Scott, LJ 2004, 'Implications of evolutionary history and population structure for the analysis of quantitative trait loci in the ancient conifer Araucaria cunninghamii', PhD thesis, Southern Cross University, Lismore, NSW.
Copyright LJ Scott 2004
Araucaria cunninghamii is an ancient tropical conifer with substantial value as a forestry species in Australia and Papua New Guinea, and has been subject to a genetic improvement program for more than 50 years. This study was undertaken to demonstrate the utility of quantitative genetic analysis in describing the genetic architecture of commercial traits in A. cunninghamii. Linkage maps were prepared using the pseudotestcross strategy in what was believed to be a wide interprovenance cross using microsatellites and AFLP. A very low rate of marker polymorphism and limited differentiation between the parental provenances was identified, resulting in low mapping efficiency. The population genetic structure of A. cunninghamii was assessed to establish the underlying causes for the limited differentiation and low marker heterozygosity and assess the implications for future analysis of quantitative traits.
Despite the limited mapping efficiency, genetic maps were generated for both parents. The maternal map for individual H15 contained 14 linkage groups comprising of 51 AFLP and one microsatellite. The map covered 1290 cM, representing 89% of the estimated genome size. The paternal map for individual Gil24 was 633 cM, consisting of eight linkage groups.
Genetic architecture of quantitative traits was examined with putative QTL identified for height, DBH and stem straightness; one was highly significant (p<0.01), three significant (0.01
The population genetic survey characterised low levels of allelic diversity across the geographic range. Three broad regions were characterised; Papua New Guinea, Cape York and northern Queensland to NSW. There was limited differentiation between provenances within these regions, and high diversity within provenances. Limited genetic differentiation between provenances seems to be the result of genetic stability due to long overlapping generations, limited founder effects and a very low mutation rate. The latter may also contribute the low heterozygosity. Limited marker polymorphism and limited differentiation between provenances within broad regions are common features in A. cunninghamii. Therefore careful parental selection and alternative experimental approaches will be required before undertaking further analysis of quantitative traits.