Gelatin–Chitosan–PVA Hydrogels Incorporating Trichoderma and Their Application in the Control of Phytopathogens

The utilization of microorganisms as biocontrol agents represents a sustainable alternative to agrochemicals. Trichoderma spp. has been identified as a fungus that promotes plant growth and suppresses phytopathogens. Nonetheless, conventional commercial formulations are constrained by factors such as their limited shelf life, environmental sensitivity, and inadequate carrier systems. In this study, Trichoderma harzianum (T22) and T. viride (T18) strains were encapsulated in a hydrogel composed of chitosan, gelatin, and polyvinyl alcohol, which was prepared by pH-induced gelation via alkaline precipitation. The characterization of the hydrogels was conducted in several domains. Initially, the water absorption of the samples was examined at varying pH values. Secondly, the morphology of the samples was investigated using scanning electron microscopy (SEM) and stereo microscopy. Thirdly, the chemical interactions in the hydrogels were analyzed by Fourier-transform infrared spectroscopy (FTIR). The final stage of the experiment involved assessing the degradation behaviour of the hydrogels in both sterile and inoculated soils. The efficacy of the isolates in protecting chilli plants from Phytophthora capsici was subsequently evaluated. As demonstrated in the extant research, encapsulation techniques have been shown to preserve the viability of fungal organisms and promote their growth after 10 days of storage at ambient temperature. These effects have been observed to exhibit strain-dependent variations. It is noteworthy that hydrogels loaded with T. viride (HT18) induced resistance against P. capsici, resulting in complete symptom suppression and enhanced plant growth, whereas hydrogels loaded with T. harzianum (HT22) showed no protective effect. These results demonstrate the potential of the hydrogel formulated with T18 as an effective carrier, as it maintains Trichoderma spp. viability and protects chilli plants against P. capsici infection.