Title： Salt stress alters the selectivity of the mature pecan on rhizosphere community and the associated functional traits

zhengjia wang ^1* Mengting Shi ^1,2 tao qin ¹ zhenyang Pu ¹ Zhengfu Yang ¹ Kean-Jin Lim ¹ Menghua Yang ¹

• ¹ Zhejiang Agriculture and Forestry University, Hangzhou, China
• ² Hangzhou Medical College, Hangzhou, Zhejiang Province, China

Salt stress is a major global environmental factor limiting plant growth.Rhizosphere bacteria, which are recruited from bulk soil, play a pivotal role in the resistance of herbaceous and crop plant species to salt stress. However, no study has yet demonstrated whether the rhizosphere bacterial community of a mature tree can change in response to salt stress, especially in saline-alkali-tolerant trees. Pecan (Carya illinoinensis), an important commercially cultivated nut tree, is considered saline-alkali-tolerant. Using amplicon sequencing, we characterized the mature pecan-associated microbiome (i.e., fruit, leaf, root, and rhizosphere soil) for the first time. We found that salt stress decreased the diversity of rhizosphere bacteria in mature pecan, altered the rhizosphere community composition, and shifted the selective pressure of pecan on proteobacteria and actinobacteria. Through shotgun metagenomic sequencing, we further identified functional traits of the rhizosphere microbiome in response to salt stress. This study expands our understanding of the microbiome associated with mature trees and supports the theory that shaping the rhizosphere microbiome may be a strategy employed by saline-alkali-tolerant mature trees to resist salt stress. These findings offer insights into salt tolerance in mature trees and potential applications, such as the development of bio-inoculants, for managing saline environments in agricultural and ecological contexts.