Postharvest Biological control of Fusarium dry-rot diseases in potato tubers using Clonostachys rosea strain IK726

Sammanfattning: The common saprophytic fungus Clonostachys rosea (Glicocladium rosea) has been reported for its biological control capacity against plant pathogenic fungi. Postharvest application of C. rosea strain IK726 and the mechanism of action against potato dry rot disease are not properly investigated. In this piece of study the biological control potential of strain IK726 against F. avenaceum and F. coeruleum was investigated considering the postharvest processing and handling procedures used in the potato industry. Moreover, its effect on the rot development, wound colonization potential and interactions with the Fusarium spp. were studied in potato tubers and culture media. In phytotron bioassay the mean number of rot incidence has reduced significantly (p= 0.018) to 16.25% and 20% in tubers treated with C. rosea strain IK726 and artificially infected with F. avenaceum and F. coeruleum, respectively. It was about 45% reductions in the mean number of rot compared to the non-treated ones. C. rosea strain IK726 had also survived the fluctuation in temperature from 12, 4 and 22°C overtime and managed to give significant control. Dual culture tests showed lack of clear inhibition zone and the mycelia of C. rosea had grown into and covering the Fusarium mycelia and gradually suppressed its growth. The microscopy study revealed a mycoparasitic-like interaction in which direct contact and growth of strain IK726 on and along the hyphae of F. avenaceum and F. coeruleum. Finally, time-lapse spore interaction tests implied delay in F. coeruleum spore germination to 8 to 10 hours and the germ tube growth was also affected in the presence of C. rosea strain IK726. Therefore, C. rosea strain IK726 has the potential to control dry-rot disease in potato tubers in combination with postharvest handling practices and storage conditions. Moreover, effective colonization of tuber wounds, antibiosis and mycoparasitic-like action could possibly be the mode of action against the Fusarium spp.