Characterization of Fusarium oxysporum isolates from tomato plants in Algeria

Fusarium oxysporum is an ubiquitous soil-borne fungus, having a high genetic and ecological diversity with the potential to cause diseases of many crop species of economic interest. Indeed, some strains of F. oxysporum known as pathogens generate common diseases such as wilting, root and crown rot on host plants. Two formae speciales are confined to the tomato: F. oxysporum f.sp. lycopersici (FOL) causing Fusarium wilt, while F. oxysporum f.sp. radicis-lycopersici (FORL) causes Fusarium crown and root rot. The study include 27 strains isolated from the stems, crown and roots of infected tomato plants; to confirm the identity of the fungus, the isolates were identified using analysis based on morphological criteria and sequencing of the translation elongation factor 1-alpha (TEF) gene using ef1 and ef2 primers. Twenty three strains belonged to F. oxysporum, three strains to Fusarium solani, and one strain to Fusarium redolens. Tomato seedlings were tested to confirm the pathogenicity of the isolates tested. Pathogenicity test confirmed that twenty two F. oxysporum isolates were pathogenic on tomato and produced crown and root rot typical of F. oxysporum f.sp. radicis-lycopersici forma specialis, while one strain initially identified as F. oxysporum did not induce disease symptoms and is considered as non-pathogenic. Additionally, no symptoms of Fusarium wilt were observed at all; therefore no strains can be affiliated to F. oxysporum f.sp. lycopersici forma specialis. Key words: Fusarium oxysporum, tomato, molecular identification, pathogenicity.