Chitosan nanoparticle based delivery systems for sustainable agriculture.

Biochar is the solid coproduct of biomass pyrolysis, a technique used for carbon-negative production of second-generation biofuels. The biochar can be applied as a soil amendment, where it permanently sequesters carbon from the atmosphere as well as improves soil tilth, nutrient retention, and crop productivity. In addition to its other benefits in soil, we found that soil-applied biochar induces systemic resistance to the foliar fungal pathogens Botrytis cinerea (gray mold) and Leveillula taurica (powdery mildew) on pepper and tomato and to the broad mite pest (Polyphagotarsonemus latus Banks) on pepper. Levels of 1 to 5% biochar in a soil and a coconut fiber-tuff potting medium were found to be significantly effective at suppressing both diseases in leaves of different ages. In long-term tests (105 days), pepper powdery mildew was significantly less severe in the biochar-treated plants than in the plants from the unamended controls although, during the final 25 days, the rate of disease development in the treatments and controls was similar. Possible biochar-related elicitors of systemic induced resistance are discussed.

https://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO-100-9-0913

Induction of Systemic Resistance in Plants by Biochar, a Soil-Applied Carbon Sequestering Agent

In recent decades, a greater knowledge of chitin chemistry, and the increased availability of chitin-containing waste materials from the seafood industry, have led to the testing and development of chitin-containing products for a wide variety of applications in the agriculture industry. A number of modes of action have been proposed for how chitin and its derivatives can improve crop yield. In addition to direct effects on plant nutrition and plant growth stimulation, chitin-derived products have also been shown to be toxic to plant pests and pathogens, induce plant defenses and stimulate the growth and activity of beneficial microbes. A repeating theme of the published studies is that chitin-based treatments augment and amplify the action of beneficial chitinolytic microbes. This article reviews the evidence for claims that chitin-based products can improve crop yields and the current understanding of the modes of action with a focus on plant-microbe interactions.

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A Review of the Applications of Chitin and Its Derivatives in Agriculture to Modify Plant-Microbial Interactions and Improve Crop Yields

In agriculture, current control of pathogens relies mainly on chemical fertilizers and pesticides. However, alternative solutions are needed due to concerns for public health, environmental protection, and development of resistant pests. Chitosan is a nontoxic, biodegradable biopolymer showing antimicrobial and plant-immunity eliciting properties. Here, we review chitosan antimicrobial activities, modes of action, and the elicitation of plant defense responses. The major points are the following: (1) Chitosan exhibits various inhibitory efficiency against bacteria, fungi, and viruses; (2) the five main modes of action of chitosan are electrostatic interactions, plasma membrane damage mechanism, chitosan-DNA/RNA interactions, metal chelation capacity of chitosan, and deposition onto the microbial surface; (3) the elicitation of plant defense responses by chitosan may be related to various pathogenesis-related proteins, defense-related enzymes, and secondary metabolites accumulation, as well as the complex signal transduction network. The facing problems and strategies for antimicrobial mechanism research and agricultural application of chitosan are also discussed.

/pdf/chitosan-antimicrobial-and-eliciting-properties-for-pest-4onc4kzsqu.pdf

Chitosan antimicrobial and eliciting properties for pest control in agriculture: a review

Stilbenic compounds recently have become the focus of a number of studies in medicine and plant physiology as well as have emerged as promising molecules that potentially affect human health. Stilbenes are relatively simple compounds synthesized by plants and deriving from the phenyalanine/polymalonate route, the last and key enzyme of this pathway being stilbene synthase. Here, we review the biological significance of stilbenes in plants together with their biosynthesis pathway and their metabolism both by fungi and in planta. Special attention will be paid to the role of stilbenic molecules as phytoalexins.

Biosynthesis, metabolism, molecular engineering, and biological functions of stilbene phytoalexins in plants.

Aziz, A., Trotel-Aziz, P., Dhuicq, L., Jeandet, P., Couderchet, M., and Vernet, G. 2006. Chitosan oligomers and copper sulfate induce grapevine defense reactions and resistance to gray mold and downy mildew. Phytopathology 96:1188-1194. Chitosan (CHN), a deacetylated derivative of chitin, was shown to be efficient in promoting plant defense reactions. CHN oligomers of different molecular weight (MW) and degree of acetylation (DA) triggered an accumulation of phytoalexins, trans- and cis-resveratrol and their derivatives e-viniferin and piceid, in grapevine leaves. Highest phytoalexin production was achieved within 48 h of incubation with CHN at 200 µg/ml with an MW of 1,500 and a DA of 20% (CHN1.5/20), while oligomers with greater MW were less efficient, indicating that a specific MW threshold could be required for phytoalexin response. Treatment of grapevine leaves by highly active CHN1.5/20 also led to marked induction of chitinase and β-1,3-glucanase activities. CHN1.5/20 applied together with copper sulfate (CuSO4) strongly induced phytoalexin accumulation. CuSO4 alone, especially at low concentrations also elicited a substantial production of phytoalexins in grapevine leaves. Evidence is also provided that CHN1.5/20 significantly reduced the infection of grapevine leaves by Botrytis cinerea and Plasmopara viticola, and in combination with CuSO4 conferred protection against both pathogens.

https://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO-96-1188

Laurent Dhuicq

Papers

Chitosan oligomers and copper sulfate induce grapevine defense reactions and resistance to gray mold and downy mildew.