Pecans [Carya illinoinensis (Wangenh.) K. Koch] are an economically important nut crop, with nitrogen nutrition critically influencing their productivity. Sustainable nutrient management strategies, including enhancing microbial associations in the rhizosphere, offer potential to optimize nutrient use efficiency and reduce fertilizer dependency. This study aimed to isolate and identify mycorrhizal fungi (beneficial) from pecan roots capable of improving nitrogen uptake efficiency, thereby reducing fertilizer inputs for pecan producers. We hypothesized that mycorrhizal fungi exhibiting stable growth across varied nitrogen sources and concentrations would be good candidates for effective inoculation of pecans. For this experiment, fine root samples of pecans were collected from six improved orchards (with cultivars Pawnee and Kanza) and two native groves across Oklahoma. Samples were collected at two sampling events (February and May 2023), obtaining composite samples by combining three subsamples per tree at 15-20 cm soil depth. Fine roots were surface cleaned, sterilized, and cultured on potato dextrose and malt agar to isolate fungi. After isolation and purification, fungi were visually screened, excluding known pathogens based on morphological traits (color, spores, etc.). Twenty selected fungi were evaluated for growth on mineral salt medium (MSM) agar supplemented with glucose, under varying nitrogen conditions (0.1, 0.05, 0.01 g/L urea and ammonium chloride), and a nitrogen-free control. Fungal growth was quantified by measuring hyphal extension daily. Four isolates demonstrating minimal growth variation across nitrogen treatments were selected for further identification. Subsequently, DNA extraction was performed on these selected four fungi using FastDNA SPIN Kit (MP Biomedicals, USA), and fungal identities were confirmed by sanger sequencing (ITS region). From the sequencing results, two fungal isolates will be selected as promising candidates for the next phase of the study, where they will be inoculated into pecan seedlings to confirm symbiosis formation and evaluate their potential to enhance nitrogen uptake efficiency under different nitrogen fertilization scenarios. Findings from this study will provide a scientific foundation for sustainable pecan rootstock nursery and orchard management, helping producers optimize fertilizer use, and reduce costs.
