Use of chemical pesticides poses a threat for environment and human health, so green technologies of crop protection are of high demand. Some microbial proteins able to activate plant defense mechanisms and prevent the development of resistance in plant pathogens, may be good alternative to chemicals, but practical use of such elicitors is limited due to need to protect them against adverse environment prior their delivery to target receptors of plant cells. In this study we examined a possibility to encapsulate heat resistant FKBP-type peptidyl prolyl cis-trans isomerase (PPIase) from Pseudomonas fluorescens , which possesses a significant eliciting activity in relation to a range of plant pathogens, in sodium alginate microparticles and evaluated the stability of resulted complex under long-term UV irradiation and in the presence of proteinase K, as well as its eliciting activity in three different “plant-pathogen” models comparing to that of free PPIase. The obtained PPIase-containing microparticles consisted of 70% of sodium alginate, 20% of bovine serum albumin, and 10% of PPIase. In contrast to free PPIase, which lost its eliciting properties after 8-h UV treatment, encapsulated PPIase kept its eliciting ability unchanged; after being exposed to proteinase K, its eliciting ability twice exceeded that of free PPIase. Using “tobacco-TMV”, “tobacco- Alternaria longipes ”, and “wheat- Stagonospora nodorum ” model systems, we showed that encapsulation process did not influence on the eliciting activity of PPIase. In the case of the “wheat- S. nodorum ” model system, we also observed a significant eliciting activity of alginate-albumin complex and almost doubled activity of encapsulated PPIase as compared to the free PPIase. As far as we know, this is the first observation of a synergistic interaction between alginate and other compound possessing any bioactive properties. The results of the study show some prospects for a PPIase use in agriculture.

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Chitosan is a biopolymer that readily forms nanoparticles, with or without additional biologically active substances loaded into them. Chitosan nanoparticles can include hydrophobic or hydrophilic compounds, metal ions, compounds poorly soluble in water, etc. Chitosan is biodegradable, biocompatible, non-toxic to plants, humans and animals. It also stimulates plant immunity and enhances crop yields. Because of that properties, there are some works about chitosan nanoparticles loaded with biologically active substances for plant protection. The major advantages of these nanoparticles are: good solubility in water, large surface for interaction with the pathogen, possibility of gradual release of active substances, protection of active substances from damage, easy entrance of the nanoparticles into plant cells. In this review current research works about use of chitosan nanoparticles that are loaded with active substances for pre-harvest plant protection are summarized.