Biocontrol Potential of Endophytic Fungi for the Eco-Friendly Management of Root Rot of Cuminum cyminum Caused by Fusarium solani

Abstract

Root rot disease of Cuminum cyminum caused by Fusarium solani is one of the most destructive diseases threatening cumin production. The present study investigates the biocontrol potential of some endophytes against F. solani and their effect on the induction of defense-related enzymes in a greenhouse. The results herein presented illustrate the strong biocontrol potential of three (out of twelve) endophytes. During the in vitro assay, three isolates demonstrated strong mycelial growth inhibition of F. solani: isolates 3, 4, and 9, with 87%, 65%, and 80% reductions, respectively, with respect to the control (100%). These isolates were identified as Trichoderma harzianum, T. longibrachiatum, and Chaetomium globosum, which produce siderophore and indole-3-acetic acid (IAA). Cumin seed priming with the culture filtrates of T. harzianum, C. globosum, and T. longibrachiatum positively affected the seed germination, as a higher germination (%) of culture filtrate-treated seeds was observed followed by infected and healthy control/untreated seeds. In the greenhouse, the application of T. harzianum, T. longibrachiatum, and C. globosum caused a reduction in disease severity (67.7%, 58.1%, and 59.3%, respectively) on cumin plants, with a lower disease severity (20%, 26%, and 25%, respectively) recorded in treated plants compared to the infected control (62%). Furthermore, a significant increase in defense-related enzymes in culture filtrate-treated cumin plants was recorded. Higher peroxidase (PO), polyphenoloxidase (PPO), and phenylalanine ammonia-lyase (PAL) activity, and a higher content of phenolic compounds, were found in culture filtrate-treated plants. These results indicate that the culture filtrates of these bioagents not only increased seed germination, but also protected the plants from F. solani infection by acting as important elements of the cellular antioxidant system in plants upon infection, conferring the biocontrol potential of C. globosum and Trichoderma species toward mitigating the root rot disease of cumin plants in a greenhouse.