Travel Bursary to attend the AquaVet program at Cornell University, in Massachusetts, USA
SCRC: Developing efficient diagnostic tools for assessing resistance to viral infection in abalone and oysters
The molluscan fisheries and aquaculture industries in Australia are threatened by herpesviruses. AbHV caused mass mortalities on Victorian farms from 2005-07 and is endemic off Victorian and possibly Tasmanian coasts. Herpesviruses are known to reactivate under stress conditions, threatening future productivity in the abalone industry and limiting movement of broodstock. Recently, OsHV-1 has been detected in Pacific Oysters in NSW, where it caused mass mortality and threatens the entire Australian oyster industry.
Research in France, where OsHV-1 is endemic, indicates that it is possible to select for higher resistance to this virus in oysters (ie. there is a strong genetic effect on resistance). Work by CSIRO and NSWI&I confirms that resistance to OsHV-1 is under strong genetic control. Screening of resistance level in the context of survivors within selected families is now being incorporated as a component of CRC project 2009/743.
Because molluscs lack acquired immunity, they cannot be vaccinated. The only feasible way to counter the threat of these viruses is to identify and develop resistant populations. As part of our current CRC PhD project (2008/739), we have developed an assay for screening antiviral activity in abalone haemolymph. The next step is to identify antiviral agents in abalone and oysters so they can be used as efficient diagnostic tools for identifying virus-resistant stocks. Biological and chemical screening assays, using antiviral activity and antiviral agent respectively, will be applied to different genetic breeding lines of abalone and oysters. We need to know if these assays could be used to improve resistance and whether genetic improvement of other traits such as growth rate might be compromised. Genetic analysis will determine whether haemolymph antiviral activity is under genetic control, is positively correlated with survival after challenge, and whether there are any undesirable associated effects.
Final report
The project examined the genetic basis of antiviral resistance in oysters and abalone in response to the significant disease threats posed by oyster and abalone herpesviruses. Laboratory-based systems for the growth and assay of such viruses are problematic. The project undertook to measure the antiviral activity of different breeding lines of oysters and abalone using as a proxy measure the antiviral activity against the human herpesvirus HSV-1. We demonstrated that oysters and abalone have antiviral activity against HSV-1, and that this trait is heritable. We identified a hemolymph compound providing antiviral activity. Our analysis of the oyster genome identified what is likely to be a key role for the protein viperin in resistance to viral infection. The project has provided outstanding value in three important areas. First, in adding to the knowledge base directing mollusc breeding programs. Second, in enhancing knowledge of molluscan immunity to viral infections. Third, in building research and development capacity in the Australian seafood industry.
SCRC: PhD : Understanding penaeid prawn sex determination and developing monosex induction strategies for commercial application (Andrew Foote)
This project will have significant impact on the industry as it will identify avenues for substantially improving farm profits by producing all-female populations. Production data from the Australian industry indicates sexual differentiation and maturation of Penaeus monodon (Giant Tiger Prawn) under commercial culture conditions occurs by 5 months of age, by which age females are on average ~30g and males are ~25g. This species is often harvested at even later ages by which time the size difference between females and males is even greater. As this project is focussed on improving pond yields it falls within the R&D priorities of the industry as outlined by the APFA
Relevant CRC Output(s) and Milestone(s):
Output 1.3 Removal or reduction of key production constraints in selected aquaculture systems
Milestone 1.3.1 New genetic tools and breeding strategies for genetic management and improvement of
at least two aquaculture species
(also refer to consultation and background)
Final report
Domestication and selective breeding programs in a number of cultured penaeid shrimp species worldwide have substantially improved commercially desirable traits compared to wild stocks. Improvements in growth rates, feed conversion efficiency, disease resistance and survival have been achieved in the important aquaculture species including Litopenaeus vannamei, Penaeus monodon, Fenneropenaeus chinensis and Marsupenaeus japonicus. However, there are substantial economic investments associated with the development of genetically superior lines in breeding programs and the intellectual property associated with such lines requires protection in the absence of effective legal mechanisms. Various technical strategies have been developed to protect these genetic resources with limited success to date.
Currently, triploidy is the only method known to guarantee inhibition of reproduction in shrimp and thus confer genetic protection. In addition, triploidy can increase the proportion of females in some shrimp species which is commercially desirable, as females grow faster than males. Triploid F. chinensis, M. japonicus and P. monodon have been produced by inhibition of polar body I or II formation during meiosis. A number of treatment agents to induce triploidy in shrimp have been trialled, with greatest success achieved using chemical and thermal shocks. However, current triploid induction methods cannot produce triploids at high or absolute rates and are not practical for commercial adoption due to the challenges associated with treating entire spawnings and the high mortality associated with the necessary handling of fragile eggs and embryos.