Diversity of Fusarium species associated with healthy and malformed Syzygium cordatum inflorescences in South Africa

Abstract

Syzygium cordatum (Myrtacease) is one of the most common encountered and widely distributed tree species indigenous to South Africa. This tree is often affected by a malformation disease characterized by grossly misshapen inflorescences that do not bear fruit. Because such symptoms have previously been attributed to Fusarium species in other plants, the aim of this study was to determine the diversity of Fusarium species associated with S. cordatum inflorescences. Healthy and malformed S. cordatum inflorescences were collected from Gauteng, Mpumalanga, Western Cape, and KwaZulu-Natal. A total of 118 Fusarium isolates were obtained from healthy (19) and malformed (99) inflorescences and identified using the translation elongation factor 1 alpha (TEF1α) gene region. The results revealed that 39 isolates belonged to the Fusarium fujikuroi species complex (FFSC), 45 isolates to the Fusarium oxysporum species complex (FOSC), 33 to the Fusarium incarnatum-equiseti species complex (FIESC) and one isolate resided in the Fusarium chlamydosporum species complex (FCSC). Phylogenetic analysis separated these isolates into 15 species, of which five (two in the FFSC, three in the FIESC) are new to science. No obvious patterns were found with respect to species recovered in different geographic areas sampled. However, FFSC species, were all recovered only from malformed inflorescences.