Genetic Diversity Of Triticum Dicoccoides L. In Israel And The Shoot And Root Growth Of Model Plant Brachypoidum Distachyon L.

Three molecular makers, including RGAP, EST-SSR and SRAP, were used for evaluating the genetic diversity of wild emmer wheat(Triticum dicoccoides L.) from Israel and their ecological relationships. The shoot and root systems of the small, grass genetic model Brachypodium(Brachypodium distachyon L.) were studied from germination to grain filling to assess its potential as a phenotypic model for wheat (T. aestivum L.) and other important cereal crops. The main results were described as following:1. Using the 8 specific primer pairs based on the conserved motifs of plant resistance genes, the plant disease resistance gene analog polymorphisms (RGAPs) in 15 wild emmer wheat populations from Israel had been detected. High genetic variations at the RGAP loci were observed in T. dicoccoides populations. A total of 254 discernible bands were obtained among 115 accessions, and 192 bands (75.6%) were polymorphic. Each genotype had a unique banding profile, and the genetic similarity coefficient ranged from 0.094 to 0.862. In T. dicoccoides, the proportion of polymorphic loci (P), the genetic diversity (He) and Shannon's information index were 0.756,0.362 and 0.541, respectively. The proportion of polymorphic loci (P) per population averaged 0.732 (range:0.515-0.932); genetic diversity (He) averaged 0.271 (range:0.212-0.338); and Shannon's information index averaged 0.404 (range:0.310-0.493). The coefficients of genetic distance (D) among populations averaged 0.107 (range: 0.043-0.178), and the results of Mantel test (r=0.168, P=0.091) showed that the estimates of genetic distance were geographically independent. Neighbor-joining cluster analysis suggested that the genetic relationships of T. dicoccoides populations were associated with their ecogeographic distribution. The hierarchical analysis of molecular variance (AMOVA) and the coefficient of gene differentiation (GST) values revealed that most of the variations were presented within populations, although significant differences among populations and regions were also detected. The values of P and Shannon's information index were negatively correlated with the two factors: Tdd (day-night temperature difference) and Ev (mean annual evaporation), whereas they were positively correlated with one water factor:Rn (mean annual rainfall). The correlation matrix between He in the RGAPs and geographic variables contained 20 significant (P<0.05) correlations. The present study established that T. dicoccoides in Israel had a considerable amount of genetic variations at RGAP loci at least partly correlated with ecological factors. 2. The differentiation of genetic diversity was estimated among 15 wild emmer wheat populations of the macrogeographic scale in Israel by 25 EST-SSR markers. A total of 92 EST-SSR alleles were detected, and the number of alleles ranged from 1 to 7 with an average of 3.68 per locus. Allele numbers and the polymorphic information content (PIC) value of EST-SSR loci on the B genome were higher than that on the A genome. The genetic similarity coefficient (GS) value varied from 0.189 to 0.966 and all genotypes were clustered into four major groups. The population Mt. Gerizim had the highest genetic variations, whereas the population Beit-Oren had the lowest genetic variations. Most of genetic variance existed within populations was observed based on the coefficient of gene differentiation (FST=0.355). The value of genetic distance (D) between the populations varied from 0.112 to 0.672 with an average of 0.406, and the results of Mantel test (r=0.104, P=0.809) showed that the estimates of genetic distance were geographically independent. The values of Nei's gene diversity (He) and Shannon's information index (I) correlated negatively with the temperature factor: mean January temperature (Tj), whereas they correlated positively with another factor: mean number of Sharav days (Sh). The correlation matrix between He in the EST-SSRs and climatic variables contained 37 significant (P<0.05) correlations. The present study established that T. dicoccoides in Israel had a considerable amount of genetic variations at EST-SSR loci at least partly correlated with ecological factors. These results suggested that SSR diversity is adaptive by natural selection and influenced by both internal and external factors and their interactions.3. Genetic diversity and population structure of 15 wild emmer wheat populations from Israel were detected by 30 sequence-related amplified polymorphism (SRAP) primer pairs. Two hundred and forty four fragments out of 438 were polymorphic. The proportion of polymorphic loci (P), the genetic diversity (He), and Shannon's information index were 0.557,0.198, and 0.295, respectively. The population Amirim had the highest genetic variation, whereas the population of Tabigha had the lowest genetic variation. The hierarchical analysis of molecular variance (AMOVA) revealed that most of the variation was presented within populations. The value of genetic distance (D) between the populations varied from 0.027 to 0.165 with an average of 0.079, and the estimates of genetic distance were geographically independent based on the Mantel test (r=0.105, P=0.168). A total of 30 significant (P<0.05) correlations were detected between 14 SRAP loci and 12 ecogeographic factors.4. The grass genetic model Brachypodium (Brachypodium distachyon L., sequenced line Bd 21) was studied from germination to seed production to assess its potential as a phenotypic model for wheat and other cereal crops. Brachypodium and wheat shoot and root development and anatomy were highly similar. Main stem leaves and tillers (side shoots) emerged at the same time in both grasses in four temperature and light environments. Both developed primary and nodal axile roots at similar leaf stages with the same number and arrangement of vascular xylem tracheary elements (XTEs). Brachypodium, unlike wheat, had an elongated a mesocotyl above the seed and developed only one fine primary axile root from the base of the embryo, while wheat generally has three to five. Roots of both grasses could develop first, second and third order branches that emerged from phloem poles. Both developed up to two nodal axile roots from the coleoptile node at leaf 3, more than eight nodal axile roots from stem nodes after leaf 4, and most (97%) of the deepest roots at flowering were branches. In long days Brachypodium flowered 30 days after emergence, and root systems ceased descent 42 cm from the soil surface, such that mature roots can be studied readily in much smaller soil volumes than wheat. Brachypodium has the overwhelming advantage of a small size, fast life cycle and small genome, and is an excellent model to study cereal root system genetics and function, as well as genes for resource partitioning in whole plants.