An integrated genetic map of Populus deltoides based on amplified fragmentlength polymorphisms

Amplified fragment length polymorphism (AFLP) is an efficient molecular tec hnique for generating a large number of DNA-based genetic markers in Populu s. We have constructed an integrated genetic map for a Populus backcross po pulation derived from two selected P. deltoides clones using AFLP markers. A traditional strategy for genetic mapping in outcrossing species, such as forest trees, is based on two-way pseudo-testcross configurations of the ma rkers (testcross markers) heterozygous in one parent and null in the other. By using the markers segregating in both parents (intercross markers) as b ridges, the two parent-specific genetic maps can be aligned. In this study, we detected a number of non-parental heteroduplex markers resulting from t he PCR amplification of two DNA segments that have a high degree of homolog y to one another but differ in their nucleotide sequences. These heterodupl ex markers detected have served as bridges to generate an integrated map wh ich includes 19 major linkage groups equal to the Populus haploid chromosom e number and 24 minor groups. The 19 major linkage groups cover a total of 2,927 cM, with an average spacing between two markers of 23. 3 cM. The map developed in this study provides a first step in producing a highly saturat ed linkage map of the Populus deltoides genome.