Breeding F1 hybrid oysters from doubled haploids
A major problem facing Pacific oyster growers throughout southern Australia is maintaining consistent product quality. High levels of genetic variability in oysters cause considerable variation in several economically important traits such as growth rate and condition. Variation in growth rate causes extra work because of the need for frequent grading, while variation in condition within a batch may prevent growers from obtaining a market for their oysters. Even for those oysters which are of sufficient quality to reach the market, supplying oysters that vary in condition, or colour for example, creates a perception of poor quality control and undermines market confidence in the suppliers (and hence in the growers). This variability in product quality is currently unavoidable simply because of the intrinsic genetic variation in oyster stocks. If genetically uniform oysters could be produced, then a major source of variation in product quality would have been removed from the oyster industry. All oysters grown from a batch of genetically identical spat should respond similarly in any given environment. Consequently, considerable improvements in consistency of product quality and appearance could be achieved. These genetically uniform oysters would still show some variation in (e.g.) growth rate and degree of condition due to differences in the environments they experience — for example, oysters which had been growing at the centre of a basket or lease may gain condition more slowly than those at the edge — however, because this variation would now be solely due to environmental factors, growers would be able to rapidly identify and control these factors. This would increase consistency of product quality still further. A second major limitation to the oyster industry at present is a lack of stock which have been genetically selected to produce commercially desirable characteristics. Given the wide variation in environmental conditions under which Pacific oysters are grown in Australia (from cold, low-salinity waters off Tasmania, to warm, high salinity waters in S.Australia) considerable opportunity exists to breed oysters which have been genetically selected to perform well in a given environment. The Pacific oyster industry has recently engaged in a research programme which aims to selectively breed oysters that match grower and market demands more closely than present stocks. However, this programme uses conventional breeding techniques, and (commercial) benefits to growers cannot be expected for some considerable time.
1. To obtain at least 20 (and preferably 100) families of doubled haploid Pacific oysters
2. From some of these doubled haploid oysters, establish inbred lines that contain both sexes so that they can be maintained by normal breeding procedures
3. To use these inbred lines to trial a range of F1 hybrids and identify the best F1 hybrid (or hybrids) for commercial production of genetically uniform batches of oysters