Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is an important pest of small grains cereals in many areas throughout the world. This research was conducted to determine the inheritance of resistance and to identify molecular markers of resistance in the barley (Hordeum vulgare L.) lines PI366444 and PI366453. Artificial infestation was performed in the field and growth chamber. Sodium dodecyl sulphate‐polyacrylamide gel electrophoresis, Southern blotting, and polymerase chain reaction (PCR) techniques were used to determine plant genotypes. The PI366444 and PI366453 lines were intercrossed and each was also crossed with the susceptible cultivars Stark and Bearpaw. Allelism tests of F2 progeny showed that the resistant lines shared common or tightly linked resistance genes. Segregation ratios from crosses among resistant and susceptible plants, measured using F3 families, indicated that there were at least two resistance genes in both of the P1 lines. Two different regions in the barley genome were associated with RWA resistance genes. Variation for both leaf chlorosis and leaf rolling in F2 plants from crosses with both resistant lines was associated with the sequence‐tagged‐site (STS) PCR markers B‐hordein and D14 on the short arm of Chromosome 5. The STS‐PCR marker ABG8 on Chromosome 2 was associated with leaf rolling in one cross. Barley breeding programs throughout North America have devoted significant time and resources to backcrossing RWA resistance genes into acceptable cultivars. The molecular markers described in this report may assist barley breeding programs in introgression and fixation of linked resistance genes into useful germplasm.

The genetic variation of sixteen wild, Spanish populations of Thinopyrum junceum and Thinopyrumjunceiforme and their interspecific relationships were analyzed. The relationships between these species and the diploids T. bessarabicum and T. elongatum were also investigated. The number of phenotypes and the composition of bands yielded by the electrophoretic separation of endosperm proteins were used to estimate intra‐ and interpopulational variability. DNA polymorphism generated by 24 arbitrary 10‐mer primers and 14 specific 20‐mer primers was used to determine interpopulational variability and interspecific relationships. Jaccard's coefficient of similarity was used to analyze presence and absence data in the DNA polymorphism and endosperm protein determinations of individual plants. Pearson's product‐moment correlation coefficient was used to analyse interpopulational variation using endosperm protein band frecuency data. Dendrograms were constructed using an unweighted pair group method with arithmetical average (UPGMA). The high level of intrapopulational variability found in T. junceum and T. junceiforme was inconsistent with the traditional classification of these species as self‐pollinating. The level of interpopulational variation varied according to the degree of polymorphism of the corresponding markers. The endosperm proteins and random amplified polymorphic DNAs (RAPDs) proved to be the most polymorphic markers to those used although only the former were able to distinguish between the different populations. Interspecific relationships were consistenly confirmed by all the PCR‐based markers, and were also in agreement with the results of other authors.

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International audienceQuantification of the variability in wild species is a necessary step before determining their possible future use in plant breeding. A collection of 29 wild Spanish populations of the genera Elymus and Thinopyrum was characterised using 22 morphological and agronomical characteristics. Field studies were performed over two years, 1994 and 1995. Frequencies were calculated for qualitative and quantitative traits. Pearson's product-moment correlation coefficient was used to analyse inter-population variation using frequency data. Means and coefficients of variation were calculated for quantitative characteristics. Analysis of variance was performed for each species to study differences between intra- and inter-populational variability. Similar degrees of variability were observed between quantitative and qualitative traits in all the species studied (T. junceum, T. junceiforme, E. caninus and E. hispanicus). Differences in variability were found at the level of species and population. The relationships between these differences and biological and environmental factors are discussed.Évaluation et caractérisation d'une collection de populations sauvages espagnoles des genres Elymus et Thinopyrum, sur la base de caractères morphologiques et agronomiques. La quantification de la variabilité des espèces sauvages est un pas nécessaire avant leur possible utilisation dans l'amélioration végétale. Une collection de 29 populations sauvages espagnoles des genres Elymus et Thinopyrum a été caractérisée à l'aide de 22 caractères morphologiques et agronomiques. Les études en champ ont été réalisées pendant deux années, 1994 et 1995. Les fréquences ont été calculées pour les caractères qualitatifs et quantitatifs. Le coefficient de la correlation produit-moment de Pearson a été utilisé pour analyser la variation interpopulationnelle, à partir des données des fréquences. Les moyennes et les coefficients de variation ont été calculés pour les caractéristiques quantitatives. L'analyse de la variance dans chaque espèce a permis d'étudier les différences entre la variabilité intra et interpopulationnelle. Des niveaux semblables de variabilité ont été observés entre caractères quantitatifs et qualitatifs dans toutes les espèces etudiées. Des différences de variabilité ont été trouvées au niveau des espèces et de la population. Les relations entre ces différences et des facteurs biologiques et de l'environnement sont discutés