Genetic variations among 17 accessions of zoysiagrasses collected from natural populations in Japan were investigated by RFLP analyses of chloroplast DNA (cpDNA) and nuclear DNA. These accessions were classified into five species based on morphological characteristics:
Zoysia japonica, Z. matrella, Z. tenuifolia, Z. sinica, and
Z. macrostachya. On the basis of eight kinds of RFLPs in cpDNAs detected across accessions, six chloroplast genome types (types A-F) were identified. Although type-A cpDNA was shared by five accessions of
japonica and four accessions of
matrella, derivative cpDNAs of type A, which each arose by a mutation, were identified in one accession of
japonica (type B) and in two accessions of
matrella (type C). One accession of
japonica which showed spikelets similar to those of shapes
macrostachya, contained type-F cpDNA as did
sinica and
macrostachya. The two accessions of
tenuifolia each showed a specific cpDNA type, i.e. types D and E.
Genetic relationships among the 17 accessions were investigated by the RFLP analyses of nuclear DNA with 20 genomic and gene probes. A dendrogram constructed with genetic distances calculated from the RFLP patterns indicated four major groups among them. Six accessions of
japonica comprised one group, whereas the one accession of
japonica possessing the type-F cpDNA was clustered with
macrostachya and
sinica. Four accessions of
matrella with type A cpDNA constituted another group in the dendrogram, showing a closer relationship to the
japonica accessions than to the other two accessions of
matrella. The remaining two accessions of
matrella and
tenuifolia accessions were grouped together. These data indicate that zoysiagrasses distributed in Japan harbor highly genetic variations, and that interspecific hybridization has occurred in natural populations.
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