Alien Substitution Lines Research Articles

Development of inter-varietal chromosome substitution lines of wheat (Triticum aestivumL.) bearing a rye genetic marker and their verification with microsatellite markers

Two monosomic alien substitution lines (MAS lines, 2n=41=40+5R) of wheat Triticum aestivum L. cv. ‘Saratovskaya 29’ were used as recipients in the development of inter-varietal substitution lines for chromosomes 5A and 5D. In the MAS lines, chromosomes 5A or 5D of ‘Saratovskaya 29’ were replaced by homoeologous univalent chromosome 5R of rye Secale cereale L. cv. ‘Onokhoiskaya’, which bears the Hp marker gene coding for hairy peduncle. The donors included 18 spring and winter wheat varieties. The MAS lines were developed by crossing monosomic lines of ‘Saratovskaya 29’ for chromosomes 5A and 5D to a wheat-rye substitution line of ‘Saratovskaya 29’ 5R(5D) followed by cytological and morphological selection of plants with chromosome configuration 20II +5RI in metaphase I of pollen mother cells from F 1 and F 2 plants with slightly hairy peduncles. It was shown that MAS lines could be maintained during long-term propagation (18 generations). Use of MAS lines with the Hp marker gene allows acceleration and abbreviation of cytological analysis and elimination of the probability of ‘univalent switch’ in the course of the development of substitution lines. The method was applied to the development of 22 ‘Saratovskaya 29’ lines with inter-varietal substitution for chromosomes 5A and 5D. Fourteen and thirteen microsatellite markers located in chromosomes 5A and 5D, respectively, were used to prove the authenticity of the inter-varietal substitution lines. According to these markers, 21 substitution lines from 22 studied were correct.

Cloning of a novel phosphateserine aminotransferase gene from a Triticum aestivum-Elytrigia elongatum alien substitution line with resistance to powdery mildew

Shannong 551, a T. aestivum-E. elongatum alien substitution line with resistance to powdery mildew, was inoculated with pathogenic spores of powdery mildew. The leaf samples were prepared 48 h after inoculation for scanning electron microscopy. The result showed that germination of spores and growth of young mycelia on leaves of Shannong 551 were suppressed at the early stage of infection. At the same time, RNAs were prepared from the leaves for the cloning of WRP1 and RPW2 by cDNA RDA and RACE technology. BLAST analysis of the sequences indicated that both WRP1 and RPW2 were novel genes. WRP1 contains no complete ORF. RPW2 contains the conserved structure domain of aminotransferase, and its DNA sequence shares high homology with genes of phosphateserine aminotransferase in many organisms. Therefore, it is speculated as a novel phosphateserine aminotransferase gene. The results of Northern blot suggested that expression of RPW2 occurred at the early stage of infection by powdery mildew. Southern blot using the probe of RPW2, in which there was strong hybridizing signals in both genome of Shannong 551 and E. elongatum, but not in those of Jinan 13 and Lumai No.5, indicated that RPW2 derived from the genome of E. elongatum.

Effect of the 5R(5A) Alien Chromosome Substitution on the Growth Habit and Winter Hardiness of Wheat

The growth habit, ear emergence time, and frost tolerance of wheat/rye substitution lines have been studied in cultivars Rang and Mironovskaya Krupnozernaya whose chromosome 5A is substituted with chromosome 5R of Onkhoyskaya rye. Hybrid analysis has demonstrated that the spring habit of the recipient cultivars Rang and Mironovskaya Krupnozernaya is controlled by dominant gene Vrn-A1 located in chromosome 5A. Onokhoyskaya rye has a dominant gene for the spring habit (Sp1) located in chromosome 5R. It has been found that the resultant 5R(5A) alien-substitution lines have a winter type of development and ears do not emerge during summer in plants sown in spring. The change in growth habit has been shown to be related to the absence of the rye Spl gene expression in the substitution lines. The winter hardiness of winter 5R(5A) alien-substitution lines has been studied under the environmental conditions of Novosibirsk. Testing the lines in the first winter demonstrated that their winter survival is 20-27%. The possible presence of the frost resistance gene homeoallelic to the known genes Fr1 and Fr2 of the common wheat located on chromosomes 5A and 5D, respectively, is discussed.

Cytological and Molecular Characterization of Wheat Lines with Thinopyrum intermedium Chromosome Additions, Substitutions and Translocations Resistant to Barley Yellow Dwarf Virus.

Barley yellow dwarf virus (BYDV) is the most serious viral disease affecting wheat and genes for BYDV resistance have not been found in wheat. BYDV-resistant alien addition and alien substitution lines produced from a wheat × Thinopyrum intermedium (species of Agropyron complex) cross were characterized. Chromosome pairing in the hybrids between two substitution lines showed that they had the same Th. intermedium chromosome. Likewise, two addition lines involved the same alien chromosome. In situ hybridization of chromosomes, confirmed that line P29 is a disomic substitution line. Double monosomic seeds and self-pollinated seeds from monosomic addition plants were irradiated to induce translocations between wheat and Th. intermedium chromosomes. Putative translocations were selected on the basis of BYDV resistance and studied by chromosome analysis, Southern hybridization using Thinopyrum specific probe and RFLP markers. A BYDV-resistant translocation was identified.

The genetic and molecular characterization of pollen-derived plant lines from octoploid triticale x wheat hybrids

Six doubled-haploid (DH) lines, derived by anther culture from octoploid triticale x wheat hybrids, were characterized using cytological, biochemical and molecular techniques. Lines varied in their wheat and rye genome composition, and were either wheat-rye chromosome multiple addition lines or had spontaneous substitutions and/or wheat-rye translocations. Most of the lines contained a pair of 4R chromosomes, whereas 1R or 7R were present in others. The results are similar to those previously obtained with hexaploid triticale x wheat crosses and indicate that it is possible to produce alien (wheat/rye) addition, substitution, and translocation lines directly from the anther culture of intergeneric hybrids.

Development and molecular cytogenetic analysis of wheat-Haynaldia villosa 6VS/6AL translocation lines specifying resistance to powdery mildew

Several Triticum aestivum L.-Haynaldia villosa disomic 6VS/6AL translocation lines with powdery mildew resistance were developed from the hybridization between common wheat cultivar Yangmai 5 and alien substitution line 6V(6A). Mitotic and meiotic C-banding analysis, aneuploid analysis with double ditelosomic stocks, in situ hybridization, as well as the phenotypic assessment of powdery mildew resistance, were used to characterize these lines. The same translocated chromosome, with breakpoints near the centromere, appears to be present in all the lines, despite variation among the lines in their morphology and agronomic characteristics. The resistance gene, conferred by H. villosa and designated as Pm21, is a new and promising source of powdery mildew resistance in wheat breeding.

A monoclonal antibody chromosome marker analysis used to locate a loose smut resistance gene in wheat chromosome 6A

Many genes have been located in wheat chromosomes, yet little is known about the location of genes for resistance to Ustilago tritici, which causes loose smut. Crosses were made between the loose smut susceptible alien substitution lines Cadet 6Ag(6A) and Rescue 6Ag(6A) (lines in which Agropyron chromosome 6 is substituted by wheat chromosome 6A) and four cultivars resistant to U. tritici race T19: 'Cadet', 'Kota', 'Thatcher' and 'TD18'. The segregating progeny were tested for reaction to race T19 and for the level of binding with a monoclonal antibody specific to a chromosome 6A-coded seed protein. The antibody, which does not bind to seed protein extracts in the absence of the 6A chromosome, was used as a chromosome marker. An association was established between resistance to race T19 and the presence of chromosome 6A for each of the cultivars tested, indicating that resistance to race T19 resides in chromosome 6A. Ustilago tritici race T19 resistance in 'Cadet' appears to be located in the short arm of chromosome 6A, based on the evaluation of the Cadet 6A long ditelosomic stock, which was susceptible, and the Cadet 6A-short: 6-Agropyron- short alien translocation stock, which was resistant.

Mapping of abscisic acid responsive genes and vp1 to chromosomes in wheat and Lophopyrum elongatum

The plant hormone abscisic acid (ABA) affects developmental and physiological processes that can impact crop production. These processes include germination, environmental stress responses in vegetative tissue, embryo maturation, and dormancy. Identification and molecular tagging of ABA-responsive genes, as well as the vp1 gene, required for ABA sensitivity, may be valuable in developing breeding strategies designed for manipulating ABA-regulated traits. Using aneuploid genetic stocks and alien substitution lines the chromosomal location of vp1 and seven abscisic acid (ABA) responsive genes was determined in wheat and Lophopyrum elongatum (Host) Löve. Clones (gene homology, if known, in parentheses) isolated from wheat hybridized to wheat and L. elongatum homoeologous chromosome groups as follows: pMA80 (dhn), chromosome 4; pMA1949 (group 3 LEA (1I)), chromosome 3S; pMA1951, chromosome 5S; pMA1959 (Em), chromosome 1L; pMA2005 (group 3 LEA), chromosome 1S; and PKABA1, chromosome 2L. Clone pBS128, corresponding to an ABA-responsive gene from Bromus secalinus, hybridized to wheat chromosome 2S. The cDNA clone pcvp23 that is homologous to vp1, a gene required for ABA responsiveness and the prevention of precocious germination in maize embryos, did not hybridize well with wheat but hybridized to chromosomes 3L and 7β in L. elongatum. Three of the clones mapped previously in barley by other researchers, pMA1949, pMA1951, pMA1959, were found here to be on the corresponding homoeologous chromosomes in wheat.

Reaction of alien chromosome substitution and addition lines of hard red spring wheat to common root rot and black point

Resistance to common root rot and black point, caused by Cochliobolus sativus, was evaluated in alien chromosome substitution and addition lines of the cultivars 'Cadet' and 'Rescue'. Substitution of chromosome 5B in 'Rescue' with 5Ag from Agropyron elongatum decreased root rot susceptibility to a level intermediate between that in the susceptible 'Rescue' and the resistant 'Cadet'. The substitution of 'Rescue' chromosome 5A or 5D with 5Ag, or the addition of 5Ag to 'Rescue' complement had no consistent effect on root rot susceptibility. The root rot resistance of 'Cadet' was unaffected by substitution of chromosomes 5A, 5B, or 5D with 5Ag, or the addition of 5Ag. This indicates that the susceptible allele of the gene Crr is the primary determinant in the reaction of wheat to common root rot. Black point resistance in the susceptible cultivar 'Rescue' was significantly increased by substitution of chromosome 5B with 5Ag, or the addition of 5Ag. No corresponding effect was demonstrated for black point incidence in the moderately resistant cultivar 'Cadet' with substitution of chromosome 5Ag for 5B, or the addition of 5Ag. Chromosome 5Ag apparently carries one or more genes conferring resistance to black point. The identity of these lines was confirmed by restriction fragment length polymorphism analysis using group 5 chromosome arm specific probes. This extends the use of these molecular probes to the Agropyron genome.

Production and identification of three 4Ag(4D) substitution lines of Triticum aestivum — Agropyron: relative transmission rate of alien chromosomes

By crossing fertile nullisomics-4D of common wheat (nullisomics 72180 and 'Tianxuan' no. 15) with three octoploid Agrotriticum lines [partial amphiploids (2n=56) 78829 from the offsprings of wheat with Agropyron intermedium (=Thinopyrum intermedium, 2n=42) and 784 and 7631 from those of wheat with Ag. elongatum (Thinopyrum elongatum, 2n=70)], backcrossing the hybrid with 4D nullisomics as recurrent parent for one to two generations, and then selfing the BC individuals, we obtained three different alien substitution lines, 4Ei (4D), 4Ee(4D) blue grain, and 4Fe(4D) hairy leaf. The F1 hybrids of 784×78829 had the basic chromosome pairing configuration of 27″ + 2', indicating that 784 and 78829 differed by only one pair of chromosomes. This means that Ag. intermedium and Ag. elongatum have a genome (or genomes) in common. The formation of 22″ +12' in the F1 of 784×7631 suggested that there was only one pair of homologous chromosomes of Ag. elongatum in 784 and 7631. Because F1 plants of 7631×78829 generally formed 21″ +14' at metaphase I, the Agropyron genomes in the two octoploid Agrotriticums were presumed to differ from each other. Upon intercrossing the three alien substitution lines, we found that all of the pollen mother cells of the F1 plants had 20″ + 2' or more univalents at metaphase I. We concluded that the three Agropyron chromosomes were not homologous but belonged to the same homoeologous group. These results were confirmed by reciprocal crosses of the three octoploids. The relative transmission rates of 4Ee, 4Fe, 4Ei, 4R and 4D were calculated using blue grain and hairy leaf as genetic markers; these were 4D>4Ee>4Ei, 4Fe>4R. The four alien chromosomes could compensate for the 4D of bread wheat, the substitution lines being vigorous and fertile.

The use of Monosomic Alien Substitution Lines in Interploidy Gene Transfer in Avena

Interploidy gene transfer in Avena is difficult because of the lack of homology and lack of pairing between chromosomes in diploid, tetraploid, and hexaploid oat species. In three Wisconsin projects, 6x amphiploids, a derived tetraploid, and a natural tetraploid were used as donor parents for resistance to crown rust [Puccinia coronata Cda. f. sp. avenae (Fraser and Ledingham)] or stem rust [Puccinia graminis Pers. f. sp. avenae (Eriks and E. Henn)J. Multiple backcrosses to susceptible A. sativa parents while constantly selecting for rust resistance resulted in the derivation of unstable, rust resistant, monosomic alien substitution (MAS) lines. Seeds from resistant MAS plants were irradiated in attempts to induce translocation of the gene for resistance from the alien chromosome to an A. sativa chromosome such that the gene would pass in normal fashion through male gametes. The sequence of irradiation, screening for resistant plants to be used as male parents, and crosses to susceptible cultivars as females resulted in the derivation of stable, resistant translocation lines in each of the three projects.

Genetics and cytogenetics of resistance to Puccinia graminis tritici in three South African wheats

Resistance to Puccinia graminis tritici pathotype 34-1, 2, 3, 4, 5, 6, 7 in a South African wheat, W3757, was attributed to a dominant gene located in an alien (possibly Agropyron elongatum) chromosome that had substituted with wheat chromosome 6D. This gene, designated SrB, and present in two additional South African wheats, W3758 and W3759, conferred a high level of adult plant resistance to pathotypes used for field assessments. Because SrB is apparently different from other genes transferred from A. elongatum to wheat, its possible exploitation following translocation to a wheat chromosome seems warranted. Key words: Puccinia graminis tritici, Triticum aestivum, wheat cytogenetics, rust resistance, alien substitution line.

The intrachromosomal mapping of a glucose phosphate isomerase structural gene, using allelic variation among stocks of Chinese Spring wheat

SUMMARYDetectable allelic variation at theGpi-1loci on the short arms of the homoeologous group 1 chromsomes in wheat is not common. However, a variant null allele at theGpi-D1locus is present in some stocks of Chinese Spring. This has allowed the locus to be mapped between the ω-gliadin locus carried distally on the short arm of chromosome 1D,Gli-D1(34·5%) and the high-molecular-weight glutenin subunit locus carried near the centromere on the long arm,Glu-D1(36·2%). The origin of this isoenzyme polymorphism in Chinese Spring stocks is described and its potential significance is discussed in relation to quantitative analysis of aneuploids, alien chromosome addition and substitution lines and intervarietal chromosome substitution lines involving Chinese Spring.

EFFECTS OF ADDITIONS AND SUBSTITUTIONS OFAGROPYRON ELONGATUMCHROMOSOMES ON QUANTITATIVE CHARACTERS IN WHEAT

Alien disomic and ditelosomic addition lines and disomic substitution lines involving the recipient wheat cultivar Chinese Spring and each of the seven chromosomes of diploid Agropyron elongatum were used to study the distribution of genes affecting date of heading, maturity, tillering, plant height and weight, seed protein content and components of seed yield in the Agropyron genome. Four Agropyron chromosomes, III, IV, V, and VI, affected days to heading and maturity but only chromosome VI conditioned early heading date. Complementary genes on opposite arms of the alien chromosome were responsible for late maturity in disomic addition line V. Tillering was affected by chromosome II which reduced the number of tillers per plant and by chromosome IV which increased the number. Plant height was increased by chromosome II and decreased in the presence of chromosomes III, IV, V and VI. Seed weight was increased in disomic addition lines II, III and VI while it was decreased in dosomic addition line V. Seed shrivelling, which was apparent in the amphiploid, Ag. elongatum × Chinese Spring, is controlled by Agropyron chromosome II. The number of seeds per spike was affected by six and seed yield by seven Agropyron chromosomes. Except for one line, the disomic addition lines and one substitution line showed significantly higher seed protein content than Chinese Spring. However, it was shown that yield depression accounted for a large portion of the increase in protein content. To remove this factor, the actual protein content in each line was compared with the adjusted protein content obtained from the regression of protein content on yield. Then it appeared that five of the seven Agropyron chromosomes are implicated in the control of seed protein. The amino acid compositions of proteins in the Agropyron-wheat derivatives were uniform and did not differ from Chinese Spring. It was shown that genes on Agropyron and wheat homoeologous chromosomes frequently have related effects on the characters studied. Because of genetic similarity among Agropyron and wheat homoeologues, the alien substitution lines tend to be superior to the alien addition lines in which the deleterious characters are largely caused by gene dosage effects. It is suggested that interlocus gene interactions play a significant role in the control of quantitative characters in this Agropyron genotype.

PRODUCTION OF ALIEN SUBSTITUTION LINES INTRITICUM AESTIVUM

Chromosomes of related species are being substituted within the seven homoeologous groups of wheat. In this way a series of 21 monosomic alien substitution (MAS) lines and the related disomic alien substitution lines can be developed. Three substitutions within each of homoeologous groups 3, 5, 6 and 7 have been isolated by the authors. Substitution of alien chromosomes in the remaining groups, viz 1, 2 and 4, is discussed.