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.     

Molecular and physical mapping of genes affecting awning in wheat

Quantitative trait loci (QTL) for three traits related to awning (awn length at the base, the middle and the top of the ear) in wheat were mapped in a doubled‐haploid line (DH) population derived from the cross between the cultivars ‘Courtot’ (awned) and ‘Chinese Spring’ (awnless) and grown in Clermont‐Ferrand, France, under natural field conditions. A molecular marker linkage map of this cross that was previously constructed based on 187 DH lines and 550 markers was used for the QTL mapping. The genome was well covered (more than 95%) and a set of anchor loci regularly spaced (one marker every 20.8 cM) was chosen for marker regression analysis. For each trait, only two consistent QTL were identified with individual effects ranging from 8.5 to 45.9% of the total phenotypic variation. These two QTL cosegregated with the genes Hd on chromosome 4A and B2 on chromosome 6B, which are known to inhibit awning. The results were confirmed using ‘Chinese Spring’ deletion lines of these two chromosomes, which have awned spikes, while ‘Chinese Spring’ is usually awnless. No quantitative trait locus was detected on chromosome 5A where the B1 awn‐inhibitor gene is located, suggesting that both ‘Courtot’ and ‘Chinese Spring’ have the same allelic constitution at this locus. The occurrence of awned speltoid spikes on the deletion lines of this chromosome suggests that ‘Chinese Spring’ and ‘Courtot’ have the dominant B1 allele, indicating that B1 alone has insufficient effect to induce complete awn inhibition.     

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.     

Substitution analysis of drought tolerance in wheat (Triticum aestivum L.)

Chromosome substitution lines of the wheat variety ‘Cappelle Desprez’ into ‘Chinese Spring’ were tested for drought tolerance in growth chambers in the Martonvásár phytotron. Three different moisture regimes were created: E1, fully irrigated control; E2, mid-season water stress (preanthesis); and E3, terminal water-stress during grain filling. Data were analysed to estimate the chromosomal location of the genes controlling relative water-content (RWC), relative water-loss (RWL), drought-susceptibility index (DSI) and phenotypic stability in each substitution line. Simultaneous consideration indicated that most of the genes controlling these characters are located on chromosomes 1A, 5A, 7A,4B, 5B, 1D, 3D and 5D.     

The effects of whole chromosome substitutions differing in alleles for hybrid dwarfing and photoperiodic sensitivity on tissue culture response (TCR) in wheat

Summary The wheat varieties Chinese Spring, Marquis and Thatcher and five intervarietal Chinese Spring substitution lines for chromosomes 2B (2 lines), 2D (2 lines) and 4A^*, differing from the recipient variety in alleles for hybrid dwarfing genes and/or the photoperiodic response genes were analysed for tissue culture response (TCR). It could be demonstrated that only chromosome 2B has a major effect on TCR. Allelic variation at the hybrid dwarfing loci seems to have no effect on tissue culture performance, even in the combination D1D2D3 which gives the grass dwarf phenotype. Also the allelic constitution at the Ppd loci, gave no indication for a direct major effect of those alleles, however there seems to exist genetical factors for TCR on the homoeologous group 2 chromosomes which may be closely linked to the Ppd loci.     

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。     

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.     

Substitution Analysis of Plant Regeneration from Callus Culture in Wheat

The genetic determination of the plant regeneration ability of tissue cultures arising from immature embryos was studied using a ‘Chinese Spring’/‘Cheyenne’ substitution series. Plant regeneration proved to be polygenically determined. In tile current experiment the chromosomes 7B, 7D and ID were found to be effective, although the possibility of other chromosome effects cannot be excluded.     

Detection of chromosomes carrying genes for seed dormancy of wheat using the backcross reciprocal monosomic method

Preharvest sprouting (PHS) in wheat represents a major constraint to the production of high‐quality grain. Genetic variation for tolerance to PHS is associated with seed dormancy. The present study was initiated to detect homologous chromosome variation associated with seed dormancy genes in a PHS tolerant cultivar ‘Zenkojikomugi’ (Zen) and ‘Chinese Spring’ (CS) using the backcross reciprocal monosomic method. The most striking effect on variation in seed dormancy was associated with chromosome 3A, and followed by group 4 chromosomes. These chromosomes of Zen increased dormancy compared with the respective CS homologues. Chromosomes 2D and 7D of Zen, and 6A of CS seemed to contribute smaller positive effects on dormancy. Chromosomes 2A of CS and Zen, as well as 3B, were equally effective in enhancing dormancy. The chromosome 3 A factors were independent of the grain‐colour gene R‐A1 because Zen was found to carry the white‐grained R‐A1a allele, which was identical to that of CS, and there was no difference in dormancy between the reciprocal F₁ seeds.     

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.     

Fluorescence in situ hybridization polymorphism using two repetitive DNA clones in different cultivars of wheat

Twenty‐two wheat cultivars and a wheat line were analysed with two‐colour fluorescence in situ hybridization (FISH) using the pSc119.2 and pAs1 repetitive DNA clones to detect if polymorphism could be observed in the hybridization patterns of different wheat cultivars. The FISH hybridization pattern of ‘Chinese Spring’ was compared with wheat cultivars of different origins. Differences were observed in the hybridization patterns of chromosomes 4A, 5A, 1B, 2B, 3B, 5B, 6B, 7B, 1D, 2D, 3D and 4D. Although a low level of polymorphism exists in the FISH pattern of different wheat cultivars, it is possible to identify 17 pairs of chromosomes according to their hybridization patterns with these two probes. This study will help to predict the expected variation in the FISH pattern when analysing wheat genetic stocks of different origin. It is presumed that variation in hybridization patterns are caused by chromosome structural rearrangements and by differences in the amount and location of repetitive sequences in the cultivars analysed.     

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.     

Substituting Ability of Individual Barley Chromosomes for Wheat Chromosomes 1. Substitutions Involving Barley Chromosomes 1, 3 and 6

In order to determine the genetic relatedness of individual barley chromosomes to wheat chromosomes, ‘Betzes’ barley chromosomes 1, 3 and 6 were substituted for individual ‘Chinese Spring’ wheat chromosomes of homoeologous groups 7, 3 and 6, respectively. The substitution status of these lines has been confirmed using isozyme selective markers, chromosome pairing behaviour in F₁ hybrids between the substitution lines and the appropriate double ditelocentric stocks of wheat, and hybridization of cDNA probes to the genomic DNA digests of these substitution lines. Each of the three barley chromosomes provided genetic compensation for the wheat chromosomes they replaced in the substitution plants. From the basis of this compensation with respect to plant vigour and fertility, barley chromosomes 1, 3 and 6 have been designated 7H, 3H and 6H.     

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.     

A New Source of Resistance to Pseudocercosporella herpotrichoides, Cause of Eyespot Disease of Wheat, Located on Chromosome 4V of Dasypyrum villosum

Resistance to Pseudocercosporella herpotrichoides in five wheat cultivars, accession W6 7283 of Dasypyrum villosum, and ‘Chinese Spring’ disomic addition lines of the D. villosum chromosomes IV, 2V, 4V, 5V, 6V and 7V, was evaluated in seedlings by measuring disease progress 6 weeks after inoculation with a β—glucuronidase—transformed strain of the pathogen and by visual estimates of disease severity. D. villosum and the disomic addition line of chromosome 4V were as resistant as wheat cultivars ‘VPM—1’ and ‘Cappelle Desprez’, but less resistant than ‘Rendezvous’. Resistance of the chromosome 4V disomic addition line was equivalent to that of D. villosum.‘Chinese Spring’ and disomic addition lines of IV, 2V, 5V, 6V and 7V were all susceptible. These results confirm Sparaguee's (1936) report of resistance in D. villosum to P. herpotrichoides and establish the chromosomal location for the genes controlling resistance. The presence of chromosome 4V in the addition line and its homocology to chromosome 4 in wheat were confirmed by Southern analysis of genomic DNA using chromosome group 4-specific clones. This genetic locus is not homoeologous with other known genes for resistance to P. herpotrichoides located on chromosome group 7, and thus represents a new source of resistance to this pathogen.     

Effects of Salinity on Growth, Ionic Relations and Physiological Traits of Wheat, Disomic Addition Lines from Thinopyrum bessarabicum, and Two Amphiploids

The effects of NaCl on the growth, ion relations and physiological characteristics at early stages of growth of bread wheat (Triticum aestivum) varieties ‘Chinese Spring’ and ‘Glennson 81’, ‘Chinese Spring’ lines tetrasomic for chromosomes 5A, 2B and 5B, ‘Chinese Spring’ disomic addition lines for chromosomes 2E^b and 5E^b from Thinopyrum bessarabicum (formerly Agropyron junceum), and amphiploids between ‘Chinese Spring’ and Thinopyrum bessarabicum and ‘Chinese Spring’ and Lophopyrum elongatum (formerly Agropyron elongatum) were examined. Plants were grown in a controlled environment cabinet, in nutrient solution with or without addition of 200 mol m^?3 NaCl. Growth in terms of leaf area, shoot and root weights was reduced by salt treatment. Salinity conditions gradually reduced the osmotic potential, though there was little effect on water potential. Turgor pressure was not much affected by salt. There was variation between genotypes for all the characteristics studied, especially in the extent of Na accumulation by leaves and roots. The amphiploids and 5E^b addition line accumulated the least Na in comparison with other genotypes. Generally roots accumulated lower quantities of Na than leaves. Genotype K contents were not affected by salt treatment. Stomatal conductance also declined whilst the ABA content increased in the salt treated seedlings. With respect to growth, the amphiploids and 5Eb addition line were most tolerant to salt while ‘Glennson 81’, tetrasomic 2B and tetrasomic 5B lines were most susceptible. The addition of homoeologous group 2 and 5 chromosomes reduced the tolerance to salt relative to ‘Chinese Spring’ euploid. It is concluded that chromosome 5E^b of Thinopyrum bessarabicum carries gene(s) for tolerance to salt and this tolerance may be due to the ability to exclude Na ions from the leaves and roots.     

Comparison of two fertility restoration systems against photoperiod-sensitive cytoplasmic male sterility in wheat

A ‘two‐line system’ using photoperiod‐sensitive cytoplasmic male sterility (PCMS) caused by Aegilops crassa cytoplasm under a long‐day photoperiod ( 15 h) has been proposed as a new means of producing hybrid varieties in common wheat. The PCMS line is maintained by self‐pollination under short‐day conditions, and hybrid seeds can be produced through outcrossing of the PCMS line with a pollinator under long‐day conditions. Two kinds of fertility restoration systems against the PCMS are known. One is involved with a set of multiple fertility‐restoring (Rf) genes in the wheat cultivar ‘Norin 61’ located on (at least) chromosomes 4A, 1D, 3D and 5D. The other is controlled by a single dominant major Rf gene, Rfd1, located on the long arm of chromosome 7B in the wheat cultivar ‘Chinese Spring’. To examine the degree of fertility restoration by these two systems, nine PCMS lines were crossed with ‘Norin 61’ and ‘Chinese Spring’ as the restorer lines, and the F₁ hybrids were investigated. The degree of fertility restoration was estimated by comparing the seed set rates in the F₁ hybrids having the Ae. crassa cytoplasm and those with normal cytoplasm. The results revealed that the fertility restoration ability of a set of multiple Rf genes in ‘Norin 61’ was higher than that of the Rfd1 gene in ‘Chinese Spring’.     

An assessment of the salt tolerance of wheat/Thinopyrum bessarabicum 5Eb addition and substitution lines

Lines of Triticum aestivum cv. Chinese Spring carrying an additional chromosome 5E^b from Thinopyrum bessarabicum or having chromosome 5A or 5D replaced by chromosome 5E^b were screened in hydroculture for tolerance to salt. The previously reported tolerance of the 5E^b addition line was confirmed and the two substitution lines were shown to have a higher level of survival in 175 mol/m³ NaCl than both the addition and the ‘Chinese Spring’ parent. Reasons for the better tolerance of the substitutions are discussed.     

Temperature as a component of the expression of developmental responses in wheat

Summary Studies were made of days to ear emergence under the constant temperatures of 9, 14, 19 and 25°C and 16 h photoperiod in three sets of wheat lines each possessing genotypes differing for developmental responses.Days to ear emergence in three near-isogenic lines of the wheat cultivar Triple Dirk, which differed for vernalization response, increased as the strength of the response increased. At the four temperatures Triple Dirk D (Vrn 1 vrn 2) was not significantly different from normal Triple Dirk (Vrn 1 Vrn 2) but Triple Dirk B (vrn 1 Vrn 2) was significantly (P=0.01) later than normal Triple Dirk at each temperature. This indicates that the vrn 1 allele confers stronger vernalization response than vrn 2 over the range of temperatures (9–24°C). However, Triple Dirk C (vrn 1 vrn 2) failed to head after 120 days at each temperature indicating strong interaction between vrn 1 and vrn 2 with each other (and possibly the Triple Dirk back-ground) to give a much stronger vernalization response than predictions from additivity of their individual effects.The second set comprised the four Chinese Spring/Thatcher chromosome substitution lines CS/T 3B, 6B, 7B and 5D, plus Chinese Spring and Thatcher, and were grown in the unvernalized condition. CS/T 5D was similar in days to ear emergence as Chinese Spring at all four temperatures but the other three lines were earlier to ear emergence, particularly as the temperature increased. Days to ear emergence was fastest at 14°C in all lines, except CS/T 3B, in which it decreased progressively from 9 to 24°C.The third set of Chinese Spring and Thatcher and the homoeologous group 2 chromosomes of Thatcher substituted in Chinese Spring, the group which is considered to be involved in the control of photoperiod sensitivity. The three substitution lines responded differently to temperature compared with Chinese Spring and with each other, with chromosome 2D being the least, and chromosome 2B the most, responsive to temperature.     

Responses to salt stress controlled by the homoeologous group 5 chromosomes of hexaploid wheat

The responses to salt stress in NFT (nutrient film) hydroponics of ‘Chinese Spring’ wheat and a number of its aneuploids involving the chromosomes of homoeologous group 5 were studied. This showed that the absence of chromosome 5D allowed plants to survive better than in the euploid condition. Much of this response could be related to the effects of Vrn3, which conditions the spring habit of ‘Chinese Spring’. The ability to survive relatively high levels of stress was promoted by the group 5 homoeologue from Thinopyrum bessarabicum.