Co-application of chitooligosaccharides and arbuscular mycorrhizal fungi enhances soybean resistance to cadmium stress

Cadmium (Cd) pollution is a serious environmental issue, and soybeans are an essential oil crop worldwide. Cd can enter the biosphere, posing a grave threat to human health. Therefore, it is imperative to study how to enhance soybean adaptability to Cd stress and manage Cd-contaminated soil. This study found that chitooligosaccharides (CHO) and arbuscular mycorrhizal fungi (AMF) can influence phenylpropane biosynthesis, flavonoid biosynthesis, phenylalanine metabolism, and betalain biosynthesis. These effects enhance the antioxidant capacity of soybeans and protect the integrity of soybean leaf ultrastructure, thereby improving the plants' resistance to Cd stress. Additionally, CHO and AMF promote the conversion of jasmonic acid (JA) to its derivatives, alleviating the inhibitory effect on soybean growth and facilitating plant development under Cd stress. Furthermore, CHO and AMF enhanced the abundance of Cd-tolerant fungi in the rhizosphere, such as Trichoderma, Trichosporon, and Cladosporium, and reduced soil Cd levels through growth dilution effects. This study provides new insights into the use of marine polysaccharides and arbuscular mycorrhizal fungi for remediation of Cd contaminated soil.