DIFFERENCES IN GENOMIC DNA EXTRACTED FROM BARK AND FROM WOOD OF DIFFERENT ZONES IN ROBINIA TREES USING RAPD-PCR

Determination of genetic differences and levels of gene expression in mature and old tissues (e.g. wood) is often difficult based on morphol ogical and anatomical characteristics, levels of metabolites or enzyma tic activity. The use of molecular markers allows assessment of polymo rphic (genetic) variation amongst individuals and between closely rela ted species directly at the DNA level, but such techniques have not be en generally applied to the bark and wood of mature trees. In this stu dy we have applied the technique of random amplification of polymorphi c DNA (RAPD) by the polymerase chain reaction (PCR) to analyse the rel ationship between the bark and variously aged wood zones of Robinia ps eudoacacia. The use of micro polyacrylamide gel electrophoresis couple d to silver staining for DNA provided a quick, reliable and sensitive method of detecting polymorphisms. It was necessary to test a small nu mber of ten-base synthetic oligonucleotide primers before arriving at a set of five which clearly identified post-transcriptional difference s between bark, sapwood, transition zone and heartwood even in the one individual tree. The variability of the technique, and in particular the origin and quality of the DNA extracted was analysed, We demonstra ted that the procedures and protocols developed are applicable to all tissue types tested from bark to the inner heartwood zones. Our result s show that RAPD-PCR technology is a versatile and sensitive method of detecting genomic changes in trees.