S16 - Session P1 - Revealing the New Mexico pecan root-soil microbiome to improve plant health and productivity

Authors: Richard Heerema *, Nicole Pietrasiak, Jennifer Randall, Andrew Dominguez

Pecan ( Carya illinoinensis ) is a large deciduous nut-bearing tree native to North America. Pecan roots lack root-hairs which allow many other plants to more efficiently explore and exploit the soil for nutrients and water. However, pecan roots can form symbiotic relationships with mycorrhizal fungi that might serve a similar function as root-hairs by dramatically increasing volume of soil "mined" by the tree's root system. Currently, little is known about the occurrence and diversity of mycorrhizal fungi forming associations with pecan roots in the Southwestern US or how orchard soils, irrigation systems, and orchard management practices may affect their presence/absence. To analyze the microbial diversity and abundance of pecan tree roots and their associated rhizospheres, samples were collected from 26 orchards located across the pecan growing belt of New Mexico, USA. The orchards represented diverse soil characteristics, climatic conditions, and management practices. Analyses included soil chemistry and next generation sequencing of root and rhizosphere samples. Total gDNA was isolated from root and soil samples using the Qiagen DNeasy Plant Mini Kit and Qiagen DNAeasy PowerLyzer PowerSoil Kit. The 16S rRNA and ITS regions were amplified for bacterial and fungal determination and DNA was sequenced on an Illumina platform. Sequences were paired, trimmed, and analyzed using the CLC Genomics Workbench 21.0.4 Microbial Module version 21.1. Differences in relative abundance of microbial operational taxonomic units were observed between roots and rhizospheres. Although alpha diversity varied among root and rhizosphere microbiomes, the fungal alpha diversity for specific root samples and their associated rhizosphere were similar. We expect this information will assist New Mexico pecan farmers to purposefully manage the root microbiome to their advantage.