Biological control of cabbage head rot ( Sclerotinia sclerotiorum ) by Coniothyrium minitans

Background Sclerotinia sclerotiorum is the causal agent of white mould, stem and head rot diseases on a wide variety, including cabbage in the field and storage. Control of this pathogen by using commercial disease management methods is extremely difficult. Therefore, this study was performed to identify the potential biological control agent. Results The antagonist fungal isolates, a mycoparasite of S. sclerotiorum , were isolated and described as KET Cm1, PAL Cm 2 and TDK Cm 3. They were subjected to morphological and microscopic observation. The growth of antagonist fungal isolates on different media revealed that PDA and half-strength Czapek dox agar medium showed the maximum mycelial growth (28.67 and 28.33 mm) and pycnidial production in the PDA medium. The studies on pH and temperature found that growth and sporulation of the antagonist fungal isolates were optimum at pH 5.5 (34 mm) and 20 °C. The molecular confirmation of antagonist fungal isolates was carried out using ITS 1 and ITS 4 primers, which target 18S-28S rRNA gene fragment. The isolates were partially sequenced and showed that more than 99% identity with Coniothyrium minitans already exist in the NCBI database. The accession numbers (MW093134, MW111282 and MW136938) were obtained for all the three isolates and also confirmed using specific primers Cm sp 1F and Cm sp 1R. Among the tested isolates, the antagonistic activity of C. minitans TDK Cm 3 showed the maximum mycelial growth inhibition of 48.8% S. sclerotiorum and was used for further studies. Penetration and formation of appressoria on the hyphae of S. sclerotiorum by C. minitans isolate TDK Cm 3 were observed through the scanning electron microscope. The ethyl acetate fractions of TDK CM 3 isolate were evaluated against S. sclerotiorum by agar well diffusion assay, paper disc assay and poison food technique in vitro. Through GC–MS analysis, the effective antifungal compounds were identified. Conclusion The present study focused on the identification and characterization of effective Coniothyrium isolates as eco-friendly, integrated disease management strategies against cabbage head rot disease.