Selective breeding programs spanning over 60 years of effort have supported production increases in the eastern oyster (Crassostrea virginica) culture industry in the Northeastern U.S. A major focus of the oyster selective breeding efforts in the region, as well as along the Atlantic and Gulf Coasts of the U.S., has been the development of disease-resistant stocks. Despite past success, shellfish breeding in the Northeast and beyond faces some significant challenges, not the least of which is that numerous estuaries along the mid-Atlantic and New England coasts where shellfish are cultured differ dramatically in habitat quality and disease pressure.
Recent advances in high-resolution and high-throughput genotyping of eastern oysters have provided an opportunity to use genomic information to estimate the breeding value of individuals in our broodstock programs. We genotyped live and dead oysters from a dermo challenge experiment with a 66K SNP array and predicted genomic estimated breeding values (GEBVs) for dermo resistance in a wild population from Delaware Bay. We produced two up-selected (based on two models), one down-selected and one average controls using oysters with highest, lowest and average GEBVs. Locally selected lines and their hybrids with Haskin NEH® were also produced and evaluated along with the four genomically selected groups over the past two growing seasons in several Northeastern states.
To date, we have observed sites-specific variation in the performance of these lines. While one of the up-selected and the average selected lines had higher yield in New Jersey, no significant difference in field survival has been observed between genomic selected and control lines probably because field survival is more complex than lab-based dermo resistance or genomic prediction is less effective across populations. Further, the triploid group had the highest yield, and the northern lines had lower survival possibly because they are less tolerant to MSX, dermo and/or heat stress. In NY, traditionally selected lines grew better while genomically selected lines suffered early high mortalities due to Roseovarius Oyster Disease (ROD, a.k.a. JOD). Similarly, in Maine, yield for the genomically selected lines from Delaware Bay wild lagged behind that of a traditionally selected line, though the difference was due more to growth rather than mortality. Our presentation will provide additional information on growth and mortality for these lines during the second field season for this ongoing project.