QUALITATIVE AND QUANTITATIVE ESTIMATION OF THE ABILITY OF Trichoderma spp. MOROCCAN ISOLATES TO SOLUBILIZE TRICALCIUM PHOSPHATE

The present study was undertaken to estimate in vitro the capacity of twenty-three isolates of Trichoderma, isolated from soil and roots collected from adjacent sites to the Khouribga and Benguerir Phosphate mines (Morocco), and seven isolates from the laboratory's mycoteca to solubilize the Tricalcium phosphate. All these isolates showed, after three days of incubation, on NBRIP medium, amended by Ca3(PO4)2, colony diameters which vary between 41.7 and 59.4 mm. Six days later, all isolates reached maximum diameters (90 mm), but no clear halo-zone was observed around the colonies. Mycelial densities of all isolates were medium to high on NBRIP agar. After 7 days of incubation, isolates TS-B 98; TR-B 98 (2); TR-B 98 (3) were found to be able of producing a large number of conidia with respective concentrations of 38.105, 39.105 and 42.105 conidia.mm-2 while others have poorly sporulated or not-forming conidia. A simultaneous increase in the concentration of soluble phosphorus was recorded in the culture filtrates. Peak concentrations are noted at ninth day after incubation in TR-B 98/2002 (2), TS-B-2000 (2), TR-CB 2000 (1), TR-TB 2000, TR-OL 1; TS-B 98, TR-EM 2, TR-B 98 (1), TR-B 98 (3), with values exceeding 10.15 μg.mL-1 and reaching a maximum value of 12.42 μg.mL-1 compared to the blank (0.52 μg.mL-1). pH values decreased to 4.12 in TR-TB 2000 compared to control (6.12). The highest fresh and dry weights were recorded in TR-TB 2000 isolates (FW = 4.1 g, DW = 2.78 g) and TR-B 98 (3) (FW = 3.9 g, DW = 3.00 g). TR-TB 2000, TS-B 98, TR-EM 2, TR-B 98 (1) isolates proved to be the most successful in phosphate solubilization, with maximum phosphorus concentrations.