SOLUBILIZACIÓN DE FUENTES INORGÁNICAS DE FÓSFORO POR MICROMICETOS AISLADOS DE LA RIZOSFERA DE PAPAYA VAR. MARADOL ( Carica papaya L.) Y SU SUSCEPTIBILIDAD A HERBICIDAS CONVENCIONALES

A high amount of phosphorus content (P) from the inorganic fertilizers that are applied in papaya var. Maradol orchards ( Carica papaya ) is precipitated within the soil cations (Ca 2+ , Mg 2+ , Fe 3+ y Al 3+ ), resulting in an immobilized and unavailable P for plants. An alternative to release immobilized P is the use of P-solubilizing microfungi (PSMF). However, these microorganisms are susceptible to herbicide residues in soils. The objectives of this study were to isolate PSMF from the rhizosphere of C. papaya plants (var. “Maradol”), to evaluate in semisolid and liquid fermentation their ability to solubilize both Ca 3 (PO 4 ) 2 and FePO 4 , and to determine their susceptibility to glyphosate and 2,4-D herbicides. In 15 isolates, qualitatively the SP5 isolate was the best solubilizer of Ca 3 (PO 4 ) 2 with a solubilization index (SI) of 5.6, while the highest SI (1.4) for FePO 4 was achieved by Beauveria bassiana SP9. In liquid fermentation, Penicillium sp. SP1 (108.5 mg/L) and Penicillium hispanicum SP16 (106.5 mg/L) solubilized at 100 % the Ca 3 (PO 4 ) 2 . In addition, P. hispanicum SP16 solubilized the highest amount of FePO 4 with 39.6 mg/L. Penicillium hispanicum SP16 resulted tolerant to glyphosate with a mean lethal concentration of (LC 50 ) of 5376.0 mg/L, a greater value than the field application rate (1836 mg/L); however, it was susceptible to 2,4-D with a LC 50 of 3256.0 mg/L, which was a smaller value than the field application recommended rate (3705.0 mg/L). Carica papaya rhizosphere host PSMF with potential to develop biofertilizers, if we take into account their ability to solubilize inorganic P sources (Ca 3 [PO 4 ] 2 and FePO 4 ) and their tolerance to conventional herbicides (glyphosate and 2,4-D).