A resistance gene to ustilago nuda in barley is located on chromosome 3H

Loose smut of barley is a common disease which can be controlled using resistant varieties. Information on the chromosome location of loci controlling loose smut resistance and the development of molecular markers to aid in selection for these genes can be beneficial in the resistant variety development process. The objectives of this work were to determine the resistance or susceptibility of doubled haploid barley lines arising from a cross of the varieties 'Steptoe' and 'Morex' to Ustilago nuda, the causal agent of loose smut of barley, and map the chromosome location of the loose smut resistance locus in 'Morex'. The reaction to Ustilago nuda of the doubled-haploid barley plants was determined by inoculating spikelets of each line at anthesis by injection of a teliospore suspension using a needle inoculation method. Mature seeds from the inoculated spikelets were grown to determine the percentage of plants that developed with smutted heads. The lines were classified as susceptible if greater than 10% of the plants were smutted. The loose smut resistance locus from the resistant source 'Morex' was mapped using an existing DNA marker map of the 'Steptoe'/'Morex' population. The distribution of the resistant and susceptible progeny from the loose smut testing fit a single gene model. The resistance gene was mapped to chromosome 3 (3H).