Ability of Fungi, Isolated from Nsukka Peppers and Garden-Egg Plant Rhizospheres, to Solubilize Phosphate and Tolerate Cadmium

Abstract

Fungi were isolated from the rhizosphere of pepper and garden-egg plants, with the aim of solubilizing the insoluble phosphate, identifying the most potent isolate from each rhizosphere and testing their tolerance to cadmium metal. The fungi isolates were obtained from the rhizosphere of pepper and garden-egg plants, using PVK agar and NBRIP-BPB broth culture to determine the quantity of phosphate solubilized. From the spectrophotometric readings, isolates GF1 ( Penicillium spp) and PF7 ( Aspergillus niger ) were identified as most potent isolates. Various concentrations of cadmium (100, 50, 10 and 1 μg/ml) were added to the broth containing different isolates for tolerance determination and a control group for different isolates were also obtained. At four-day interval, a quantity of phosphates solubilized at different concentrations of cadmium and control were recorded. The quantity solubilized in 100, 50, 10 and 1 μg/ml treatment groups increased progressively from Day 4 to Day 12 in both isolates, with a sharp increase observed in isolate GF1. The tolerance of GF1 to cadmium showed that there was no significant difference (P < 0.05) in quantity solubilized in the control group when compared with Day 8 and Day 12 of 1 μg/ml concentration of cadmium metal, except at Day 4 which may be as a result of acclimatization. The quantity solubilized for PF7 at control when compared with 1, 10, 50 and 100 μg/ml differed significantly although there were higher quantity of phosphates solubilized when compared with GF1 and other results obtained from most published works. Our results suggested that these two isolates could be used for phosphate solubilization in cadmium metal environment though GF1 tolerates more than PF7, and could be employed for bioremediation of cadmium heavy metals.