Resistencia al encamado

Se conoce como encamado el proceso por el que los tallos de las plantas son desplazados de una manera permanente de su posición vertical. Puede culminar en que las plantas se queden dobladas o tumbadas sobre el suelo, y a veces puede llevar rotura de los tallos. Los tallos pueden permanecer rectos en su encamado o adoptar formas curvas. El encamado a menudo no se distribuye uniformemente en el campo afectado, puede afectar solo a ciertas secciones del campo. El grado de encamado, es decir, el grado en que los tallos se desplazan de la perpendicular puede también variar en diferentes lugares dentro del campo. La permanencia, junto con el grado, determina la severidad del encamado. Este proceso afecta principalmente a cultivos pertenecientes a las familias de cereales y leguminosas. Normalmente ocurre después de que las inflorescencias, es decir, espigas, panículas, etc. hayan emergido. Se ha observado que los cereales pueden encamar en cualquier tiempo desde la emergencia de su espiga hasta que los granos han madurado. Y las plantas son más propensas al encamado conforme avanzan en el desarrollo y llegan a la maduración. El encamado puede reducir la producción hasta casi anularla, y causa además diferentes daños en el cultivo, como disminuir la calidad, e incrementa los gastos de la cosecha. El encamado es un fenómeno complejo que está influenciado por muchos factores ambientales, incluyendo el viento, la lluvia, la topografía, el tipo de suelo, las enfermedades e incluso el cultivo previo. Frecuentemente está asociado con condiciones que promueven el crecimiento de la planta como puede ser un abundante abonado

Temporal trends in the diversity of durum wheat varieties grown in Spain based on gliadin alleles

Gliadin alleles are inherited co-dominantly, they have revealed large levels of inter-varietal polymorphism and identification of a genotype is possible immediately by the electrophoretic protein phenotype. The gliadin loci control the synthesis of a group of proteins named as blocks of gliadins. The main Gli loci are located on the chromosomes of the first (Gli-1) and sixth (Gli-2) homoeologous groups. Alleles at each locus differin number and electrophoretic mobility of encoded gliadins. This ensures a great diversity of the A-PAGE patterns and, therefore, provides a great possibility to distinguish a high number of wheat genotypes and to describe them in terms of gliadin allele composition (Fig.1). Comparative analysis of gliadin markers indifferent groups of wheats (old and new varieties, several samples of a cultivar…) may reveal genetic erosion, different types of selection and loss of genetic identity

Diversity and Genetic structure of the Spanish collection of durum wheat (Triticum turgidum L) landraces

The objectives of this study were to assess diversity and genetic structure of a collection of Spanish durum wheat (Triticum turgidum L) landraces, using SSRs, DArTs and gliadin-markers, and to correlate the distribution of diversity with geographic and climatic features, as well as agro-morphological traits. A high level of diversity was detected in the genotypes analyzed, which were separated into nine populations with a moderate to great genetic divergence among them. The three subspecies taxa, dicoccon, turgidum and durum, present in the collection, largely determined the clustering of the populations. Genotype variation was lower in dicoccon (one major population) and turgidum (two major populations) than in durum (five major populations). Genetic differentiation by the agro-ecological zone of origin was greater in dicoccon and turgidum than in durum. DArT markers revealed two geographic substructures, east-west for dicoccon and northeast-southwest for turgidum. The ssp. durum had a more complex structure, consisting of seven populations with high intra-population variation. DArT markers allowed the detection of subgroups within some populations, with agro-morphological and gliadin differences, and distinct agro-ecological zones of origin. Two different phylogenetic groups were detected; revealing that some durum populations were more related to ssp. turgidum from northern Spain, while others seem to be more related to durum wheats from North Afric

Nuevo locus que codifica la subunidad de glutenina C-LMW-5 en el cromosoma 6B de trigo panadero.

En el análisis genético de las prolaminas en granos F2 procedentes de dos cruzamientos entre cultivares de trigo panadero, se ha encontrado un estrecho ligamiento entre una subunidad de glutenina de bajo peso molecular (LMW) de tipo C y gliadinas codificadas por el locus Gli-B2 situado en el cromosoma 6B. Se ha denominado Glu-B6 al locus que codifica dicha glutenina C-LMW

Genetic redundancy among durum wheat accessions as assessed with SSRs and endosperm proteins

Reducing duplication in ex-situ collections is complicated and requires good quality genetic markers. This study was conducted to assess the value of endosperm proteins and SSRs for validation of potential duplicates and monitoring intra-accession variability. Fifty durum wheat (Triticum turgidum ssp. durum) accessions grouped in 23 potential duplicates, and previously characterised for 30 agro-morphological traits, were analysed for gliadin and high molecular weight glutenin (HMWG) subunit alleles, total protein, and 24 SSRs, covering a wide genome area. Similarity and dissimilarity matrices were generated based on protein and SSRs alleles. For heterogeneous accessions at gliadins the percent pattern homology (PH) between gliadin patterns and the Nei’s coefficient of genetic identity (I) were computed. Eighteen duplicates identical for proteins showed none or less than 3 unshared SSRs alleles. For heterogeneous accessions PH and I values lower than 80 identified clearly off-types with more than 3 SSRs unshared. Only those biotypes differing in no more than one protein-coding locus were confirmed with SSRs. A good concordance among proteins, morphological traits, and SSR were detected. However, the discrepancy in similarity detected in some cases showed that it is advisable to evaluate redundancy through distinct approaches. The analysis in proteins together with SSRs data are very useful to identify duplicates, biotypes, close related genotypes, and contamination

Desarrollo de nuevos marcadores de DNA para la identificación de gluteninas de alto peso molecular (HMW) en trigo

Las subunidades de gluteninas de alto peso molecular (HMW-GS) son las principales responsables de la calidad pandera del trigo (T. aestivum ssp vulgare L.). Su estudio se realiza por métodos electroforéticos en geles SDS-PAGE, habiéndose identificado así una gran cantidad de alelos distintos con diferente influencia en la calidad. Sin embargo, la correcta asignación de alelos puede ser a veces complicada usando sólo este método, por ello se están desarrollando marcadores basados en la secuencia de ADN que complementen el análisis electroforético y ayuden a la correcta discriminación alélica. En este trabajo se han desarrollado marcadores nuevos para diferenciar inequívocamente las subunidades 2¨ vs 2* del locus Glu-A1, y, la 7 vs 7* y la 7 vs 13 del locus Glu-B1

Analysis of genetic variability in a sample of the durum wheat (Triticum durum Desf.) Spanish collection based on gliadin markers

In this work gliadin proteins were used to analyse the genetic variability in a sample of the durum wheat Spanish collection conserved at the CRF-INIA. In total 38 different alleles were identified at the loci Gli-A1, Gli-A3, Gli-B5, Gli-B1, Gli-A2 and Gli-B2. All the gliadin loci were polymorphic, possessed large genetic diversity and small and large differentiation within and between varieties, respectively. The Gli-A2 and Gli-B2 loci were the most polymorphic, the most fixed within varieties and the most useful to distinguish among varieties. Alternatively, Gli-B1 locus presented the least genetic variability out of the four main loci Gli-A1, Gli-B1, Gli-A2 and Gli-B2. The Gli-B1 alleles coding for the gliadin γ-45, associated with good quality, had an accumulated frequency of 69.7%, showing that the Spanish germplasm could be a good source for breeding quality. The Spanish landraces studied showed new gliadin alleles not catalogued so far. These new alleles might be associated with specific Spanish environment factors. The large number of new alleles identified also indicates that durum wheat Spanish germplasm is rather unique

Genetic variation for glutenin and gliadins associated with quality in durum wheat (Triticum turgidum L. ssp. turgidum) landraces from Spain.

The allelic variation at seven prolamin loci involved in quality has been studied in a set of durum wheat landraces from all the Spanish regions where this crop has been traditionally cultivated. The genetic variability was higher than that found in other germplasm collections. All the loci, except Glu-B2, displayed a genetic variability higher than 0.62, with Glu-3 the most polymorphic. In total, five alleles were studied at Glu-A1, nine at Glu-B1, 15 at Glu-A3, 18 at Glu-B3, two at Glu- B2, and eight at Gli-A1 and Gli-B1. New allelic variants not previously identified in durum wheat were detected. The 30 different genotypes of B low-molecular-weight (B-LMW) glutenin subunits analysed, of which 25 are novel, provide an important source of genetic variability for quality breeding. Protein patterns for convars. durum and turgidum, and for the North and South of Spain were identified for the loci with significant influence on quality. Higher variability was observed in convar. turgidum and in the North zone than in convar. durum and the South, respectively, mainly for the Glu-B1 and Glu-B3. Also, convar. turgidum appeared to be a valuable source for new alleles for the LMW glutenin subunits. Wheats from the South were, however, more diverse for prolamins encoded at Glu-A3 - Se ha estudiado la variación alélica en siete loci de prolaminas relacionados con la calidad en un grupo de variedades locales de trigo duro procedentes de todas las provincias españolas donde se cultivaba tradicionalmente. La variabilidad genética encontrada fue mayor que la observada en otras colecciones de germoplasma. Todos los loci, excepto el Glu-B2, mostraron una variabilidad genética mayor que 0,62, siendo los Glu-3 los más polimórficos. En total se estudiaron cinco alelos en el Glu-A1, nueve en el Glu-B1, 15 en el Glu-A3, 18 en el Glu-B3, dos en el Glu-B2 y ocho en el Gli-A1 y Gli- B1. Se han detectado variantes alélicas nuevas que no se habían identificado antes. Los 30 genotipos diferentes analizados de subunidades B de gluteninas de bajo peso molecular (B-LMW), de los cuales 25 son nuevos, representan una fuente importante de variabilidad genética para la mejora de la calidad. Se identificaron patrones de proteínas para las convars. durum y turgidum, y para el norte y sur de España para los loci con influencia significativa en calidad. En la convar. turgidum y en el norte se observó mayor variabilidad que en la convar. durum y en el sur, respectivamente, principalmente en el Glu-B1 y Glu-B3. Además, la convar. turgidum parece ser una fuente valiosa de nuevos alelos para las subunidades LMW de gluteninas. Sin embargo, los trigos del sur son más diversos para las prolaminas codificadas en el Glu-A3

Thermographic imaging: assessment of drought and heat tolerance in Spanish germplasm of Brachypodium distachyon.

The annual grass Brachypodium distachyon has been recently recognized as the model plant for functional genomics of temperate grasses, including cereals of economic relevance like wheat and barley. Sixty-two lines of B. distachyon were assessed for response to drought stress and heat tolerance. All these lines, except the reference genotype BD21, derive from specimens collected in 32 distinct locations of the Iberian Peninsula, covering a wide range of geo- climatic conditions. Sixteen lines of Brachypodium hybridum, an allotetraploid closely related to B. distachyon were used as reference of abiotic-stress well-adapted genotypes. Drought tolerance was assessed in a green-house trial. At the rosette-stage, no irrigation was applied to treated plants whereas their replicates at the control were maintained well watered during all the experiment. Thermographic images of treated and control plants were taken after 2 and 3 weeks of drought treatment, when stressed plants showed medium and extreme wilting symptoms. The mean leaf temperature of stressed (LTs) and control (LTc) plants was estimated based upon thermographic records from selected pixels (183 per image) that strictly correspond to leaf tissue. The response to drought was based on the analysis of two parameters: LTs and the thermal difference (TD) between stressed and control plants (LTs – LTc). The response to heat stress was based on LTc. Comparison of the mean values of these parameters showed that: 1) Genotypes better adapted to drought (B. hybridum lines) presented a higher LTs and TD than B. distachyon lines. 2) Under high temperature conditions, watered plants of B. hybridum lines maintained lower LTc than those of B. distachyon. Those results suggest that in these species adaptation to drought is linked to a more efficient stomata regulation: under water stress stomata are closed, increasing foliar temperature but also water use efficiency by reducing transpiration. With high temperature and water availability the results are less definite, but still seems that opening stomata allow plants to increase transpiration and therefore to diminish foliar temperature