Assessment of Genetic Diversity in Barley Germplasm and Sequencing of Ppd-H1Gene for Genetic Variation in Natural Populations of Barley from Middle East

【摘要】：Jordan is unanimously considered to be one of the centers of genetic diversity for barley where wild and landraces barleys grow under different climatic conditions. The collections of crop germplasm resources are essential for on going plant breeding efforts. To exploit such a valuable genetic reservoirs according to their full of potential, however, scientists need vast knowledge about the extent and distribution of genetic diversity resided within the collections. Current study was aimed to investigate the genetic diversity and genetic structure within and between cultivated and wild barley populations in primary gene pool of barley at country scale in Jordan. We analyzed a total of7populations comprising of4barley landraces and3wild barleys using7Intron-Exon Splice Junction (ISJ) markers. The genetic diversity index He of barley landraces was ranged from0.049to0.060; while that of wild barley populations was ranged from0.084to0.146, which suggest that wild gene pool of barley harbored significantly higher genetic diversity than its domesticated counterpart, a reflection that domestication of barley was accompanied by a genetic bottleneck. AMOVA revealed high genetic variations among populations rather than within the populations, indicating that high genetic differentiation of populations could be resulted by geographical and genetic isolation of the populations in the harsh environment of Middle East. PCA, clustering and STRUCTURE analysis distinguished not only wild and cultivated barley, but also each single population, which representing their hereditarybasis and original sample site. Our results also showed that there is lower genetic communication between wild and cultivated barley under natural conditions. The present findings put forward a range of implications and ramifications to the theories and practice for plant germplasm collection, conservation, and storage. The genetic diversity based on quantitative traits and hordein polymorphism was also assessed in seven populations of two barley species. In order to investigate the genetic variability on11quantitative traits, a field trail was conducted for two consecutive years. Significantly different results were recorded within and between the populations for all the traits i.e. days to heading, days to flowering, plant height, spike length, awn length, flag leaf length, peduncle length, seeds per spike, total number of fertile tillers per plant and flag leaf width. However, more number of variant traits was observed in wild than landraces barley, inferring that wild populations harbor more genetic diversity. Principle component analysis was conducted on quantitative traits, which further confirmed the higher genetic variances of first three components for wild than landraces barley. Cluster analysis was also applied on the mean value of each quantitative trait of the both species; however, the accessions of wild barley did not group together to their respective population sites, while most number of wild barley accessions clumped together according to their predefined population site. For hordein, A-PAGE was used to reveal seed storage protein polymorphism:ten different bands were distinguished for D, thirteen for C, and eleven for the B hordein regions. Among the146accessions of two species, total34distinct bands were identified. PCA and cluster analysis showed similar kind of results which obtained on the basis of quantitative traits. Moreover, the genetic affinity was exceptionally high within and between species than expected. The genetic study of hordein showed the amount of genetic relatedness between two species whereas the characterization of quantitative traits allowed the identification of accessions with promising agronomical traits from landraces and wild barley. Both approaches can be useful to explore the germplasm for future breeding strategies. Wild barley (Hordeum spontaneum C. Koch) has been considered as an important source of new genes for crop improvement, due to its largely untapped genetic resources and adaptability to a wide range of environments. However, extensive genetic analysis of agronomic traits with wide crosses of barley has not been carried out yet. Our current study aimed to shed light on the estimates of heterosis, heritability, genetic advance and correlation of some agronomic traits in interspecific crosses and its comparison with intraspecific crosses. The parental genotypes were crossed and subsequently F1hybrids were obtained during the growing seasons of2010-2011and2011-2012at the experimental field of Northwest AF University, Yangling, China. Two kind of F1hybrid populations, intra and interspecific, were developed from two-row barley genotypes including cultivars (varieties and landraces) and wild barleys collected from different geographical areas. High positive heterosis was observed in both of these F1populations, demonstrating the usefulness of intraspecific as well as interspecific wide crosses in breeding for heterosis. Higher heritability and genetic advance estimates were observed for all studied agronomic traits, with the exception of plant height, in interspecific than in intraspecific crosses, indicating that these traits were predominantly controlled by additive gene effects and direct selection may be effective in interspecific crosses. Significantly positive inter-character associations were shown in both of the F1populations for various agronomic traits, thus indicating the value of these traits in practical breeding programs. On the basis of our current results, we envisage that interspecific crosses could be efficiently utilized in breeding for better agronomic traits in barley. The flowering at a proper time for reproduction and survival of any plant species is an important adaptive trait. Ppd-H1has been considered as one of the major gene which control photoperiod response in landraces and natural barley populations. Previous studies has shown that the polymorphic site called SNP48marker of Ppd-H1gene which is situated in exon six of Ppd-H1, demonstrated significant affect on days to heading in different barley cultivars. In the current study, a fragment of460bp successfully amplified and sequenced in twelve natural barley populations which collected from different geographical areas of Israel and Jordan. Moreover, days to heading was also examined among these wild barley populations/accessions under field conditions during the growing season of2010-2011, the heading days data showed a difference of15days between early and late accessions. Based on results obtained, the early and late genotypes all retained wild allele and did not reveal any polymorphisms at SNP48. It is concluded that there are additional factors which are responsible for heading day's differences rather than only SNP48in wild populations of barley. Furthermore, this study was also aimed to identify the genetic association among SNPs of Ppd-H1gene with a range of agro-morphological traits in barley. The generated data was tested using General Linear Model (GLM) provided by TASSEL software. Total11SNPs discovered in coding region and only1in non-coding region. The majority of the SNPs were non-synonymous and few of them were significantly correlated with TT, TFT and FLW. Results indicated that SNPs in Ppd-H1gene might alter the protein biosynthesis and then lead to changes in phenotypic traits of the barley crop. The association between SNPs and these agro-morphological traits may provide new insight for study of the gene's potential contribution to barley breeding.