Genetic Diversity Of Peach [Prunus Persica(L.)Batsch] Germplasm Revealed By Biological Characters And SSR Markers

Peach (Prunus persica (L.) Batsch), a member of the Prunus genus, originated in the Western of China. Along with the several thousands years of cultivation and genetic improvement, there are abundant of genetic resources and ecological types as well as divergent cultivars in China. In addition, lots of new cultivars were released in the second half of the 19th century after a few seedlings of "Chinese Cling" peach were introduced from Southern China into the United States and Japan. A consequence of the overfull cultivars caused a lot of problem in resources preserving, breeding and production. In order to reveal the genetic diversity and provide valuable information for breeding program and core collection establishing, two types of marker, SSR molecular marker and biological characters, were employed to detect the genetic relationships among 102 peach cultivars, which originated in China, Japan, America and Canada. Some main conclusions in this study are as follows:1. In 14 biological characters, fruit shape and fruit flavor two characters which both had 6 scales were at the highest level and petiole gland shape which had 2 scales was at the lowest level in grade index; the coefficients of variation of four characters: flesh color, titratable acidity content, flavor and flesh texture were exceed 40%, respectively.2. PCR reactions were performed in a volume of 10μL containing 1×buffer, 10ng of genomic DNA, 1.5mmol·L^-1Mg²⁺,0.15mmol·L^-1 of each dNTP, 0.55μmol·L^-1 each primer and 1.0U of Taq polymerase.3. A collection of 102 peach cultivars, originated from different countries, have been screened with 34 SSR primer pairs in order to analyze their genetic diversity. 245 bands were amplified by 13 informative and reliable primers, of which 238 (97.1%) were polymorphic loci. A relatively low level of genetic diversity (Nei's gene diversity 0.1938 and Shannon index 0.3134) was revealed at population level.4. The number of genetic similarity between cultivars ranged from 0.57 to 0.95 for SSR marker and from 0 to 0.93 for biological character with an average of 0.74 and 0.38 in SSR marker and biological character, respectively. The reason for difference between two results may be that the number of biological characters was too few.5. UPGMA cluster analysis based on biological characters data classified these peaches into 5 groups: "Peach and flat peach", "Nectarine and yellow peach", "Yexiandongtao, Lihepantao and Roupantao", "American cultivars having short chilling requirement" and ""Ornamental cultivars", respectively. That based on SSR markers data also classified into 5 groups: "Chinese southern peach and American & Japanese cultivars", "Chinese Northern and northwestern cultivars", "Yunnan yellow peach and Xinjiang nectarine", "Chinese flat peach" and "American cultivars having short chilling requirement". The former and the latter groupings were generally consistent with the classification of the fruit flesh types and the regions of origin of cultivars, respectively. In addition, discrepancy occurred in some cultivar discriminating when the two cluster analysis along with their respective PCA applied.6. There is remarkable difference between two values of gene flow obtained from different countries populations (6.97) and from different types (0.63) populations. The reason for this smaller one may be physiological difference hindering the generation of progeny from the various types of peach.7. The correlation between the biological similarity matrix and the matrix of genetic similarity based on SSR markers was very weak (r=0.2386).