Identify and map MSX-disease resistant genes

Ecology of Infectious Diseases

Collaborative Research: Field and Modeling Studies in Support of
Understanding Disease Resistance in Estuarine Populations and Response to Climate Change

In earlier work, we began constructing genetic maps of oysters using 96 microsatellite and 460 amplified fragment length polymorphism markers. We used composite interval mapping to identify potential disease-resistance loci with infection intensity as a measure of resistance. Initial efforts were focused on loci associated with Dermo disease resistance.

Composite interval mapping to identify genes or markers associated with resistance to Dermo disease. Using a combination of infection intensity and days to death after challenge in an F2 family as an index to resistance, we identified two QTLs (quantitative trait loci) associated with resistance on one of the oyster chromosomes.

Estimated density (number per gram wet weight) of MSX plasmodia as a function of intensity category in a sample of 150 oysters exposed to natural infections in May and collected in September.

For this project, we were interested in identifying loci associated with resistance to MSX disease. We produced a family of oysters by crossing resistant with susceptible parents, and then exposed it to MSX infections. Several months later, oysters showed a range of infection intensities, as measured by parasite density in the tissues. We assume that individuals with few parasites can be considered more resistant than those with abundant parasites. We used this information to identify sites on the chromosomes that are associated with parasite burden.

To date, we have found three loci affecting MSX infection intensity and two affecting Dermo intensity, which are identified on female and male maps.

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