Mapping quantitative trait loci controlling the early height growth of longleaf pine and slash pine.

摘要

The delay in early height growth (EHG) known as the "grass stage" has been one important factor that limits the artificial regeneration of longleaf pine (Pinus palstris Mill.). Genetic improvement of the "grass stage" by interspecific hybridization between longleaf pine and slash pine (Pinus elliottii Engelm) followed by recurrent backcrosses aiming at the introgression of genes controlling the EHG from slash pine into longleaf pine may be a solution. Developing markers tightly linked to these genes and using them in backcross breeding programs may speed the process of the introgression. Random amplified polymorphic DNA (RAPD) markers were employed to map the genorne of longleaf pine and slash pine in a (longleaf pine x slash pine) x slash pine BC1 family consisting of 258 progeny. A total of 266 RAPD markers were identified for both the F1 parent and the slash pine parent. One hundred and thirteen of the 150 F1 parent-specific markers were mapped into 17 linkage groups covering a genetic distance of 1338.2cM. Eighty-three of the 116 slash pine parent-specific markers were mapped into 19 linkage groups covering a genetic distance of 994.6cM. Single marker regression and MapMaker/QTL were used to detect QTLs. The two methods gave similar results. By using MapMaker/QTL, a total of 19 putative QTLs were detected for 6 height growth measurements and 6 collar diameter measurements at three growth stages using a LOD threshold of 2.0. Seventeen of the 19 putative QTLs were from the F1 parent and only two were from the slash pine parent. The amount of phenotypic variance explained by the putative QTLs ranged from 3.6 to 11.0%. The derivation of sequence characterized amplified region (SCAR) markers from random amplified polymorphic DNAs (RAPDs) were demonstrated to be feasible. Nine RAPD fragments that segregate in a longleaf pine x slash pine F1 family were cloned and end sequenced. A total of 13 SCAR primer pairs, with lengths between 17 and 24 nucleotides, were developed. Six of the 13 SCARs were found to be polymorphic. The segregation of four of the six polymorphic SCARs was confirmed in 64 longleaf x slash F1 individuals.