The influence of the rye genome on expression of heat shock proteins in triticale

Summary The heat shock protein profiles from Secale cereale L. cv Imperial, Triticum aestivum L. cv Chinese Spring, S. cereale x T. aestivum amphiploid, and the seven disomic S. cereale addition lines to T. aestivum were used to compare the wheat, rye, and triticale Heat Shock Protein profiles and to study the influence of the rye genome on heat shock protein expression in triticale. Three-day-old seedlings were heat shocked for 2 h at 40 °C in the presence of ³⁵S-methionine, and polypeptides from root tissues were subjected to one- or two-dimensional gel electrophoresis. The wheat and rye heat shock protein profiles each consisted of > 150 heat shock proteins, of which 94 were sufficiently reproducible to construct a standard map. There were 11 unique rye heat shock proteins compared to 22 unique wheat heat shock proteins. The triticale heat shock protein profile resembled the rye parent more than the wheat parent. There were 22 heat shock proteins expressed uniquely by wheat that were not expressed in triticale. Rye chromosomes 1 and 3 exhibited a substantial repressive influence on the expression of 95% of the unique wheat heat shock proteins in triticale, while rye chromosome 4 appeared to have the least repressive influence on expression of the unique wheat heat shock proteins in triticale.Mention of a trade name or proprietary product does not constitute a guarantee, warranty, or recommendation of the product by the United States Department of Agriculture or the University of Missouri and does not imply its approval to the exclusion of other products that may be suitable     

Genetic interactions between wheat and rye genomes in triticale

Summary Six primary triticale lines were produced from two advanced breeding lines of Triticum durum and three inbred genotypes of Secale cereale. The wheat and rye parents and the triticale derivatives were crossed in all possible combinations within each species group. Chiasma and univalent frequency of parents and hybrids were determined. The primary triticale lines had more univalents and less chiasmata per pollen mother cell than the corresponding wheat and rye parents together. The parental wheat F₁ exhibited negative heterosis for chiasma frequency whereas all rye hybrids had much higher chiasma frequencies than their inbred parents. Triticale F₁s generally showed lower chiasma frequencies and more univalents than their parents, but the degree of pairing failure was dependent upon which of the parental species within the triticale, wheat or rye, was in the heterozygous state. F₁s with heterozygous wheat genome only showed the least reduction in chiasma number (presumably caused by gene actions within the wheat genome), while F₁s with heterozygous rye genome showed high reduction in chiasma frequency and an increase in pairing failure (induced by negative interactions between the heterozygous rye and the wheat genome in triticale). A high correlation was found between the frequency of undisturbed pollen mother cells and the frequency of aneuploids in the subsequent generation. A higher number of aneuploids occurred in those populations which were heterozygous for the rye genome.     

Molecular mapping of hybrid necrosis genes Ne1 and Ne2 in hexaploid wheat using microsatellite markers

Hybrid necrosis is the gradual premature death of leaves or plants in certain F₁ hybrids of wheat (Triticum aestivum L.), and it is caused by the interaction of two dominant complementary genes Ne1 and Ne2 located on chromosome arms 5BL and 2BS, respectively. To date, molecular markers linked to these genes have not been identified and linkage relationships of the two genes with other important genes in wheat have not been established. We observed that the F₁ hybrids from the crosses between the bread wheat variety ‘Alsen’ and four synthetic hexaploid wheat (SHW) lines (TA4152-19, TA4152-37, TA4152-44, and TA4152-60) developed at the International Maize and Wheat Improvement Center (CIMMYT) exhibited hybrid necrosis. This study was conducted to determine the genotypes of TA4152-60 and Alsen at the Ne1 and Ne2 loci, and to map the genes using microsatellite markers in backcross populations. Genetic analysis indicated that Alsen has the genotype ne1ne1Ne2Ne2 whereas the SHW lines have Ne1Ne1ne2ne2. The microsatellite marker Xbarc74 was linked to Ne1 at a genetic distance of 2.0 cM on chromosome arm 5BL, and Xbarc55 was 3.2 cM from Ne2 on 2BS. Comparison of the genetic maps with the chromosome deletion-based physical maps indicated that Ne1 lies in the proximal half of 5BL, whereas Ne2 is in the distal half of 2BS. Genetic linkage analysis showed that Ne1 was about 35 cM proximal to Tsn1, a locus conferring sensitivity to the host selective toxin Ptr ToxA produced by the tan spot fungus. The closely linked microsatellite markers identified in this study can be used to genotype parental lines for Ne1 and Ne2 or to eliminate the two hybrid necrosis genes using marker-assisted selection. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture.     

Ear culture as a technique to overcome hybrid necrosis in wheat

Hybrid necrosis in wheat is a problem for gene transfer in wheat breeding. Hybrid necrosis occurs due to dominant complementary interaction of two genes, Ne1 and Ne2. A cross between wheat (Triticum aestivum L.) varieties C306 (drought tolerant, Ne1 carrier) and WL711(high yielding, Ne2 carrier) produced necrotic F1 hybrids, which died before ear emergence and produced no seeds. To overcome the problem of hybrid necrosis, ears enclosed in the leaf sheath were taken and cultured to maturity in liquid medium containing 5% sucrose and 0.04% glutamine. The necrotic hybrids produced only a few seeds per ear compared to parents, but individual grain weight was similar in the hybrid and the parents. The F1 ear culture study has been repeated for three years and F2 seeds obtained. In 1996–97, the cultured ears of F1 hybrids produced 62 seeds, of which only 52 showed germination and were grown under normal field conditions. Out of the 52 seeds, 50% were non-necrotic and showed segregation for various physiological traits. The results reveal that hybrids ears had the potential to form viable seeds. Culturing of wheat ears before ear emergence and production of viable F2 seeds from necrotic hybrids is a simple and efficient method for overcoming the problem of hybrid necrosis. This revised version was published online in June 2006 with corrections to the Cover Date.     

Development and assessment of DArT markers in triticale

Triticale (X Triticosecale Wittm.) is a hybrid derived by crossing wheat (Triticum sp.) and rye (Secale sp.). Till date, only a limited number of simple sequence repeat (SSRs) markers have been used in triticale molecular analyses and there is a need to identify dedicated high-throughput molecular markers to better exploit this crop. The objective of this study was to develop and evaluate diversity arrays technology (DArT) markers in triticale. DArT marker technology offers a high level of multiplexing. Development of new markers from triticale accessions was combined with mining the large collection of previously developed markers in rye and wheat. Three genotyping arrays were used to analyze a collection of 144 triticale accessions. The polymorphism level ranged from 8.6 to 23.8% for wheat and rye DArT markers, respectively. Among the polymorphic markers, rye markers were the most abundant (3,109) followed by wheat (2,214) and triticale (719). The mean polymorphism information content values were 0.34 for rye DArT markers and 0.37 for those from triticale and wheat. High correlation was observed between similarity matrices derived from rye, triticale, wheat and combined marker sets, as well as for the cophenetic values matrices. Cluster analysis revealed genetic relationships among the accessions consistent with the agronomic and pedigree information available. The newly developed triticale DArT markers as well as those originated from rye and wheat provide high quality markers that can be used for diversity analyses and might be exploited in a range of molecular breeding and genomics applications in triticale.     

Dynamics of hybrid necrosis genes in Russian cultivars of common wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Study of necrosis genotypes of 72 Russian cultivars of winter common wheat has confirmed a tendency towards “washing off“ of genotypes with the Ne1 gene. Fifty-six percent of cultivars have the genotype ne1ne1Ne2Ne2, and 44% have the genotype ne1ne1ne2ne2; i.e., they are free of hybrid necrosis genes. The results of the study indicate that the diversity of the original ancestors in the groups of cultivars with the ne1ne1Ne2Ne2 and ne1ne1ne2ne2 genotypes is almost the same. This determines the instability of the tendency towards a higher prevalence of the ne1ne1Ne2Ne2 genotype in recent years. The changes in the diversity of the original ancestors with time have shown an increase in the diversity index. These processes may somewhat decrease the rate of genetic erosion caused by the fact that the Ne1Ne1ne2ne2 falls out of breeding. The routes of transmission of necrosis gene alleles from ancestors to descendants have been traced using extended pedigrees, and this information has been used to identify the probable donors and sources of hybrid necrosis gene alleles. In most cases, the cultivars Mironovskaya 808 and Krasnodarskaya 39 are the putative sources of the Ne2 allele (60.6 and 27.3% of all cases, respectively). The old cultivar Gostianum 237 from Saratov oblast is the putative source of the Ne2 allele in the cultivar Krasnodarskaya 39. The cultivars Bezostaya 1 and Odesskaya 51 (whose pedigree also includes Bezostaya 1) are the donors of the recessive genotype ne1ne1ne2ne2 in 93.5% of cases. The old Ukrainian cultivar Ukrainka is the most frequent source of recessive alleles. The strength of the Ne2 allele has been estimated in 36 cultivars. The results indicate that modifier genes affect the expression of tumor necrosis genes.     

Use of tissue culture to bypass wheat hybrid necrosis

Summary Hybrid necrosis in wheat is a barrier to gene transfer in wheat breeding practice. It is based on two complementary genes, Ne1 and Ne2. Recovery mutants (Re1, Re2 and Re3) which can grow to maturity were recovered from immature embryo cultures of necrotic hybrids between T. aestivum and T. durum. Cytological observation demonstrated that Re1 had 34 chromosomes instead of 35. This indicated that one of the chromosomes carrying the Ne genes was lost. Genetic study suggested that for Re1, the lost chromosome was chromosome 5B of the durum parental line. Re mutants are male sterile but can be maintained through a young ear culture method. Re mutants could be successfully pollinated by either parental line and the BC1 progeny is partially fertile. Re mutants were repeatedly induced in about 1% of the regenerated plants from immature embryo culture. This technique provides a practical way to bypass hybrid necrosis.     

Influence of R genome on the nutritional value of triticale for broiler chicks

The following grain characteristics: protein, arabinoxylan and dietary fibre content, viscosity and water holding capacity of wheat, rye and triticale of different ploidy levels were studied as to their effect on body weight gain (BWG), feed to gain ratio (FCR), apparent metabolizable energy (AME_n), dry matter digestibility (DMD) and apparent protein retention (APR) in young broiler chicks fed isograin and isoprotein diets based on these cereals. Highly significant correlations (p≤0.01) were found between physicochemical and biological quality indicators when all cereals were taken into account. A negative response of chicks to triticale was obtained only when chicks were fed diets containing the tetraploid forms, while the nutrition parameters of chicks fed diets containing the octo- and hexaploid triticale, with rye genome shares of 1 : 3 and 1 : 2, did not differ (p≥0.05) from those fed a wheat diet. Rye diets yielded the lowest BWG, AME_n and DMD and the poorest FCR. The results indicate that as long as the share of the R genome is a minor component of the total triticale genome pool, its antinutritional effect is masked by the wheat genome. The results also indicate that hexaploid triticale can constitute the sole cereal component in the diets of young broiler chicks.     

The Effect of Parental Genotypes of Rye Lines on the Development of Quantitative Traits in Primary Octoploid Triticale: Plant Height

When breeding the primary spring octoploid triticale derived from crosses of various inbred rye lines to wheat Chinese Spring, the effects of the rye genotype and growth conditions on the plant height and proportion of the first, second, and final (pedicle) internodes to the entire stem length were studied. Two triticale groups were examined: homozygotes for the dominant (Ddw1) and recessive (ddw1) alleles of the gene responsible for short stem in rye. In the short stem triticale lines carrying the Ddw1 alleles, the plants were 20 cm shorter on average than those in the ddw1-carrying lines, and the distribution of the two triticale groups overlapped significantly. In both groups, the lines significantly differing in plant height could be differentiated, because of allelic diversity of the additional genes controlling this trait along with the Ddw gene. In most triticale lines, especially in theDdw1-carrying ones, the plant height was much reduced under unfavorable growth conditions. At the same time, a short-stem line was isolated, which is characterized by ecological plasticity, like the maternal wheat cultivar. In the triticale studied, the stem structure depended on the short-stem rye genotype. The two-year study showed that in the triticale carrying the dominant allele of this gene, the first internode is significantly extended, whereas the upper (pedicle) internode is reduced, which increases plant lodging resistance. The differences revealed between the rye lines as well as their effect on the quantitative triticale traits are discussed in view of a variant of the hybridological analysis, which had been previously proposed for identification and mapping of the correspondent rye genes.     

Segregation distortion caused by weak hybrid necrosis in recombinant inbred lines of common wheat

Segregation distortion of molecular markers is closely related to hybrid incompatibility in progeny from intraspecific crosses. Recent reports in higher plants have demonstrated that hybrid sterility results in segregation distortion at the causal gene regions in progeny of intraspecific crosses. Ne1 and Ne2 complementary loci are known to control hybrid necrosis in intraspecific crosses of common wheat cultivars. Here, we examine the effect of a weak necrosis allele Ne1 ^w on the segregation ratio of molecular markers in recombinant inbred lines (RILs) of common wheat. Some RILs showed accelerated cell death in the leaves at the heading stage due to the epistatic interaction between two quantitative trait loci (QTL) on chromosomes 5B and 2B. Chromosomal localization of these QTL corresponding to Ne1 ^w and Ne2 showed distorted segregation ratios of assigned markers having oppositely biased direction. Although the Ne1 ^w and Ne2 interaction had no obvious effect on seed fertility, Ne1 ^w reduced completion of grain development under the Ne2-homozygous background. This reduction might be one of causes that induces segregation distortion in the 5B and 2B chromosomal regions of RILs. The present study demonstrated that weak hybrid necrosis has limited phenotypic effects; it causes segregation distortion in progeny from intraspecific crosses.     

rRNA gene activity and control of expression mediated by methylation and imprinting during embryo development in wheat x rye hybrids

Ribosomal RNA genes originating from one parent are often suppressed in interspecific hybrids. We show that treatments during germination with the cytosine analogue 5-azacytidine stably reactivate the expression of the suppressed rRNA genes of rye origin in the wheat x rye amphiploid, triticale, by preventing methylation of sites in the rye rDNA. When 5-azacytidine is applied to embryos of triticale and wheat x rye F₁ hybrids nine, or more, days after fertilization, rye rRNA gene expression is stably reactivated in the resulting seedling. Earlier treatments have no effect on rye rRNA gene expression, indicating that undermethylation of DNA early in embryo development is reversible. After 9 days, the methylation status of rRNA genes in maintained throughout development. Since the change in expression follows a methylation change at particular restriction-enzyme sites, the data establish a clear correlation between gene activity and methylation in plants.     

Polyploidization-induced genome variation in triticale.

Polyploidization-induced genome variation in triticale (x Triticosecale Wittmack) was investigated using both AFLP and RFLP analyses. The AFLP analyses were implemented with both EcoRI-MseI (E-M) and PstI-MseI (P-M) primer combinations, which, because of their relative differences in sensitivity to cytosine methylation, primarily amplify repetitive and low-copy sequences, respectively. The results showed that the genomic sequences in triticale involved a great degree of variation including both repetitive and low-copy sequences. The frequency of losing parental bands was much higher than the frequency of gaining novel bands, suggesting that sequence elimination might be a major force causing genome variation in triticale. In all cases, variation in E-M primer-amplified parental bands was more frequent in triticale than that using P-M primers, suggesting that repetitive sequences were more involved in variation than low-copy sequences. The data also showed that the wheat (Triticum spp.) genomes were relatively highly conserved in triticales, especially in octoploid triticales, whereas the rye (Secale cereale L.) genome consistently demonstrated a very high level of genomic sequence variation (68%-72%) regardless of the triticale ploidy levels or primers used. In addition, when a parental AFLP band was present in both wheat and rye, the tendency of the AFLP band to be present in triticale was much higher than when it was present in only one of the progenitors. Furthermore, the cDNA-probed RFLP analyses showed that over 97% of the wheat coding sequences were maintained in triticale, whereas only about 61.6% of the rye coding sequences were maintained, suggesting that the rye genome variation in triticale also involved a high degree of rye coding sequence changes. The data also suggested that concerted evolution might occur in the genomic sequences of triticale. In addition, the observed genome variation in wheat-rye addition lines was similar to that in triticale, suggesting that wheat-rye addition lines can be used to thoroughly study the genome evolution of polyploid triticale.     

Nucleolar organizer activity in wheat,rye and derivatives analyzed by a silver-staining procedure

Nucleolar activity was analyzed in wheat (Triticum sp.), rye (Secale cereale) and several types of wheat-rye derivatives using a modified, highly reproducible, silver staining procedure (Lacadena et al. 1984). A comparative analysis of the nucleolar organizer regions (NORs) of somatic metaphase chromosomes was made by phase contrast, C-banding, and silver staining. The frequency distribution of the number of nucleoli visualized at interphase by silver staining was also used to infer the activity of NORs. The results agree quite well with data from in situ hybridization reported by other authors. The behavior of euploid, ditelosomic and nulli-tetrasomic plants of common wheat showed the relative nucleolar activity of the four organizer chromosomes to be: 6B > 1B > 5D > 1A. — Several types of wheat-rye derivatives were analyzed: interspecific hybrid, triticale, addition and substitution lines, and plants with the genome constitutions, AABBDR, ABDR + 5D, ABRR, and ABRRR. In all cases the nucleolar organizer chromosome 1R of rye was suppressed by the presence of wheat chromosomes.     

Transferability of SSR markers among wheat,rye, and triticale

Simple sequence repeat (SSR) markers are a valuable tool for many purposes, such as mapping, fingerprinting, and breeding. However, they are only available in some economically important crops because of the high cost and labor intensity involved in their development. Comparative mapping reveals a high degree of colinearity between closely related species, which allows the exchange of markers between them. Our objective was to examine the transferability of SSR markers among wheat (Triticum aestivum L.), rye (Secale cereale L.), and triticale (X Triticosecale Wittmack). One hundred forty-eight wheat and 28 rye SSR markers were used to amplify genomic DNA extracted from five lines each of wheat, rye, and triticale. Transferability of wheat SSR markers to rye was 17%, whereas 25% of rye markers were amplifiable in wheat. In triticale, 58% and 39% transferability was achieved for wheat and rye markers, respectively. Wheat markers gave an average of 2.6, 2.7, and 2.4 polymorphic bands in wheat, rye, and triticale, respectively, while rye markers gave an average of 2.0 in rye and none in wheat and triticale. These transferable markers can now be exploited for further genetic and breeding studies in these species.Nebraska Agricultural Research Division, Journal Series No. 14243Communicated by B. Friebe     

Genetic Control of Embryo Lethality in Crosses between Common Wheat and Rye

The phenotypic manifestation and genetic control of embryo lethality observed in crosses between common wheat and rye were studied. It was found that crosses between common wheat and inbred self-fertile rye lines L2 and 535 gave rise to ungerminating grains, in which the development and differentiation of the hybrid embryo are arrested. Study of the degree of embryo development in the hybrid grains obtained by crossing common wheat varieties with inbred rye lines L2 and 535 showed that genotypes of the parents affected the ratio between undifferentiated embryos of various sizes. Analysis of this trait was performed by test crosses according to a novel pedigree program with the use of interlinear hybrids and a set of fourth-generation hybrid recombinant inbred lines. Rye line L2 was shown to bear the Eml (Embryo lethality) gene, which terminates the development of the hybrid embryo in amphihaploids. The suggestion of complementary interaction between wheat and rye genes during formation of a “new” character in wheat-rye F₁ hybrids is discussed. A method of detecting an allele not complementary to the rye Eml allele in wheat is proposed. The proposed test program allows appropriate study of the system of wheat and rye genes involved in complementary interaction in the genotype of a distant hybrid.__________Translated from Genetika, Vol. 41, No. 8, 2005, pp. 1075–1083.Original Russian Text Copyright © 2005 by Tikhenko, Tsvetkova, Voylokov.     

Molecular Analysis of the Triticale Lines with Different <Emphasis Type="Italic">Vrn</Emphasis> Gene Systems Using Microsatellite Markers and Hybridization In Situ

Hexaploid triticale (×Triticosecale Wittmack) lines were examined using molecular markers and the hybridization in situ technique. Triticale lines were generated based on wheat varieties differing by the Vrn gene systems and the earing times. Molecular analysis was performed using Xgwm and Xrms microsatellite markers with the known chromosomal localization in the common wheat Triticum aestivum, and rye Secale cereale genomes. Comparative molecular analysis of triticale lines and their parental forms showed that all lines contained A and B genomes of common wheat and also rye homoeologous chromosomes. In the three lines the presence of D genome markers, mapped to the chromosomes 2D and 7D, was demonstrated. This was probably the consequence of the translocations of homoeologous chromosomes from wheat genomes, which took part during the process of triticale formation. The data obtained by use of genomic in situ hybridization supported the data of molecular genetic analysis. In none of the lines wheat-rye translocations or recombinations were observed. These findings suggest that the change of the period between the seedling appearance and earing time in triticale lines compared to the initial wheat lines, resulted from the inhibitory effect of rye genome on wheat vernalization genes.     

Salt Tolerance in the Triticeae: Ion Discrimination in Rye and Triticale

When rye and triticale accessions were grown in saline hydroponicculture they exhibited the low Na and high K concentrationsin their leaves which are characteristic of the enhanced K/Nadiscrimination trait originally found in the D genome of wheat.This trait was not consistently improved by the presence ofthe D genome in octaploid triticale or in D genome substitutionlines of hexaploid triticale. The presence of the rye genomedid not significantly affect anion concentrations within theleaves. At high salt concentrations (250 mol m^–3 NaCl+12.5mol m^–3 CaCl₂) the triticales were more tolerant thanthe rye accessions or a DDRR-genome tetraploid, with two triticalelines being almost as salt-tolerant as barley. Key words: Salt, ion transport, R genome, rye (Secale cereale L.)     

Characterisation of cDNAs for ribulose bisphosphate carboxylase small subunit genes in different species of Avena (Poaceae)

ABSTRACT

We report the cloning and sequencing of 14 rbcS cDNAs in six species of Avena (Poaceae) with different genome and ploidy levels. The nucleotide sequences 504 bp long were aligned with the published sequences of cultivated hexaploid oat, wheat, barley, rye, rice and corn and subjected to cladistic and phenetic analyses. The parsimonious analysis generated a tree with a topology very similar to the phenogram generated by the Neighbor-Joining analysis based on the Jukes and Cantor distances. Within the monophyletic assemblage of the tribe Aveneae, consistent clades composed of rbcS clones belonging to different species are recognized. It is suggested that they correspond to orthologous genes belonging to different subfamilies, and that the “within-species?d homogenisation may have occurred at a slow rate with respect to species evolution. In the monophyletic group of Pooideae, the topologies place barley rbcS sequences closer to wheat and rye than to oat sequences. This grouping agrees with most taxonomic and phylogenetic views.