Introgression and characterization of barley yellow dwarf virus resistance from Thinopyrum intermedium into wheat.

Wheatgrasses (species of Agropyron complex) have previously been reported to be resistant to barley yellow dwarf virus (BYDV). To introgress this resistance into wheat, Triticum aestivum x Thinopyrum (Agropyron) intermedium hybrids were advanced through a backcrossing program and reaction to BYDV, as determined by enzyme-linked immunosorbent assay (ELISA), is reported for the first time in backcross populations of wide hybrids between wheat and wheatgrasses. ELISA values revealed highly resistant to highly susceptible segregants in backcrosses. BYDV resistance was expressed in some backcross derivatives. Continued selection, based on cytology and ELISA in each generation, eliminated most of the unwanted wheatgrass chromosomes and produced self-fertile BYDV resistant wheat lines. The BYDV resistant lines with 2n = 42 had normal chromosome pairing similar to wheat, and their F1 hybrids with wheat had two univalents. DNA analyses showed that the source of alien chromatin in these BYDV resistant wheat lines is distinguishable from that in other Th. intermedium derived BYDV resistant wheat lines. Chromosome pairing and restriction fragment length polymorphism analyses indicated that the 42 chromosome resistant Purdue wheat lines are substitution lines in which chromosome 7D was replaced by a chromosome from Th. intermedium that was carrying gene(s) for BYDV resistance.     

Disomic Thinopyrum intermedium addition lines in wheat with barley yellow dwarf virus resistance and with rust resistances.

Zhong 5 is a partial amphiploid (2n = 56) between Triticum aestivum (2n = 42) and Thinopyrum intermedium (2n = 42) carrying all the chromosomes of wheat and seven pairs of chromosomes from Th. intermedium. Following further backcrossing to wheat, six independent stable 2n = 44 lines were obtained representing 4 disomic chromosome addition lines. One chromosome confers barley yellow dwarf virus (BYDV) resistance, whereas two other chromosomes carry leaf and stem rust resistance; one of the latter also confers stripe rust resistance. Using RFLP and isozyme markers we have shown that the extra chromosome in the Zhong 5-derived BYDV resistant disomic addition lines (Z1, Z2, or Z6) belongs to the homoeologous group 2. It therefore carries a different locus to the BYDV resistant group 7 addition, L1, described previously. The leaf, stem, and stripe rust resistant line (Z4) carries an added group 7 chromosome. The line Z3 has neither BYDV nor rust resistance, is not a group 2 or group 7 addition, and is probably a group 1 addition. The line Z5 is leaf and stem rust resistant, is not stripe rust resistant, and its homoeology remains unknown.     

The use of cell culture for subchromosomal introgressions of barley yellow dwarf virus resistance from Thinopyrum intermedium to wheat.

Barley yellow dwarf virus (BYDV) resistance has been transferred to wheat from a group 7 chromosome of Thinopyrum (Agropyron) intermedium. The source of the resistance gene was the L1 disomic addition line, which carries the 7Ai-1 chromosome. The resistance locus is on the long arm of this chromosome. BYDV resistant recombinant lines were identified after three or more generations of selection against a group 7 Th. intermedium short arm marker (red coleoptile) and selection for the presence of BYDV resistance. One recombinant line produced by ph. mutant induced homoeologous pairing and 14 recombinant lines induced by cell culture have been identified. Resistance in seven of the cell culture induced recombinants has been inherited via pollen according to Mendelian segregation ratios for up to eight generations. Meiotic analysis of heterozygotes indicates that the alien chromatin in the cell culture induced recombinants is small enough to allow regular meiotic behaviour. The ph-induced recombinant was less regular in meiosis. A probe, pEleAcc2, originally isolated from Th. elongatum and that hybridizes to dispersed repeated DNA sequences, was utilised to detect Th. intermedium chromatin, which confers resistance to BYDV, in wheat backgrounds. Quantification of these hybridization signals indicated that the translocations involved a portion of alien chromatin that was smaller than the complete long arm of 7Ai-1. Restriction fragment length polymorphism analysis confirmed the loss of the short arm of 7Ai-1 and indicated the retention of segments of the long arm of 7Ai-1. Two 7Ai-1L DNA markers always assorted with the BYDV resistance. A third 7Ai-IL DNA marker was also present in seven of eight recombinants. In all recombinants except TC7, the 7Ai-1L markers replaced the 7DL markers. None of the wheat group 7 markers was missing from TC7. It is concluded that all the resistant lines are the result of recombination with wheat chromosome 7D, except line TC7, which is the result of recombination with an unidentified nongroup 7 chromosome.     

Molecular characterization of a Thinopyrum intermedium group 2 chromosome (2Ai-2) conferring resistance to barley yellow dwarf virus.

The wheat--Thinopyrum intermedium addition lines Z1 and Z2 carry 21 pairs of wheat chromosomes and one pair of Th. intermedium chromosomes (2Ai-2) conferring resistance to barley yellow dwarf virus (BYDV). GISH results using the genomic DNA of Pseudoroegneria strigosa (S genome) as the probe indicated that the 2Ai-2 chromosome in Z1 and Z2 is an S-J intercalary translocation. Most of the 2Ai-2 chromosome belongs to the S genome, except for about one third in the middle region of the long arm that belongs to the J genome. The results of detailed RFLP analyses confirmed that the 2Ai-2 chromosome is extensively homoeologous to wheat group 2 chromosomes. Some new RFLP markers specific to the 2Ai-2 chromosome were identified. A RAPD marker, OP-R16(340), specific to the 2Ai-2 chromosome, was screened. We converted the RAPD marker into a sequence-characterized amplified region (SCAR) marker (designated SC-R16). The study establishes the basis for selecting translocation lines with small segments of the 2Ai-2 chromosome and localizing the BYDV resistance gene when introgressed into a wheat background.     

The effects of barley yellow dwarf virus, aphids and honeydew on Cladosporium infection of winter wheat and barley

Prior infection of both wheat and barley plants by BYDV predisposed their ears to infection by Cladosporium spp. and Verticillium spp. Aphids and honeydew increased the incidence of Cladosporium on wheat ears but not on barley. This difference between crops was attributed to the larger number ot aphids on the wheat. In the glasshouse, aphids and honeydew, but not honeydew alone, increased Cladosporium populations.     

Inheritance and effectiveness of genes in barley that condition tolerance to barley yellow dwarf virus

Tolerance to barley yellow dwarf virus (BYDV) in five Ethiopian barley genotypes was conditioned by major genes which apparently occurred at, or near, the same chromosome locus in each genotype. The genes or alleles differed in effectiveness, one providing a high, three an intermediate and one a low level of tolerance. In plants having a slow rate of growth, the effectiveness of the tolerance genes tended to be masked, but the effectiveness of the gene or allele which provided the highest level of tolerance was masked to a lesser extent than that of genes or alleles providing low or intermediate levels of tolerance.     

抗白粉病小麦——中间偃麦草异附加系的细胞学和RAPD鉴定

利用细胞学和ＲＡＰＤ技术,对从小麦与中间偃麦草杂种后代中选育的抗白粉病异附加系ＤＡＬ６６进行了鉴定。结果证明ＤＡＬ６６根尖细胞染色体数为４４,花粉母细胞减数第一分裂中期（ＰＭＣ ＭＩ）杂色体模型为２ｎ＝２２Ⅱ。对ＤＡＬ６６及其双亲进行ＲＡＰＤ分析,从４０个随机引物中筛选出１个特异引物（ＯＰＥ－０２）能够稳定地扩增出特异带型。     

Properties and isolates of barley yellow dwarf virus

Barley yellow dwarf virus is persistently transmitted by a number of aphid species of which three, Rhopalosiphum padi, Sitobion avenae and Metopolophium dirhodum, are common in most years. Other aphids may be locally important. Isolates of the virus differ in their virulence and geographical distribution and are not transmitted equally well by all aphid vectors. Isolates with similar properties are grouped into strains according to their transmission by vectors and their severity. Changes in strain and aphid occurrence from year to year alter the incidence of virus and its effect on yield. These changes emphasize the need for detailed knowledge of cereal aphid biology and epidemiology of BYDV before effective control can be used.     

小麦—中间偃麦草异附加系条锈病抗性的研究

应用缺体回交法,以阿勃缺体为母本,中4为父本,培育出小偃麦二体异附加系7个,其中St3,St5,St7对目前流行条锈病小种表现免疫,二体异附加系与阿勃杂交及其相互杂交的F1PMCM1结果表明,所有附加系分别附加了一对中4的外源染色体,其中St5和St7附加的染色体相同,但不同于St3所附加的外源色体,这表明中4的中间偃麦草St染色体组中至少有两条染色体携带有抗条锈病基因。     

Evaluation of oat cultivars and lines under infection with barley yellow dwarf virus

Thirteen domestic and foreign oat cultivars and eight breeding lines bred from the University of Illinois were evaluated for resistance to barley yellow dwarf (BYD) using artificial inoculation with Rhopalosiphum padi viruliferous for an isolate of Barley yellow dwarf virus-PAV endemic to Moscow region origin. Cultivar Blaze and six Illinois lines showed the best grain yields under disease pressure that resembled a BYD epidemic.     

Sequence and organization of barley yellow dwarf virus genomic RNA.

The nucleotide sequence of the genomic RNA of barley yellow dwarf virus, PAV serotype was determined, except for the 5'-terminal base, and its genome organization deduced. The 5,677 nucleotide genome contains five large open reading frames (ORFs). The genes for the coat protein (1) and the putative viral RNA-dependent RNA polymerase were identified. The latter shows a striking degree of similarity to that of carnation mottle virus (CarMV). By comparison with corona- and retrovirus RNAs, it is proposed that a translational frameshift is involved in expression of the polymerase. An ORF encoding an Mr 49,797 protein (50K ORF) may be translated by in-frame readthrough of the coat protein stop codon. The coat protein, an overlapping 17K ORF, and a 3'6.7K ORF are likely to be expressed via subgenomic mRNAs.     

A single wheatgrass chromosome reduces the concentration of barley yellow dwarf virus in wheat

Seedlings of a series of addition or substitution lines of wheat containing different Thinopyrum intermedium chromosomes were inoculated with the PAV and RPV serotypes of barley yellow dwarf virus (BYDV). Reduced virus titres in infected plants were ascribed to a single pair of homoeologous group 7 chromosomes from Th. intermedium in the disomic addition lines L1 and TAF 2. The group 7 chromosome is associated with red pigmentation of coleoptiles, which was also observed in two lines ditelosomic for the α arm of the chromosome. However, when infected with the PAV serotype of BYDV, the ditelosomic lines had normal virus titres and it is concluded that potential determinants of BYDV resistance are located on the β arm of the Group 7 chromosome.     

Influence of aphid species and barley yellow dwarf virus on soft red winter wheat yield

Yield loss in soft red winter wheat, Triticum aestivum L., caused by aphid-transmitted barley yellow dwarf virus (family Luteoviridae, genus Luteovirus, BYDV) was measured over a 2-yr period in central Missouri. Rhopalosiphum padi (L.) was the most common and economically important species, accounting for > 90% of the total aphids. Schizaphis graminum (Rondani), Rhopalosiphum maidis (Fitch), and Sitobion avenae (F.) made up the remainder of the aphids. Aphid numbers peaked at wheat stem elongation in 2003 with 771 R. padi per meter-row. In the 2003-2004 growing season, aphid numbers averaged seven aphids per meter-row in the fall and peaked at 18 aphids per meter-row at jointing. Wheat grain yield was reduced 17 and 13% in 2003 and 2004, respectively. Thousand kernel weights were reduced 10 and 5% in the untreated plots compared with the treated control in 2003 and 2004, respectively. Padi avenae virus was the predominate strain, accounting for 81 and 84% of the symptomatic plots that tested positive for BYDV in 2003 and 2004. Our results indicate that economic thresholds for R. padi are 16 aphids per meter-row in the fall and 164 aphids per meter-row at jointing.     

抗条锈病小麦—中间偃麦草异附加系的生化与分子标记

对小麦-中间偃麦草部分双二倍体无芒中4、异附加系C076、宛7107和中国春进行了肽链内切酶（EP-1）等电聚焦电泳。结果表明,肽链内切酶在阳极处有一特异带。肽链内切酶已定位于小麦第7部分同源群,故附加的染色体为第7部分同源群的2条染色体,对中间偃麦草,无芒中4、C076和宛7107进行了RAPD分析。获得了可用于检测C076中外源染色体的3个RAPD标记,即OPI05-800、OPI10-600、OPK01-900。     

The effect of barley yellow dwarf virus on the amino acid composition of spring wheat

Leaf extracts of barley yellow dwarf virus-infected and healthy spring wheat (cv. Highbury) plants at three growth stages were analysed by gas liquid chromatog-raphy to determine their free amino acid content. Eleven free amino acids were identified. Virus infection increased the total amino acid content of sampled leaves at each growth stage but more so at the later stages. Alanine and glutamine were consistently present in greater amounts in infected than in healthy leaves at all three growth stages.     

Structural organization of an alien Thinopyrum intermedium group 7 chromosome in U.S. soft red winter wheat (Triticum aestivum L.).

Barley yellow dwarf virus (BYDV) resistance in soft red winter wheat (SRWW) cultivars has been achieved by substituting a group 7 chromosome from Thinopyrum intermedium for chromosome 7D. To localize BYDV resistance, a detailed molecular genetic analysis was done on the alien group 7 Th. intermedium chromosome to determine its structural organization. Triticeae group 7 RFLP markers and rye specific repetitive sequences used in the analysis showed that the alien chromosome in the P29 substitution line has distinguishing features. The 350-480 bp rye telomeric sequence family was present on the long arm as determined by Southern and fluorescence in situ hybridization. However, further analysis using a rye dispersed repetitive sequence indicated that this alien chromosome does not contain introgressed segments from the rye genome. The alien chromosome is homoeologous to wheat chromosomes 7A and 7D as determined by RFLP analysis. Presence of the waxy gene on chromosomes 7A, 7B, and 7D but its absence on the alien chromosome in P29 suggests some internal structural differences on the short arm between Th. intermedium and wheat group 7 chromosomes. The identification of rye telomeric sequences on the alien Thinopyrum chromosome and the homoeology to wheat chromosomes 7A and 7D provide the necessary information and tools to analyze smaller segments of the Thinopyrum chromosome and to localize BYDV resistance in SRWW cultivars.     

Development and characterization of a new barley yellow dwarf virus (BYDV)-resistant wheat germplasm

A barley yellow dwarf virus (BYDV)-resistant line HG295 was selected from a cross between cv. 77-5433 and Zhong 5 after extensive investigation in field, greenhouse and ELISA. Cytological analysis revealed that it was an euploid line and genetically stable. The existence of alien DNA in HG295 was identified by RAPD and Southern hybridization analyses showed that the alien DNAs came from Zhong 5 or Th. intermedium. The differences of BYDV resistance between L1 and HG295 are discussed.