Exploring volcanic material as a carrier substrate for the formulation of low-cost fungal bioinoculants

Abstract

One of the challenges associated with microbial inoculants is selecting the appropriate carrier material that ensures reliable and consistent performance in field conditions. This performance is critical in arid environments, which have extreme temperatures and low humidity. Pyroclastic material has been explored as a potential alternative due to its beneficial physical and chemical properties that promote the growth of microorganisms and plants. Our research focuses on evaluating a new fungal carrier that utilizes volcanic particles impregnated with spent grain for its potential incorporation into seed coating technology. We assessed the ability of native fungal strains (Trichoderma aff. virens, Beauveria bassiana, and Zopfiella aff. erostrata) to thrive in this pyroclastic material, monitoring their viability over a six-month period. To evaluate the infective capability of the arbuscular mycorrhizal strain Rizophagus clarus, we used the most probable number method. We also tested seed coating with formulated ashes as a practical method for incorporating these bioinoculants into traditional crops. Our results indicated that this pyroclastic material serves as an effective carrier, maintaining viability above 55% for B. bassiana and 72% for T. virens conidia after six months. For the mycorrhizal strain R. clarus, the volcanic ash contained 39 infective propagules (per g−1 of soil) after three months. Moreover, the seed coating demonstrated a high effectiveness rate of over 90% for the treatments involving T. virens and B. bassiana. The development of bioformulations using this novel, highly available and easy-to-handle carrier material of volcanic origin provides a feasible product with potential worldwide application.