Investigation of soil-borne fungi, causal agents of olive trees wilt and dieback in Tunisia

• Published in: Archiv für Phytopathologie und Pflanzenschutz 2020-07, Vol.53 (17-18), p.828-843
• Main Authors: Gharbi, Yaakoub, Bouazizi, Emna, Cheffi, Manel, Ben Amar, Fathi, Triki, Mohamed Ali
• Format: Article
• Language: English
• Subjects: Clay soils; Collars; Colonization; dieaback disease; Dieback; Fruit trees; Fungal diseases; Fungi; Fusarium oxysporum; Fusarium solani; Inoculation; Irrigation water; Macrophomina phaseolina; Mycoflora; Neonectira radicicola; Olea europaea; Rhizoctonia solani; root rot; Saline water; Signs and symptoms; Soil investigations; Soil microorganisms; Trees; Verticillium dahliae; Wilt
• ISSN: 0323-5408; 1477-2906
• DOI: 10.1080/03235408.2020.1800559

The incidence of fungal diseases affecting olive trees increased in Tunisia. Mycoflora isolated from diseased olive trees revealed their colonisation by several fungal species such as Fusarium oxysporum, F. solani, F. lateritium, Macrophomina phaseolina, Rhizoctonia solani, Athelia rolfsii, Neonectria radicicola, Verticillium dahliae, Armillaria mellea, Phytophthora megasperma, P. palmivora and Pythium sp. These fungi were also isolated from roots and collars of young olive cuttings in the nursery, where they caused severe losses. Most of the fungi were pathogenic and caused typical symptoms of dieback upon their inoculation on olive plants, which fullfill the Koch's postulate. These pathogenic fungi showed the ability to infect, either separately or jointly the olive tree. Moreover, cropping of olive in high clay soil and irrigation with high saline water increase the fungal incidence and plays a major role in the disease outbreak.