Progress 07/01/06 to 08/31/09
Outputs
OUTPUTS: No further research accomplishments due to resignation of P.I. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
No further research accomplishments due to resignation of P.I.
Publications
- No publications reported this period
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Peach Tree Short Life (PTSL) is a complex disease syndrome involving many biotic and abiotic factors. The disease occurs commonly in the s.e.-U.S., and possibly in other areas of the U.S. and the world. PTSL causes premature tree death during the 2nd to 6th year post planting, resulting in large economic losses. Guardian rootstock was selected for its tolerance to PTSL. The genetic basis for this tolerance is unknown. Nemaguard, a PTSL-susceptible rootstock, and Guardian selection 3-17-7 were crossed. Each F1 plant was selfed to create segregating F2 populations. One hundred and seventy microsatellite (SSR) markers, each mapped to unique locations in the Prunus reference genome (http://www. rosaceae.org), were used to screen F1-11 and the parents. Forty-seven SSRs were polymorphic. F2 segregation data, for SSR marker inheritance and their PTSL-response, were compiled to identify genomic regions associated with PTSL response. Of the 47 polymorphic SSRs, nine (distributed on 4 LGs) were linked with the response to PTSL (Analysis of Variance, SAS). Such SSR markers can be used to select PTSL-tolerant rootstocks. Using JoinMap 3.0, a genetic map was constructed from the polymorphic markers. QTL analysis was conducted using PLABQTL1.2 by implementing the interval mapping method. QTLs were detected between 0 to 10 cM from the upper terminus of LG 2, in each of the five years evaluated. Two markers located within the QTL were also found to be associated with the response to PTSL by individual marker analysis. Major genes controlling tolerance/susceptibility to PTSL may reside in this region of LG-2. Developing other SSR/ high-resolution markers to saturate this region will further define the specific locus, and ultimately identify the candidate genes. Seedlings are difficult to distinguish morphologically, and once grafted as rootstocks, no above ground material is available for identification. To avoid misidentification and protect plant varieties/patents, DNA fingerprinting was investigated as an identification tool. Twenty-two polymorphic SSRs were screened on the eight parental (clonal) rootstocks (Lovell, Nemaguard, Nemared, Guardian 3-17-7, Bailey, Halford, S-37 and Kakamas). Although no single SSR could distinguish all rootstocks, BPPCT008 amplified seven patterns and was capable of identifying six rootstocks. Identifying open-pollinated seedlings was more difficult than parent genotype identification, because heterozygous patterns of rootstock clones segregated in the seedlings. However, the seedlings of several rootstocks could be identified by single SSR markers (e.g., Nemared with marker BPPCT017). Other rootstock seedlings required combinations of markers (e.g., EMPAS11, BPPCT001 & pacita16 for 3-17-7 and S-37). This technology will allow nurseries and peach growers to test rootstocks they purchase for trueness to type, and also will help protect seed propagated proprietary rights (i.e., PVP) for fruit tree breeders. The above information/outputs were disseminated to stakeholders/interest groups through presentations at International, national and regional meetings (oral and posters), and peer-reviewed publications. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Acquired information and developed outputs were disseminated to stakeholders/interest groups through presentations at International, national and regional meetings (oral and posters), and peer-reviewed publications. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Peach tree short life (PTSL), a disease syndrome of peach [Prunus persica (L.) Batsch] primarily in the southeastern United States, occurs on more than 70% of the peach acreage in the southeastern U.S. Identifying the chromosomal region(s), and eventually the gene(s), associated with/responsible for this syndrome is critical to developing improved germplasm for the peach industry. Ideally that new germplasm, produced through a combination of breeding and biotechnology (e.g., marker assisted selection and/or gene cloning and transformation), will be highly tolerant to the syndrome and provide a sustainable solution to the agronomic problem of PTSL. In addition, molecular markers are being identified that uniquely characterize the rootstocks important to the peach industry. These (i.e., DNA fingerprinting) will be valuable in identifying germplasm, as well as protecting the rights and property of nursery wholesalers, growers and breeders.
Publications
- Liu, X., G.L. Reighard, G.A. Swire-Clark and W.V. Baird (2008). Peach Rootstock Identification by DNA-fingerprinting with microsatellite (SSR) markers. Amer. Pom. Soc. 61: 162-166.
- Zhebentyayeva, T.N., G. Swire-Clark, L.L. Georgi, L. Garay, S. Jung, S. Forrest, D. Main, B. Blackmon, J. Tomkins, W.V. Baird, G.L. Reighard, A.G. Abbott (2008). A framework physical map for peach, a model Rosaceae species. Tree Gen. Genomes 4: 745-746.
- Yemets, A., V. Radchuk, O. Bayer, G. Bayer, A. Pakhomov, V. Baird and Y. Blume (2008). Development of transformation vectors based upon a modified α-tubulin gene as the selectable marker. Cell Bio. Intl. 32: 566-570.
- Polomski, B., W.V. Baird and P.D. McMillan (2008) Basic Botany - Chapter 3 (32 pp) in South Carolina Master Gardner Training Manual (B. Polomski, ed.)
- Yemets, A., W.V. Baird and Y. Blume (2008). Plant transformation vectors based upon a modified tubulin genes as selectable marker. in The Plant Cytoskeleton: Genomic and Bioinformatic Tools for Biotechnology and Agriculture (Y. Blume, V. Baird, D. Breviario, eds.) Springer-Verlag publisher.
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Progress 01/01/07 to 12/31/07
Outputs
Peach tree short life (PTSL) is a devastating disease syndrome of peach [Prunus persica (L.) Batsch] caused by multiple factors; the molecular biology of its tolerance/ susceptibility is unknown. The difficulty of studying PTSL is that tree survival or death is not obvious until 3 to 5 years after planting when the symptoms of PTSL first appear. Tolerance to PTSL was unknown in Prunus until the rootstock Guardian(Registered Trademark) BY520-9 was introduced into commercial orchards in 1994. To study the genetics of the response to PTSL, a controlled cross was made between Guardian BY520-9 selection 3-17-7 (PTSL-tolerant) and Nemaguard (PTSL-susceptible). An F1 hybrid was then selfed to generate an F2 population expected to segregate for PTSL response. One hundred fifty-one AFLPs and 21 SSRs, including anchor loci from the Prunus reference genetic map, were used to construct a molecular genetic map based on 100 F2 seedlings. This map covers a genetic distance of 737 cM
with an average marker spacing of 4.7 cM and will be used as a framework to construct a highly saturated molecular genetic map. Of the 140 mapped AFLP markers, 38 were associated with PTSL response, as identified previously by bulked segregant analysis. The distribution of the markers associated with PTSL response on the newly constructed genetic map was compared with the recently published Prunus resistance map. This comparison revealed that some resistance gene analogs and several PTSL-associated AFLP markers were located in the same regions in several Prunus linkage groups: G1, G2, G4, G5, and G6. This peach rootstock map can also be viewed and compared with other Prunus maps in comparative map viewer CMap in the Genome Database for Rosaceae (GDR) at http://www. rosaceae.org.
Impacts
Peach tree short life (PTSL) is a disease syndrome of peach [Prunus persica (L.) Batsch] primarily in the southeastern United States, which is caused by a complex of biotic, climatic and other environmental factors, rather than a single pathogen or condition. This problem occurs on more than 70% of the peach acreage in the southeastern U.S. Identifying the chromosomal region(s), and eventually the gene(s), associated with/responsible for this syndrome is critical to developing improved germplasm for the peach industry. Ideally that new germplasm, produced through a combination of biotechnology and breeding (e.g., marker assisted selection or cloning), will be highly tolerant to the syndrome and provide a sustainable solution to the agronomic problem of PTSL. In addition, molecular markers are being identified that uniquely characterize the rootstocks important to the peach industry. These will be valuable in identifying germplasm (i.e., DNA fingerprinting) as well as
protecting the rights and property of nursery wholesalers, growers and breeders.
Publications
- Zhebentyayeva, T.N., R. Horn, J. Mook, A-C. Lecouls, L. L. Georgi, A.G. Abbott, G.L. Reighard, G. Swire-Clark and W.V Baird (2006). A physical framework for the peach genome. Acta Hort. 713: 83-88.
- Weston, D.J., W.L. Bauerle, G.A. Swire-Clark, B.d. Moore, W.V. Baird (2007) Molecular characterization of Rubisco activase from thermally contrasting genotypes of Acer rubrum L. (Aceraceae). Am. J. Bot. 94: 926-934.
- Blenda, A.V., I. Verde, L.L. Georgi, G.L. Reighard, S.D. Forrest, M. Munoz-Torres, W.V Baird, A.G. Abbott (2007). Construction of a genetic linkage map and identification of molecular markers for response to peach tree short life syndrome in peach rootstocks. Tree Gen. Genomes 3: 342-350.
- Breviario, D., W.V. Baird, S. Sangoi, K. Hilu, P. Blumetti, and S. Giani (2007). High polymorphism and resolution in targeted fingerprinting with combined beta-tubulin introns. Molecular Breeding 20: 249-259.
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Progress 01/01/06 to 12/31/06
Outputs
Peach Tree Short Life (PTSL) is a complex disease syndrome caused by multiple factors, genetics of which is not known. Amplified fragment length polymorphism (AFLP) technology and bulked segregant analysis (BSA) were used to identify diagnostic markers for PTSL syndrome in peach rootstocks. Both bulk of tolerant and bulk of susceptible trees were screened with 144 AFLP EcoRI/MseI primer combinations. Sixty primer combinations were polymorphic between tolerant and susceptible bulks, and produced a total of 117 polymorphic fragments. Of those sixty primer combinations, forty-four were selected as potential PTSL-tolerance associated markers based on the results of screening a number of tolerant and susceptible genotypes with the polymorphic primer combinations. The use of EAC/MCCC primer combination in conjunction with bulked segregant analysis resulted in the identification of a single amplification product in the bulk of DNA from ten susceptible trees (died from PTSL),
and its absence in the bulk of DNA from ten tolerant trees. The AFLP fragment also was detected in the susceptible rootstocks Lovell and Nemared. In addition, the fragment was found in the susceptible parent Nemaguard but not the tolerant parents, in four controlled crosses segregating for response to PTSL. The segregation ratio in two F2 families from those crosses was 2:1, implying distortion. Testing of this AFLP primer combination on additional 111 trees that either died or survived on a severe PTSL site revealed the presence of the diagnostic fragment in 18 trees of which 17 were Lovell. PTSL death was observed in 61% of the trees with the fragment, which was significantly (P ≤ 0.05) higher in comparison with those that did not have the fragment. Furthermore, the PTSL rating of symptoms was significantly higher and the cumulative tree life was significantly shorter (P ≤ 0.05) for Lovell compared with the other 93 rootstocks lacking the AFLP fragment.
Impacts
Peach tree short life (PTSL) is a disease syndrome of peach [Prunus persica (L.) Batsch] in the southeastern United States, which is caused by a complex of biotic, climatic and other environmental factors, rather than a single pathogen or condition. This problem occurs on more than 70% of the peach acreage in the southeastern U.S. Identifying the chromosomal region(s), and eventually the gene(s), associated with/responsible for this syndrome is critical to developing improved germplasm for the peach industry. Ideally that new germplasm, produced through a combination of biotechnology and breeding (e.g., marker assisted selection or cloning), will be highly tolerant to the syndrome and provide a sustainable solution to the agronomic problem of PTSL.
Publications
- Blenda A.V., W.P. Wechter, G.L. Reighard, W.V. Baird and A.G. Abbott (2006). Development and characterization of diagnostic AFLP markers in Prunus persica for its response to peach tree short life syndrome. J. Hort. Sci. Biotech. 81: 281-288.
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