Maturation of perithecia and ascospores discharge in South American leaf blight of rubber tree

摘要

The Ascomycota fungus Microcyclus ulei is a major threat for natural rubber production. The ascospores play a major role in the survival and dissemination of the fungus. The present study indicates that the ascospores are present on the leaves shortly after infection. Although their abundance is higher on leaflets 50-70 days after they reach maturity, ascospores are still found on 6 months-old leaves, ensuring the survival of the fungus during the dry season in the case of no defoliation of the rubber trees. Indeed, their viability does not depend on the age of the leaf. The pycnidiospores, whose role in the lifecycle of the fungus is not established, are also present on the leaves several months after their maturity. The ascospores are disseminated only if the leaves are wetted and exposed to an airflow. The discharge of ascospores starts a few minutes after a single wetting event but the number of ascospores discharged decreases rapidly and stops 90 min after the wetting event. However, the perithecia are rapidly able to discharge ascospores if wetted again but at a lower level. Compared to other Ascomycota, the discharge of ascospores is quick but brief.