El trigo candeal o trigo duro (Triticum turgidum L. ssp. durum) es una especie de trigo tetraploide (2n= 4x= 28 AABB) que se utiliza, principalmente, para la elaboración de pastas secas de calidad. El mejoramiento de esta especie está focalizado en la obtención de variedades de alta productividad con endosperma duro, vítreo, alto contenido proteico y pigmentos amarillos. Las variedades disponibles en Argentina son de hábito primaveral de ciclo corto a intermedio, y la siembra se realiza en el periodo comprendido entre junio y agosto. La principal zona de cultivo en nuestro país, es el sur de la provincia de Buenos Aires donde la ocurrencia de heladas entre abril y noviembre afecta al cultivo en estadio vegetativo y reproductivo. Los genes de desaturasas que introducen dobles enlaces en los ácidos grasos de cadena larga, se encuentran involucrados en la tolerancia a estrés por bajas temperaturas. La disponibilidad de secuencias de ADN, ARN y proteínas de desaturasas de gramíneas en las bases de datos públicas, permitió realizar un análisis in silico de las mismas, logrando caracterizar estructural y funcionalmente esta familia de proteínas. Se observó una distribución cromosómica dispersa y se predijo la localización subcelular más probable. Teniendo en cuenta que no existen secuencias de desaturasas caracterizadas de trigo candeal disponibles en GenBank (https://www.ncbi.nlm.nih.gov/), se realizó un análisis de la variabilidad genética en cinco genotipos, con diferencias en su grado de tolerancia a bajas temperaturas. Se detectó un bajo número de polimorfismos en la estearoil-ACP desaturasa (SAD) y ω- 3 lípido desaturasa (FAD3), mientras que ω- 6 lípido desaturasa (FAD2) mostró una mayor variabilidad. No se encontraron relaciones entre los polimorfismos en secuencia y el comportamiento frente a frío. El mapeo in silico de FAD2 permitió detectar la presencia de cuatro copias del gen localizadas en el cromosoma 6, incluyendo pseudogenes y un elemento transponible (TE, transponible element) insertado en la cuarta copia del genoma B. Las proteínas deducidas de las secuencias de trigo candeal fueron incluidas en el análisis in silico de gramíneas antes mencionado. Las regiones promotoras de los genes de desaturasas contienen sitios de unión a factores de transcripción de respuesta a estrés abiótico. Por otra parte, se realizó un estudio de respuesta a bajas temperaturas, en tres genotipos de trigo candeal, dos primaverales (BUCK AMBAR y CBW 0101) y uno invernal (MVTD 10- 98). Experimentos previos habían mostrado tolerancia a temperaturas bajo cero en cámara, de los genotipos MVTD 10-98 y CBW 0101 en estado vegetativo. El presente estudio incluyó el análisis de expresión del gen FAD2, la obtención del perfil de ácidos grasos y ensayos de conductividad eléctrica. Los ácidos grasos insaturados oleico (18:1), linoleico (18:2) y linolénico (18:3) fueron los que presentaron mayor nivel de cambios frente a bajas temperaturas. Se observó que las líneas CBW 0101 y MVTD 10-98, presentaron similares incrementos de 18:1 y 18:2 ante el tratamiento con frío y perfiles de expresión de FAD2 concordantes con los niveles de su producto 18:2. Las evaluaciones de integridad de membrana también estuvieron de acuerdo con las diferencias fenotípicas en la tolerancia. Además, se realizaron ensayos de rendimiento a campo en tres fechas de siembra (mayojunio- julio), durante dos años consecutivos en la Estación Experimental Agropecuaria Integrada Barrow - INTA (EEAI). Las variables evaluadas fueron: duración del ciclo a antesis, periodo de llenado de granos, rendimiento y medidas relacionadas (peso de granos, número de granos y sus subcomponentes, biomasa en antesis y madurez fisiológica, índice de cosecha y altura de planta), contenido de proteína en grano y peso hectolítrico. Se encontraron diferencias significativas entre años, fechas y genotipos en todas las variables. El primer año presentó un rendimiento promedio menor que el segundo (57 %), atribuido principalmente a las diferentes condiciones ambientales en relación a precipitaciones, suelo y temperaturas, mientras que el contenido de proteína en grano fue menor en el segundo año (22,25 %). En cuanto al momento de siembra, el rendimiento promedio fue mayor en fechas más tempranas en ambos años. La determinación de los periodos desde emergencia a antesis y de llenado de granos, combinados con diferentes fechas de siembra, permitieron explicar variaciones en el rendimiento. Además, los valores promedio de biomasa aérea total, peso de las espigas alcanzado en el periodo de llenado de granos (PEAT-MF) y peso promedio de granos por unidad de superficie (PG), fueron superiores en las fechas más tempranas. El peso de los granos por unidad de superficie, fue el principal componente numérico del rendimiento. Del análisis de componentes principales entre rendimiento y las variables asociadas, se deduce que el índice de cosecha, PG y PEAT-MF fueron las variables que mejor explicaron cambios en el rendimiento en todos los ensayos. Se evaluó, además, el daño por heladas en etapa de floración en el año 2016. Se identificaron tres formas de daño en espiga (deformada, por zonas y blanca) y el porcentaje promedio total varió entre genotipos desde 0,25 a 9,47 %. En general, los materiales menos afectados por heladas, fueron los de ciclo más largo, aunque también se observaron algunas diferencias en el nivel de daño entre genotipos de fenología similar. Este estudio aporta información de Triticum turgidum L. ssp. durum relacionada con su genoma, respuesta a estrés abiótico y efecto de fecha de siembra en el sudoeste de Buenos Aires. / Durum wheat, also called pasta wheat, (Triticum turgidum L. ssp. durum) is a tetraploid species of wheat (2n= 4x= 28 AABB), mainly produced for the elaboration of high quality dry pasta. Breeding of this species is focused on the obtention of high yield varieties, with hard and glassy endosperm, high protein contents, and yellow pigmentation. Available varieties in Argentina are spring-habit, short to intermediate cycle, with a sowing period that spans from June to August. The main cultivation area in our country is in the South of the Buenos Aires province, where frost occurrences (which may happen between April and November) negatively affect the crops during vegetative and reproductive stages. Fatty acid desaturase genes, which introduce double bonds in long-chain fatty acids, are related to low temperature stress tolerance. Availability of ADN, ARN, and desaturase sequences of grasses in public databases enabled in silico analyses, which in turn allowed to structurally and functionally characterize this protein family. A sparse chromosome distribution was observed, and a most likely sub-cellular location was predicted. Taking into account that there are no featured durum wheat desaturase sequences available in GenBank (https://www.ncbi.nlm.nih.gov/), a genetic variability analysis was performed in five different genotypes, each with different low temperature tolerance degrees. A low number of polymorphisms in the estearoil-ACP desaturase (SAD) and in the ω-3 desaturase (FAD3) where detected, while the ω-6 desaturase (FAD2) exhibited higher variability. No relationships between sequence polymorphisms and low temperature tolerance were detected. In silico mapping of FAD2 enabled to detect four copies of the gen, located in chromosome 6, including pseudogenes and a transponible element (TE) inserted in the fourth copy of the B genome. Proteins deduced from durum wheat sequences were included in the in silico gramineae analyses mentioned above. The promoting regions in the desaturase genes contain sites with bonding to transcription factors related to abiotic stress response. On the other hand, an analysis of low temperature response was performed on three genotypes of durum wheat, two spring-like (BUCK AMBAR and CBW 0101) and one wintry (MVTD 10-98). Previous experiments showed below-zero chamber temperature tolerance in genotypes MVTD 10-98 and CBW 0101 in vegetative state. The present study includes the expression analysis of the gene FAD2, the obtention of the fatty acid profile, and electric conductivity studies. The insaturated fatty acids oleic (18:1), linoleic (18:2), and linolenic (18:3), presented greater change levels under low temperatures. The lines CBW 0101 and MVTD 10-98, presented similar increments in 18:1 y 18:2 upon low temperature exposure, and FAD2 expression profiles in accordance with its product 18:2. Membrane 8 integrity evaluations were also in accordance with phenotypic differences in low temperature tolerance. In addition, field yield tests were performed in the Barrow Integrated Experimental Farming Station (Estación Experimental Agropecuaria Integrada, EEAI Barrow) of the National Agricultural Technology Institute (INTA), during three different sowing dates (May, June and July) along two consecutive years. The evaluated variables were: cycle length up to anthesis, grain filling period length, yield, and related mesures (grain weight, number of grains and their subcomponents, biomass during anthesis and physiological maturity, harvest index, and plant height), the protein contents in grain, and the hectolitre weight. Meaningful differences were found among years, sowing dates, and genotypes in all the evaluated variables. The first year presented an average yield 57 % lower than the second, which can be attributed to environmental conditions related to precipitation, soil, and temperatures, while the average protein contents in the grain was 22.25 % lower during the second year. Regarding the sowing date, average yield was higher in earlier dates in both years. Period determination from emergency to anthesis, and grain fill, combined with different sowing dates, are able to explain these yield differences. In addition, average total aerial biomass, spikes weight achieved during the grain filling period (PEAT-MF), and average grain weight per surface unit (PG), were all higher in earlier sowing dates. From Principal Component Analyisis between yield and the associate variables, it can be established that PG was the most important component of the yield, while PG and PEATMF were the variables that best explained yield changes in all the trials. In addition, the frost related damage during the flowering period was evaluated during 2016. Three different damage forms were identified (deformed, by zones, and white), where the average percentage varied between 0.25 and 9.47 %. In general, the genotypes less affected by frost were the ones of longest cycles, even though some differences were observed in the damage level among genotypes of similar phenology. This study provides information related to the genome and abiotic stress response of Triticum turgidum L. ssp. durum, and the effects of sowing date in the Southwest of Buenos Aires.

La fusariose de l’épi est une maladie fongique qui touche toutes les cultures de céréales à paille à travers le monde entrainant des baisses de rendements et de la qualité des grains. La fusariose pose également un problème pour la sécurité alimentaire lié à la contamination des grains infectés par des mycotoxines. Le développement de variétés résistantes est considéré comme la méthode la plus efficace et la plus durable pour réduire les dommages causés par la maladie et pour limiter la contamination par les mycotoxines. L’amélioration de la résistance à la fusariose chez le blé dur (Triticum durum Desf.) demeure un défi du fait de son extrême sensibilité à la maladie et de la faible variabilité génétique disponible pour ce caractère. L’objectif principal de cette thèse a été d’évaluer l’effet de Fhb1, le QTL majeur de résistance à la fusariose chez le blé tendre (Triticum aestivumL.), au sein de fonds génétiques de blé dur élite. Pour cela, trois populations de cartographie, comprenant chacune environ 100 F7-RIL (lignées pures recombinantes ou « recombinant inbred lines »), ont été développées à partir de croisements entre la lignée expérimentale de blé dur DBC-480, portant une introgression de Fhb1, et les cultivars de blé dur Karur, Durobonus et SZD1029K. Les lignées ont été évaluées au champ, sur trois saisons, pour leur résistance globale à la fusariose après inoculation en spray de Fusarium culmorum. Des notations morphologiques (date de floraison, hauteur des plantes) ont également été réalisées afin d'évaluer leur influence sur l'infestation. Les lignées ont été génotypées à l’aide de marqueurs SSR et de marqueurs GBS (génotypage par séquençage ou « genotyping-by-sequencing ») développés par DArTseq. L’analyse de liaison a permis d’identifier des QTL de résistance sur les bras des chromosomes 2BL, 3BS, 4AL, 4BS, 5AL et 6AS. DBC-480 contribuait à l’allèle de résistance à tous ces loci. Le QTL sur 3BS a été détecté au sein des trois populations centré sur l’intervalle de Fhb1, confirmant, pour la première fois, son introgression dans le blé dur. L’évaluation de la résistance à la propagation après inoculation ponctuelle, réalisé au sein d’une des trois populations, a également permis de valider l’effet de Fhb1 sur la résistance de type 2 chez le blé dur. La hauteur des plantes influe fortement sur la résistance globale à la fusariose et, en particulier, l’allèle de nanisme Rht-B1b est associé à une plus grande sensibilité à la maladie dans les trois populations. Cependant, l’effet négatif de Rht-B1b sur la résistance est largement compensé dans les lignées possédant Fhb1. Des lignées semi-naines avec un meilleur niveau de résistance ont été sélectionnées et favoriseront le développement de cultivars de blé dur résistants à la fusariose. / Fusarium head blight (FHB) is a devastating disease affecting small-grain cereals worldwide causing yield and quality losses. FHB affects food safety due to the contamination of infected grains by mycotoxins. Host plant resistance is considered the most efficient and sustainable approach to contain FHB and mycotoxin contaminations. In durum wheat (Triticum durum Desf.) breeding for FHB resistance remains a challenge due to its extreme susceptibility and to lack of genetic variation available in the primary durum wheat gene pool. The primary goal of this thesis was to evaluate the effect of Fhb1, the major common wheat (Triticum aestivum L.) FHB resistance QTL, in elite durum wheat background. Three F7-RIL (recombinant inbred lines) mapping populations of about 100 lines were developed from crosses between the durum wheat experimental line DBC-480, harboring Fhb1, and the durum wheat cultivars Karur, Durobonus and SZD1029K. The RILs were tested under field conditions by artificial spray inoculation with Fusarium culmorum in three seasons. Morphological traits (flowering date, height) were also recorded to assess their influence on FHB infestation. Genotyping of the lines was performed with SSR and genotyping-by-sequencing (GBS) DArTseq markers. QTL analysis identified genomic regions associated with FHB resistance on chromosome arms 2BL, 3BS, 4AL, 4BS, 5AL and 6AS. DBC-480 contributed the resistant allele at all loci. Fhb1 was detected in all three populations, demonstrating for the first time its successful deployment in durum wheat. The effect of Fhb1 on FHB resistance in durum wheat was further verified by evaluating type 2 resistance in one of the three populations. Plant height had a strong influence in modulating FHB severity. Although the semi-dwarf allele Rht-B1b was associated with increased FHB susceptibility, its negative effect was efficiently counterbalanced in lines carrying Fhb1. Semi-dwarf lines with enhanced levels of resistance were selected and will assist the development of FHB resistant cultivars.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.

Current trends in population growth suggest that global food production is unlikely to satisfy future demand under predicted climate change scenarios. Therefore, further improvements on wheat yield potential will be essential to meet future food demand. Thus, to further raise wheat grain yield it is critical to understand the physiological basis of grain number per m2 determination. Yield responsiveness to resource availability is usually related to grain number per m2 in most of grain crops, such as durum wheat. Under Mediterranean conditions, wheat yields vary widely, mainly in response to erratic rainfall, but it has been proposed that part of this variability may be reduced through nitrogen (N) management. Wheat yield responses to N fertilisation are usually related to those of grains per m2, which in turn is the consequence of processes related to floret development (floret initiation followed by floret death/survival) during stem elongation. However, there are almost no studies published relating floret primordia generation and survival in response to increases in N availabilities in wheat. Understanding the dynamics of floret primordia development as a physiological determinant of grain setting can be relevant to further increase grain yield in wheat. The focus of this thesis was to study the effects of N availability and the differences among modern cultivars (and, in some cases, combined with availability of other resources) on dynamics of floret development and survival determining the fate of these primordia and the generation of grain number in durum wheat. Six experiments were conducted (4 semi-controlled and 2 field conditions) during four consecutive growing seasons at Catalonia, NE Spain, with a combination of different N and water availabilities and contrasting modern durum wheat cultivars. Across all experiments, yield responsiveness to N was, in general, related to grain number increases as an indirect response to N through its effect on increasing growth. This is not only based on the fact that the relationship of grain number with spike dry matter was not improved if spike N were used instead, but also on the fact that detillering did increased grain number through the same relationships to spike dry matter. Also, improved spike fertility was due to both producing more fertile florets (in response to N and water or to the removal of competing shoots) and to reduce the percentage of failure of fertile florets in becoming grains. Responsiveness of the number of fertile florets was determined by a developmental response of floret primordia, which under high resource availability conditions continued developing normally in some distal florets of the spikelets, at any position of the spike, whilst in more stressful conditions their development stopped. Genotypic variation in fruiting efficiency was found for modern durum wheat cultivars and there was a tendency for some cultivars to have higher values of fruiting efficiency in most of the environments. Differences in fruiting efficiency were responsible for genotypic differences in grain number. A functional negative relationship was found between grain weight and fruiting efficiency, revealing a trade-off related to spike growth per floret developing normally.