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Abstracts
Workgroup: Genetics and Oyster Populations
Breeding, Evaluation and Molecular Analysis of Oyster Strains Selected for Resistance to MSX, Dermo and JOD
Principal Investigator(s):
Ximing Guo, Rutgers University, xguo@vertigo.hsrl.rutgers.edu
Co-Investigator(s):
Susan Ford, Rutgers University; Gregory DeBrosse, Rutgers University; Roxanna Smolowitz, Marine Biological Lab
Funding Period: 10/1/01-9/30/03
This study is a continuation of a previous ODRP project (9915) aimed at breeding and evaluation of oyster strains selected for disease-resistance and superior growth. Part of the study is to continue field evaluation of five strains for a third year. The other part is to use these strains and other families for molecular analysis with the goal of mapping disease-resistance genes.
During the first two years, we produced and deployed the Rutgers NEH strain (selected for MSX- and Dermo-resistance), Flower's FMF strain (selected for JOD), their hybrids, along with a global control (ME, susceptible, from Maine) and local strains that would normally be used by the participating growers. For each strain, two bags of two thousand seed each were deployed at four sites in July 2000: Cotuit Harbor in MA, Milford in CT, Cape Shore and Cape May in NJ. In addition to monthly checks, experimental oysters were sampled 10 times over the past three years: 09/00, 12/00, 03/01, 05/01, 08/01, 11/01, 03/02, 05/02, 08/02 and 11/02. At each sampling, thirty oysters from each replicate (60/group) were taken for disease analysis and size measurements. Dermo infection was heavy at most sites, while MSX and JOD infections were low or absent. At Cape Shore (NJ) where infection was the heaviest, NEH and HYB had the lowest cumulative mortality, 43.5% and 43.6% respectively, compared with 82.3% for FMF, 99.4% for ME and 81.1% for the local control (Delaware Bay wild). In growth, heterosis was no longer statistically significant in most measurement and at most sites. Overall, HYB grew the same as FMF and faster than NEH, while ME and the local controls grew the slowest. The hybrid offered the highest yield by surviving as well as the NEH strain and growing as fast as the FMF strain.
For molecular analysis, we have developed 396 AFLP markers and two linkage maps during the third year. The male map consisted of 114 markers in 12 linkage groups, covering 647 cM. We are also searching for host-defense genes in response to Dermo and MSX infections.
IMPACTS and/or BENEFITS:
This study confirms disease-resistance in the Rutgers strain and the superior growth in the FMF strain. More importantly, results show that the hybrid strain grows as fast as the FMF strain and survives as well as the Rutgers strain. The hybrids are clearly the best choice for aquaculture production. This finding is significant, and the use of the hybrids may bring considerable benefits to oyster farmers in the NE region.
The genetic map produced in this study is the first in the eastern oyster. The moderately dense genetic maps provide a foundation for further mapping other markers and disease-resistant genes. The project is on-going.
PROJECT PUBLICATIONS:
Guo, X., S. Ford, G. DeBrosse and R. Smolowitz, 2003. Breeding and evaluation of eastern oyster strains selected for MSX, Dermo and JOD resistance. Submitted to the 95th Annual Meeting of the National Shellfisheries Association, 2003, New Orleans.
Yu, Z. and X. Guo. 2003. A genetic linkage map for the eastern oyster, Crassostrea virginica Gmelin. Biol. Bull., submitted.
Guo, X., Y. Wang, Z. Yu and L. Li, 2002. Physical and linkage mapping in Crassostrea oysters. Presented at the World Aquaculture 2002 conference, April 23-28, Beijing, China.
Tanguy, A., S. Ford and X. Guo. 2002. Characterisation of gene expression in response to Perkinsus marinus and Haplosporidium nelsoni infections in the eastern and pacific oysters. J. Shellfish Res., 21(1):421. (abstract)
Yu, Z. and X. Guo. 2002. A basic AFLP linkage map for the eastern oyster, Crassostrea virginica Gmelin. J. Shellfish Res., 21(1):382. (abstract)
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