Effect of Selective Substrates on Germination of Pomegranate (Punica granatum) and Trifoliate Orange (Poncirus trifoliata) Seeds with and Without the Presence of Plant-Beneficial Microorganisms

Insect-based (silkworm cocoons) and plant-based (cotton wool pads and gauzes) fiber substrates were used to support and ameliorate seed germination originating from trifoliate orange (Poncirus trifoliata) and pomegranate (Punica granatum) trees. Three different commercial formulations of beneficial microorganisms (Bacillus spp.-Azotobacter spp., Saccharomyces boulardii, and Saccharomyces cerevisiae) were administered to seeds in order to evaluate their contribution to germination and growth. The silkworm cocoons provided better germination rates for P. trifoliata seeds (83.33%) among the tested media without any microbial supplementation. These rates increased towards the absolute maximum (100%) when Bacillus spp.-Azotobacter spp., S. boulardii and S. cerevisiae were applied. Furthermore, inoculums of Bacillus spp.-Azotobacter spp. 2 mL and S. cerevisiae 3 g raised the pomegranate seed germination ability by 30–33.33% and 50–67.7%, respectively, on silkworm cocoon substrates when compared to plant-derived, cellulosic fiber substrates under the same biotic exposure. On increasing the size of applied microbial inoculums, seed germination moved from optimum to suboptimum for all germination media. Examination of multipartite pH compatibility (between seeds, microorganisms, and germination media) was beneficial and of functional value. In conclusion, the germination rates of both tree species can be raised using bacterial and yeast supplementation, including medical-grade S. boulardii, on environmentally friendly materials such as insect- and plant-based fiber substrates.