The replicative spread of retrotransposons in the genome creates new insertional polymorphisms, increasing retrotransposon numbers and potentially both their share of the genome and genome size. The BARE-1 retrotransposon constitutes a major, dispersed, active component of Hordeum genomes, and BARE-1 number is positively correlated with genome size. We have examined genome size and BARE-1 insertion patterns and number in wild barley, Hordeum spontaneum, in Evolution Canyon, Lower Nahal Oren, Mount Carmel, Israel, along a transect presenting sharply differing microclimates. BARE-1 has been sufficiently active for its insertional pattern to resolve individuals in a way consonant with their ecogeographical distribution in the canyon and to distinguish them from provenances outside the canyon. On both slopes, but especially on the drier south-facing slope, a simultaneous increase in the BARE-1 copy number and a decrease in the relative number lost through recombination, as measured by the abundance of solo long terminal repeats, appear to have driven the BARE-1 share of the genome upward with the height and dryness of the slope. The lower recombinational loss would favor maintenance of more full-length copies, enhancing the ability of the BARE-1 family to contribute to genome size growth. These local data are consistent with regional trends for BARE-1 in H. spontaneum across Israel and therefore may reflect adaptive selection for increasing genome size through retrotransposon activity.

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Chromosomal change is one of the more hotly debated potential mechanisms of speciation. It has long been argued over whether – and to what degree – changes in chromosome structure contribute to reproductive isolation and, ultimately, speciation. In this review we do not aim to completely analyze accumulated data about chromosomal speciation but wish to draw attention to several critical points of speciation-related chromosomal change, namely: (a) interrelations between chromosomal rearrangements and repetitive DNA fraction; (b) mobility of ribosomal DNA clusters; and (c) rDNA and transposable elements as perpetual generators of genome instability.

Drought and salinity are the major abiotic stresses that dramatically threaten the food supply in the world. Tribe Triticeae, including wheat and barley, possesses tremendous potential for drought and salt tolerance that has been extensively and practically identified, tested, and transferred to wheat cultivars with proven expression of tolerance in experimental trials. Triticum dicoccoides and Hordeum spontaneum, the progenitors of cultivated wheat and barley, have adapted to a broad range of environments and developed rich genetic diversities for drought and salt tolerances. Drought-and salt-tolerant genes and quantitative trait loci (QTLs) have been identified in T. dicoccoides and H. spontaneum and have great potential in wheat and barley improvement. Advanced backcross QTL analysis, the introgression libraries based on wild wheat and wild barley as donors, and positional cloning of natural QTLs will play prevailing roles in elucidating the molecular control of drought and salt tolerance. Combining tolerant genes and QTLs in crop breeding programs aimed at improving tolerance to drought and salinity will be achieved within a multidisciplinary context. Wild genetic resistances to drought and salinity will be shifted in the future from field experiments to the farmer.

Climate change is a major environmental stress threatening biodiversity and human civilization. The best hope to secure staple food for humans and animal feed by future crop improvement depends on wild progenitors. We examined 10 wild emmer wheat (Triticum dicoccoides Koern.) populations and 10 wild barley (Hordeum spontaneum K. Koch) populations in Israel, sampling them in 1980 and again in 2008, and performed phenotypic and genotypic analyses on the collected samples. We witnessed the profound adaptive changes of these wild cereals in Israel over the last 28 y in flowering time and simple sequence repeat allelic turnover. The revealed evolutionary changes imply unrealized risks present in genetic resources for crop improvement and human food production.climate warming | phenotypic and genotypic diversity | plant genetic resources I n recent decades there have been increasing concerns about the future of food production influenced by climate change (1-7) to feed a fast growing world population reaching 9-10 billion by 2050 (8). Aridization has alarmingly increased in summer, resulting in dry regions of wheat growing areas, particularly in the Americas, Asia, and Africa, and in the area of origin and diversity of wild emmer wheat in the Near East (9). Cultivated wheat, the number one world food staple, is genetically impoverished by long-term selective breeding (10). The wild progenitors of cultivated cereals, especially wild emmer wheat Triticum dicoccoides Koern. (TD) (9) and wild barley Hordeum spontaneum K. Koch (HS) (11), have become eroded by urbanization and agriculture (12). Both progenitors are rich in genetic resources adapted to abiotic (e.g., solar radiation, temperature, drought, and mineral poverty) and biotic (e.g., pathogens and parasites) stresses. These progenitors are the best genetic hope for improving genetically impoverished cultivars for human food production (9-17). Thus, it is crucial to evaluate the evolutionary adaptation in natural populations of the progenitors under climate change and to understand the hidden risk in human food security. Here we examined 10 TD populations and 10 HS populations in Israel from 1980 and again in 2008 and performed phenotypic and genotypic analyses on the collected samples. We witnessed the profound adaptive changes of these wild cereals in Israel over the last 28 y in flowering time (FT) and simple sequence repeat (SSR) allelic turnover. ResultsPhenotypic Analysis. In a greenhouse experiment, we compared the time from germination until flowering of ∼800 genotypes in 20 natural populations from different habitats and climates that were subjected to 28 y of climate change. The sampled populations (16, 17) were distributed across 350 km of their Israeli range (SI Appendix, Fig. S1 and Table S1). A total of 57 independent pair-wise comparisons were made under dry (300 mm) and wet (600 mm) irrigation regimes. Dramatically, in all TD and HS populations, without exception, the 2008 populations reached FT earlier than those collected in 1980 (Sign test, P < 1...

The Near East Fertile Crescent is well recognized as a primary center of barley origin, diversity, and domestication. A large number of wild barleys have been collected from the Tibetan Plateau, which is characterized by an extreme environment. We used genome-wide diversity array technology markers to analyze the genotypic division between wild barley from the Near East and Tibet. Our results confirmed the existence of Tibetan wild barley and suggested that the split between the wild barleys in the Near East and those in Tibet occurred around 2.76 million years ago (Mya). To test the concept of polyphyletic domestication of barley, we characterized a set of worldwide cultivated barley. Some Chinese hulless and six-rowed barleys showed a close relationship with Tibetan wild barley but showed no common ancestor with other cultivated barley. Our data support the concept of polyphyletic domestication of cultivated barley and indicate that the Tibetan Plateau and its vicinity is one of the centers of domestication of cultivated barley. The current results may be highly significant in exploring the elite germplasm for barley breeding, especially against cold and drought stresses.adaptation | evolution | harsh environment

The blind mole rat (BMR), Spalax galili, is an excellent model for studying mammalian adaptation to life underground and medical applications. The BMR spends its entire life underground, protecting itself from predators and climatic fluctuations while challenging it with multiple stressors such as darkness, hypoxia, hypercapnia, energetics and high pathonecity. Here we sequence and analyse the BMR genome and transcriptome, highlighting the possible genomic adaptive responses to the underground stressors. Our results show high rates of RNA/DNA editing, reduced chromosome rearrangements, an over-representation of short interspersed elements (SINEs) probably linked to hypoxia tolerance, degeneration of vision and progression of photoperiodic perception, tolerance to hypercapnia and hypoxia and resistance to cancer. The remarkable traits of the BMR, together with its genomic and transcriptomic information, enhance our understanding of adaptation to extreme environments and will enable the utilization of BMR models for biomedical research in the fight against cancer, stroke and cardiovascular diseases.

Wild emmer wheat ( Triticum turgidum spp. dicoccoides (Körn.) Thell.), the tetraploid progenitor of cultivated wheat, is a potential source for various agronomical traits, including drought resistance. The objectives of this study were to characterize (1) the genetic diversity for drought resistance in wild emmer wheat, and (2)