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Abstract

Psidium guajava L. is a perennial fruit tree in subtropical and tropical areas. In Taiwan, P. guajava has been used as anthro-pharmacological plants by aboriginal people to treat acute diarrhea, cough and intestinal spasmodic diseases. The classification and functional identification of P. guajava remains unsolved these days. In this study, molecular markers 18S rRNA, internal transcribe spacer (ITS) region of ribosomal DNA, trnL intron and trnL-trnF intergenic spacer (IGS) of chloroplast DNA (cpDNA), and random amplified polymorphic DNA (RAPD) were used for the molecular identification of 18 P. guajava samples from different indigenous tribes, 2 from non-indigenous tribe, and 12 commercial cultivars from markets in Taiwan. Molecular methods restricted fragment length polymorphism (RFLP) and denatured gradient gel electrophoresis (DGGE) are found time-consuming and less efficient as compared to RAPD, thus are not suitable for samples of high homology. In this study, 18S rDNA, ITS and cpDNA trnL intron and trnL-trnK intergenic spacer were also tested molecular marker; however, results analyzed by molecular algorithm UPGMA, Neighbor-Joining, Parsimony or Maximum likelihood showed no discriminations (data not shown). On the other side, ten 10-mer oligonucleotide primers were used in RAPD to amplify the specific genes from 32 guava samples. Four primers, OPB 17, OPG 6, OPY 15 and OPY 18, were able to direct the amplification and yielded a total of 82 polymorphic RAPD patterns. Thirty-two genotypes on the dendrogram were identified and were divided into two major groups, the uncultivated and commercial cultivars. Based on the cluster analysis, the red-flesh Psidium samples that were believed to have high medical function were grouped independently. The results suggest that RAPD is useful for the discrimination of uncultivated, cultivars and potential Psidium of high economy.

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