Evidence for the dispersal of a unique lineage from Asia to America and Africa in the sugarcane fungal pathogen Ustilago scitaminea

• Published in: Fungal genetics and biology Vol. 44; no. 1; pp. 64 - 76
• Main Authors: Raboin, Louis-Marie, Selvi, Athiappan, Oliveira, Karine Miranda, Paulet, Florence, Calatayud, Caroline, Zapater, Marie-Françoise, Brottier, Philippe, Luzaran, Rosalyn, Garsmeur, Olivier, Carlier, Jean, D’Hont, Angélique
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 2007
• Subjects: Africa; Americas; Asia; Basidiomycetes; biogeography; epidemiology; founder effect; Fungus dispersal; genetic polymorphism; Genetic Variation; Genetics, Population; geographical variation; loci; microsatellite repeats; Microsatellite Repeats - genetics; Microsatellites; Outcrossing; Phylogeny; plant pathogenic fungi; Population genetic structure; Saccharum - microbiology; Selfing; Smut; Spores, Fungal - physiology; Sugarcane; Ustilago - genetics; Ustilago - pathogenicity; Ustilago - physiology; Ustilago scitaminea; South America; Asia; United States; Africa; Americas; Microsatellites; Population genetic structure; Outcrossing; Fungus dispersal; Selfing; Ustilago scitaminea; Sugarcane; Smut
• ISSN: 1087-1845; 1096-0937
• DOI: 10.1016/j.fgb.2006.07.004

The basidiomycete Ustilago scitaminea Sydow, which causes sugarcane smut disease, has been spreading throughout Africa and America since the 1940s. The genetic diversity and structure of different populations of this fungus worldwide was investigated using microsatellites. A total of 142 single-teliospore were isolated from 77 distinct whips (sori) collected in 15 countries worldwide. Mycelium culture derived from on generation of selfing of these single teliospores were analysed for their polymorphisms at 17 microsatellite loci. All these strains but one were homozygous at all loci, indicating that selfing is likely the predominant reproductive mode of U. scitaminea. The genetic diversity of either American or African U. scitaminea populations was found to be extremely low and all strains belong to a single lineage. This lineage was also found in some populations of Asia, where most U. scitaminea genetic diversity was detected, suggesting that this fungal species originated from this region. The strong founder effect observed in U. scitaminea African and American populations suggests that the fungus migrated from Asia to other continents on rare occasions through movement of infected plant material.