Chromosomal location of genes affecting tissue-culture response in wheat

Six ‘Chinese Spring/Triticum spelta’ substitution lines for chromosomes 1A, 1D (duplicates), 3D (duplicates), 6D, and one ‘Chinese Spring/ Marquis’ substitution line for chromosome 2B were studied for tissue-culture response (TCR). The results reported here indicate that chromosomes 2B and 6D are critical for TCR, whereas chromosome ID affects callus weight only. Chromosomes 1A and 3D were not found to be critical, however, these chromosomes may carry genes with minor effects.     

干旱胁迫对小麦染色体代换系旗叶相对含水量和离体失水速率的影响

以中国春-Synthetic 6x小麦染色体代换系及其亲本为材料,对其旗叶相对含水量(RWC)、离体叶片失水速率(RWL)进行测定。结果表明,在干旱胁迫下,1A,2D和3D代换系叶片的相对含水量及其干旱/对照值显著或极显著高于中国春,3A,3B,4B,5B,6B,1D,2D和4D代换系叶片离体失水速率及其干旱/对照值显著或极显著低于中国春。由此表明,Synthetic 6x的1A,2D和3D染色体上可能存在干旱胁迫下调控相对含水量的基因,Synthetic 6x的3A,3B,4B,5B,6B,1D,2D和4D染色体上可能存在干旱胁迫下调控离体失水速率的基因。     

Hexaploid triticales from hybrids of 'Langdon' durum D-genome substitutions with 'Gazelle' rye

The formation of unreduced gametes in some hybrids between disomic D‐genome substitutions (DS) of durum wheat cv.‘Langdon’ and rye provides a convenient approach for the rapid introduction of D‐genome chromosomes into hexaploid triticale. Meiotic pairing at metaphase I and seed fertility in spontaneous and colchicine‐induced amphidiploids derived from F₁ hybrids between a set of ‘Langdon’ DS and ‘Gazelle’ rye were analysed. The purpose was to determine the effects of the substitution of D‐genome chromosomes for their A‐ and B‐genome homoeologues on hexaploid triticale and to select stable disomic D‐genome substitutions of hexaploid triticale. The results showed that the disomic substitutions with D‐genome slightly increased the frequency of univalents (1.0‐3.13) compared with the ‘Langdon’ control primary hexaploid triticale (0.76). Substitutions 2D(2A) and 3D(3B) were partly desynaptic. The substitutions 1D(1A), 1D(1B) and 7D(7B) exhibited high seed fertility but the others had decreased fertility. Except for 2D(2A), 5D(5A), 3D(3B) and 5D(5B), 10 of the 14 possible hexaploid triticale D‐genome disomic substitutions have been obtained. The results suggest that the poor compensation ability of some D‐genome chromosomes for their homoeologous A‐ and B‐genome chromosomes is a major factor affecting meiotic stability and fertility in the hexaploid triticale D‐genome substitutions.     

Chromosome location of genes affecting polyphenol oxidase activity in seeds of common and durum wheat

This study used cytogenetic stocks to investigate the chromosomal location of genes responsible for polyphenol oxidase (PPO) activity in common and durum wheat seeds. Substitution lines of chromosome 2A of hexaploid varieties ‘Cheyenne’, ‘Thatcher’ and ‘Timstein’ in ‘Chinese Spring’ showed significantly higher PPO activity than all other substitution lines of the same variety, with the exception of substitutions of ‘Cheyenne’ chromosome 3A and ‘Thatcher’ chromosome 4B. Substitution lines of chromosome 2A of Triticum turgidum var. dicoccoides and of chromosome 2D of ‘Chinese Spring’ into the tetraploid variety ‘Langdon’ showed a significant increase in PPO activity relative to all other substitution lines in Langdon. The gene(s) responsible for high PPO activity in chromosome 2D from ‘Chinese Spring’ was mapped on the long arm within a deletion that represents 24% of the distal part of the arm. This study shows that genes located in homoeologous group 2 play a major role in the activity of PPO in wheat.     

Reciprocal substitutions analysis of freezing resistance in wheat (Triticum aestivum L.)

To investigate the effects of individual chromosomes on freezing resistance, as well as their interactions with the genetic background, reciprocal sets of chromosome substitution lines between two hard red winter wheat cultivars, ‘Cheyenne’ and ‘Wichita’, were used in this study. Duplicate lines for each chromosome were included to check background homogeneity. Two experiments were carried out in complete block designs with two replications for each duplicate. Crown and leaf water content and leaf wet weight were measured in the field experiments. Crown survival, electrolyte leakage and 50% lethality temperature (LT50) were measured in the laboratory. The results showed that ‘Cheyenne’ was more resistant than ‘Wichita’. Crown survival was significantly correlated with crown water content, crown wet weight and electrolyte leakage. Chromosomes 6A, 3B and 5D substituted from ‘Wichita’ into ‘Cheyenne’ (‘CNN‐WI’), decreased the crown survival, and increased membrane stability, crown water content and crown wet weight of ‘Cheyenne’. Thus, these chromosomes from ‘Wichita’ decreased freezing resistance in ‘Cheyenne’. Reciprocally, chromosomes 5A, 5D, 3B and 4D from ‘Cheyenne’ into ‘Wichita’ increased crown survival and decreased crown water content and crown wet weight of ‘Wichita’. It was concluded that these chromosomes from ‘Cheyenne’ cause freezing resistance in ‘Wichita’ and carry freezing‐resistance genes.     

First-division restitution in hybrids of Langdon durum disomic substitution lines with rye and Aegilops squarrosa

Durum wheat ‘Langdon’(LDN) caused a high frequency of first‐division restitution (FDR) and partial fertility in hybrids with rye, Secale cereale L., and Aegilops squarrosa L. In order to determine the genetic control of FDR, a complete set of 14 Langdon durum D‐genome disomic substitution lines (LDNDS) was crossed with ‘Gazelle’ rye and one accession (RL5286) of A. squarrosa. The microsporogenesis and fertility of the hybrids were studied. The results showed that most of the hybrids expressed a high frequency of FDR and partial fertility. However, the hybrids of 2D(2A), 4D(4A), 5D(5B) and 6D(6B) crossed with both rye and A. squarrosa, as well as 1D(1A) with A. squarrosa, had either little or no FDR and were completely sterile. These hybrids had different types of first meiotic divisions compared with LDN control hybrids. The hybrids with 2D(2A), 4D(4A) and 6D(6B) had a high frequency of random segregation of chromosomes at the first division. The hybrids with 5D(5B), as expected, showed high homoeologous pairing. The hybrid of 1D(1A) with A. squarrosa had a high frequency of equational division at first division. These results suggest that the reduced or absent FDR in such hybrids might be related to the substitution of chromosomes with an FDR gene and poor compensation ability of the D‐genome chromosomes for their homoeologous A‐ or B‐ genome chromosomes. Cytological analysis suggested that chromosome 4A in LDN most likely carries a gene for high frequency of FDR in hybrids. In addition, some monads were observed at the end of meiosis in the hybrids of 3D(3A) and 6D(6A) crossed with rye. They were formed from FDR cells that failed to divide at second division, suggesting that the LDN 3A and 6A chromosomes might carry genes for normal second division of FDR cells in the rye crosses.     

Chromosomal effects in the endogenous contents of non-structural carbohydrates and proteins measured in wheat substitution lines

In hexaploid bread wheat, Triticum aestivum (2n = 6x = 42), little work has been carried out to study the genetic control of the synthesis of reduced, non‐reduced and total non‐structural carbohydrates and soluble proteins in aerial and rooting structures. The aim of this paper was to determine the chromosomal location of genes determining carbohydrate and protein synthesis that could be used for diagnostic selection in segregating breeding populations. A set of wheat intervarietal chromosome substitution lines [‘Chinese Spring’ (CS) × synthetic wheat (Triticum diccocoides×Aegilops squarrosa) (Syn)], was used. Plants were cultivated in hydroponic solutions to the fully expanded third leaf stage. Carbohydrate and protein contents and dry matter were determined for aerial and root parts. The root dry weight did not show significant differences between the parental varieties and the substitution lines, except for 5A, 2B and 6B, which had significantly lower dry weights. The aerial dry weight was significantly higher for Syn and the 2A substitution line. The ratio aerial dry weight/root dry weight was significantly higher in Syn, 1A, 2A and 4B. The protein content of the plant showed highly significant differences between both parental lines but 6A and 1D of the substitution lines showed highly significant differences, with contents as high as that for Syn. Syn produced significantly lower total aerial carbohydrates. The substitution lines 2A, 5A, 6A, 7A, 2B, 3D, 5D and 6D showed highly significant total carbohydrate content increases in the aerial parts compared with both parental lines. The non‐reduced carbohydrate contents showed a pattern similar to that of the total carbohydrates. Syn had a lower reduced carbohydrate content than CS. Only the 5A, 2B, and 1D substitution lines had a highly significantly different content of reduced carbohydrates than CS. In roots, Syn produced the lowest values for every type of sugar. The highest significant values for total carbohydrates were found in substitution lines 2B, 4B, 5B, 6B, 1D and 6D. The non‐reduced carbohydrate levels were significantly higher than CS in 2B, 5B, 6B and 6D substitution lines. Only the substitution lines 3B and 1D showed a significantly higher reduced carbohydrate content in roots compared with CS. The photoassimilate partitioning in Syn, 1 A, 2A and 4B favoured the aerial parts but, in contrast, higher partitioning to the roots was found in the 7B, 1D and 3D substitution lines. Both groups appear to carry interesting patterns worth incorporating in wheat cultivars.     

Cytological analyses of hybrids and derivatives of hybrids between durum wheat and Thinopyrum bessarabicum,using multicolour fluorescent GISH*

The wheat progenitors and other wild relatives continue to be important sources of genes for agronomically desirable traits, which can be transferred into durum wheat (Triticum turgidum; 2n = 4x = 28; AABB genomes) cultivars via hybridization. Chromosome pairing in durum × alien species hybrids provides an understanding of genomic relationships, which is useful in planning alien gene introgression strategies. Two durum cultivars, ‘Lloyd’ and ‘Langdon’, were crossed with diploid wheatgrass, Thinopyrum bessarabicum (2n = 2x = 14; JJ), to synthesize F₁ hybrids (2n = 3x = 21; ABJ) with Ph1. ‘Langdon’ disomic substitution 5D(5B) was used as a female parent to produce F₁ hybrids without Ph1, which resulted in elevation of pairing between durum and grass chromosomes – an important feature from the breeding standpoint. The F₁ hybrids were backcrossed to respective parental cultivars and BC₁ progenies were raised. ‘Langdon’ 5D(5B) substitution × Th. bessarabicum F₁ hybrids were crossed with normal ‘Langdon’ to obtain BC₁ progeny. Chromosome pairing relationships were studied in F₁ hybrids and BC₁ progenies using both conventional staining and fluorescent genomic in situ hybridization (fl‐GISH) techniques. Multicolour fl‐GISH was standardized for characterizing the nature and specificity of chromosome pairing: A–B, A–J and B–J pairing. The A–J and B–J pairing will facilitate gene introgression in durum wheat. Multicolour fl‐GISH will help in characterizing alien chromosome segments captured in the durum complement and in their location in the A and/or B genome, thereby accelerating chromosome engineering research.     

Frost resistance of 'Chinese Spring'/'Cheyenne' chromosome substitution lines under short- and long-day hardening conditions

Investigations were carried out under phytotronic conditions to study the effect of daylength on the frost resistance of a ‘Chinese Spring’/‘Cheyenne’ chromosome substitution series. The frost resistance of the 5A, 7A, 4B, 5B, 1D and 5D lines was significantly better when raised and hardened with long-day (16 h) rather than short-day (8h) illumination. The frost resistance-increasing effect of daylength could be demonstrated after freezing lines 5A and 5D at both - 10°C and -12°C. An increase in the duration of illumination in the course of preliminary growth and hardening promoted the development of a higher level of frost resistance. This positive effect was most pronounced for chromosome substitution lines, where the frost resistance was significantly better than that of ‘Chinese Spring’ even with normal daylengths.     

干旱胁迫对小麦叶片细胞膜透性效应的染色体定位研究

通过测定干旱胁迫下小麦中国春-Synthetic 6x染色体代换系及其亲本品种中国春(受体)和Synthetic 6x(供体)叶片的相对电导率和K 相对渗出率,对调控干旱胁迫下功能叶片细胞膜稳定性的染色体进行了定位研究。结果表明,1D,2D,2B,3A,3D,4A,4B,6A,6B,7D和7A等染色体代换系的相对电导率和K 相对渗出率均显著或极显著低于中国春,而其他代换系差异均不显著。表明Synthetic 6x的1D,2B,2D,3A,3D,4A,4B,6A,6B,7D和7A染色体上具有耐旱性基因,而其他染色体与Synthetic 6x的耐旱性无关。研究结果可为小麦抗旱遗传育种研究提供参考依据。     

Chromosomal Assignment of Three Enzyme Coding Loci (Icd1, Nad-Mdh1 and Aco1) Using Primary Trisomics in Beet (Beta vulgaris L.)

Resistance to Septoria nodorum was investigated in seedlings of an amphiploid generated from Triticum dicoccum Shübl. and Aegilops squarrosa Tausch, and in a series of substitution lines of single chromosomes from this synthetic hexaploid into Triticum aestivum cv. ‘Chinese Spring’ in three tests to determine the chromosomal location of resistance. From the Ae. squarrosa parent (D genome), chromosome 5D was found to confer a high level of resistance, reducing lesion cover to near that of the amphiploid in the three tests. Chromosomes 3D, and to a lesser extent, 7D were also found to confer significant resistance to the amphiploid. Three chromosomes, 2A, 3B and 5A, from the T. dicoccum parent (AB genomes) also conferred resistance but to a lesser extent than 7D. Two chromosomes, 2B and 2D, caused a significant decrease in resistance. ‘Chinese Spring’ may thus carry genes for resistance to S. nodorum on these chromosomes which are absent in the synthetic hexaploid.     

Nitrogen and phosphorus uptake and utilization efficiency in D(R) substitution lines of hexaploid triticale

Two sets of disomic substitution lines, derived from the cultivars ‘Presto’ and ‘Rhino’ of triticale, with rye chromosome pairs replaced by their wheat D‐genome homoeologues, were tested in hydroponic culture for nitrogen and phosphorus uptake and utilization efficiency. The effect of a substitution on the amount of absorbed nutrients was predominantly negative and proportional to the effect on plant dry matter. Significant decreases were found for the substitutions 5D(5R), 6D(6R) of both cultivars, 2D(2R), 4D(4R) of ‘Presto’ and 3D(3R) of ‘Rhino’. On the other hand, the nitrogen utilization efficiency was significantly increased in all substitution lines, with the exception of the 1D(1R) ones. The differences in phosphorus utilization were generally positive, but less pronounced, and significant only in the lines 2D(2R) and 6D(6R). The data suggest that presence of both rye and D‐genome chromosomes is conducive for the best effect of the applied N and P fertilizers.     

The effect of single D-genome chromosomes on aluminum tolerance of triticale

Aluminum tolerance of two sets of hexaploidtriticale (×Triticosecale Wittmack)lines with disomic substitutions of theD-genome chromosomes from Triticumaestivum L. was analyzed by themodified-pulse method. Of the 20substitution lines in winter triticalePresto, and 18 lines of spring triticaleRhino, six and nine lines, respectively,showed improved tolerance relative to thatobserved in the control lines. The D-genomechromosomes in substitutions 1D(1B),3D(3A), 3D(3B), 4D(4A), 4D(4B) and 6D(6B)significantly (p<0.01) improved Altolerance in both sets of lines. Highpercentages of tolerant plants were alsoobserved in 2D(2B) and 5D(5A) substitutionsin Presto and in 2D(2A), 2D(2B), 5D(5B),6D(6A) and 7D(7A) substitution lines ofRhino. In no instance, the removal ofindividual rye chromosomes, bysubstitutions, improved Al tolerance of therecipient line. Moreover, the presence of acomplete rye genome, and especially ofchromosome 3R, was necessary for triticale'stolerance to aluminum. The results alsoindicated some effects of allelic variationpresent on both rye and wheat chromosomes,and a possibility of interactions ofvarious factors.     

Influence of water availability on fertility restoration of CMS lines with the 'M35', A4 and '9E' CMS-inducing cytoplasms of sorghum

Male fertility restoration in new types of sorghum cytoplasmic male sterility‐inducing cytoplasms (A4, ‘9E’, ‘M35’), characterized by the formation of non‐dehiscent anthers, is difficult. Lines with fertility‐restorer genes for these unique cytoplasms do occur, but rarely, and when found tend to be unstable in their inheritance and expression. The aim of this research was to explore reasons for this instability. Seven lines in three unique cytoplasms, ‘9E’, A4 and ‘M35’, and six lines that restore with these cytoplasms were grown at the Agricultural Research Institute for South‐East Region in Saratov, Russia from 1993 to 2004. Levels of male fertility restoration and various environmental factors were recorded. It is reported that for sorghum hybrids in the A4, ‘9E’ and ‘M35’ male‐sterile cytoplasms, the level of plant male fertility is determined by the level of water available to plants during anther and pollen formation that which ‘switches on’ the expression of fertility‐restoring genes, and is possibly involved in an unusual type of male fertility inheritance in these cytoplasms. The creation of reliable line‐fertility restorers capable of the restoration of male fertility of F₁ hybrids in ‘M35’ cytoplasm under conditions of water stress is also reported. Current research explore mechanisms involved possible in responses to water levels at various growth stages and their influence on fertility within these cytoplasms.     

Monosomic analysis of Helminthosporium leaf blight resistance genes in wheat

A set of 21 monosomic (2n ‐ 1) and the disomic (2n) lines of the ‘Chinese Spring’ cultivar were crossed with ‘Chirya‐3′, the CIMMYT synthetic wheat line which has been identified as highly resistant for Helminthosporium leaf blight disease (HLB), in order to locate the genes governing disease resistance. The F₁ and segregating populations were challenged and screened against the most virulent pure mono‐conidial HLB isolate KL‐8 (Karnal, India). The F₁ progenies of the crosses were found to be susceptible because of the recessive nature of resistance. The F₂ progeny of the control cross (‘Chinese Spring’בChirya‐3’), segregated in the ratio of 1: 15 (resistant: susceptible), indicating that resistance to HLB was controlled by a pair of recessive genes. While the F₂ progeny of 19 monosomic crosses segregated in the ratio of 1: 15 (resistant: susceptible), the progeny of the remaining two crosses, 7B and 7D, deviated significantly from the ratio, revealing that 7B and 7D were the critical chromosomes for resistance genes that were located one on each chromosome. Moreover, the critical lines, 7B and 7D, confirmed the digenic complementary recessive nature of gene action by fitting well with the overall pooled F₂ segregation ratio of 13: 51 (resistant: susceptible) as expected for digenic complementary recessive resistance. The F₃ segregation ratios of the critical crosses, based on their pooled F₂ analysis, was estimated as 19: 32: 13 (non‐segregating susceptible: segregating as susceptible and resistant: non‐segregating resistant). F₃ progenies when tested with these ratios showed goodness‐of‐fit, confirming that the two pairs of recessive resistance genes were located on chromosomes 7B and 7D.     

Evaluation of cold hardiness in two sets of near-isogenic lines of wheat (Triticum aestivum) with polymorphic vernalization alleles

In wheat, variation at the orthologus Vrn‐1 loci, located on each of the three genomes, A, B and D, is responsible for vernalization response. A dominant Vrn‐1a allele on any of the three wheat genomes results in spring habit and the presence of recessive Vrn‐1b alleles on all three genomes results in winter habit. Two sets of near‐isogenic lines (NILs) were evaluated for DNA polymorphisms at their Vrn‐A1, B1 and D1 loci and for cold hardiness. Two winter wheat cultivars, ‘Daws’ and ‘Wanser’ were used as recurrent parents and ‘Triple Dirk’ NILs were used as donor parents for orthologous Vrn‐1 alleles. The NILs were analysed using molecular markers specific for each allele. Only 26 of 32 ‘Daws’ NILs and 23 of 32 ‘Wanser’ NILs had a plant growth habit that corresponded to the marker genotype for the markers used. Freezing tests were conducted in growth chambers programmed to cool to ?21.5°C. Relative area under the death progress curve (AUDPC), with a maximum value of 100 was used as a measure of death due to freezing. The average relative AUDPC of the spring habit ‘Daws’Vrn‐A1a NILs was 86.15; significantly greater than the corresponding winter habit ‘Daws’Vrn‐A1b NILs (42.98). In contrast, all the ‘Daws’Vrn‐A1bVrn‐B1aVrn‐D1b and Vrn‐A1bVrn‐B1bVrn‐D1a NILs (spring habit) had relative AUDPC values equal to those of their ‘Daws’ sister genotypes with Vrn‐A1bVrn‐B1bVrn‐D1b NILs (winter habit). The average AUDPC of spring and winter habit ‘Wanser’ NILs differed at all three Vrn‐A1, Vrn‐B1 and Vrn‐D1 locus comparisons. We conclude that ‘Daws’ and ‘Wanser’ have different background genetic interactions with the Vrn‐1 loci influencing cold hardiness. The marker for Vrn‐A1 is diagnostic for growth habit and cold hardiness but there is no relationship between the Vrn‐B1 and Vrn‐D1 markers and the cold tolerance of the NILs used in this study.     

Plant survival after freezing in wheat 'Cappelle Desprez' ('Bezostaya 1') intervarietal chromosome substitution lines

The effect of individual chromosomes of the wheat variety ‘Bezostaya 1’ on plant resistance to low temperatures was studied using the available set of intervarietal ‘Cappelle Desprez’ (‘Bezostaya 1’) chromosome substitution lines. The number of plants surviving after freezing at ?12, ?15 and ?17°C was determined for both parents and lines in trials in 2004/2005 and 2005/2006. Significant differences between the three temperature treatments and between lines were found, implying that two factors, the level of temperature stress and chromosome substitutions, were influencing plant survival. Improved frost resistance in both trials was associated with genes located on five chromosomes: 5A, 2D, 4A, 5D and 6A. An increase in the plant frost resistance because of the effects of 7A and 1A chromosomes was also observed in the 2005/2006 trial, when the overall autumn and winter (January) temperatures were lower than in 2004/2005.     

Genetic Control of Vernalization, Day-length Response, and Earliness per se by Homoeologous Group-3 Chromosomes in Wheat

To identify homoeologous group-3 chromosomes that carry genes for vernalization, day-length responses, and earliness per se, a series of aneuploid lines (mono-somics and tetrasomics) and chromosome-substitution lines in ‘Chinese Spring’ (CS) were surveyed under different vernalization and day-length regimes in controlled environments. The results indicated that genes on all three chromosomes of group 3 can have striking effects on ear-emergence time. The replacement of CS 3B by its homologues in ‘Lutescens 62’ and ‘Cheyenne’ produced an increased insensitivity to vernalization, while 3B homologues from ‘Ceska Presivka’ gave CS a remarkable sensitivity to vernalization. This provided evidence for multiple allelism at a new Vrn locus on chromosome 3B. A negative association between gene dosage and day-length response was found in CS 3D which was thought to carry a gene for promoting insensitivity to day-length. The behaviour of CS monosomic 3A and CS (Timstein 3A), in reducing numbers of days to heading independently of environmental stimuli, suggested the presence of earliness per se genes on this chromosome.     

Utilization of Intervarietal Chromosome Substitutions in Breeding Winter Wheat

Using monosomic lines of wheat cultivars ‘Palur’ and ‘Compal’ as recipient parents as well as disomic substitution lines of chromosomes 5A and 5D of the wheat cv. ‘Atlas 66’, F₃-populations and BC₁′- to BC₃′-populations with limited and free recombination of the 20 and 21 parental chromosomes, respectively, were realized and tested in field trials in comparison to the corresponding recipient cvs. ‘Palur’ and ‘Compal’. F₃- and BC'-populations with the homozygous chromosomes 5A and 5D of the wheat cv. ‘Atlas 66’ expressed higher and more stable grain protein values than the comparable populations with free recombination of the same chromosomes. The grain protein content of populations with limited recombination was significantly increased compared with the recipient cultivars. Some advantages of using intervarietal substitutions in wheat breeding are discussed.