BREEDING A “BETTER” DISEASE RESISTANT OYSTER – THE TRADE-OFFS

Steve McOrrie¹ and Michael Dove¹ and Wayne O’Connor¹

¹New South Wales Department of Primary Industries, Australia

e-mail: steve.mcorrie@dpi.nsw.gov.au

Key words: Saccostrea glomerata, breeding, selection, disease

The New South Wales (NSW) oyster industry is located on the east coast of Australia and is based predominantly on the cultivation of the Sydney Rock Oyster (Saccostrea glomerata) (SRO). The development of hatchery techniques for SROs by NSW Department of Primary Industries in the 1980’s paved the way for a mass-selection based breeding program. The aim of this program was the development of a faster growing SRO that was resistant to winter mortality disease which occurs sporadically in southern NSW.

In 1994 the breeding program was expanded to include resistance to QX disease (infective agent; Marteilia sydneyi), which occurs in the northern half of the state. Mass-selection lines were developed that grew 30% faster, could survive QX disease outbreaks and reduce losses attributable to winter mortality by more than half. The unforeseen trade-off for these gains was a reduction in oyster meat condition, a market place trait prized by both retailers and consumers. The priority weights assigned to individual oyster traits by government industry managers and individual oyster growers can often be quite different. Industry managers will often seek to future proof stocks against potential disease incursions. While this approach is also supported by industry, where disease is a risk rather than a reality, individual farm based decisions are often weighted towards increased profitability realized by faster growth and product marketability. Meat condition is responsive to selection and industry is keen to see this trait be given a high priority in the breeding program. This requirement and the inability of mass-selection program to adequately manage inbreeding and to predict genetic gains led to mass-selection being replaced with a pedigree family-based breeding program that could adequately meet the desired goal of improved disease resistance and growth characteristics but not at the expense of meat condition.

Currently more than 200 families have been produced and assessed for a range of traits including QX and winter mortality disease resistance, growth, condition and shell shape. This talk will outline the approach that has been taken in NSW to balance the needs of all stakeholders.