Materials and Methods
1. Plant materials Twenty-five local mulberry cultivars from Nakhonratchsima Sericulture Research Center were chosen. This included, 21 local, and 4 fruit accessions (Table 1). 2. Methods Genomic DNA was extracted from young leaves by the modified protocol of Doyle and Doyle (1990). Amplification was performed in a DNA Thermal cycler (Gene Amp PCR System 9600, Perkin Elmer) using 16 arbitrary different primers (Operon Technologies, USA) (Table 2) and followed the modified protocol of Williams et. al.(1990). The amplification products were size-analyzed by electrophoresis in 1.5 % (W/V) agarose gels using 1 X TBE buffer and visualized by ethidium bromide staining.
Three replications were performed for each genomic DNA sample. Consistent and reproducible polymorphic bands were binary scored i.e., 1 (band present) or 0 (band absent). Cluster analysis was conducted using NTsys-pc version 2.0 (Numerical Taxonomy System, Exeter Software. New York. USA). A pair wise similarity matrix was constructed by using Dice similarity index. Similarity amongst varieties was estimated by the unweighted pair-group method of arithmetic averages (UPGMA). The resulting clusters were expressed in a dendrogram. Initially, 243 decamer primers were screened with a Thai local mulberry. Of these, 67 primers which yielded distinct banding patterns of bright intensity, were chosen for a second round screening using different DNA samples of mulberry (Promboon’s unpublished data and Saksoong’s unpublished data). Finally, the PCR reactions were conducted using 16 primers with best bands.