Fig. 2. Pearl cleaning operation. Before commencing a selective breeding program with P maxima the genetic basis of traits such as growth rate, disease resistance and pearl quality has to be established. Reliable estimates are essential because traits will only respond to selection if they have a strong genetic basis and, as such, are heritable. Generally, traits such as growth rate in animals have moderate heritability approximating 30 percent. This means that of the total observed variation in growth in a population a third is due to heritable genetic factors and can be selected for to produce faster growing individuals. However, there are no estimates at present of the degree to which the genetic makeup of P maxima affects pearl quality traits. Hence, a major goal of the current project will be to determine the genetic basis of these important traits through a heritability trial. It has been shown that the long-term genetic response during a selective breeding program is positively correlated with the amount of genetic diversity within the initial founder population. If the genetic diversity of a founder population is low, then traits are likely to have limited variation from which to select. Additonally, starting a breeding program with a depauperate genetic base will ultimately lead to rapid increases in inbreeding within the population. Therefore, as part of the initial study, a genetic audit on P maxima will be undertaken to determine the degree of genetic variability both in wild stocks and hatchery-produced farm populations across Indonesia. Moreover, we will examine the effect hatchery cultivation methods have on genetic diversity. Through controlled experiments, we will identify which husbandry factors need to be considered in order to maintain genetic diversity within cultured populations. This genetic 26 MARCH 2007 Fig. 3. Freshly harvested South Sea pearls from Indonesia. audit is an important tool that can help us avoid potential problems associated with possible future inbreeding. Finally, cutting edge molecular techniques will be utilized to develop a DNA-based pedigreeing system. This technology is frequently used in human forensics and paternity assignment and allows the familial identification of progeny in the selective breeding program without prior identification and tagging of broodstock. The main advantage of such a DNA pedigreeing system is that it will dramatically improve the efficiency of the selective breeding program by allowing many more individuals to be evaluated than with physical tagging, as well as allowing the direct quantification of inbreeding levels. The fundamental data obtained during this initial phase of the research project will then form the basis on which to develop a selective breeding program for P maxima. While characteristics such as faster growth and disease resistance may form part of the program, ultimately the major objective will be to increase the yield of high-value pearls harvested. The complexities of establishing the genetics of commercially important traits required to develop an appropriate selective breeding program demand a long-term view. However, the patience required during the initial phase of development will be repaid rapidly through the enormous gains in productivity that will be achieved through a properly researched, fully integrated, selective breeding program. Notes 'Atlas Pacific Limited/PT Cendana lndopearls, Jalan Sekar Jepun V/21, Gatot Subroto Timur, Denpasar, Indonesia 2School of Marine Biology and Aquaculture, James Cook University, Townsville QLD 4811, Australia Reference Anonymous. 2005. Golay's cultured pearl market overview for 2004/2005. Pearl World 14(1).
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