Studies On Diversity Of J.regia And Homology Of Cross-species By Microsatellite Marker

Juglans. L, which has species to produce edible nuts, is the most important genus in Juglandaceae. There are 5 species in China. As a high energy food, rich in oil and and vitamins and minerals, J. regia and J. sigillata in them have been horticulturally developed and widely planted in China for nearly 500 years. More than 300 varieties have been selected from seedlings in walnut-producing regions since the 1970s. Recently, J. hopeiesis was considered being commercially important since the nut is greatly valuable in sculpture crafts and health. Some species was also introduced into China by exchange of germplasm resource.Along with development of the commercial plant and cultivar, the morphological marker, geographic origin and isozyme are not satisfy requirements in breeding, identification, collection and protection of variety in related species of the genus Juglans because of their limitations. The molecular marker is increasingly considered as a powerful tool to deal with these problems and widely practical in genetic analysis.Microsatellite, simple sequence repeats (SSR), has high homology, length polymorphism and codomain inheritance. Isolation and application of microsatellite from black walnut and pecan were reported recently. Successful application of SSR in other woody crops showed that SSR of black walnut was a powerful tool for genetic analysis of plants in the genus Juglans.17 pairs of primer from 49 microsatellite DNA screened showed clear strip and high length polymorphism in 4 accessories in C.illiinoensis K. and 41 accessories in Juglans L.. Result indicated that the flanking regions of those SSRs were high conservation in species of the genus Juglans and polymorphism of SSR in species tested was high than that of the traditional ways, but PIC (polymorphic information content), expected heterozygosity and observed heterozygosity in related species were obviously lower than those of black walnut.The same alleles found in J. hopeiesis, J. regia and J. mandshurica, the similarities and genetic distance indicated that there was a closed relationship among three species. Our study supported the hypothesis that J. hopeiesis originated from the nature hybrid of J. regia and J. mandshurica. J. sigillata with special alleles in 3 loci was suggested to be parallel with J. regia in dendrogram and was considered being an independence species. The longer genetic distance and litter similarity are the evidences that J. regia was independently developed in various regions of China. Our result based on the limited accessories and locus should be further studied.