Virus resistance. Barley Yellow Dwarf Virus
Bdv2
References
1. The use of cell culture for subchromosomal introgressions of barley yellow dwarf virus resistance from Thinopyrum intermedium to wheat. Banks, P. M.; Larkin, P. J.; Bariana, H. S.; Lagudah, E. S.; Appels, R.; Waterhouse, P. M.; Brettell, R. I. S.; Chen, X.; Xu, H. J.; Xin, Z. Y.; Qian, Y. T.; Zhou, X. M.; Cheng, Z. M.; Zhou, G. H. In:Genome, 1995. 38(2):395-405.
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-1L 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.
2. Introgression and characterization of barley yellow dwarf virus resistance from Thinopyrum intermedium into wheat .Sharma, H.; Ohm, H.; Goulart, L.; Lister, R.; Appels, R.; Benlhabib, O.In: Genome, 1995. 38(2):406-413.
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 times 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 F-1 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
3. Registration of barley yellow dwarf virus resistant wheat germplasm line P29. Sharma, H. C.; Ohm, H. W.; Perry, K. L.In: Crop Science, 1997. 37 (3): 1032-1033.
4. Novel germplasm providing resistance to barley yellow dwarf virus in wheat.. Francki, M. G.; Ohm, H. W.; Anderson, J. M. In: Australian Journal of Agricultural Research, 2001. 52 (11-12):1375-1382
The lack of suitable genes in existing wheat germplasm collections makes breeding for specific traits a difficult task. Although tolerance to barley yellow dwarf viruses (BYDV) has been reported in wheat accessions, there are no suitable levels of resistance to BYDV, so genes are sought from wild relatives. The ability for Thinopyrum species to inhibit replication of BYDV makes them attractive sources of resistance for germplasm development. Breeding programs are exploiting Thinopyrum species to develop wheat germplasm resistant to BYDV. The transfer of genes from Thinopyrum into wheat by wide crossing and selecting progeny using molecular markers identified suitable material to some strains of BYDV. The implementation of molecular marker technology has been useful for rapid selection of wheat lines with resistance to some strains of BYDV in a breeding program. However, it is now clear that Thinopyrum species contain a number of resistance genes on different genomes and homoeologous chromosomes. In order to achieve broad-spectrum resistance to the various serotypes of the BYDV complex it will be best to combine a number of these genes. Research efforts are now focussed on introgressing other genes from Thinopyrum into wheat that provide resistance to several additional strains of BYDV. Molecular markers will play an important role during selection in pyramiding genes to develop wheat germplasm with broad-spectrum BYDV resistance.
5. Molecular cytogenetic analysis of Agropyron chromatin specifying resistance to barley yellow dwarf virus in wheat.. Hohmann, U.; Badaeva, K.; Busch, W.; Friebe, B.; Gill, B.S. In: Genome, 1996. 39 (1996): 336-347.
Nine families of bread wheat (TC5, TC6, TC7, TC8, TC9, TC10, TC14, 5395-(243AA), and 5395) with resistance to barley yellow dwarf virus and containing putative translocations between wheat and a group 7 chromosome of Agropyron intermedium (L1 disomic addition line, 7Ai 1 chromosome) induced by homoeologous pairing or tissue culture were analyzed. C-banding, genomic in situ hybridization (GISH), and restriction fragment length polymorphism (RFLP) in combination with repetitive Agropyron-specific sequences and deletion mapping in wheat were used to determine the relative locations of the translocation breakpoints and the size of the transfer-red alien chromatin segments in hexaploid wheat-Agropyron translocation lines. All homoeologous compensating lines had complete 7Ai l or translocated 7Ai 1-7D chromosomes that substitute for chromosome 7D. Two complete 7Ai 1 (7D) substitution lines (5395-(243AA) and 5395), one TIBS-7Ai 1S center dot 7Ai IL addition line (TC7), and two different translocation types, T7DS-7Ai 1S center dot 7Ai IL (TC5, TC6, TC8, TC9, and TC10) and T7DS center dot 7DL-7Ai 1L (TC14), substituting for chromosome 7D were identified. The substitution line 5395-(243AA) had a reciprocal T1BS center dot 1BL-4BS/TIBL-4BS-4BL translocation. TC14 has a 6G (6B) substitution. The RFLP data from deletion mapping studies in wheat using 37 group 7 clones provided 10 molecular tagged chromosome regions for homoeologous and syntenic group 7 wheat or Agropyron chromosomes. Together with GISH we identified three different sizes of the transferred Agropyron chromosome segments with approximate breakpoints at fraction length (FL) 0.33 in the short arm of chromosome T7DS-7Ai 1S center dot 7Ai 1L (TC5, TC6, TC8, TC9, and TC10) and another at FL 0.37 of the nonhomoeologous translocated chromosome T1BS-7Ai 1S center dot 7Ai 1L (TC7). One breakpoint was identified in the long arm of chromosome T7DS-7DL-7Ai 1L (TC14) at FL 0.56. We detected some nonreciprocal translocations for the most proximal region of the chromosome arm of 7DL, which resulted in small duplications.
6. Identification and characterization of wheat-wheatgrass translocation lines and localization of barley yellow dwarf virus resistance. . Crasta, O. R.; Francki, M. G.; Bucholtz, D. B.; Sharma, H. C.; Zhang, J.; Wang, R.-C.; Ohm, H. W.; Anderson, J. M. In: Genome, 2000. 43(4):698-706.
Stable introgression of agronomically important traits into crop plants through wide crossing often requires the generation and identification of translocation lines. However, the low efficiency of identifying lines containing translocations is a significant limitation in utilizing valuable alien chromatin-derived traits. Selection of putative wheatgrass-wheat translocation lines based on segregation ratios of progeny from gamma-irradiated seed using a standard phenotypic analysis resulted in a low 4% success rate of identifying barley yellow dwarf virus (BYDV) resistant and susceptible translocation lines. However, 58% of the susceptible progeny of this irradiated seed contained a Thinopyrum intermedium chromosome-specific repetitive sequence, which indicated that gamma-irradiation-induced translocations occurred at high rate. Restriction fragment length polymorphism (RFLP) analysis of susceptible lines containing alien chromatin, their resistant sister lines and other resistant lines showed that more than one third of the progeny of gamma-irradiated double monosomic seeds contained wheatgrass-wheat translocations. Genomic in situ hybridization (GISH) analysis of selected lines confirmed that these were wheatgrass-wheat translocation lines. This approach of initially identifying BYDV susceptible deletion lines using an alien chromosome-specific repetitive sequence followed by RFLP analysis of their resistant sister lines efficiently identified resistant translocation lines and localized the BYDV resistance to the distal end of the introgressed Th. intermedium chromosome.
7. A diagnostic molecular marker allowing the study of Th. intermedium-derived resistance to BYDV in bread wheat segregating populations.. Ayala, L.; Henry, M.; Gonzalez-de-Leon, D.; van Ginkel, M.; Mujeeb-Kazi, A.; Keller, B.; Khairallah, M.In: Theoretical and Applied Genetics, 2001. 102(6-7):942-949.
Barley yellow dwarf (BYD) is the most important viral disease of small cereal grains. True resistance to the disease is not found in wheat (Triticum aestivum L.), but it has been introgressed from Thinopyrum intermedium (Ti) on chromosome 7DL of recombinant wheat lines designated TC. The objectives of our study were to identify a high through-put scoring tool for the presence of the translocated Th. intermedium fragment and to assess its suitability for evaluating resistance to BYDV in segregating populations. Segregation of the Ti fragment was followed in the F2 population of an Anza (bread wheat) by TC14/2*Spear (TC14) cross. Resistance to BYDV isolates PAV-Mex and MAV-Mex in F3, F4, and F5 populations was evaluated under field and/or greenhouse conditions by measuring the virus titers of infected plants using ELISA, and the number of infected plants per plot. The SSR marker gwm37 was polymorphic for the translocation. In F4 lines it was associated with the physical presence of an intact translocation on chromosome 7DL and with low virus titers of BYDV-PAV. Reductions in virus titer of 27% and 55% in the F3 and 18% and 45% in the F5 populations were observed when the fragment was present in the heterozygous and homozygous states, respectively, confirming a dosage effect of the resistance allele. A lower proportion of infected individuals in the field was associated with the presence of the fragment, indicating a mechanism that may interfere with aphid feeding or virus translocation within infected plants. Despite significant differences between groups with and without the fragment, the OD values of infected lines overlapped, and it was not possible to definitively detect the fragment based solely on ELISA. We conclude that gwm37 is a reliable marker for the Ti translocation that will allow efficient detection of the translocation in breeding populations and greatly assist in selecting BYDV-resistant wheats in the absence of the disease.
8. PCR-based molecular marker for the Bdv2 Thinopyrum intermedium source of barley yellow dwarf virus resistance in wheat.. Stoutjesdijk, P.; Kammholz, S. J.; Kleven, S.; Matsay, S.; Banks, P. M.; Larkin, P. J. In: Australian Journal of Agricultural Research, 2001. 52(11-12):1383-1388.
Because of the importance of BYDV in wheat production worldwide, and given the difficulties of bioassaying for resistance, a molecular marker was developed for the resistance known as Bdv2 that originates on the long arm of chromosome 7Ai1 of Thinopyrum intermedium. This resistance was identified in a partial amphiploid line TAF46, a disomic addition line to wheat (L1), a telosomic addition line (7Ai1 L), and a series of recombinants and translocation. A RAPD (random amplified polymeric DNA) marker for the resistant germplasm was cloned and sequenced, and primers were designed against that sequence to produce a sequence characterised amplified region (SCAR) marker. A single PCR product is produced only with genotypes carrying the resistance from any of the available recombinants. The cloned sequence, recommended primers, and PCR protocols are described. The usefulness of the marker has been demonstrated for following Bdv2 in segregating wheat breeding germplasm, with the imminent release of a BYDV-resistant cultivar.
9. Implementation of probes for tracing chromosome segments conferring barley yellow dwarf virus resistance.. Zhang, W.; Carter, M.; Matsay, S.; Stoutjesdijk, P.; Potter, R.; Jones, M. G. K.; Kleven, S.; Wilson, R. E.; Larkin, P. J.; Turner, M.; Gale, K. R. In: Australian Journal of Agricultural Research, 2001. 52(11-12):1389-1392.
Two PCR-based assays were examined for tracing the presence of a Thinopyrum chromosome segment (Tc6 or Tc14) conferring barley yellow dwarf virus (BYDV) resistance in wheat breeding lines. The microsatellite gwm37 was used to assay the Thinopyrum chromosome segment or its wheat, Group 7, homoeologous segment, and was effective in characterising breeders material since heterozygous lines could be identified. A new set of primers derived from a Thinopyrum-specific DNA segment (csTiB1) provided a dominant marker that was readily scored by agarose gel electrophoresis. It was also demonstrated that the csTiB1 primers could be used to establish a solid phase PCR assay that avoided the requirement for gel electrophoresis and was amenable to use in a high-throughput, microtitre plate format. Depending on the number of DNA samples to be assayed, both primer pairs appear to have a place in breeding programs.