Alloplasmic Wheat Research Articles

The Effect of Chromosome Arm 1BS on the Fertility of Alloplasmic Recombinant Lines in Bread Wheat with the Hordeum vulgare Cytoplasm

The genetic mechanisms of fertility restoration in alloplasmic bread wheat with the barley cytoplasm are poorly explored. The effect of the 1BS chromosome arm on the fertility of bread wheat with the H. vulgare cytoplasm was studied depending on the incompleteness/completeness of the cytonuclear compatibility. (i) Three self-fertile (SF) lines and one partially fertile (PF) line with an incomplete cytonuclear compatibility and (ii) four self-fertile (SF) lines with a complete cytonuclear compatibility were studied. For the lines in group (i), the heteroplasmy (simultaneous presence of barley and wheat copies) of the 18S/5S mitochondrial (mt) repeat was revealed as well as the barley-type homoplasmy of chloroplast simple sequence repeats (cpSSRs). In the lines in group (ii), the 18S/5S mt repeat and cpSSRs were found in the wheat-type homoplasmic state. In all of the lines, the 1BS chromosome arm was substituted for the 1RS arm. The F1 plants of SF(i)-1BS × 1RS hybrids were fertile. The results of a segregation analysis in the F2 plants of SF(i)-1BS × 1RS showed that 1BS carries a single dominant fertility restorer gene (Rf) of bread wheat with the H. vulgare cytoplasm. All of the F1 plants of PF(i)-1BS × 1RS hybrids were sterile. A single dose of this restorer gene is not sufficient to restore fertility in this alloplasmic PF(i) line. All of the F1 and F2 plants of SF(ii)-1BS × 1RS hybrids were self-fertile.

Chromosomes 1BS and 1RS for control of male fertility in wheats and triticales with cytoplasms of Aegilops kotschyi, Ae. mutica and Ae. uniaristata.

Engineered chromosomes 1BS and 1RS offer a new alternative in the development of hybrid systems in bread wheat and triticale. In the cytoplasmic male sterility system for hybrid wheat based on the cytoplasm of Triticum timopheevi fertility restoration is difficult, with few good restorer genes available. In the system based on the cytoplasms of Aegilops kotschyi, Ae. uniaristata and Ae. mutica, essentially all chromosomes 1B carry locus Rf multi that restores male fertility; male sterility manifests itself in wheats with the 1RS.1BL translocation where 1BS chromosome arm is missing. To generate male sterile wheats without the 1RS.1BL translocation, the 1BS arm was cytogenetically engineered to replace the segment with Rf multi with two short inserts of rye chromatin. Conversely, to enhance fertility restoration by doubling the number of restorers present for eventual use in wheat and triticale, a region of 1BS with Rf multi was inserted into 1RS. Alloplasmic wheats with Rf multi removed were completely male sterile; alloplasmic wheats with engineered 1RS carrying Rf multi and without normal 1B were male fertile. An exception to the ubiquitous presence of Rf multi is T. spelta var. duhamelianum; four accessions tested in this study gave inconsistent results but some did not restore male fertility. Engineered chromosomes 1BS and 1RS and chromosomes 1B of T. spelta offer a new alternative for practical application of a cytoplasmic male sterility system in the development of hybrid wheat and hexaploid triticale.

Nuclear-cytoplasmic compatibility and the state of mitochondrial and chloroplast DNA regions in alloplasmic recombinant and introgressive lines (H. vulgare)-T. aestivum

Alloplasmic lines combining alien nuclear and cytoplasmic genomes are convenient models for studying the mechanisms of nuclear-cytoplasmic compatibility/incompatibility. In the.present study, we have investigated the correlation between the characters and state of mitochondrial (mt) and chloroplast (cp) DNA regions in alloplasmic recombinant common wheat lines with barley cytoplasm characterized by partial or total fertility. Fertility restoration in the studied lines (Hordeum vulgare)-Triticum aestivum is determined by different ratios of the genetic material of common wheat variety Pyrotrix 28, which is a fertility restorer in the cytoplasm of barley, and varietySaratovskaya 29, which is a fixer of sterility. In partially fertile lines with nuclear genomes dominated by the genetic material of Saratovskaya 29, plant growth and development are suppressed. In these lines we have identified the barley homoplasmy of cpDNA regions infA and rpoB and the heteroplasmy of the 18S/5S mt repeat and the cpDNA ycf5 region. Nuclear-cytoplasmic compatibility in lines with reduced fertility (the genetic material of Pyrotrix 28 predominates in their nuclear genomes) is associated with restoration of normal plant growth and development and the changes in thestate of the studied cpDNA and mtDNA regions towards the wheat type. Thus, in fertile lines, the cpDNA regions (infA, rpoB) and the 18S/5S mt repeat were identified in the homoplasmic wheat state; though the cpDNAycf5 region was in the heteroplasmic state, it was dominated by the wheat type of the copies. The nuclearicytoplasmic compatibility is not broken as a result of introgression of the alien genetic material into the nuclear genome of one of the fertile lines; the plants of introgressive lines are fertile and normally developed, and the states of the cpDNA and mtDNA regions correspond to their states in fertile recombinant lines.

Analysis ofATP6sequence diversity in theTriticum–Aegilopsspecies group reveals the crucial role of rearrangement in mitochondrial genome evolution

Mutation and chromosomal rearrangements are the two main forces of increasing genetic diversity for natural selection to act upon, and ultimately drive the evolutionary process. Although genome evolution is a function of both forces, simultaneously, the ratio of each can be varied among different genomes and genomic regions. It is believed that in plant mitochondrial genome, rearrangements play a more important role than point mutations, but relatively few studies have directly addressed this phenomenon. To address this issue, we isolated and sequenced the ATP6-1 and ATP6-2 genes from 46 different euplasmic and alloplasmic wheat lines. Four different ATP6-1 orthologs were detected, two of them reported for the first time. Expression analysis revealed that all four orthologs are transcriptionally active. Results also indicated that both point mutation and genomic rearrangement are involved in the evolution of ATP6. However, rearrangement is the predominant force that triggers drastic variation. Data also indicated that speciation of domesticated wheat cultivars were simultaneous with the duplication of this gene. These results directly support the notion that rearrangement plays a significant role in driving plant mitochondrial genome evolution.

Characterization of fertility restoration in alloplasmic lines derived from hybridization of self-fertilized offspring of barley-wheat (Hordeum vulgare L. × Triticum aestivum L.) amphiploid with common wheat varieties Saratovskaya 29 and Pyrotrix 28

The problems of fertility restoration in the progeny of barley-wheat hybrids (H. vulgare × T. aestivum) are explained by incompatibility between the cytoplasm of cultivated barley and the nuclear genome of common wheat. Appropriate models for studying these problems are alloplasmic lines that combine the cytoplasm of barley and the nuclear genome of wheat. In this work, the differences of fertility restoration in alloplasmic common wheat lines (H. vulgare)-T. aestivum were studied depending on the influence of wheat varieties Saratovskaya 29 (Sar29) and Pyrotrix 28 (Pyr28) used to produce these lines. The alloplasmic lines were created using hybrids between the 48-chromosome offspring (Amph1) of the barley-wheat amphiploid H. vulgare (ya-319) × T. aestivum (Sar29) and these wheat varieties. Backcrossing of the Amph1 (2n = 48) × Sar29 hybrid with the wheat variety Sar29 resulted in the complete sterility in the (H. vulgare)-Sar29 line, which suggests the incompatibility of the nuclear genome of the common wheat variety Sar29 with the cytoplasm of H. vulgare. Crossing of Amph1 (2n = 48) with Pyr28 resulted in the restoration of self-fertility in the hybrid with 2n = 44. In the alloplasmic lines (2n = 42) formed based on plants of the self-fertilized generations of this hybrid, the barley chromosomes were eliminated, and recombination between the nuclear genomes of the parental wheat varieties Sar29 and Pyr28 took place. Alloplasmic recombinant lines (H. vulgare)-T. aestivum with different levels of fertility were isolated. As was shown by the SSR analysis, differences in the fertility between these lines are determined by differences in the content of the genetic material from the wheat varieties Sar29 and Pyr28. The complete restoration of fertility in these alloplasmic recombinant lines is accompanied by the formation of a nuclear genome in which the genetic material of Pyr28 significantly prevails. The conclusion is made that the common wheat variety Pyrotrix 28 is a carrier of a gene (or genes), which determines the restoration of common wheat fertility on the cytoplasm of cultivated barley.

Identification of a novel homolog for a calmodulin-binding protein that is upregulated in alloplasmic wheat showing pistillody

Intracellular signaling pathways between the mitochondria and the nucleus are important in both normal and abnormal development in plants. The homeotic transformation of stamens into pistil-like structures (a phenomenon termed pistillody) in cytoplasmic substitution (alloplasmic) lines of bread wheat (Triticum aestivum) has been suggested to be induced by mitochondrial retrograde signaling, one of the forms of intracellular communication. We showed previously that the mitochondrial gene orf260 could alter the expression of nuclear class B MADS-box genes to induce pistillody. To elucidate the interactions between orf260 and nuclear homeotic genes, we performed a microarray analysis to compare gene expression patterns in the young spikes of a pistillody line and a normal line. We identified five genes that showed higher expression levels in the pistillody line. Quantitative expression analysis using real-time PCR indicated that among these five genes, Wheat Calmodulin-Binding Protein 1 (WCBP1) was significantly upregulated in young spikes of the pistillody line. The amino acid sequence of WCBP1 was predicted from the full-length cDNA sequence and found to encode a novel plant calmodulin-binding protein. RT-PCR analysis indicated that WCBP1 was preferentially expressed in young spikes at an early stage and decreased during spike maturation, indicating that it was associated with spikelet/floret development. Furthermore, in situ hybridization analysis suggested that WCBP1 was highly expressed in the pistil-like stamens at early to late developmental stages. These results indicate that WCBP1 plays a role in formation and development of pistil-like stamens induced by mitochondrial retrograde signaling.

Heteroplasmic and homoplasmic states of mitochondrial and chloroplast DNA regions in progenies of distant common wheat hybrids of different origins

The states of 18S/5S mitochondrial (mt) repeat and some chloroplast (cp) DNA regions have been investigated in alloplasmic lines of common wheat carrying cytoplasm of the barley species Hordeum marinum subsp. gussoneanum Hudson and H. vulgare L. and in the progenies of the reciprocal hybrids between Triticum aestivum L. and Secale cereale L. The heteroplasmic state of the 18/5S mt repeat, which was a result of a biparental mtDNA transmission, has been observed in rye × wheat hybrids and in their progeny carrying rye cytoplasm. For the first time, the heteroplasmic state of cpDNA associated with the heteroplasmy of 18S/5S mt repeat has been detected in cereals with the use of alloplasmic wheat lines. The transition of mt- and cpDNA heteroplasmy and barley cpDNA homoplasmy to wheat homoplasmy is associated with complete restoration of fertility and elimination of the barley chromosome from the newly developing nuclear wheat genome of alloplasmic lines.

Characterization of wheat Bell1-type homeobox genes in floral organs of alloplasmic lines with Aegilops crassa cytoplasm

BackgroundAlloplasmic wheat lines with Aegilops crassa cytoplasm often show homeotic conversion of stamens into pistils under long-day conditions. In the pistillody-exhibiting florets, an ectopic ovule is formed within the transformed stamens, and female sterility is also observed because of abnormal integument development.ResultsIn this study, four wheat Bell1-like homeobox (BLH) genes were isolated and named WBLH1 to WBLH4. WBLH1/WBLH3/WBLH4 expression was observed in the basal boundary region of the ovary in both normal pistils and transformed stamens. WBLH2 was also strongly expressed in integuments not only of normal ovules in pistils but also of the ectopic ovules in transformed stamens, and the WBLH2 expression pattern in the sterile pistils seemed to be identical to that in normal ovules of fertile pistils. In addition, WBLH1 and WBLH3 showed interactions with the three wheat KNOX proteins through the BEL domain. WBLH2, however, formed a complex with wheat KNOTTED1 and ROUGH SHEATH1 orthologs through SKY and BEL domains, but not with a wheat LIGULELESS4 ortholog.ConclusionsExpression of the four WBLH genes is evident in reproductive organs including pistils and transformed stamens and is independent from female sterility in alloplasmic wheat lines with Ae. crassa cytoplasm. KNOX-BLH interaction was conserved among various plant species, indicating the significance of KNOX-BLH complex formation in wheat developmental processes. The functional features of WBLH2 are likely to be distinct from other BLH gene functions in wheat development.

Heteroplasmy and expression of mitochondrial genes in alloplasmic and euplasmic wheat

The plant chondriome confers a complex nature. The atp4 gene (formerly called orf25) of Aegilops crassa (CR) harbors the promoter sequence of the rps7 gene from common wheat (Triticum aestivum cv. Chinese Spring, CS). The rps7 gene of CR has the promoter sequence of CS atp6. The atp6 gene of CR contains an unknown sequence inside of its coding region. Since repeat sequences have been found around the breaking points, these structural alterations are most likely generated through homologous recombination. In this study, PCR analysis was performed to detect structural alterations in each of three lines: euplasmic lines of Ae. crassa, Chinese Spring, and alloplasmic Chinese Spring wheat with the cytoplasm of Ae. crassa ((cr)-CS). We found that each of these lines contained both genotypes, although mitochondrial genotypes of CR in Chinese Spring wheat and CS genotypes in Ae. crassa were still retained as minor fractions (less than 10%). On the other hand, CS mitochondrial gene frequencies in ((cr)-CS) were shown to be ca. 30%. SNP analysis after DNA sequencing of these genes indicated that minor types of all three mitochondrial genes in alloplasmic wheat contained the mitochondrial gene types from pollens. Since the frequencies of paternal mitochondrial gene types in F(1) were about 20%, successive backcrossing increased the frequencies of paternal mitochondrial gene types to around 30% in alloplasmic wheat. Expression profiles of these mitochondrial genes were quantitatively analyzed by RT-PCR. Transcripts of paternal mitochondrial gene types were scarcely found. This suggests that minor fractions including paternal mitochondrial gene types are maintained and silenced in the descendants.

Molecular and cytological characterization of an extra acrocentric chromosome that restores male fertility of wheat in the msH1 CMS system

A new CMS system designated as 'msH1' has been reported in bread wheat using the cytoplasm of H. chilense. While testing this system in different wheat backgrounds, a highly fertile line with chromosome number 42 plus an extra acrocentric chromosome was obtained. The extra chromosome did not pair with any wheat chromosome at meiosis, and progeny from this line which lack the acrocentric chromosome showed pollen abortion and male sterility. In order to establish the origin of this chromosome, FISH using H. chilense genomic DNA as probe was used and showed that it had originated from H. chilense chromosome(s). The novel chromosome did not possess sequences similar to wheat rDNA; however, the probe pSc119.2 from S. cereale containing the 120bp family was found to occur at the end of its long arm. Data obtained from FISH and EST molecular markers confirm that the long arm of the acrocentric chromosome is indeed, the short arm of chromosome 1H(ch) from H. chilense. We suggest that the novel chromosome originated from a deletion of the distal part of the long arm of chromosome 1H(ch). Neither the 1H(ch)S short arm, nor the whole chromosome 1H(ch) restores pollen fertility of the alloplasmic wheat. Therefore, the restorer gene on the acrocentric chromosome must be located on the retained segment from the hypothetical 1H(ch)L, while some pollen fertility inhibitor could be present on the deleted 1H(ch)L distal segment. Disomic addition of the acrocentric chromosome was obtained and this line resulted fully stable and fertile.

The adaptability of wheat alloplasmic lines during hybridization

The adaptability of alloplasmic wheat lines and their hybrids with a wheat-allogenic amphiploid and wheat was studied. The influence of the nuclear genome and the interaction of nuclear and cytoplasm genomes on the adaptability of wheat and its hybrids has been established. For an assessment of adaptability, it is necessary to use a complex of attributes (morphological, cytogenetic, and resistance to abiotic and biotic factors of the environment).

Class D and Bsister MADS-box genes are associated with ectopic ovule formation in the pistil-like stamens of alloplasmic wheat (Triticum aestivum L.)

Homeotic transformation of stamens into pistil-like structures (pistillody) has been reported in cytoplasmic substitution (alloplasmic) lines of bread wheat (Triticum aestivum L.) that have the cytoplasm of a related wild species, Aegilops crassa. An ectopic ovule differentiates in the pistil-like stamen in the alloplasmic wheat. The SEEDSTICK (STK)-like class D MADS-box gene, wheat STK (WSTK), was expressed in the primordia of ectopic ovules in the pistil-like stamens as well as in the true pistil, suggesting that ectopic ovule formation results from WSTK expression in the pistil-like stamens of alloplasmic wheat. The ectopic ovule is abnormal as it fails to form complete integuments. Based on the expression pattern of WSTK and B(sister) MADS-box gene, WBsis (wheat B ( sister )), we conclude that WSTK plays a role in determination of ovule identity in the pistil-like stamen, but complete ovule development fails due to aberrant expression of WBsis.

Altered expression of wheat AINTEGUMENTA homolog, WANT-1, in pistil and pistil-like transformed stamen of an alloplasmic line with Aegilops crassa cytoplasm

Homeotic transformation of stamens into pistil-like structures, called pistillody, has been reported in some alloplasmic common wheat lines with Aegilops crassa cytoplasm. An alloplasmic line of Chinese Spring ditelosomic 7BS (CSdt7BS) with Ae. crassa cytoplasm lacking the long arm of the chromosome 7B shows pistillody, and the pistils and transformed stamens are sterile due to abnormal ovule development. To elucidate the molecular mechanism of the ovule abnormality, we compared the expression profiles of floral organs between euplasmic and alloplasmic CSdt7BS lines. Two differential display methods of mRNA profiling demonstrated that Ae. crassa cytoplasm largely affects nuclear gene expression profiles of common wheat. Of the differentially expressed genes, a wheat AINTEGUMENTA (ANT) homolog, WANT-1, was preferentially expressed in pistils but not in stamens, and accumulation of the transcript was limited to ovule primordia at the floral organ development stage. In alloplasmic wheat, WANT-1 expression was patchy and weak at the ovule-development stages. On the other hand, no significant difference in gene expression patterns of wheat AGAMOUS (AG) homologs (WAG-1 and WAG-2) was observed between fertile and sterile pistils. These results indicated that alteration of gene expression after initiation of ovule primordia results in abnormal ovule development, and that the aberrant ovule formation is at least partly associated with the weak expression of WANT-1 around ovule primordia in alloplasmic wheat with Ae. crassa cytoplasm.

Use of ccSSR markers for the determination of the purity of alloplasmic wheat in different Hordeum cytoplasms

AbstractWe tested three different consensus chloroplast simple sequence repeat (ccSSR) primers to identify amplified polymorphic products in Hordeum chilense, Hordeum vulgare and other Triticeae species with a double aim. First, to use chloroplast‐specific primers as an indirect method for the assessment of wheat cytoplasmic male sterile purity in seedlings during multiplication and in the development of alloplasmic lines. Second, to analyse cytoplasmic relationships among H. chilense accessions and between H. chilense and other members of the Triticeae tribe. The products from primer ccSSR‐4 were easily discriminated using agarose gel electrophoresis. Based on the lengths of amplification products, three groups were identified: the first included almost exclusively H. chilense accessions, the second contained H. vulgare accessions and the third comprised the wheat and the rest of the analysed accessions. Sequencing of PCR products revealed point mutations and insertions/deletions in addition to the expansion/contraction of the microsatellite repeat length. Data analyses of sequenced fragments revealed six groups of accessions among the material studied. No significant differences were found among H. chilense accessions.

Orf260cra, a Novel Mitochondrial Gene, is Associated with the Homeotic Transformation of Stamens into Pistil-Like Structures (Pistillody) in Alloplasmic Wheat

Homeotic transformation of stamens into pistil-like structures (pistillody) can occur in cytoplasmic substitution (alloplasmic) lines of bread wheat (Triticum aestivum) that have the cytoplasm of the related species, Aegilops crassa. Previously we showed that pistillody results from altered patterns of expression of class B MADS-box genes mediated by mitochondrial gene(s) in the Ae. crassa cytoplasm. The wheat cultivar Chinese Spring does not show pistillody when Ae. crassa cytoplasm is introduced. The absence of an effect is due to a single dominant gene (designated Rfd1) located on the long arm of chromosome 7B. To identify the mitochondrial gene involved in pistillody induction, we performed a subtraction analysis using cDNAs derived from young spikes of a pistillody line and a normal line. We found that mitochondrial cDNA clone R04 was abundant in the young spikes of the pistillody line but was down-regulated in the normal line that carried nuclear Rfd1. Sequencing of the full-length cDNA corresponding to clone R04 showed that two genes were present, cox I (cytochrome c oxidase subunit I) and orf260(cra). orf260(cra) shows high sequence similarity to orf256, the T. timopheevii mitochondrial gene responsible for cytoplasmic male sterility (CMS). orf260(cra) was also present in the cytoplasms of Ae. juvenalis and Ae. vavilovii, which induce pistillody, but not in the cytoplasms of other species not associated with pistillody. Furthermore, Western blot analysis revealed that the ORF260cra protein was more abundant in the pistillody line than in the normal line. We suggest therefore that orf260(cra) is associated with pistillody induction.

The Origin of a “Zebra” Chromosome in Wheat Suggests Nonhomologous Recombination as a Novel Mechanism for New Chromosome Evolution and Step Changes in Chromosome Number

An alloplasmic wheat line, TA5536, with the "zebra" chromosome z5A was isolated from an Elymus trachycaulus/Triticum aestivum backcross derivative. This chromosome was named "zebra" because of its striped genomic in situ hybridization pattern. Its origin was traced to nonhomologous chromosome 5A of wheat and 1H(t) of Elymus; four chromatin segments were derived from chromosome 1H(t) and five chromatin segments including the centromere from 5A. In this study, our objective was to determine the mechanism of origin of chromosome z5A, whether by nonhomologous recombination or by multiple translocation events. Different crossing schemes were used to recover recombinants containing various Elymus chromatin segments of the z5A chromosome. In addition, one z5AL telocentric chromosome and three z5AL isochromosomes were recovered. The dissection of the Elymus segments into different stocks allowed us to determine the chromosomal origin of the different chromosome fragments on the basis of the order of the RFLP markers employed and suggested that the zebra chromosome originated from nonhomologous recombination. We present a model of possible mechanism(s) of chromosome evolution and step changes in chromosome number applicable to a wide range of organisms.

Male fertility restoration of wheat in Hordeum chilense cytoplasm is associated with 6HchS chromosome addition

We report a new cytoplasmic male sterility (CMS) source in bread wheat (Triticum aestivum L.) designated as msH1. CMS has been identified during the process of obtaining alloplasmic bread wheat in different Hordeum chilense Roem. Schultz. cytoplasms. It was observed that when using the H. chilense H1 accession, the corresponding alloplasmic line was male sterile. This alloplasmic wheat is stable under different environmental conditions and it does not exhibit developmental or floral abnormalities, showing only slightly reduced height and some delay in heading. On examining microsporogenesis in the alloplasmic line, it was found that different stages of meiosis were completed normally, but abnormal development occurred at the uninucleate-pollen stage at the first mitosis, resulting in failure of anther exertion and pollen abortion. Fertility restoration of the CMS phenotype caused by the H. chilense cytoplasm was associated with the addition of chromosome 6HchS from H. chilense accession H1. Thus, some fertility restoration genes appear to be located in this chromosome arm. Considering the features displayed by the msH1 system, we consider that it has a great potential for the development of viable technology for hybrid wheat production.

Identification of a protein kinase gene associated with pistillody, homeotic transformation of stamens into pistil-like structures, in alloplasmic wheat

Homeotic transformation of stamens into pistil-like structures (called pistillody) has been reported in cytoplasmic substitution (alloplasmic) lines of bread wheat (Triticum aestivum) having the cytoplasm of a wild relative species, Aegilops crassa. Our previous studies indicated that pistillody is caused by alterations of the class B MADS-box gene expression pattern associated with mitochondrial gene(s) in the Ae. crassa cytoplasm. To elucidate the nuclear gene involved in the cross-talk between pistillody-related mitochondrial gene(s) and nuclear homeotic genes, we performed cDNA subtraction analysis using cDNAs derived from young spikes of a pistillody line and a normal line. As a result, we identified a protein kinase gene, WPPK1 (wheat pistillody-related protein kinase 1), which is upregulated in the young spikes of the pistillody line. RT-PCR analysis indicated that WPPK1 is strongly expressed in pistils and pistil-like stamens in the pistillody line, suggesting that it is involved in the formation of pistil-like stamens as well as pistils. The full-length cDNA sequence for WPPK1 showed high similarity with a flowering plant PVPK-1 protein kinase, and phylogenetic analysis indicated that it is a member of AGC group protein kinases. Furthermore, a phosphorylation assay indicated that it has protein kinase activity. In situ hybridization analysis revealed that WPPK1 is expressed in developing pistils and pistil-like stamens as well as in their primordia. These indicate that in the alloplasmic line, WPPK1 plays a role in formation and development of pistil-like stamens.

The nuclear–cytoplasmic interaction controls carotenoid content in wheat

In greenhouse studies of three alloplasmic wheat series, plant height, flowering date and yield per plant were least affected when the native cytoplasm was replaced by donor cytoplasm of the Triticum–Aegilops complex than when replaced by Hordeum chilense cytoplasm. On the other hand, significant differences for seed lutein content were found between euplasmic controls and their respective alloplasmic lines in all the alloplasmic lines studied, underscoring the important role of the cytoplasm to determine the seed carotenoid content. Both T. aestivum subesp. macha and Ae. squarrosa cytoplasms increased the lutein content. They may be the most useful sources of cytoplasmic variability for broadening the genetic diversity of wheat for seed carotenoid content since both cytoplasm types do not produce any detrimental effect on agronomic traits, as previously reported by other researchers. These findings demonstrate the role of the nuclear × cytoplasm interaction in the accumulation of carotenoids in wheat.

Physiological mechanisms of adaptation of alloplasmic wheat hybrids to soil drought

We studied physiological mechanisms of plant adaptation to drought for two alloplasmic wheat (Triticum aestivum L.) hybrids (APHs) on the cytoplasm of rye (Secale cereale L.) or ovate goatgrass (Aegilops ovata L.) and two standard regionalized spring wheat cultivars, Kometa and Priokskaya. In response to plant tissue dehydration, APHs rapidly reduced the transpiration rate and lost much less water than standard cultivars. During drought, peroxidase activity was significantly increased only in APH on the rye cytoplasm, whereas it declined substantially in cv. Kometa. Peroxidation of lipids (POL) was activated in cv. Kometa stronger than in hybrids, which also indicates that, in this cultivar, there was no complete detoxification of hydrogen peroxide under stress conditions. After watering resumption, APHs displayed a better capacity for reparation than standard cultivars, which was manifested in peroxidase activation and POL suppression, i.e., in more complete reduction of the oxidative stress consequences. We concluded that a higher APH drought resistance, as compared with standard cultivars, was determined by their more efficient antioxidant defense and a better capacity for recovery.