Studies on characterization of fungi Aspergillus from different rhizospheric samples for zinc solubilization under in-vitro condition

Abstract

Zinc is an essential micronutrient for plant growth, and its availability in soil is often limited due to its complex formation which leads to insolubility. The current work concentrated on zinc-solubilization, in which zinc mineral salt media was supplemented with insoluble ZnO and Methyl red as an indicator for the production of organic acid. A total of 26 isolates were taken out of which 20 were isolated from rhizospheric soil collected from local regions of Meerut, Uttar Pradesh, and the other 06 isolates were isolated by environmental exposure. After culturing these samples, 20 no. were identified as Aspergillus spp., 05 Trichoderma, and 01 Penicillium, these isolates were maintained on PDA media. Out of these, 24 isolates were tested for zinc-solubilizing abilities on zinc mineral salt media, and further best solubilizers 13 isolates were selected for studying zinc solubilization ability and production of organic acid by supplementing zinc mineral salt media with methyl red. Few fastest solubilizers include S7A3(2.35; 25.83), S7A1 (1.82; 20.33), and S4 (1.81; 20.17) which completed solubilization on the 5th day and were Aspergillus sp. Efficient Trichoderma isolates were S3A (1.30; 10.50) and S3B (1.18; 2.42) with Penicillium solubilization efficiency were also high. The solubilizing index and solubilizing efficiency of isolates vary in a range of (1.01-4.54) and (0.08-35.08) respectively. Among, 13 isolates (12 Aspergillus and 01 Penicillium), leading organic acid producing isolates were Aspergillus S3C (1.73; 18.92) and S10 (2.67; 28.17). The solubilizing index and solubilizing efficiency for methyl red supplemented media of isolates vary in a range of (1.03-3.38) and (0.75-31.67) respectively. These organic acids chelate with zinc, converting it into a more soluble form. Understanding the diversity of zinc-solubilizing fungi from various rhizospheric niches and uncovering their abilities to have important implications for sustainable agriculture and environmental remediation. Furthermore, these results highlight the potential of various fungi to enhance zinc availability in soils and could contribute to improved crop yields and soil health, while also offering a promising approach for the remediation of zinc-contaminated sites.