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Bioencapsulation as a sustainable targeted agricultural delivery of bioactive agents in the conventional cultivation of Lactuca sativa L.

The simultaneous encapsulation of biologically active agents such as fungi and agrochemicals is a useful way of nutrient delivery for an ecological and sustainable plant production. The benefits of encapsulation of bioactive agents are: slow and controlled release, more efficient use of agrochemicals with better safety and environmental protection. Encapsulation of single bioactive agents is a standard method used in agriculture. Successful delivery of active agents at the right place and the right time is an attainable and desirable characteristic for all bioactive agent delivery systems. In order to obtain the required microparticles, effective for simultaneous encapsulation of multiple controlled release bioactive agents, it is important to optimize the parameters during the preparation of the microcapsule/microspheres. Since numerous microorganisms, especially those associated with roots, have the ability to increase plant growth and productivity, Trichoderma viride (STP) was used in this research. Trichoderma species are among the most prevalent culturable fungi in soils, based upon the frequency of isolation on suitable media. The dual roles of antagonistic activity against plant pathogens and promotion of soil fertility make Trichoderma species as a promising alternative to standard plant protection and nutrition technologies. Recently, microparticles containing both biological and chemical agents were investigated in terms of physicochemical properties, microparticle morphology, and release kinetics. The effects of different cations (calcium and copper ions), microparticle size, the presence of outer chitosan layer on the release of the cations as well as the release of Trichoderma viride (STP) spores from alginate-based microcapsules were investigated [1, 2]. Optimization was performed with the intention to produce microparticles with delivering active agents to the plants at the rate that closely approximates plant demands over an extended period. The investigation pointed out that proper selection of agroformulation variables helps in designing microcapsules/microspheres with the desirable release of Trichoderma viride (STP) spores and copper/calcium ions for plant nutrition. After the optimization, microparticles containing different combinations of Ca2+/Cu2+ ions, T. viride, alginate and chitosan were applied to the soil in the conventional planting of lettuce (Lactuca sativa L.). The application was performed just before planting. After the lettuce harvest, fresh samples were used for the preparation of extracts. Extracts were analyzed in terms of biological activity, with regards to the total polyphenols, antioxidant activity, chlorophyll, total sugars as well as the Ca2+/Cu2+ ions content. Principal component analysis and agglomerative hierarchical clustering were performed to see the significant differences between the treatments. Results revealed significant differences when comparing the treated lettuce against the control (untreated) with regards to almost all of the measured parameters, i.e. the obtained biomass yield, rosette diameter and height as well as the content of bioactive compounds and antioxidant activity. Bioencapsulation alongside the presence of chemical agents revealed a promising, sustainable, environmentally friendly, rapid, convenient, economical and efficient delivery of biological and chemical agents for plant nutrition.

microspheres/microcapsules, Trichoderma viride, chemical agents, lettuce

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