Genetic diversity and virulence variation of Sporisorium destruens isolates and evaluation of broomcorn millet for resistance to head smut.

Broomcorn millet ( Panicum miliaceum L.) is one of the most important minor grain crops in China. Head smut caused by Sporisorium destruens is a serious threat to broomcorn millet production. However, there is no information on the genetic diversity and virulence variation of S. destruens in China. To address this, a total of 51 S. destruens isolates were collected from broomcorn millet growing areas in China and characterized in genetic diversity with RAPD markers and 16 isolates representing different geographic origins and genotypes were tested in virulence. The Unweighted Pair Group Method with Arithmetic averages (UPGMA) dendrogram showed that the 51 isolates were divided into three lineages at an average similarity of 0.7022. There was no significant correlation between genotypes and geographic origins of the isolates. To determine the virulence variation of S. destruens isolates, a three-year resistance evaluation for 280 accessions was conducted and the results showed that the numbers of immune, highly resistant, resistant, susceptible and highly susceptible accessions were 8, 7, 108, 152 and 5, respectively. Ten accessions were selected as potential differential hosts. In virulence test, the 16 isolates tested were separated into three pathotypes and implied a virulence differentiation. This study demonstrated that S. destruens isolates had a moderate genetic diversity and a certain degree of virulence variation. Eight accessions were identified to be immune to S. destruens which were not previously discovered in China. The paper will provide a basis of knowledge for resistance breeding to broomcorn millet head smut. [ABSTRACT FROM AUTHOR]