The rootstock genotype shapes the diversity of pecan (Carya illinoensis) rhizosphere microbial community

Authors: REN, WEI - Oklahoma State University; ZHANG, LU - Oklahoma State University; Tondre, Braden; Wang, Xinwang; XU, TINGYING - Oklahoma State University

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2024
Publication Date: 10/3/2024
Citation: Ren, W., Zhang, L., Tondre, B.S., Wang, X., Xu, T. 2024. The rootstock genotype shapes the diversity of pecan (Carya illinoensis) rhizosphere microbial community. Frontiers in Microbiology. 15. https://doi.org/10.3389/fmicb.2024.1461685.
DOI: https://doi.org/10.3389/fmicb.2024.1461685

Interpretive Summary: The study explored how different pecan rootstocks (the underground part of the tree) influence the microbial communities in the soil and roots. We looked at two rootstocks, one from the southern U.S. (87MX5-1.7) and one from the northern U.S. (Peruque), both grafted with the same top part of the tree (Pawnee scion). There were significant differences in the microbial communities between the two rootstocks, which could impact nutrient uptake and overall tree health. The Peruque rootstock had more fungi that break down organic matter, potentially aiding in the release of nutrients from the soil. Conversely, the 87MX5-1.7 rootstock had more fungi that form symbiotic relationships with the tree, particularly ectomycorrhizal fungi, and bacteria that help fix nitrogen. These microbes are likely to help the tree take up nutrients more effectively and may improve the tree growth and yield. The study indicates that choosing the right rootstock could be a key factor in the health and productivity of pecan trees by influencing the microbial environment around their roots. Understanding these rootstock-microbe interactions can help pecan growers make more informed decisions about which rootstocks to use for better tree growth, disease resistance, and nut production.

Technical Abstract: Pecans (Carya illinoinensis), one of the most valuable native North American nut crops, are commonly propagated through grafting to preserve the desired characteristics of parent trees. Rootstocks supporting these scions are a crucial consideration. This study investigated the microbial communities in the soils and roots of southern (87MX5-1.7) and northern (Peruque) rootstocks in a rootstock test orchard. Both rootstocks were grafted with the 'Pawnee' scion cultivar. Bacterial 16S ribosomal RNA and fungal ITS were amplified from both roots and rhizosphere soils of the two 10-year-grafted trees, then sequenced and annotated into trophic and nutrient-related groups to characterize the rhizosphere microbiota. The Peruque roots had a higher relative abundance of saprotrophic fungi, while the 87MX5-1.7 exhibited higher levels of symbiotic fungi and nitrogen fixation-related bacteria. The presence of symbiotic fungi, particularly ectomycorrhizal fungi, notably differed between the two rootstocks, with a significantly higher presence observed in the roots of 87MX5-1.7 compared to Peruque. This variation likely leads to divergent pathways of nutrient translocation: multiple fungi (such as Russula and Inocybe) may enhance plant nutrition for Peruque, while a beneficial symbiosis may have formed with specific fungi (e.g., Tuber) and nitrogen fixation-related bacteria (Bradyrhizobium) in 87MX5-1.7. The findings of this study suggest that rootstocks from different origins shape rhizosphere microbes differently, potentially affecting nutrient uptake and nut yield. By understanding how different rootstock-microbe interactions influence pecan tree development, growers can strategically select root/scion combinations that promote beneficial symbiotic relationships, enhancing nutrient uptake, disease resistance, and overall tree vigor.