The genetic diversity of several local p opulations of the fungal pathogen Cochliobolus sativus, collected over 3 years fromdifferent regions of the Czech Republic, was examined using amplified fragment length polymorphism (AFLP). A high levelof variability was found even among isolates from one lesion. Measures of multilocus linkage disequilibrium suggested thatrecombination has a minor impact on the genetic structure of populations. Coch liobolus sativus forms genetically divergentpopulations ( FST=0Æ33), indi cating a low level of genefl ow between populations.

ABSTRACT. Barley spot blotch (SB), caused by Cochliobolus sativus, is an important barley disease which causes extensive grain yield losses. These losses may not always correlate directly with the amount of diseased leaf area. Two barley cultivars, Quebracho (susceptible to SB) and Carumbé (with intermediate susceptibility to SB), were compared in field experiments in 2003, 2004 and 2006. Plots of each cultivar were either inoculated with C. sativus or protected with fungicide under field conditions to generate contrasting treatments:i) diseased, and ii) free of disease, respectively.

ABSTRACT:Genomic regions infl uencing resistance to powdery mildew [Blumeria graminis (DC.) E.O.Speer f. sp. hordei Ém. Marchal] were detected in a doubled haploid (DH) barley (Hordeum vulgare L.) population derived from a cross between the breeding line ND24260 and cultivar Flagship when evaluated across four fi eld environments in Australia and Uruguay. Signifi cant quantitative trait loci (QTL) for resistance to B. graminis were detected on six of the seven chromosomes (1H, 2H, 3H, 4H, 5H, and 7H).