A wide range of genetic diversity in pear (<Emphasis Type="Italic">Pyrus ussuriensis</Emphasis> var. <Emphasis Type="Italic">aromatica</Emphasis>) genetic resources from Iwate,Japan revealed by SSR and chloroplast DNA markers |
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Authors: | Hironori Katayama Shiho Adachi Toshiya Yamamoto Chiyomi Uematsu |
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Institution: | (1) Food Resources Education and Research Center, Faculty of Agriculture, Kobe University, Hyogo 675-2103, Japan;(2) National Institute of Fruit Tree Science, Tsukuba, Ibaraki 305-8517, Japan;(3) Botanical Gardens, Graduate School of Science, Osaka City University, Osaka 576-0004, Japan |
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Abstract: | Iwateyamanashi (Pyrus ussuriensis var. aromatica) is one of the Pyrus species which grows wild in Japan. The number of Iwateyamanashi trees has been decreasing, so conservation and evaluation
is urgently needed. Over 500 accessions of Pyrus species collected from Iwate in northern Tohoku region are maintained at Kobe University as an Iwateyamanashi germplasm collection.
In order to investigate the genetic diversity, five SSR (simple sequence repeat) markers, developed from Japanese and European
pear were examined for 86 Pyrus individuals including 58 accessions from Iwate. These SSR loci could discriminate between all the Iwate accessions except
for 10 that bear seedless fruit, as well as determine the genetic diversity in Iwateyamanashi germplasms. High levels of variation
were detected in 41 alleles and the mean observed heterozygosity across 5 loci was 0.50 for the Iwate accessions. Seedless
accessions sharing identical SSR genotype with the local pear variety “Iwatetanenashi” were supposed to have been propagated
vegetatively via grafting. In an UPGMA phenogram, Japanese pear varieties (P. pyrifolia) were clustered into two groups with some Iwate accessions including seedless ones. Another 38 Iwate accessions were not
clustered clearly, and there was no clear relationship between these accessions and geographical distribution or morphological
characters. Allele frequency revealed that the Iwate accessions were genetically more divergent than the Japanese pear varieties.
Most Japanese pears possessed a 219 bp deletion at a spacer region between the accD and psaI genes in the chloroplast DNA (cpDNA), but other Pyrus species and two Iwateyamanashi trees did not. In the Iwate accessions, 79.3% had a deletion type cpDNA and others had a standard
type cpDNA without deletion. These results are indicative of the wide range of genetic diversity in the Iwate accessions which
include Japanese pear varieties. A combination of SSR and cpDNA analyses revealed high heterogeneity in Iwateyamanashi and
coexistence of Iwateyamanashi and hybrid progeny with P. pyrifolia. These could be reasons for the wide range of continuous morphological variation described previously. |
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Keywords: | Genetic diversity Iwateyamanashi Pear Pyrus SSR Chloroplast DNA Genetic resources |
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