Rootstocks impact on 'Pawnee' pecan growth, physiological traits, and soil microbial communities

Authors: Wang, Xinwang; Kubenka, Keith; Chatwin, Warren; Hilton, Angelyn; Tondre, Braden; XU, TONDRE - Oklahoma State University; ZHANG, LU - Oklahoma State University

Submitted to: Frontiers in Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pecan trees are a vital part of nut production in the southern United States, providing high-quality nuts valued for their nutritional benefits and culinary uses. As global demand for pecans increases, farmers face challenges in improving cultivation methods to ensure consistent yields and sustainable practices. One key issue is determining which rootstocks—the parts of trees below the graft—can best support healthy growth and robust nut production. This work compared 12 different rootstocks and their effects on the growth and physiology of a popular pecan variety called 'Pawnee.' The work discovered important differences in how these rootstocks impact the timing of budbreak (when new growth begins), tree size, photosynthesis efficiency, leaf nutrient levels, and even the composition of beneficial microbes in the soil. Southern rootstocks from Mexico produced significantly larger trees, while northern rootstocks delayed budbreak. Certain rootstocks enhanced photosynthesis and water use efficiency, and others influenced soil microbial diversity, promoting nutrients that help trees grow stronger. These findings provide farmers with essential information about choosing the right rootstocks to optimize pecan tree growth. By selecting rootstocks based on their region-specific traits, growers can improve tree size, nut yield, and soil health—leading to more productive orchards and better-quality pecans to meet global demand. This research offers a scientific basis for improving both the economic viability and sustainability of pecan cultivation.

Technical Abstract: Pecan (Carya illinoinensis), native to North America, is the most commercially important species within the Carya genus. Central to nut production across the southern United States, pecans are cultivated for their premium-quality nuts used in various culinary applications. The increasing global demand for pecans, driven by their nutritional value—rich in healthy fats, proteins, vitamins, and antioxidants—has emphasized the need for improved cultivation practices to ensure both economic viability and sustainability. This study examined the impact of 12 different rootstocks on the growth and physiological characteristics of the 'Pawnee' scion in different years. Key traits assessed included budbreak timing, tree size, leaf size, leaf retention, photosynthesis, leaf nutrient content, and soil microbial community composition. Significant differences in budbreak timing were observed among the rootstocks, with northern rootstocks, particularly Peruque, exhibiting the latest budbreak, while eastern rootstocks showed the earliest. Regarding tree growth, southern (Mexican) rootstocks significantly outperformed northern rootstocks in terms of scion plant height, trunk diameter, and canopy width. Rootstocks from the southern regions demonstrated superior growth, highlighting the potential for selecting Mexican rootstocks to enhance pecan tree size in orchards. Leaf size showed variation across rootstocks, with northern and eastern rootstocks producing larger leaves, although these differences were not statistically significant. Leaf retention did not differ significantly across rootstocks, but northern and eastern rootstocks retained more leaves into early November compared to southern and western rootstocks. 'Giles' (northern) and 'VC1-68' (western) had the highest photosynthesis rates and water use efficiency (WUE), while Elliott (eastern) exhibited lower lowest rates of photosynthesis and WUE. Nutrient analysis revealed that most leaf nutrients varied across the rootstocks but were not significantly influenced by rootstock origins. ‘Riverside’ had the highest Zn content, while ‘Peruque’ had the lowest. Similarly, 'Major' exhibited the highest B content, and 'Frutoso' had the lowest. Soil microbial analysis revealed differences in microbial composition between the rootstocks, with 'Peruque' promoting ectomycorrhizal fungi and 87MX5-1.7 supporting nitrogen-fixing bacteria, indicating that rootstocks can influence soil microbial diversity and nutrient cycling. These results highlight the importance of rootstock selection for improving tree growth, photosynthetic efficiency, and soil health in pecan orchards.