Effects of Alginate Oligosaccharides on Alleviating Atrazine Phytotoxicity in Tobacco

The objective of this study is to explore the function and pathway of alginate oligosaccharides in alleviating atrazine pesticide residues in tobacco, develop new uses of alginate oligosaccharides as biostimulants, verify its potential in the field of crop protection, and to enrich green agricultural techniques.

This experiment was carried out at Jimo Experimental Base of Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao City, Shandong Province, from March to June 2025. A pot experiment was conducted using the atrazine-sensitive tobacco cultivar YunYan 87 as the test material. Three treatments were established: atrazine + water (T1), atrazine + alginate oligosaccharides (T2), and an untreated control (CK). Atrazine was applied at a concentration of 3.35×10^-3 mg·kg^-1, while alginate oligosaccharides were 200 mg·L^-1. Agronomic traits were recorded at 7, 14, and 28 d after treatment, and inhibition rates were calculated. In addition, leaf and rhizosphere soil samples were collected at 28 d for transcriptome and rhizosphere microbial community analyses.

The results showed that 200 mg·L^-1 alginate oligosaccharides could alleviate the inhibition of atrazine on tobacco growth: treatment for 7, 14, 28 d, the leaf length, leaf width, root length and plant weight of atrazine + alginate oligosaccharides (T2) were higher or significantly higher than those of atrazine + water (T1) treatment group. Moreover, after treatment with alginate oligosaccharides (T2), the photosynthetic rate of leaves was increased and the inhibition of atrazine on tobacco root development was alleviated. Compared with the atrazine + water (T1) treatment group, 6 784 genes were up-regulated and 5 792 genes were down-regulated after alginate oligosaccharides (T2) treatment. KEGG analysis showed that 17 metabolic pathways were significantly enriched. Among them, the highest enrichment factor was the metabolic pathway of photosynthesis-antenna proteins. The results were highly consistent with the physiological and biochemical determination results. In terms of rhizosphere microorganisms, alginate oligosaccharides treatment increased the richness and diversity of soil rhizosphere microbial communities, the microbial community structure was changed. Among them, Pseudolabrys with growth-promoting function and Flavisolibacter with pesticide degradation function were significantly enriched.

As a biostimulant, alginate oligosaccharide can effectively alleviate the phytotoxicity caused by atrazine residues. Its potential mechanism of action is mainly reflected in the following three aspects: alleviating the inhibition of atrazine on the morphological structure of tobacco; enhancing plant photosynthesis efficiency by up-regulating the expression of photosynthesis-antenna protein pathway genes; regulating the rhizosphere microenvironment to induce the directional enrichment of beneficial microorganisms.