Diversity changes of rhizosphere and endophytic bacteria in Allium senescens L. under drought stress and rewatering

Xue Song ¹ Haotian Li ¹ Chuhan Fu ¹ Jiahong Li ¹ Jihong Xiang ² Xuetong Sun ¹ Jielin Liu ³ Ligang Qin ^1*

• ¹ Northeast Agricultural University, Harbin, China
• ² Grassland Station of Heilongjiang, Harbin, China
• ³ Institute of Forage and Grassland Science, Heilong Academy of Agricultural Science, Harbin, China

Drought stress severely impacts plant growth and productivity, yet the role of microbial communities in enhancing drought tolerance remains underexplored, particularly in non-cultivated species like Allium senescens L. (A. senescens). This study investigates how drought stress and rehydration reshape the rhizosphere and endophytic bacterial communities of A. senescens, focusing on tissue-specific responses and functional adaptations. Using 16S rRNA sequencing, we analyzed bacterial communities in rhizosphere soil, roots, bulbs, and leaves under drought gradients (5%, 15%, 25% PEG-6000) and post-rehydration recovery. Drought reduced rhizosphere bacterial diversity by 42% (Chao1: 850 ± 32 vs. 493 ± 28; P < 0.01) but increased leaf diversity by 52% (Shannon: 2.1 ± 0.2 vs. 3.2 ± 0.3; P < 0.01). The 15% PEG treatment emerged as a critical threshold, triggering the most pronounced shifts in microbial composition and diversity. Enrichment of Streptomyces (8.4% in roots under 15% PEG; P < 0.001) and functional predictions suggest its role in phenylalanine biosynthesis and osmotic regulation. These findings provide a foundation for developing microbial-based strategies to enhance drought resilience in Allium crops and other arid-adapted species.