Effects of selection by host cultivars on populations of Ustilago hordei

Abstract

The barley – Ustilago hordei (Pers.) Lagerh. system was examined in selection experiments. Three populations were formed with teliospores originating from 15 different dikaryons (5 dikaryons per population). The teliospores were heterozygous for a gene governing virulence to the barley cultivar Trebi. Each population was subdivided such that one subpopulation was selected on 'Trebi' and the other was simultaneously selected on 'Odessa', partially resistant and susceptible cultivars, respectively. Changes in the virulence allele frequency were monitored during each generation of selection for each population. There were no major changes in percentage of smutted plants that could be attributed to the cultivar on which selection took place. Increases of the virulent phenotype were observed for all populations regardless of cultivar. Whether these changes were the result of changes of allele frequency or other factors is not known.