Establishment Of Molecular Detection System For Cultivars Purity And Identification For New Cultivars Of Apple (Malus Domestica Borkh.)

SSR (simple sequence repeat) markers were applied in total 67 apple cultivars including cultivars of 'Golden Delicious' family, 'Fuji' family, sport cultivars from 'Fuji' and other commercial cultivars for identification. The main results were as follows:1. A SSR analysis system of apple was established and optimized. 50ng genomic DNA was used as the template for polymerase chain reaction (PCR). The optimized concentration of Mg²⁺, dNTP, primer and Taq polymerase was 1.67 mmol/L, 0.25 mmol/L, 0.33 μmol/L and 1U/15μL respectively. The PCR products were analyzed on 6% denatured polyacrylamide gel and then the gel was silver-stained.2. 219 loci were detected in 25 cultivars of 'Golden Delicious' family. 2-17 loci were detectable for each pair of primers and the average detectable loci was 8.1. 12 pairs of useful primers were obtained, any of which was enough to distinguish more than 13 cultivars from each other. They were No.ltol2. No.10 and 11 could be used to identify 21 and 19 cultivars. Total they cover 25 cultivars' identification. They will be valuable commercial markers to protect breeder's rights. SSR markers were also effective to distinguish sport cultivars.3. Cluster analysis based on the 12 selected pairs of primers was conducted. The result was consistent with the pedigree data, except that several closely related cultivars according to pedigree were not clustered together. The possible reasons for inconsistence of my research and the pedigree data could be as follows: some highly informative SSR markers were not closely linked to agronomic important traits of commercial cultivars, random segregations of SSR alleles happened in hybrid population; secondly, the different selection criterion applied perhaps caused significant genetic diversity among siblings; thirdly, due to the complexity of apple genome, a small number of SSR loci could not be representative of the whole genome sufficiently, which might lead to a degree of deviation in cluster results. Compared with pedigree information, SSR markers could reveal more genetic variation among genotypes.