Rhizospheric Trichoderma harzianum TBR-7 in combination with chitosan for eco-friendly management of crown rot disease in Egyptian clover ( Trifolium alexandrinum L.)

Egyptian clover suffers from high yield losses due to crown rot ( Sclerotinia trifoliorum ) disease. Varieties with complete resistance to crown rot are not available and application of fungicides is not an ecologically viable option in Egyptian clover. In such a scenario, knowledge based and integrated use of different biocontrol agents can be explored, as this strategy has not been utilized for disease management in Egyptian clover. In this study, Trichoderma isolates were isolated from the rhizosphere of Egyptian clover. Low and medium molecular weight chitosan was evaluated for their antagonistic ability against clover rot pathogens and compatibility with Trichoderma isolates . Among different Trichoderma isolates, Trichoderma harzianum TBR-7 was found to be highly antagonistic against clover rot pathogens and also found compatible with low molecular weight chitosan. Mycelial biomass accumulation and protein leakage studies clearly showed the differential effect of low molecular weight chitosan on clover rot pathogens and Trichoderma isolates. Seed treatment with Trichoderma harzianum TBR-7 followed by foliar spray of chitosan (0.05%) led to consistent upregulation of various defense enzymes (PAL, Phenols, SOD, H 2 O 2 and Proline) in Egyptian clover. Field trials showed that seed treatment with Trichoderma harzianum TBR-7 followed by a foliar spray of chitosan (0.05%) decreased crown rot incidence, and increased green fodder and seed yield significantly compared to other treatments. Through this study, an effective and knowledge-based utilization of different biocontrol agents ( Trichoderma and chitosan) for disease management in Egyptian clover has been proposed.