Effects of Root Exudates on Seed Germination and Seedling Growth of Wolfberry (Lycium barbarum L.) and the Development of Root Rot Diseases

Root exudates play a critical role in enabling plants to respond to environmental stresses and mediate information exchange within the rhizosphere. These compounds regulate plant–rhizosphere interactions and significantly influence the structural and functional properties of the rhizosphere micro-ecosystem. Under continuous cropping systems, allelochemicals derived from root exudates progressively accumulate in the root zone, thereby contributing to the development of continuous cropping obstacles. In this study, root exudates were collected from wolfberry (Lycium barbarum L.) and four forages under controlled conditions to test their effects on seed germination and seedling growth in mangold (Betu vulgaris L.) and wolfberry, as well as on the root rot pathogen. Our research shows that forage root exudates could promote wolfberry seedling growth. White clover (Trifolium repens L.) and alfalfa (Medicago sativa L.), especially, could have their growth increased by up to 61% and 90% (p < 0.05). Wolfberry root exudates could promote the seed germination and seedling growth of white clover and mangold, the seed germination of Ryegrass (Lolium perenne L.), and the seedling growth of alfalfa. In addition, mangold root rots were identified as Molds, Aspergillus niger, and Fusarium solani and wolfberry root rots were Mucor cirrus, Rhizopus, Fusarium oxysporum, and Fusarium solani. What is more, wolfberry root exudates could promote Fusarium plaque expansion and mycelial growth. Ryegrass inhibited the growth of Mucor, Fusarium putrum, and oxysporum, and alfalfa and white clover promoted the plaque expansion of Rhizopus, Aspergillus niger, and Fusarium fulcrum, but inhibited the mycelial growth of related pathogens; mangold root exudates could inhibit wolfberry root rot, which affects interspecific relationships. This study provides robust technical support for elucidating interspecific relationships and promoting the development and application of the wolfberry-forage intercropping system.