REPRODUCIBILITY OF THE DIFFERENTIAL AMPLIFICATION BETWEEN LEAF AND ROOT DNAS IN SOYBEAN REVEALED BY RAPD MARKERS

Random amplified polymorphic DNA (RAPD) was used to determine whether such markers can be employed for detecting genomic modification during plant development or under certain stress environments. Pairwise comp arisons in RAPD patterns of leaf and root DNA amplifications were stud ied for 11 soybean accessions representing different origins. Hydropon ic culture was used for the ease of harvesting roots. From a total of 40 primers screened, it was found that 16 can detect leaf DNA polymorp hism, 19 for root DNA polymorphism, while 10 show a greater consistenc y for detecting polymorphism between leaf and root (L/R) DNAs. Neverth eless, problems were encountered when the newly synthesized oligo-prim ers and different thermal cyclers were used to check the data. Several factors were then tested for their reproducibility, The results indic ated that the amplified differences between root and leaf DNAs are mos tly not affected by template DNA concentrations. The addition of DMSO (dimethyl sulphoxide) or TMAC (tetramethyl-ammonium chloride) also did not mask the L/R differences. However, DNA polymerase and oligo-prime rs synthesized from different manufacturers, as well as the thermal cy clers, reacted differently sometimes; Regardless of the general proble ms of reproducibility in RAPD patterns, some amplified differences rem ain between the L/R DNAs. The most distinct patterns involve differenc es in the relative intensity of amplified bands. Differential amplific ation might have occurred during plant leaf and root development. Sout hern hybridization of the eluted polymorphic bands against restriction digestion of total genomic DNA confirms their being homologous to soy bean DNA fragments. Polymorphism of these specific L/R differences als o exists among varieties. RAPD should be a useful tool in detecting ge nomic alterations during plant development or under certain stress env ironments, as long as the factors affecting the reproducibility of RAP D patterns can be properly controlled. An additional cycle of selectio n would be possible if such a type of polymorphism is proved to be cor related with certain developmental characters.