C-banding pattern and meiotic pairing in five rye chromosomes of hexaploid triticale

Summary The meiotic behaviour of rye chromosomes 1R, 2R, 3R, 6R and 7R/4R of hexaploid triticale Cachirulo is analyzed using the C-banding technique. These chromosomes show different C-banding patterns and present different pairing levels at metaphase I. A decreasing effect of large telomeric heterochromatin bands on pairing is deduced from the following two main facts: i) The chromosome 7R/4R shows the highest pairing associated with the smallest amount of heterochromatin, ii) pairing levels of 2 R short arm and 3 R long arm which carry large telomeric bands are less than their respective long and short arms lacking telomeric heterochromatin. Possible desynaptic effects of heterochromatin are discussed although an asynaptic effect cannot be rejected.     

Role of rye chromosomes in improvement of zinc efficiency in wheat and triticale

Using the disomic wheat-rye addition lines (Triticum aestivum L., cv. Holdfast-Secale cereale L., cv. King-II) and an octoploid triticale line (xTriticosecale Wittmark L. "PlutoxFakon") as well as the respective wheat and rye parents, greenhouse experiments were carried out to study the role of rye chromosomes on the severity of Zn deficiency symptoms, shoot dry matter production, Zn efficiency, shoot Zn concentration and Zn content. Plants were grown in a Zn-deficient calcareous soil with (10 mg Zn kg-1 soil) and without Zn supply. Zinc efficiency was calculated as the ratio of dry weight produced under Zn deficiency to the dry weight produced under Zn fertilization. In the experiments with addition lines, visual Zn deficiency symptoms were slight in the rye cultivar King-II, but were severe in the wheat cultivar Holdfast. The addition of rye chromosomes, particularly 1R, 2R and 7R, into Holdfast reduced the severity of deficiency symptoms. Holdfast showed higher decreases in shoot dry matter production by Zn deficiency and thus had a low Zn efficiency (53 %), while King-II was less affected by Zn deficiency and had a higher Zn efficiency (89 %). With the exception of the 3R line, all addition lines had higher Zn efficiency than their wheat parent: the 1R line had the highest Zn efficiency (80 %). In the experiment with the triticale cultivar and its parents, rye cv. Pluto and wheat cv. Fakon, Zn deficiency symptoms were absent in Pluto, slight in triticale and very severe in Fakon. Zinc efficiency was 88 % for Pluto, 73 % for triticale and 64% for Fakon. Such differences in Zn efficiency were better related to the total amount of Zn per shoot than to the amount of Zn per unit dry weight of shoot. Only in the rye cultivars, Zn efficiency was closely related with Zn concentration. Triticale was more similar to rye than wheat regarding Zn concentration and Zn accumulation per shoot under both Zn-deficient and Zn-sufficient conditions.The results presented in this study show that rye has an exceptionally high Zn efficiency, and the rye chromosomes, particularly 1R and 7R carry the genes controlling Zn efficiency. To our knowledge, the result with triticale and its rye parents is the first report showing that the genes controlling Zn efficiency in rye are transferable into wheat and can be used for development of new wheat varieties with high Zn efficiency for severely Zn-deficient conditions.     

Possible role of β-endoglucanase in the degradation of the cell wall polysaccharides in more and less resistant to pre-harvest sprouting triticale varieties

The β-endoglucanase is one of the enzymes taking part in the degradation of the cell wall structural polysaccharides. The use of two Triticale varieties differing in their resistance to the preharvest sprouting allowed the comparison of that enzyme activity and changes in the internal structure of the cell wall observed in the light and electron microscope. The most interesting observations seem to be the channels and even the holes in the walls of aleurone cells found mostly in the samples showing the elevated activities of β-endoglucanase. As those samples concern the grains of a lower resistance to pre-harvest sprouting, it might be suggested that the loosening of the wall structure may be one of the probable mechanisms in facilitating the enzyme, metabolite and water translocations through the grain tissues. Those changes can accelerate the water imput into the grain, the metabolic process and thus the increased susceptibility to sprouting.     

Abscisic acid and the pre-harvest sprouting in cereals

Pre-harvest sprouting (PHS) leads to loss of grain weight and a reduction in the end use quality of kernels in cereals, especially in wheat, and PHS in rice also becomes a more and more serious problem recent years. Many factors are involved in the controlling this complex trait. Only recently, we have reported the large scale screening and charactersation of the rice phs mutants, providing insight into the molecular mechanism of pre-harvest sprouting in rice. It has been shown that mutations of genes in synthesis of the carotenoid precursors of ABA resulted in the pre-harvest sprouting, which is consequence of ABA deficiency, and photobleaching is likewise due to the absence of photoprotective carotenoids. The further study of all different rice phs mutants will help us to elucidate the complex phenomena and finally capture the target for improving PHS in rice or other cereals.Key words: pre-harvest sprouting, ABA, carotenoids, rice     

Physical mapping of the 5S rRNA multigene family in 6x triticale and rye: identification of a new rye locus.

In situ hybridization was used to physically map the 5S rRNA multigene family in three selected lines of hexaploid triticale and five lines of diploid rye. Using this technique, evidence for a new locus on the 3RS arm of the three triticale lines was first obtained, as well as confirmation of the presence of 5S rRNA loci on wheat and rye chromosomes of homoeologous groups 1 and 5. The new locus on the 3RS arm was confirmed in two lines of rye, Secale cereale L., although it was not present in the other rye varieties studied. We propose that the new 5S rRNA locus be referred to as 5SDna-R3.     

Cytogenetic investigations in rye,wheat and triticale

Summary Chromosomes of tetra- and hexaploid wheat have been individually characterized by Giemsa and/or Leishman C-banding techniques. Appropriate methodological modifications resulted in almost identical staining of chromosomes of tetraploid wheat with Giemsa and Leishman solutions. Additionally comparison of Giemsa banded chromosomes of the A- and B-genome of Triticum turgidum 34 and Triticum aestivum cv Jubilar reveals similar or corresponding patterns in all homologous chromosomes with the exception of chromosome 7B. Apart from this intervarietal variation in certain homologous chromosomes of both wheat cultivars, intravarietal polymorphism is verified.     

小麦穗发芽鉴定方法的比较与分析

穗发芽是小麦生产中较为严重的灾害之一,易受外界环境的影响,一旦发生不仅会影响产量,而且还会严重影响小麦的品质,因此培育抗穗发芽的小麦品种至关重要。该研究通过对65份小麦材料进行穗发芽试验,比较分析了小麦穗发芽抗性的常用方法,即籽粒发芽法、整穗发芽法和大田穗发芽法。结果表明:三种方法之间均呈极显著正相关关系,而且在1%水平上均存在极显著性差异;发芽指数与籽粒发芽率的相关性最高,能够更好地评价小麦材料的休眠特性,但不能得出材料的总体抗性;籽粒发芽法和整穗发芽法的变异程度相对较小,试验条件更易控制,可作为小麦穗发芽抗性评价的简易方法;多数参试材料的平均籽粒发芽率平均整穗发芽率平均大田穗发芽率,且三者差异程度均达到极显著水平,这说明麦穗的外部结构及外部环境对小麦穗发芽的影响显著。因此,籽粒发芽法可以从休眠性方面,对小麦种子资源进行初步筛选;整穗发芽法可用于穗发芽抗性的进一步鉴定和验证,评价小麦材料穗发芽的综合抗性;大田穗发芽法较易受自然条件的影响、变异程度较大,其结果可以作为室内发芽试验的参考数据。     

Association mapping for pre-harvest sprouting resistance in white winter wheat

Association mapping identified quantitative trait loci (QTLs) and the markers linked to pre-harvest sprouting (PHS) resistance in an elite association mapping panel of white winter wheat comprising 198 genotypes. A total of 1,166 marker loci including DArT and SSR markers representing all 21 chromosomes of wheat were used in the analysis. General and mixed linear models were used to analyze PHS data collected over 4 years. Association analysis identified eight QTLs linked with 13 markers mapped on seven chromosomes. A QTL was detected on each arm of chromosome 2B and one each on chromosome arms 1BS, 2DS, 4AL, 6DL, 7BS and 7DS. All except the QTL on 7BS are located in a location similar to previous reports and, if verified, the QTL on 7BS is likely to be novel. Principal components and the kinship matrix were used to account for the presence of population structure but had only a minor effect on the results. Although, none of the QTLs was highly significant across all environments, a QTL on the long arm of chromosome 4A was detected in three different environments and also using the best linear unbiased predictions over years. Although previous reports have identified this as a major QTL, its effects were minor in our biparental mapping populations. The results of this study highlight the benefits of association mapping and the value of using elite material in association mapping for plant breeding programs.     

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.     

Chiasma distribution in rye chromosomes of diploid rye and in wheat/rye addition lines in relation to C-heterochromatin

Summary In five genetically different inbred lines of rye and in the seven Chinese Spring/Imperial wheatrye addition lines, chiasma distribution in rye chromosomes was studied with respect to the amount and position of constitutive heterochromatin (Giemsa C-bands). In all inbred lines, rye chromosomes with one primary terminal band were more frequently found as univalents than those with primary bands on both telomeres. These chromosomes were most probably 5R and/or 6R. In the addition lines a highly significant reduction in the number of arms bound by chiasmata was found for rye chromosomes 5R and 6R. Because of the similar chiasma distribution in the inbred lines and in the rye chromosomes of the addition lines, no effect of the wheat genome on the number of chiasmata in the rye chromosomes can be ascertained. However, a relationship between chiasma frequency and chromosome arm length seems to exist, since under reduced chiasma conditions the two shortest arms of the rye complement, those of chromosomes 5R and 6R, frequently fail to form a chiasma. No effect of the large blocks of constitutive heterochromatin in the telomeres of the rye chromosomes on the position of chiasmata within a bivalent could be established.This study was financially supported by the Deutsche Forschungsgemeinschaft     

C-banded wheat chromosomes in wheat and triticale

Summary The C-banding patterns of wheat chromosomes in 7 hexaploid triticale and 7 wheat genotypes are described and compared. All 14 wheat chromosome pairs were individually identified in the triticales and a tetraploid wheat, and all the B and two A genome chromosome pairs in the hexaploid wheat genotypes. Little variation was found between genotypes in the distribution of C-bands but considerable variation was found in their size, total number and total length.     

Genes controlling seed dormancy and pre-harvest sprouting in a rice-wheat-barley comparison

Pre-harvest sprouting results in significant economic loss for the grain industry around the world. Lack of adequate seed dormancy is the major reason for pre-harvest sprouting in the field under wet weather conditions. Although this trait is governed by multiple genes it is also highly heritable. A major QTL controlling both pre-harvest sprouting and seed dormancy has been identified on the long arm of barley chromosome 5H, and it explains over 70% of the phenotypic variation. Comparative genomics approaches among barley, wheat and rice were used to identify candidate gene(s) controlling seed dormancy and hence one aspect of pre-harvest sprouting. The barley seed dormancy/pre-harvest sprouting QTL was located in a region that showed good synteny with the terminal end of the long arm of rice chromosome 3. The rice DNA sequences were annotated and a gene encoding GA20-oxidase was identified as a candidate gene controlling the seed dormancy/pre-harvest sprouting QTL on 5HL. This chromosomal region also shared synteny with the telomere region of wheat chromosome 4AL, but was located outside of the QTL reported for seed dormancy in wheat. The wheat chromosome 4AL QTL region for seed dormancy was syntenic to both rice chromosome 3 and 11. In both cases, corresponding QTLs for seed dormancy have been mapped in rice.C. Li and P. Ni contributed equally to this work     

QTL mapping of pre-harvest sprouting resistance in a white wheat cultivar Danby

Key message

One major and three minor QTLs for resistance to pre-harvest sprouting (PHS) were identified from a white wheat variety “Danby.” The major QTL on chromosome 3A is TaPHS1, and the sequence variation in its promoter region was responsible for the PHS resistance. Additive?×?additive effects were detected between two minor QTLs on chromosomes 3B and 5A, which can greatly enhance the PHS resistance.

Abstract

Pre-harvest sprouting (PHS) causes significant losses in yield and quality in wheat. White wheat is usually more susceptible to PHS than red wheat. Therefore, the use of none grain color-related PHS resistance quantitative trait loci (QTLs) is essential for the improvement in PHS resistance in white wheat. To identify PHS resistance QTLs in the white wheat cultivar “Danby” and determine their effects, a doubled haploid population derived from a cross of Danby?×?“Tiger” was genotyped using genotyping-by-sequencing markers and phenotyped for PHS resistance in two greenhouse and one field experiments. One major QTL corresponding to a previously cloned gene, TaPHS1, was consistently detected on the chromosome arm 3AS in all three experiments and explained 21.6–41.0% of the phenotypic variations. A SNP (SNP?222) in the promoter of TaPHS1 co-segregated with PHS in this mapping population and was also significantly associated with PHS in an association panel. Gene sequence comparison and gene expression analysis further confirmed that SNP?222 is most likely the causal mutation in TaPHS1 for PHS resistance in Danby in this study. In addition, two stable minor QTLs on chromosome arms 3BS and 5AL were detected in two experiments with allele effects consistently contributed by Danby, while one minor QTL on 2AS was detected in two environments with contradicted allelic effects. The two stable minor QTLs showed significant additive?×?additive effects. The results demonstrated that pyramiding those three QTLs using breeder-friendly KASP markers developed in this study could greatly improve PHS resistance in white wheat.

     

Identification of the chromosomes showing neocentric activity in rye

Summary Chromosomes showing neocentric activity were identified with the aid of the C-banding technique in an inbred line of rye, 1940-129 of cv. Stålråg. The frequency of cells with neocentrics varied from 34 to 35.7% at first anaphase, and from 32 to 68% at second metaphase. In most cells only one chromosome showed the activity. It always belonged to the group 4-5-6R, and in cells where individual identification of chromosomes was possible the activity was invariably located at the telomere of the arm 4RS. When in rare cases two or three chromosomes were active, one chromosome again belonged to the group 4-5-6R, the other was identified in four cells as a member of the group 2-3-7R, but it is possible that all the telomeres with a prominent C-band can occasionally show the activity. It is assumed that certain telomeric regions remain in the active state at both meiotic divisions and offer secondary accumulation sites for kinetochoric proteins.     

Proteomic analysis of developing rye grain with contrasting resistance to preharvest sprouting

Significant differences in the two-dimensional electrophoresis patterns of proteins from developing rye grain were found to be associated with resistance and susceptibility to preharvest sprouting (PHS). Mass spectrometry of individual spots showing different abundance in PHS-resistant and PHS-susceptible lines identified proteins involved in: reaction to biotic and abiotic stresses, including oxidative stress, energy metabolism and regulation of gene expression. Highly differentiated abundance of proteins found in developing grain suggest that the diversification of processes leading to developing PHS resistance or PHS susceptibility starts from an early stage of grain development. A part of the identified proteins in rye grain were also reported to be associated with PHS in wheat and rice, which suggests that some mechanisms affecting precocious germination might be common for different cereal species.