Inbreeding levels of two Ustilago maydis populations

Abstract

Little is known about the population mating behavior of the smut fungus Ustilago maydis DC (Corda). To determine the amount of inbreeding that occurs in local U. maydis populations, two cornfields were sampled, one in North America (NA) at Le Sueur, Minnesota, and one in South America (SA) at Tarariras, Uruguay. These fields were chosen because of their geographic isolation and host management differences. Inbreeding coefficients (F_is) were calculated using data derived from amplified fragment length polymorphism (AFLP) markers. Mean F_is values estimated for both the NA (−0.08), and the SA (−0.02) populations statistically are not different from zero. The results of this study demonstrate that the U. maydis population structure in both cornfields results predominately from out-crossing and suggests that teliospores infrequently act as single infection units. The genetic differentiation between populations was high (F_st = 0.25).

• corn smut
• Hardy-Weinberg Equilibrium
• heterozygosity
• maximum parsimony analysis
• Wright’s inbreeding coefficient

We thank the Department of Plant Pathology and the Center for Community Genetics at the University of Minnesota, the Instituto Nacional de Investigación Agropecuaria (INIA) in Uruguay, and the NSF BioComplexity grant awarded to G. May (DMS-0083468) for financial support. We also would like to thank Alexi Balmuth, Kim Phuong Nguyen and Sandra Scherrer for their technical assistance.