Emerging Fig Black Necrosis incited by Butlerelfia eustacei and its potential impact on various fig cultivars

The widespread occurrence of fig cankers in the fig orchards of the central regions of Fars Province, Iran, prompted us to investigate the causative agents responsible for this decay. During this study we identified a newly emerged disease in fig trees, which we termed “Fig Black Necrosis”, in the commercially important fig cultivar Sabz. This disease is characterized by black wood necrosis under the bark of the infected fig branches. Our morpho-molecular investigation of fungal isolates from the infected fig trees exhibiting symptoms of black necrosis led to identifying the isolates as the basidiomycete, Butlerelfia eustacei, of the order Atheliales sensu lato. We conducted a comprehensive pathogenicity assessment on detached shoots and one-year-old saplings of eight distinct fig cultivars. The results revealed that B. eustacei could induce conspicuous brown lesions and wood discoloration. Moreover, our study demonstrated that this pathogen could cause wood necrosis and discoloration in detached shoots of 14 distinct tree species associated with various economically significant fruit, landscape, and ornamental trees growing alongside fig trees. In our survey, we clustered the inoculated fig cultivars based on six distinct pathogenicity characteristics using the principal component analysis approach. The results indicated that most fig cultivars, including all dried and most fresh figs, were moderately-susceptible to Fig Black Necrosis. The findings of this study provide insight into the newly emerged disease in fig orchards, aiming to better understand the causal agent and develop effective integrated management strategies against the disease.