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12 páginas.-- et. al ; [EN]: Both gradual and catastrophic events have been involved on the mass extinction events on the planet Earth. Although the greatest mass extinction with currently identified fossil remains was the Great Dying, the greatest of all mass extinctions on planet Earth should have been the Great Oxygenation Event (GOE), assuming that no life was present at the time of the Moon formation. In general, and excluding the unique GOE, the climate changes have been the most common causes of mass extinctions on Earth. A comet or large meteorite may cause mass extinctions not only on land, but also on the oceans. Indeed, a bolide of a few kilometers in diameter may release as much energy as several million nuclear bombs. On the other hand, localized oceanic extinctions may arise from special events like the quasi-periodic climate pattern known as "El Niño" Southern Oscillation (ENSO). Such events may have also a significant impact on terrestrial ecosystems, causing extinctions of plants and animals. Up to five major mass extinctions have been recorded in the last 540 million years, killing an average of 50% or more of all living species at the time of the event. The fossil record suggests that mass extinctions on the planet Earth occur about every 26 million years. This is a very serious matter indeed, because if such hypothesis holds true, it is just a matter of time before the Earth is hit by a huge bolide with catastrophic consequences. It is revealing to note that 99% of all species that ever lived on planet Earth are now extinct. That includes all our hominid ancestors. Besides other considerations and factors, the human activity is significantly disrupting the planet Earth ecosystems. It should be also taken into account that now –for the first time–, the human activity can also cause mass extinctions. In fact, the current rate of species extinctions is shocking; estimated at about 10,000 times the past average as deduced from the fossil record. The conclusion is clear and definitive: our only chance to survive is to colonize the cosmos. On the other hand, we must take care of many possible causes of extinction, but particularly on those derived from the synergistic effects of human activities, in order to take action to prevent the global contamination and warming of the planet Earth. In a practical way, halting and reversing such trends requires significant changes not only in industries in general, but also in human behavior in particular (food wastefulness, unnecessary travel and pleasure tourism, fashion squandering, etc), in order to effectively reduce both the contamination and the emissions of the greenhouse gases. Obviously, that requires a global economic and marketing change. A pacific revolution involving a global social and political agreement is needed. It should be also clear that each and every one of us has the responsibility to take care of our planet Earth. ; [ES]: Tanto acontecimientos graduales como catastróficos han estado implicados a las extinciones masivas en el planeta Tierra. A pesar de que la mayor extinción masiva, según restos fósiles identificados actualmente, fue la Gran Mortandad (del inglés, "Great Dying"), la mayor de todas las extinciones masivas en el planeta Tierra debió haber sido la Gran Oxidación (del inglés, "Great Oxygenation"); también llamada crisis del oxígeno, revolución del oxígeno o catástrofe del oxígeno (suponiendo la no existencia de vida en el momento de la formación de la Luna). En general y excluyendo el suceso de la Gran Oxidación, los cambios climáticos han sido las causas más comunes de extinciones masivas en la Tierra. Un cometa o un gran meteorito pueden causar extinciones masivas, no sólo en la tierra, sino también en los océanos. De hecho, un aerolito de unos pocos kilómetros de diámetro puede liberar tanta energía como varios millones de bombas nucleares. Por otro lado, las extinciones oceánicas localizadas pueden derivarse de sucesos especiales como el patrón climático cuasiperiódico conocido como la Oscilación del Sur de "El Niño" (del inglés, "'El Niño' Southern Oscillation"; ENOS). Estos eventos pueden tener también un impacto significativo en los ecosistemas terrestres, causando la extinción de plantas y animales. Hasta cinco importantes extinciones masivas han sido registradas en los últimos 540 millones años, aniquilando a un promedio del 50% o más de todas las especies vivientes en el momento del evento. El registro fósil sugiere que las extinciones masivas en el planeta Tierra se producen aproximadamente cada 26 millones de años. Se trata, ciertamente, de un asunto muy grave, porque de ser cierta esa hipótesis, es simplemente una cuestión de tiempo que la Tierra pueda ser alcanzada por un enorme aerolito que generaría consecuencias catastróficas. Es interesante tener en cuenta que el 99% de todas las especies que alguna vez vivieron en el planeta Tierra están ahora extintas. Esto incluye a todos nuestros antepasados homínidos. Además de otras consideraciones y factores, la actividad humana está interfiriendo considerablemente en los ecosistemas del planeta Tierra. Debe tenerse también en cuenta que ahora –por primera vez–, la actividad humana puede también causar extinciones masivas. De hecho, la tasa actual de extinción de especies es alarmante; estimada en alrededor de 10.000 veces la media con respecto al pasado, como se deduce del registro fósil. La conclusión es clara y definitiva: nuestra única posibilidad de sobrevivir es colonizar el cosmos. Por otra parte, debemos preocuparnos por muchas posibles causas de extinción, pero sobre todo por aquellas derivadas de los efectos sinérgicos de las actividades humanas, a fin de tomar medidas para prevenir la contaminación y calentamiento global del planeta Tierra. De un modo práctico, detener y revertir esas tendencias requiere importantes cambios no sólo en las industrias en general, sino también en el comportamiento humano en particular (despilfarro de comida, viajes superfluos turismo de placer, derroche en moda, etc.), a fin de reducir eficazmente la contaminación y las emisiones de los gases de efecto invernadero. Indiscutiblemente, esto requiere un cambio global a nivel económico y comercial. Se necesita una revolución pacífica que implique un acuerdo global a nivel social y político. Es también evidente que todos y cada uno de nosotros tenemos la responsabilidad de cuidar de nuestro planeta Tierra. ; Supported by projects 041/C/2007, 75/C/2009 & 56/C/2010 of "Consejería de Agricultura y Pesca, Junta de Andalucía"; "Grupo PAI" AGR-248 of "Junta de Andalucía"; and "Ayuda a Grupos" of "Universidad de Córdoba" (Spain). ; Peer reviewed

This article belongs to the Special Issue Molecular Marker Technology for Crop Improvement. ; Final grain production and quality in durum wheat are affected by biotic and abiotic stresses. The association mapping (AM) approach is useful for dissecting the genetic control of quantitative traits, with the aim of increasing final wheat production under stress conditions. In this study, we used AM analyses to detect quantitative trait loci (QTL) underlying agronomic and quality traits in a collection of 294 elite durum wheat lines from CIMMYT (International Maize and Wheat Improvement Center), grown under different water regimes over four growing seasons. Thirty-seven significant marker-trait associations (MTAs) were detected for sedimentation volume (SV) and thousand kernel weight (TKW), located on chromosomes 1B and 2A, respectively. The QTL loci found were then confirmed with several AM analyses, which revealed 12 sedimentation index (SDS) MTAs and two additional loci for SV (4A) and yellow rust (1B). A candidate gene analysis of the identified genomic regions detected a cluster of 25 genes encoding blue copper proteins in chromosome 1B, with homoeologs in the two durum wheat subgenomes, and an ubiquinone biosynthesis O-methyltransferase gene. On chromosome 2A, several genes related to photosynthetic processes and metabolic pathways were found in proximity to the markers associated with TKW. These results are of potential use for subsequent application in marker-assisted durum wheat-breeding programs. ; This research was funded by project P12-AGR-0482 from Junta de Andalucía (Andalusian Regional Government), Spain (Co-funded by FEDER). ARB is supported by the UK Biotechnology and Biological Sciences Research Council (BBSRC) 'Designing Future Wheat' cross-institute strategic programme (BB/P016855/1). PH is supported by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO) project AGL2016-77149-C2-1-P.

[Background and Aims] It is accepted that contemporary allopolyploid species have originated recurrently, but very few cases have been documented using multiple natural formations of the same species. To extend our knowledge, we have investigated the multiple origins, genetic variation and structure of the allotetraploid grass Brachypodium hybridum with respect to its progenitor diploid species B. distachyon (D genome) and B. stacei (S genome). For this, our primary focus is the Iberian Peninsula, an evolutionary hotspot for the genus Brachypodium. ; [Methods] We analysed 342 B. hybridum individuals from 36 populations using ten nuclear SSR loci and two plastid loci. The B. hybridum genetic profiles were compared with those previously reported for B. stacei and B. distachyon. In addition, phylogenetic analysis of the plastid data was performed for a reduced subset of individuals. ; [Key Results] The nuclear simple sequence repeat (SSR) genetic analysis detected medium to high genetic diversity, with a strong south-to-north genetic structure cline, and a high selfing rate in B. hybridum. Comparative genetic analysis showed a close relatedness of current B. hybridum D allelic profiles with those of B. distachyon, but a lack of similarity with those of B. stacei, suggesting another B. stacei source for the B. hybridum S alleles. Plastid analysis detected three different bidirectional allopolyploidization events: two involved distinct B. distachyon-like ancestors and one involved a B. stacei-like ancestor. The south-eastern Iberian Peninsula B. hybridum populations were more genetically diverse and could have originated from at least two hybridization events whereas north-eastern/north-western Iberian Peninsula B. hybridum populations were less diverse and may have derived from at least one hybridization event. ; [Conclusions] The genetic and evolutionary evidence supports the plausible in situ origin of the south-eastern and northern Iberian Peninsula B. hybridum allopolyploids from their respective local B. distachyon and unknown B. stacei ancestors. The untapped multiple origins and genetic variation detected in these B. hybridum populations opens the way to future evolutionary analysis of allopolyploid formation and genomic dominance and expression in the B. hybridum–B. distachyon–B. stacei grass model complex. ; This work was supported by the Spanish Ministry of Economy and Competitivity (Mineco) CGL2016-79790-P and University of Zaragoza UZ2016_TEC02 grant projects. V.S. was funded by a Russian Ministry of Science and Higher Education fellowship and grant RFBR no. 18-34-00901. P.C. and I.M. were partially funded by a European Social Fund and Aragón Government Bioflora grant.

[Background] Brachypodium distachyon (Poaceae), an annual Mediterranean Aluminum (Al)-sensitive grass, is currently being used as a model species to provide new information on cereals and biofuel crops. The plant has a short life cycle and one of the smallest genomes in the grasses being well suited to experimental manipulation. Its genome has been fully sequenced and several genomic resources are being developed to elucidate key traits and gene functions. A reliable germplasm collection that reflects the natural diversity of this species is therefore needed for all these genomic resources. However, despite being a model plant, we still know very little about its genetic diversity. As a first step to overcome this gap, we used nuclear Simple Sequence Repeats (nSSR) to study the patterns of genetic diversity and population structure of B. distachyon in 14 populations sampled across the Iberian Peninsula (Spain), one of its best known areas. ; [Results] We found very low levels of genetic diversity, allelic number and heterozygosity in B. distachyon, congruent with a highly selfing system. Our results indicate the existence of at least three genetic clusters providing additional evidence for the existence of a significant genetic structure in the Iberian Peninsula and supporting this geographical area as an important genetic reservoir. Several hotspots of genetic diversity were detected and populations growing on basic soils were significantly more diverse than those growing in acidic soils. A partial Mantel test confirmed a statistically significant Isolation-By-Distance (IBD) among all studied populations, as well as a statistically significant Isolation-By-Environment (IBE) revealing the presence of environmental-driven isolation as one explanation for the genetic patterns found in the Iberian Peninsula. ; [Conclusions] The finding of higher genetic diversity in eastern Iberian populations occurring in basic soils suggests that these populations can be better adapted than those occurring in western areas of the Iberian Peninsula where the soils are more acidic and accumulate toxic Al ions. This suggests that the western Iberian acidic soils might prevent the establishment of Al-sensitive B. distachyon populations, potentially causing the existence of more genetically depauperated individuals. ; The study has been funded by two consecutive Spanish Ministry of Economy and Competitiveness grant projects (CGL2012–39953-C02–01, CGL2016–79790-P) and one Aragon Government and European Social Fund Bioflora grant to PC and IM. DL-A and VS were funded by a Spanish Ministry of Science and Innovation and a Tomsk State University PhD fellowship, respectively. DL-A was also supported by a Spanish Instituto de Estudios Altoaragoneses grant. IM received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007–2013) under REA grant agreement PIOF-GA-2011-301,257. PH was funded by Spanish Junta de Andalucia project AGR-0482. ; Peer reviewed

29 Pags.- 6 Figs. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license. ; Dehydration proteins (dehydrins, DHNs) confer tolerance to water-stress deficit in plants. We performed a comparative genomics and evolutionary study of DHN genes in four model Brachypodium grass species. Due to limited knowledge on dehydrin expression under water deprivation stress in Brachypodium, we also performed a drought-induced gene expression analysis in 32 ecotypes of the genus' flagship species B. distachyon showing different hydric requirements. Genomic sequence analysis detected 10 types of dehydrin genes (Bdhn) across the Brachypodium species. Domain and conserved motif contents of peptides encoded by Bdhn genes revealed eight protein architectures. Bdhn genes were spread across several chromosomes. Selection analysis indicated that all the Bdhn genes were constrained by purifying selection. Three upstream cis-regulatory motifs (BES1, MYB124, ZAT) were detected in several Bdhn genes. Gene expression analysis demonstrated that only four Bdhn1-Bdhn2, Bdhn3, and Bdhn7 genes, orthologs of wheat, barley, rice, sorghum, and maize genes, were expressed in mature leaves of B. distachyon and that all of them were more highly expressed in plants under drought conditions. Brachypodium dehydrin expression was significantly correlated with drought-response phenotypic traits (plant biomass, leaf carbon and proline contents and water use efficiency increases, and leaf water and nitrogen content decreases) being more pronounced in drought-tolerant ecotypes. Our results indicate that dehydrin type and regulation could be a key factor determining the acquisition of water-stress tolerance in grasses. ; This research was funded by Spanish Ministry of Science and Innovation grant number PID2019-108195GB-I00, European Social Fund/Spanish Aragón Government grant number A01-20R, Spanish Junta de Andalucía grant number P18-RT-992, USDA grant number NIFA-2011-67012- 30663. MD was funded by a Spanish Mineco FPI PhD fellowship. BCM was funded by Spanish Fundación ARAID. ; Peer reviewed

Climatic conditions affect the growth, development and final crop production. As wheat is of paramount importance as a staple crop in the human diet, there is a growing need to study its abiotic stress adaptation through the performance of key breeding traits. New and complementary approaches, such as genome-wide association studies (GWAS) and genomic selection (GS), are used for the dissection of different agronomic traits. The present study focused on the dissection of agronomic and quality traits of interest (initial agronomic score, yield, gluten index, sedimentation index, specific weight, whole grain protein and yellow colour) assessed in a panel of 179 durum wheat lines (Triticum durum Desf.), grown under rainfed conditions in different Mediterranean environments in Southern Spain (Andalusia). The findings show a total of 37 marker-trait associations (MTAs) which affect phenotype expression for three quality traits (specific weight, gluten and sedimentation indexes). MTAs could be mapped on the A and B durum wheat subgenomes (on chromosomes 1A, 1B, 2A, 2B and 3A) through the recently available bread wheat reference assembly (IWGSC RefSeqv1). Two of the MTAs found for quality traits (gluten index and SDS) corresponded to the known Glu-B1 and Glu-A1 loci, for which candidate genes corresponding to high molecular weight glutenin subunits could be located. The GS prediction ability values obtained from the breeding materials analyzed showed promising results for traits as grain protein content, sedimentation and gluten indexes, which can be used in plant breeding programs. ; This work was funded by project P12-AGR-0482 to PH from Junta de Andalucía (Andalusian Regional Government), Spain (Co-funded by FEDER). PH is supported by project AGL2016-77149-C2-1-P from MINECO (Spanish Ministry of Economy, Industry and Competitiveness). ; Peer reviewed