Phosphorus fertilizer enhances the tolerance of rhizosphere microbial community to low-light stress in Tartary buckwheat

Abstract

Low-light stress has become an important factor limiting crop yield and quality improvement. Appropriate phosphorus (P) addition can enhance soil microbial activity and nutrient availability, thereby alleviating the negative impacts of low-light stress. However, the role of crop rhizosphere microorganisms in the mitigation of low-light stress by P addition in agroecosystems remains unclear. In this study, three light conditions (normal light, S0; moderate low-light stress, S1; severe low-light stress, S2) and three P addition levels (0 kg ha^− 1, P0; 35 kg ha^− 1, P1; 70 kg ha^− 1, P2) were applied to analyze the combined effects on the rhizosphere microbial diversities, compositions, co-occurrence patterns, and assembly mechanisms during critical growth stages (flowering, filling, and maturity stages). The results showed that both low-light stress and P appreciably affected rhizosphere microbial community composition, with P promoting the proliferation of rhizosphere beneficial microbes under low-light stress. Low-light stress reduced rhizosphere microbial α-diversity, and S2 simplified microbial networks. In contrast, P1 increased bacterial network complexity, connectivity, and stability. Indicator taxa analysis revealed that P1 increased the abundance of shared and specific species in rhizosphere microbial networks. Under S1, P1 enhanced keystone taxa abundance. Community assembly analysis indicated that bacterial communities were governed by deterministic processes, whereas low-light stress reduced fungal stochasticity, which was increased by P addition. These findings highlight that P addition under low-light stress can enhance the tolerance of Tartary buckwheat rhizosphere microbial community by modulating rhizosphere microbial diversity, composition, and network stability, providing insights into alleviating low-light stress.