Assessment of Qx and Winter Mortality Disease Resistance of Mass Selected Sydney Rock Oysters, Saccostrea glomerata (Gould, 1850), in the Hawkesbury River and Merimbula Lake, NSW Australia

ABSTRACT The Sydney rock oyster, Saccostrea glomerata, mass selection breeding program was established in 1990 in the Georges River, New South Wales, and has successfully developed lines of oysters resistant to QX disease (Marteilia sydneyi) and winter mortality disease (WM; Bonamia roughleyi). Each new generation is assessed in the Georges River, but the performance of these oysters in other estuaries affected by these diseases is unknown. To investigate the potential for genotype and environment interactions, and to assure farmers, survival and growth of progeny of the fourth-generation breeding lines developed in Georges River were assessed in two other key farming areas; the Hawkesbury River and Merimbula Lake, NSW, Australia. Hawkesbury River is affected by QX and was used to assess the QX-resistant oysters (QXr). Merimbula Lake is affected by WM, and this estuary was used to assess the WM-resistant oysters (WMr) and the dual WM and QX resistant line (WM + QXr). Oysters that are QXr in the Hawkesbury...