Progress 09/15/97 to 09/30/02
Outputs
This project resulted in the development of a bacterial artificial library for Russian Seedling R12740-7A, known to contain two genes designated Vr and Vx conferring resistance to the fungal pathogen causing apple scab. The Vr gene confers a stellate nectrotic response to infection with Venturia inaequalis (apple scab). The Vx gene has a pit type reaction. Markers were identified for these two genes and their map location was determined. Markers from other research groups were also tested. SSRs helped to align our map with those of other groups researching the Vf gene for scab resistance from Malus floribunda 821. Additional primers were identified with linkage to Vr and Vx. While the project has been terminated, research continues on our goal of cloning these genes for resistance.
Impacts
Genetic resistance to the fungal pathogen Venturia inaequalis that causes apple scab of fruit and foliage has been a goal of breeders and molecular biologists. The characterization of a bacterial artificial library from Russian Seedling R12740-7A is of even greater importance now that the Vf gene from Malus floribunda has been found to be susceptible to new races of scab. Thus far, Russian seedling R12740-7A remains resistant to these new races. All BAC libararies in apple have concentrated on Vf. Our BAC contains two genes for resistance to scab, distinct from Vf. Cloning these genes for resistance would offer greater prospects for resistance to scab by transformation. The study of this library has furthered our understanding of these genes for resistance, their location and their interaction with other resistance genes.
Publications
- Hemmat, M. S.K. Brown and N.F. Weeden. 2002. Tagging and mapping scab resistance genes from R12740-7A. J. Amer. Soc. Hort. Sci. 127:365-370.
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Progress 01/01/01 to 12/31/01
Outputs
Additional markers were identified for the Vr and Vx genes that confer resistance to apple scab (Venturia inaequalis) in populations derived from 'Russian seedling R12740-7A'. These genes are distinct from Vf. Our Bacterial Artficial Chromosome (BAC) work was on hold last year due to loss of personnel, but it is being resumed. Other (BAC) libraries have been developed in apple, but they have all concentrated on Malus floribunda 821, the source of the Vf gene for resistance, or have used material derived from Malus floribunda 821, such as 'Florina' or 'Goldrush'. The Vf gene is now susceptible to race 6, a race reported in Europe. The BAC work on other apple cultivars has been progressing and their research findings will complement our work towards the isolation and characterization of the Vr and Vx genes present in 'Russian Seedling R12740-7A'.
Impacts
Genetic resistance to the fungal pathogen apple scab (Venturia inaequalis) is important in conventional breeding and in the development of transgenic apple lines. The majority of effort since the early 1920s has emphasized the use of the Vf gene from Malus floribunda 821. Over 80% of the resistant cultivars released to date possess this source of resistance and the BAC libraries developed have used material derived from Malus floribunda, or have used Malus floribunda 821 itself. This source of resistance has been found to be susceptible to a new race of scab identified in Europe. Our emphasis on developing a BAC library from Russian seedling R12740-7A focuses on 2 genes , Vr and Vx, that are distinct from Vf, have not been used extensively in breeding, and have not been shown to be susceptible to the race 6 of scab that is virulent on Vf materials. We now have markers for use in pyramiding these genes in convential breeding and to aid our goal of cloning this gene.
The results of BAC development in the Vf material should aid our investigations and the cloning of Vr and Vx will provide distinct genes for use in transgenic development.
Publications
- Bessho, H., S.K. Brown, J.L. Norelli, and H.S. Alwinckle.2001. Observations on the susceptibility of Japanese apple cultivars and rootstock selections to fire blight. J. Amer. Pomol. Soc.55:120-124.
- Bolar, J.P., J.L. Norelli, G.E. Harman, S.K. Brown and H.S. Aldwinckle. 2001. Sunergistic activity of endochitinase and exochitinase from Trichoderma atrovide (T. harzainum) against the pathogenic fungus (Venturia inaequalis) in transgenic apple plants. Transgenic Research 10:533-543.
- Just, B.J. 2001. Molecular markers for weeping plant habit and powdery mildew (Podosphaera leucoticha) resistance from the ornamental crabapple 'Red Jade'. M.S. Thesis, Cornell. Univ.
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Progress 01/01/00 to 12/31/00
Outputs
Populations derived from 'Russian seedling R12740-7A' were used to find markers closely linked to the Vr gene for scab resistance (conferring a stellate necrotic lesion in response to inoculation) and for the Vx gene (conferring a pit type reaction that is distinct from the pit type of M. micromalus and M. atrosanguinea 804). When the primers for Vr, and previously published markers for Vf, were used on a segregating progeny (Vfvf x Vrvr) we were able to identify all susceptible individuals, apparent escapes, and individuals possessing both resistance genes. These markers for Vr and Vx were mapped and flanking markers were identified to aid selection. For the BAC screening we were delayed awaiting the reposting of the faculty position and hiring of a new postdoctoral fellow. We have initiated the search for a replacement and will work to characterize the libraries. We are trying to coordinate our work with other research groups in Europe who have developed a BAC
library of 'Florina' which possesses the Vf gene for resistance to scab.
Impacts
(N/A)
Publications
- Ko, K., J.N. Norelli, J.-P. Reynoird, E.E. Borejsza-Wysocka, S.K. Brown and H.S. Aldwinckle. 2000. Effect of untranslated leader sequence of AMV RNA 4 and signal peptide of pathogenesis -related protein 1b on attacin gene expression and resistance to fire blight in transgenic apple. Biotechnology Letters 22:373-381.
- Sakurai, K., S.K. Brown and N.F. Weeden. 2000. Self-incompatibility alleles of apple cultivars and advanced selections. HortScience 35:116-119.
- Ko, K., J.N. Norelli, S.K. Brown, and H.S. Aldwinckle. 1999. Anti-attacin polyclonal antibody from an in-vitro derived antigen used for immunoblot to quantify attacin expressed in transgenic apple. Biotwechnology techniques 13:839-857.
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Progress 01/01/99 to 12/31/99
Outputs
We have produced a 60,00 clone BAC library of apple DNA in the vector pBeloBAC11. The apple DNA was extracted from 'Russian Seedling R12740-7A', an apple slection known to contain two major genes conferring resistance to apple scab. Our primary BAC library appears to have an average insert size of about 100 kb and therefore represents an approximately 6-fold coverage of the apple genome. The library has been stored in microtiter plates at -80C. Row, column, and plate pools from each microtitre plate have been made and are ready for screening. A second, smaller BAC library (approximately 20,000 clones) has been generated in pECSBAC4 using EcoR1 as the restriction endonuclease. Although this BAC library represents only a 2-fold coverage of the apple genome, it represents a different set of clones capable of being screened in the event that the pBeloBAC11 does not contain the gene of interest because of problems associated with the HindIII library. Screening has yet to
be performed on either library because the post doctoral fellow conducting the research left this position for other employment.
Impacts
(N/A)
Publications
- None. A preliminary report was presented as a poster at the 1999 Plant and Animal Genome meeting (Fu, J., N.F. Weeden, J.R. Kikkert, Bin Wang and S.K. Brown. Development of a BAC library from Russian Seedling R12740-7A, an apple selection with two genes conferring resistance to scab. Plant and Animal Genome VII. San Diego, 1999.)
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Progress 01/01/98 to 12/31/98
Outputs
The project was initiated in August, and we have have little time for publishable results. High molecular weight DNA has been extracted from `Russian Seedling R12740-7A', an apple clone possessing two major genes for resistance to apple scab. The DNA was partially digested with Hind III, size fractionated, and ligated into pBELOBAC 11. We have obtained approximately 20,000 clones with an average insert size of 100 kb, which is equivalent to about three genome equivalents.
Impacts
(N/A)
Publications
- No publications reported this period
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