Pathogenicity of Toxigenic Fusarium proliferatum from Date Palm in Saudi Arabia.

Fusarium proliferatum was isolated for the first time from roots and leaves of declining date-palm trees (Phoenix dactylifera L.) in the Al-Qassim and Al Medina Al Monawara regions in Saudi Arabia. The disease symptoms caused by F. proliferatum, which include wilt and dieback, were similar to those caused by F. oxysporum f. sp. albedinis, the causal agent of Bayoud, the most important disease of date palm found in North Africa. Koch's postulates were completed by stem injection of date-palm seedlings using two strains of F. proliferatum. The pathogenicity tests, performed on local cv. Succary using two strains of F. proliferatum isolated from roots, produced severe symptoms of disease. The identity of F. proliferatum was confirmed by comparing the data obtained by partial sequences of a large subunit of rDNA to American and European Gene Bank data. All nine F. proliferatum strains isolated from diseased plants were shown to belong to mating population D of Gibberella fujikuroi. Finally, the strains were also tested for the production of beauvericin, fumonisin B, fusaproliferin, fusaric acid, and moniliformin. Two strains out of nine were able to produce all five toxins and all strains produced at least three of them. This is the first time that toxigenic F. proliferatum strains known to belong to mating population D of G. fujikuroi were isolated from diseased date-palm plants.