East Fertile Crescent Research Articles

Transcriptome and Metabolite Insights into Domestication Process of Cultivated Barley in China.

The domestication process of cultivated barley in China remains under debate because of the controversial origins of barley. Here, we analyzed transcriptomic and non-targeted metabolic data from 29 accessions together with public resequencing data from 124 accessions to explore the domestication process of cultivated barley in China (Cb-C). These analyses revealed that both Cb-C and Tibetan wild barley (Wb-T) were the descendants of wild barley from the Near East Fertile Crescent (Wb-NE), yielding little support for a local origin of Wb-T. Wb-T was more likely an intermediate in the domestication process from Wb-NE to Cb-C. Wb-T contributed more genetically to Cb-C than Wb-NE, and was domesticated into Cb-C about 3300 years ago. These results together seem to support that Wb-T may be a feralized or hybrid form of cultivated barley from the Near East Fertile Crescent or central Asia. Additionally, the metabolite analysis revealed divergent metabolites of alkaloids and phenylpropanoids and these metabolites were specifically targeted for selection in the evolutionary stages from Wb-NE to Wb-T and from Wb-T to Cb-C. The key missense SNPs in the genes HORVU6Hr1G027650 and HORVU4Hr1G072150 might be responsible for the divergence of metabolites of alkaloids and phenylpropanoids during domestication. Our findings allow for a better understanding of the domestication process of cultivated barley in China.

APLICACIÓN DE DIFERENTES METODOLOGÍAS EN EL MEJORAMIENTO DE LENTEJA (Lens culinaris MEDIK)

Lentil (Lens culinaris Medik.) is a self-pollinating diploid (2n=2x=14) species belonging to the Fabaceae family. It is one of the oldest crops known, with 8,000 to 9,000 years of history and it is among the earliest domesticates from the Near East Fertile Crescent. The seeds have high nutritional value. This crop is an interesting substitute to wheat in cereal rotations but its importance is low due to a lack of suitable varieties with local adaptation. Some of the major problems that Argentinian lentil breeders face are the narrow genetic base of the current cultivated germplasm and its low yield potential. A lentil breeding program was initiated in 2004 to develop new varieties with adaptation to prevalent conditions in growing areas of Argentina. Germplasm was obtained from ICARDA (International Center for Agricultural Research in the Dry Areas) and local producers. Conventional breeding methods using hybridization and selection are being carried out to develop improved varieties, broad the genetic base, and isolate superior recombinant inbred lines. Two new varieties have been obtained, one of the macrosperm type (Boyerito FCA) and the other of the microsperm type (Tacuarita FCA) through the application of mass selection in F2 populations from the cross of selected materials. This program complements traditional breeding methods with biotechnological techniques such as transgenesis, use of molecular markers, in vitro embryo culture combined with the SSD method to shorten the breeding time, and digital phenotyping. Key words: Lentil, conventional methodologies, in vitro embryo culture, biotechnology techniques, digital phenotyping.

Variation in Stripe Rust Resistance and Morphological Traits in Wild Emmer Wheat Populations

Wild emmer wheat (Triticum dicoccoides), the tetraploid progenitor of cultivated wheats, is indigenous to the Near East Fertile Crescent. An important center of distribution is found today in and around the catchment area of the upper Jordan Valley in Israel and surrounding regions. In the current study, the field stripe rust resistance and morphological traits were analyzed using 98 sample accessions that represented the geographical distribution of wild emmer populations in Israel and its vicinity. The resistance tests at two field locations revealed that the majority of the wild emmer accessions possess quantitative resistance against stripe rust. This could be due to the high frequency of Yr36 in the wild emmer populations. The identification of potentially novel stripe rust resistance in this set of germplasm is highly significant. In total, 11 morphological traits were examined in this study. Wide range of natural variation was revealed in the tested morphological traits. Most of the morphological traits had significant correlations with climate variables, indicating that the local environmental conditions have a profound effect on shaping the genetic structure of wild emmer wheat. Our results suggest that wild emmer wheat has the enormous potential to improve stripe rust resistance and various important agronomical traits in wheat.

Agronomic and genetic characterization of wild emmer wheat (Triticum turgidum subsp. dicoccoides) introgression lines in a bread wheat genetic background

During a long evolutionary history across a range of environmental conditions in the Near East Fertile Crescent, wild emmer wheat (Triticum turgidum subsp. dicoccoides) has accumulated a wealth of genetic diversity and adaptations to multiple biotic and abiotic stress conditions. The joint effects of the domestication and subsequent selection in man-made agro-ecosystems have considerably reduced the genetic variation in cultivated crop species as compared to their wild progenitors. The wild emmer gene pool harbors a rich allelic repertoire for improving numerous agronomically important traits. A set of advanced wild emmer wheat introgression lines (ILs) was previously established on a bread wheat genetic background. It combines genetic diversity from the wild progenitor as well as the genetic background of the cultigen. Based on field evaluations, the set of ILs (divided hierarchically into different families based on the genetic background) has exhibited high phenotypic variance in agronomically important traits. Analyses of variance (ANOVA) have shown that the effect of the hierarchical genetic factors was significant in the vast majority of the traits. Similarly, characterizations by molecular markers of known traits have shown that the genetic profile differs between ILs from different genetic backgrounds. Multivariate principal component analysis has revealed interesting associations between vegetative and reproductive traits and illustrated the impact of some of these traits on ILs distribution in the PC1 and PC2. The exploitation of the wild emmer wheat ILs as a tool for reintroduction of alleles that were lost during domestication and possible implications for wheat breeding are discussed.

Molecular evidence of RNA polymerase II gene reveals the origin of worldwide cultivated barley.

The origin and domestication of cultivated barley have long been under debate. A population-based resequencing and phylogenetic analysis of the single copy of RPB2 gene was used to address barley domestication, to explore genetic differentiation of barley populations on the worldwide scale, and to understand gene-pool exchanges during the spread and subsequent development of barley cultivation. Our results revealed significant genetic differentiation among three geographically distinct wild barley populations. Differences in haplotype composition among populations from different geographical regions revealed that modern cultivated barley originated from two major wild barley populations: one from the Near East Fertile Crescent and the other from the Tibetan Plateau, supporting polyphyletic origin of cultivated barley. The results of haplotype frequencies supported multiple domestications coupled with widespread introgression events that generated genetic admixture between divergent barley gene pools. Our results not only provide important insight into the domestication and evolution of cultivated barley, but also enhance our understanding of introgression and distinct selection pressures in different environments on shaping the genetic diversity of worldwide barley populations, thus further facilitating the effective use of the wild barley germplasm.

Tibet is one of the centers of domestication of cultivated barley

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.

Correlation between hordatine accumulation, environmental factors and genetic diversity in wild barley (Hordeum spontaneum C. Koch) accessions from the Near East Fertile Crescent

Wild barley shows a large morphological and phenotypic variation, which is associated with ecogeographical factors and correlates with genotypic differences. Diversity of defense related genes and their expression in wild barley has been recognized and has led to attempts to exploit genes from H. spontaneum in breeding programs. The aim of this study was to determine the variation in the accumulation of hordatines, which are Hordeum-specific preformed secondary metabolites with strong and broad antimicrobial activity in vitro, in 50 accessions of H. spontaneum from different habitats in Israel. Differences in the accumulation of hordatines in the seedling stage were significant between different H. spontaneum genotypes from different regional locations and micro-sites. Variation in the hordatine accumulation within genotypes was between 9% and 45%, between genotypes from the same location between 13% and 38%, and between genotypes from different locations up to 121%. Principal component analysis showed that water related factors explain 39%, temperature related factors explain 33% and edaphic factors account for 11% of the observed variation between the populations of H. spontaneum. Genetic analysis of the tested accessions with LP-PCR primers that are specific for genes involved in the biosynthetic pathway of hordatines showed tight correlations between hordatine abundance and genetic diversity of these markers. Multiple regression analyses indicated associations between genetic diversity of genes directly involved in hordatine biosynthesis, ecogeographical factors and the accumulation of hordatines.

Variation in response to infection with Erysiphe graminis hordei and Puccinia hordei in some wild barley populations in a centre of diversity

The Near East Fertile Crescent extending from Iran to Israel is the centre of origin of cultivated barley and a region of great genetic diversity in wild barley, Hordeum spontaneum C. Koch (syn. H. vulgare ssp. spontaneum (C. Koch Thell)). Wild barley accessions collected from different parts of this region were evaluated for their reactions to infection with three isolates of Erysiphe graminis hordei and two of Puccinia hordei. One culture of each pathogen was isolated in Israel and the others, either in Japan or the United States. Out of a total of 330 wild barley accessions collected from 14 sites in Iran, Turkey and Syria, only 18.8% were resistant to the Israeli culture, and 14.8% were resistant to a composite of the Japanese and American cultures of E. graminis hordei. Out of 105 accessions collected from six sites in Iran and Turkey, none was found to be resistant to the Israeli culture and 34.3% were resistant to the American culture of P. hordei. Considerable variation was observed both within and among sites for reactions to infection with different cultures of each of the two pathogens. The results of this study were compared with those of an earlier study involving wild barley accessions from Israel to illustrate the relative importance of different subregions in the Near East Fertile Crescent as sources of new genes for resistance to E. graminis hordei and P. hordei. Implications of these studies for in situ conservation of genetic diversity in wild barley are discussed.

Genetic resources of wild barley in the Near East: structure, evolution and application in breeding

Genetic diversity and structure of populations of the wild progenitor of barley, Hordeum spontaneum, from three countries, Israel, Turkey and Iran, in the Near East Fertile Crescent, are compared and contrasted. The analysis is based on electrophoretically discernible allozymic variation in proteins encoded by 27 shared loci in 2125 individuals representing 52 populations of wild barley. The results indicate that: (a) H. spontaneum in the Near East Fertile Crescent is very variable genetically; (b) genetic differentiation of populations includes some clinal but primarily regional and local patterns often displaying sharp geographic differentiation over short distances; (c) the average relative genetic differentiation (Gst) was 54% within populations, 39% among populations, and 8% between the three countries; (d) allele distribution is characterized by a high proportion of unique alleles (51%), and a high proportion of common alleles that are distributed either locally or sporadically; (e) discriminant analysis by allele frequencies successfully clustered wild barley of each of the three countries (96% correct classification); (f) a substantial portion of the patterns of allozyme variation in the wild gene pool is significantly correlated with the environment and is predictable ecologically, chiefly by a combination of humidity and temperature variables; (g) natural populations of wild barley are, on the average, more variable than two composite crosses and land races of cultivated barley. The spatial patterns and environmental correlates and predictors of genetic variation of H, spontaneum in the Fertile Crescent indicate that genetic variation in wild barley populations is not only rich but at least partly adaptive and predictable by ecology and allozyme markers. Consequently, conservation and utilization programmes should optimize sampling strategies by following the ecological-genetic factors and allozyme markers as effectively predictive guidelines.