Development of random amplified polymorphic DNA markers for genetic mapping in Pacific yew (Taxusbrevifolia)

Abstract

A genetic linkage map was constructed for Pacific yew (Taxusbrevifolia Nutt.) based on random amplified polymorphic DNA (RAPD) markers. A series of optimization experiments were conducted to develop a highly repeatable protocol for Pacific yew. In these experiments, a high MgCl2 concentration (5.5 mM) together with a low primer concentration (0.2 μm) in the polymerase chain reaction (PCR) mixture yielded the best amplification products. PCR amplification products were further improved by treating the template DNAs with RNase. Experiments showed that bovine serum albumine had the same effect as RNase on PCR amplification. The segregating mapping population consisted of 39 haploid megagametophytes from a single mother tree. DNA extracted from a subset of 6 megagametophytes was screened with 345 ten-base oligonucleotide primers of arbitrary sequence. Of the screened primers, 28% revealed at least one polymorphic locus. Eighty-six of these primers revealed at least one polymorphic locus and were used with the entire set of megagametophyte DNAs. One-hundred-two loci were scored and segregated in the expected 1:1 ratio (1.19 locus per primer). Linkage analysis was conducted using MAPMAKER. Forty-one of 102 markers were distributed into 17 linkage groups and covered 305.8 centimorgans. The remaining 61 unlinked markers should be assigned to linkage groups as more markers are added to the map.

Effects of megagametophyte removal on DNA yield and early seedling growth in coastal Douglas-fir

“…The megagametophytes of conifers are haploid and originate mitotically from the same meiotic product as the megaspore. Because they allow maternal genes to be mapped directly in progeny of single trees without complications of dominance, megagametophytes are widely used for genome mapping (e.g., Binelli and Bucci 1994;Göçmen et al 1996;Kaya and Neale 1995;Krutovskii et al 1995;Nelson et al 1993Nelson et al , 1994Plomion et al 1995;Tulsieram et al 1992) and quantitative trait loci (QTL) mapping (e.g., Grattapaglia et al 1992) using random amplified polymorphic DNA (RAPD) markers. The maternal contributions to the genotypes of individual seedlings can be determined by analysis of megagametophytes rescued during germination, allowing segregation of QTL heterozygous in maternal parents to be related to traits expressed in seedlings or later stages.…”