First report of fig tree dieback caused by Lasiodiplodia theobromae in Tunisia

Abstract

In Tunisia, common fig (Ficus carica L., Moraceae) is a very ancient fruit crop, very important and still regaining interest. It is cultivated throughout Tunisia from the south to the north and from the east to the west. In July 2020, a severe unusual branch dieback and stem canker was observed on fig cv. ‘Zidi’ trees in a commercial orchard in north‐eastern Tunisia. Disease incidence was 50% and symptoms observed on the 10‐year‐old infected trees included wilt, defoliation, branch dieback and trunk and shoot cankers. The current study aimed to characterize the pathogen (s) associated with observed fig dieback and to study their pathogenicity. The causal agent has been identified as belonging only to the species Lasiodiplodia theobromae based on morphological characters and phylogenetic analyses, using combined sequences of ITS, tef1 and β‐tubulin (tub2) genes. Pathogenicity tests performed on 1‐year‐old detached and green shoots demonstrated that L. theobromae was pathogenic to common fig cv. ‘Zidi’. Symptom development was visible after 7–15 days of incubation at 25°C showing the aggressive behaviour of L. theobromae towards fig shoots. Cvs. ‘Chetoui’, ‘Zidi’, ‘Bidhi Bghal’ and ‘Bither Abyadh’ were less susceptible compared to the more susceptible cvs. ‘Soltani’ and ‘Bidhi 2’. To our knowledge, this study is the first report on common fig canker and dieback disease caused by L. theobromae in Tunisia and Africa. Considering the severe and rapid progress of this disease, prevention and management strategies should be implemented urgently to reduce its incidence and reduce fig tree losses.