic stresses