No abstract

An electrophoretie study of gliadin and glutenin proteins, mainly low-moleeular-weight (EMW) glutenin subunits, was undertaken to investigate possible associations between these proteins and gluten strength. Thirty-eight durum wheat cultivars having different origins and currently grown in Spain were analysed. Different electrophoretic methods were used to analyse the seed storage proteins. Protein grain content was estimated and gluten strength was measured by the SDS-sedimentation test. New patterns for LMW glutenins were observed. Besides the known patterns of EMW-1, associated with ygliadin 42, and EMW-2 associated with y-gliadin 45, six cultivars had EMW-2" associated with y-gliadin 45, one cultivar showed LMW-2"-associated with ygliadin 44, and another eultivar, null for y-42 and y-45, had LMW-1". Significant differences for gluten strength were found among groups of cultivars with different LMW patterns. High molecular weight glutenins were found in general to be poor indieators of viscoelastic properties, although band 20 showed a negative influence on quality. The results are discussed in relation to development of cultivars with good gluten strength.

Background: One of the main goals of the plant breeding in the twenty-first century is the development of crop cultivars that can maintain current yields in unfavorable environments. Landraces that have been grown under varying local conditions include genetic diversity that will be essential to achieve this objective. The Center of Plant Genetic Resources of the Spanish Institute for Agriculture Research maintains a broad collection of wheat landraces. These accessions, which are locally adapted to diverse eco-climatic conditions, represent highly valuable materials for breeding. However, their efficient use requires an exhaustive genetic characterization. The overall aim of this study was to assess the diversity and population structure of a selected set of 380 Spanish landraces and 52 reference varieties of bread and durum wheat by high-throughput genotyping. Results: The DArTseq GBS approach generated 10 K SNPs and 40 K high-quality DArT markers, which were located against the currently available bread and durum wheat reference genomes. The markers with known locations were distributed across all chromosomes with relatively well-balanced genome-wide coverage. The genetic analysis showed that the Spanish wheat landraces were clustered in different groups, thus representing genetic pools providing a range of allelic variation. The subspecies had a major impact on the population structure of the durum wheat landraces, with three distinct clusters that corresponded to subsp. durum, turgidum and dicoccon being identified. The population structure of bread wheat landraces was mainly biased by geographic origin. Conclusions: The results showed broader genetic diversity in the landraces compared to a reference set that included commercial varieties, and higher divergence between the landraces and the reference set in durum wheat than in bread wheat. The analyses revealed genomic regions whose patterns of variation were markedly different in the landraces and reference varieties, indicating loci that have been under selection during crop improvement, which could help to target breeding efforts. The results obtained from this work will provide a basis for future genome-wide association studies.

Gliadin alleles were identified in 100 common wheat cultivars registered and/or grown in Spain during the last 40 years. A very high level of genetic polymorphism was found: in total, 103 allelic variants including one null‐allele were found at the six major Gli loci in the Spanish wheats studied. An average genetic diversity for these six loci was found to be higher (H=0.844) than in any group of wheat cultivars studied previously. Spanish wheats bred in Spain demonstrated even higher genetic diversity (H=0.868), probably because of the occurrence in this group of some landraces (local varieties) assumed to be strongly differentiated to fit local environments. The high level of genetic diversity of wheats grown in Spain was maintained by the introduction of distantly related wheat germplasm from different sources, especially from Italy and CIMMYT. A slight decrease of genetic diversity in recently registered cultivars might be caused by the excessive introduction of French wheats. Thirteen new alleles found in Spanish wheats were catalogued, including Gli‐D2w which encodes the first Gli‐D2‐controlledγ‐gliadin to be found.

The allelic variation of high molecular weight glutenins as principal determinants of bread quality has been analyzed in 165 Spanish wheat (Triticum aestivum ssp. vulgare L.) landraces provided by the Plant Genetic Resources Centre. The identification by standard electrophoresis techniques has been supported by a new PCR screening method, allowing the identification of the 2•• glutenin subunit from the Glu-A1 locus in some landraces. The relation of high molecular weight glutenins and bread quality has been evaluated by SDS-sedimentation tests and mixographs. A positive influence on quality has been found for the 2•• glutenin subunit from the Glu-A1 locus, pairs 7 + 8 and 13 + 16 from the Glu-B1 locus, and pair 5 + 10 from the Glu-D1 locus. The presence of a wide range of values for quality traits in landraces with the same high molecular weight glutenin composition points to the possible influence of other prolamins such as the low molecular weight glutenins. Their influence on bread quality will be assessed in future studies. A complete description of the high molecular weight glutenin composition and quality values of all the landraces analyzed in this study is provided for use in wheat breeding programs.Additional key words: mixograph; sedimentation volume; Triticum aestivum. ResumenVariación en gluteninas de alto peso molecular (HMW) en variedades tradicionales españolas de trigo y su relación con la calidad panaderaEn este trabajo, se ha analizado la variación alélica para gluteninas de alto peso molecular (HMW) en una colección de 165 variedades tradicionales españolas de trigo blando (Triticum aestivum ssp. vulgare L.) provenientes del Centro Nacional de Recursos Fitogenéticos. La identificación mediante técnicas estándar de electroforesis se ha complementado con un método de análisis por PCR que ha permitido la identificación de la subunidad 2•• del locus Glu-A1 en varios cultivares. La relación entre la composición en gluteninas de alto peso molecular y la calidad panadera se ha analizado mediante la prueba del volumen de sedimenatción con SDS y los datos del mixógrafo. Se ha encontrado una influencia positiva en la calidad por parte de la subunidad 2•• del locus Glu-A1, los pares de subunidades 7 + 8 y 13 + 16 del locus Glu-B1, y el par 5 + 10 del locus Glu-D1. Variedades con la misma composición en gluteninas de alto peso molecular han mostrado un amplio rango de valores en los parámetros de calidad, apuntando a la participación de otras prolaminas, como las gluteninas de bajo peso molecular, cuya influencia en la calidad será analizada en el futuro. En el presente trabajo, se incluye la descripción detallada de la composición en gluteninas de alto peso molecular y de parámetros de calidad de todos los cultivares analizados para su posible utilización en programas de mejora de trigo.Palabras clave adicionales: mixógrafo; Triticum aestivum; volumen de sedimentación.