Use of biocontrol fungi (BF) such as Trichoderma spp. minimizes fungicide input and increases both plant nutrition and protection from disease. Thus, the introduction of BF by novel inoculants in crop management is an excellent strategy to promote sustainable antagonism activity. Within these strategies, encapsulation in polymeric matrices such as hydrogel beads will play a prominent role in providing an effective carrier/protector and long-lasting bioproduct. These studies have used biomaterials with tunable physicochemical features, providing differential morphologies, compaction, and disintegration, among other parameters. Aiming at developing bioproducts within polymeric hydrogel beads, viability of encapsulated conidia, storage stability, release of active ingredient, and particle size are essential. However, there are no reports that detail standardized and comprehensive methods to evaluate the characterization of these bioproducts. We describe step-by-step protocols that go from sample preparation to testing the viability and storage stability using vacuumsealed aluminum foil bags. We also describe a high-throughput in vitro method for quantifying released fungal conidia of BF at different pH values. Finally, the particle size of beads is established by bright-field microscopy. These protocols could be transferable to other biological actives, accessible to researchers in the microbiology and bioengineering communities.

Biological control (BCAs) such as Trichoderma spp. minimize fungicides inputs in agriculture, and increase both the plant nutrition and the efficacy against fungal diseases. Novel bioproducts in crop management are called to guarantee sustainable antagonism activity of BCAs and increase the acceptance of the farmers. The encapsulation in polymeric matrices play a prominent role for providing an effective carrier/protector and long-lasting bioproduct. This research aimed to compare two hydrogel capsules prototypes based on alginate (P1) and amidated pectin (P2), containing Trichoderma koningiopsis Th003 conidia. Capsules were prepared by the ionic gelation method and calcium gluconate as crosslinker was used. The capsules were characterized by various properties such as conidia releasing at different pH values, drying conidia survival, storage stability, and biocontrol activity against sheath blight (R. solani) in rice. P2 prototype provided higher survival to Th003 up to 98% in fluid bed drying, faster conidia release at pH 5.8, storage stability > 6 months at 18°C, and a disease reduction up to 67%. Amidated pectin provides advantages on drying survival and conidia release at pH 5.8. Both biopolymers facilitate the antagonistic activity against R. solani, and therefore can be incorporated in hydrogel capsules for novel bioinoculants development. This research highlights the knowledge regarding the influence of biopolymer in hydrogel capsules on survival and shelf-life of Trichoderma spp conidia.

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