Isolamento e caracterização de fungos com potencial para promoção de crescimento vegetal e biocontrole

Abstract

The industrial agriculture system utilizes chemical products to fight diseases and enrich nutrient-deficient soil to boost productivity. Bigger doses are used every cycle, given the resistant phytopathogens and agricultural pests that emerge and continual soil depletion. An alternative is microorganisms-based products that are capable of biological pest and phytopathogen control or capable of providing plant nutrition by biological solubilization and fixation of essential nutrients. This research applied itself to the isolation, identification, and evaluation of in vitro potential of fungi to inhibit phytopathogenic fungi mycelial growth, produce the auxin indole-3-acetic acid (IAA) and solubilize inorganic phosphorus. The fungi were evaluated for antagonistic action against the phytopathogens Fusarium graminearum, Fusarium solani, Macrophomina phaseolina Rhizoctonia solani and Sclerotinia sclerotiorum, with inhibition by culture pairing and metabolic action. Phosphorus solubilization was assayed quantitatively in liquid media containing calcium, aluminum and iron phosphates, insoluble forms present in Brazilian soil. IAA production was evaluated in media containing tryptophan, stimulant for this phytohormone. The isolates were identified as the genera Cladosporium, Entomortierella, Fusarium, Mucor, Paecilomyces, Penicillium, Pochonia and Purpureocillium. Between the 10 fungal isolates 8 of them could solubilize at least one phosphorus source, with 4 isolates solubilizing all 3 inorganic phosphates. The Penicillium isolate was the biggest solubilizer, with reaching 503 μg/mL of soluble phosphorus after 14 days. For phytopathogen inhibition, 7 isolates inhibited at least 3 of the phytopathogen, with 2 antagonists inhibiting all five. The Purpureocillium isolate inhibited all the phytopathogen assessed in the culture pairing and inhibited two of them by metabolics action. Only 3 isolates could produce IAA, from the genera Cladosporium, Entomortierella and Mucor. The biggest IAA productor was the Mucor isolate with 18,59 μg/mL after 14 days.