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Twenty genic-and genomic SSR markers were used to study genetic diversity and geographical differentiation of barley from 29 countries through analysis of a worldwide collection of 304 ICARDA's barley landraces. Of these, 19 loci were highly polymorphic in the material studied. Based on Neidistance matrix, Principal Component Analysis (PCoA) and cluster analysis using UPGMA associated with AMOVA the data revealed countries' grouping within regions. Three distinct germplasm pools were identified in the landraces. The first of these was from Eastern Africa (Eritrea and Ethiopia) and South America (Ecuador, Peru and Chile) suggesting that barley introduced to South America might have originated specifically from East Africa or that they share a common genetic basis for adaptation. The second was the Caucasus (Armenia and Georgia) and the third included the remaining regions of Central Asia, Near East, Northern Africa and Eastern Asia. Genetic diversity of barley subspecies (Six-rowed barley, Two-rowed barley, H. spontaneum C. Koch and H. agriocrithon Å berg) also discriminates them into three groups: cultivated barleys (Sixrowed barley and Two-rowed barley), wild barley H. spontaneum and subspecies H. agriocrithon. These results associated with parsimony analysis demonstrate that H. agriocrithon and H. spontaneum might be distinct and do not support a hybrid origin for H. agriocrithon suggesting further investigation of the basis of more intense sampling of the two subspecies H. spontaneum and H. agriocrithon.

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Molecular techniques have created the opportunity for great advances in plant mutation genetics and the science of mutation breeding. The powerful targeted induced local lesions in genomes (TILLING) technique has introduced the possibility of reverse genetics-the ability to screen for mutations at the DNA level prior to assessing phenotype. Fundamental to TILLING is the induction of mutant populations (or alternatively, the identification of mutants in the environment); and mutation induction requires an understanding and assessment of the appropriate mutagen dose required. The techniques of mutation induction, dose optimization, and TILLING are explained.