Malus sieversii (Ldb.) Roem. is the original species of modern cultivated apple and a key national essential conservation plant in China. In recent years, degradation and death of wild apple has been exacerbated by imbalances in the rhizosphere micro-ecosystems of wild apple forests due to soil nutrient loss, grazing, climate change and pest and disease outbreaks. However, the structure, diversity and response to environmental factors of wild apple rhizosphere microbial communities are so far unclear. In this study, the rhizosphere bacterial and eukaryotic communities of M. sieversii (Ldb.) Roem. in eight regions of the Yili River were analyzed using 16S/18S rDNA high-throughput sequencing technology. The results indicated that the bacterial operational taxonomic units (OTUs), Shannon index, and community composition were significantly lower in regions A, E, and F than in other regions. By contrast, the dominant eukaryotic communities in all regions were relatively similar in composition and differed less than the relative abundance of bacterial communities. Geographical and climatic distance were found to be key factors influencing the composition and diversity of wild apple rhizosphere microbial communities through mantel analysis. Moreover, these factors above were more correlated with bacterial diversity than with eukaryotes. This study identified the structure of wild apple rhizosphere microbial communities in Xinjiang and their interaction mechanisms under geographical and environmental gradients. It provides guidance for the sustainable management and ecological construction of wild apple forests in China.

Malus sieversii (Ldb.) Roem., the original species of modern cultivated apples, is a national essential protected plant in China. Due to soil nutrient loss, grazing, climate change, and diseases and insect pest outbreaks, the rhizosphere microecological imbalance of wild apple forests has aggravated the degradation and death of wild apples in recent years. So far, the structural diversity, function, and response to environmental drivers of the wild apple rhizosphere microbial community are not unclear. 16S/18S rDNA high-throughput sequencing were used in this study to analyze the rhizosphere bacterial and eukaryotic communities of M. sieversii (Ldb.) Roem. in eight regions of the Ili River. The results indicated that the bacterial operational taxonomic units (OTUs), Shannon value, and community composition were significantly lower in regions A, E, and F than in other regions. However, the composition of dominant eukaryotic communities in the eight regions was relatively similar, and the difference was smaller than the relative abundance of bacterial communities. Through redundancy analysis, it was found that Acidobacteriota, Verrucomicrobiota, Planctomycetota, Chloroflexi, and Methylomirabilota microbial communities with a lower relative abundance in regions A, B, E, and F, was affected by soil pH, alkaline-hydrolyzable nitrogen (AN), available phosphorus (AP), and potassium (AK), altitude, and relative humidity (RH). The results showed that the relative abundance of microorganisms in regions A, B, E, and F could be increased by rationally increasing soil nutrients.