Development Of EST-CAPS Markers And Their Application To Linkage Map Construction In Eucalyptus

Some problems still exist in forest tree linkage map construction, such as low density, a small number of co-dominant markers used, and few gene-based markers included, though linkage mapping has been a hot topic in plant genetics studies. Solution to these problems was very important in both theoretical and applicational terms. Eucalypts plays a crucial role in global forestry and serve as a model in forest tree genetics; their linkage map construction would be considerably valuable and useful.Primers were designed based on 54 ESTs in Eucalyptus tereticornis derived from Genebank. There were 35 pairs of primers amplied successfully in PCR reaction optimization. Studies were carried out on segregation and linkage mapping of these EST-CAPS markers using an F, pedigree of E. tereticornis x E. urophylla.There were 7 EST-CAPS segregating among the F, population when analyzed with appropriate restriction enzymes. Of the seven markers, there were five EST-CAPS markers had a segregation ratio 1:1, four out of which segregated normally at a Mendelian mode (a=0.05), while the left two EST-CAPSs segregated 1:1:1:1 at a Medelian inheritance mode. The relatively high ratio of normal segregating EST-CAPS markers (6/7 = 85.7%) implies that the marker type could be reliably used as genetic marker in genetic mapping and the related studies in Eucalyptus species.Seven EST-CAPS markers were integrated to the two RAPD linkage maps constructed previously. The new constructed E. urophylla linkage map had 24 linkage groups, including one newly built linkage group consisting EST-CD668626 and three RAPD markers. The total linkage length was 1545.2cM, with an average interval of 10.8cM. Three other CAPS markers located in the 1st ^ 11th, and 15th linkage group, respectively, while the left one distorted EST-CAPS marker was not located to any linkage group. There were four CAPS markers integrated to the E. tereticornis linkage map, locating on the 6l\ 7th ^ 8th, and 10th linkage group, respectively. The total map distance was 1094.8cM, with an average interval 10.2cM. Comparing the integration maps of E. urophylla and E. tereticornis with their RAPD markers maps, the total map distance was increased by 40.6cM and 59.1cM, respectively. The results demonstrate that EST-CAPS marker technology could be reliably applied to genetic map construction in Eucalyptus and other forest trees.