Frequent numerical and structural chromosome changes in early generations of synthetic hexaploid wheat

Modern hexaploid wheat (Triticum aestivum L.; AABBDD) evolved from a hybrid of tetraploid wheat (closely related to Triticum turgidum L. ssp. durum (Desf.) Husn., AABB) and goatgrass (Aegilops tauschii Coss., DD). Variations in chromosome structure and ploidy played important roles in wheat evolution. How these variations occurred and their role in expanding the genetic diversity in modern wheat is mostly unknown. Synthetic hexaploid wheat (SHW) can be used to investigate chromosome variation that occurs during the early generations of existence. SHW lines derived by crossing durum wheat ‘Langdon’ with twelve Ae. tauschii accessions were analyzed using oligonucelotide probe multiplex fluorescence in situ hybridization (FISH) to metaphase chromosomes and SNP markers. Cluster analysis based on SNP markers categorized them into three groups. Among 702 plants from the S8 and S9 generations, 415 (59.12%) carried chromosome variations involving all 21 chromosomes but with different frequencies for each chromosome and sub-genome. Total chromosome variation frequencies varied between lines, but there was no significant difference among the three groups. The non-random chromosome variations in SHW lines detected in this research may be an indication that similar variations occurred in the early stages of wheat polyploidization and played important roles in wheat evolution.

Resistance of synthetic hexaploid wheat to the leaf rust pathogen

Background. One of the promising sources for enrichment of the common wheat (Triticum aestivum L.) gene pool with new alleles is synthetic hexaploid wheat (SHW), or allopolyploids from crossing tetraploid wheats (2n = 4x = 28, BBAA) with accessions of Aegilops tauschii Coss. (2n = 2x = 14, DD), and subsequent doubling of the chromosome number in the hybrids. Objectives of the study were to evaluate the SHW accessions from the VIR collection for resistance to Puccinia triticina Erikss. populations collected in Russia; genotype the accessions; and summarize information from the published sources concerning the resistance of the studied accessions to other harmful diseases and pests.Materials and methods. Resistance of 36 SHW accessions from the VIR collection to the populations of P. triticina was assessed in the laboratory and in the field, under artificial infection pressure, using the techniques developed by the Institute of Plant Protection. A phytopathological test and PCR markers were used to identify the Lr genes.Results and conclusion. The SHW accessions were characterized according to their resistance to the Russian populations of the wheat leaf rust pathogen. The sources of resistance in the phase of emergence and in adult plants were identified. The phytopathological test isolated three accessions with Lr23; the PCR marker of Lr21=Lr40 was found in 11 accessions, Lr39=Lr41 in 19, and Lr22a in 3. At the same time, k-65496, k-65515 and k-65517 had si multaneously Lr21=Lr40 and Lr39=Lr41, while k-65497, k-65503 and k-65508 had Lr22a and Lr39=Lr41. The analysis of published data showed that many of the studied SHW accessions were also resistant to other harmful diseases and insect pests, so they are of interest for further studying and possible use in domestic breeding.

Development and Identification of Four New Synthetic Hexaploid Wheat Lines with Solid Stems

Stem solidness is an important agronomic trait for increasing the ability of wheat to resist lodging. In this study, four new synthetic hexaploid wheat with solid stems were developed from natural chromosome doubling of F1 hybrids between a solid-stemmed durum wheat (Triticum turgidum ssp. durum, 2n = 4x = 28, AABB) and four Aegilops tauschii (2n = 2x = 14, DD) accessions. The solid expression of the second internode at the base of the stem was stable for two synthetic hexalpoid wheat Syn-SAU-117 and Syn-SAU-119 grown in both the greenhouse and field. The lodging resistance of four synthetic solid-stem wheats is stronger than that of CS, and Syn-SAU-116 has the strongest lodging resistance, followed by Syn-SAU-119. The paraffin sections of the second internode showed that four synthetic wheat lines had large outer diameters, well-developed mechanical tissues, large number of vascular bundles, and similar anatomical characteristics with solid-stemmed durum wheat. The chromosomal composition of four synthetic hexaploid wheat was identified by FISH (fluorescence in situ hybridization) using Oligo-pSc119.2-1 and Oligo-pTa535-1. At adult stage, all four synthetic hexaploid wheat showed high resistance to mixed physiological races of stripe rust pathogen (CYR31, CYR32, CYR33, CYR34). These synthetic hexaploid wheat lines provide new materials for the improvement of common wheat.

The study of the effects of reducing the negative influence of 1BL-1RS translocation on the bread making quality in spring bread wheat lines

The effects of the combinations 7DS-7DL-7Ae#1L (Lr19 gene) and 1BL-1RS (Lr26 gene) translocations, substitution of 6D(6Agi) (Lr6Agi gene) and 1BL-1RS translocation, as well as translocations of 7DS-7DL-7Ae#1L, 1BL-1RS and Lr39 gene on the bread making quality were evaluated in spring bread wheat introgressive lines. It was found that the genotype of recipient, the 1BL-1RS translocation donor, and the vegetation conditions have a great influence on the parameters quality of flour and bread. The role of selection within a single crosses combination for production of lines with good quality indicators is revealed. The high compensatory ability of the cultivar L505 and the synthetic hexaploid line with the pedigree Croc/Ae.squarosa(205)//Weaver (1BL-1RS translocation + Lr39 gene) for reducing the negative effect of the 1BL-1RS translocation on bread making quality was noted.

Chromosome Karyotype and Stability Identification of New Synthetic Hexaploid Wheat

Synthetic hexaploid wheats offer breeder ready access to potentially novel genetic variations in wild ancestral species. In present study, we used MY3478 (2n = 4x = 28, AABB) as female crossing with SY41 (2n = 2x = 14, DD) of stripe rust resistant as male through natural chromosome doubling to constructed the new hexaploid wheat line NA0928. Agronomic traits and cytological analysis were characterized in NA0928 of S8-S9 generations. The major study and results were described as follows, agronomic character variation coefficient in NA0928 of S8 generation showed that the effective tiller number (55.3%) > spike length (15.3%) > number of spikelets (13.9%) > plant height (8.7). It is suggested that the effective tiller number and spike length have great utilization value in breeding. Cytological observation and fluorescence in situ hybridization (FISH) results showed that the chromosome number and configuration have rich variations in S9 of NA0928. Chromosome number variation range of 36–44. Numerous chromosome karyotype variations were almost detected in A and B subgenomes. In addition, more diverse types of chromosomal structure variations were observed in the stripe rust resistant strains with more excellent performance than susceptible strains in agronomic traits. Especially, the tillering number of the resistant strains were much higher. Here, Meiosis stage of pollen mother cells and multicolor-GISH (Mc-GISH) results showed that two new synthetic hexaploid wheat lines were obtained, which showed genetic stability, one line was resistance to stripe rust, and the other one line was susceptible stripe rust, at the same time, there had two excellent characteristics with high 1000-grain weight and multiple tillers. They will be valuable germplasm materials in wheat breeding utilization.

Additive genetic variance and covariance between relatives in synthetic wheat crosses with variable parental ploidy levels

Cultivated bread wheat (Triticum aestivum L.) is an allohexaploid species resulting from the natural hybridization and chromosome doubling of allotetraploid durum wheat (T. turgidum) and a diploid goatgrass Aegilops tauschii Coss (Ae. tauschii). Synthetic hexaploid wheat (SHW) was developed through the interspecific hybridization of Ae. tauschii and T. turgidum, and then crossed to T. aestivum to produce synthetic hexaploid wheat derivatives (SHWDs). Owing to this founding variability, one may infer that the genetic variances of native wild populations vs improved wheat may vary due to their differential origin and evolutionary history. In this study, we partitioned the additive variance of SHW and SHWD with respect to their breed origin by fitting a hierarchical Bayesian model with heterogeneous covariance structure for breeding values to estimate variance components for each breed category, and segregation variance. Two data sets were used to test the proposed hierarchical Bayesian model, one from a multi-year multi-location field trial of SHWD and the other comprising the two species of SHW. For the SHWD, the Bayesian estimates of additive variances of grain yield from each breed category were similar for T. turgidum and Ae. tauschii, but smaller for T. aestivum. Segregation variances between Ae. tauschii—T. aestivum and T. turgidum—T. aestivum populations explained a sizable proportion of the phenotypic variance. Bayesian additive variance components and the Best Linear Unbiased Predictors (BLUPs) estimated by two well-known software programs were similar for multi-breed origin and for the sum of the breeding values by origin for both data sets. Our results support the suitability of models with heterogeneous additive genetic variances to predict breeding values in wheat crosses with variable ploidy levels.