Screening microsatellites for their effectiveness to identify and differentiate among Actinidia genotypes

The aim of this study was to evaluate a set of microsatellites (SSRs) for their effectiveness in genotyping Actinidia cultivars or genotypes in an effort to determine their genetic identity and establish the appropriate DNA fingerprinting patterns. A set of 23 genotypes, 13 of A. deliciosa and 10 of A. chinensis were subjected to PCR- mediated DNA fingerprinting using SSRs as molecular markers. Thirty-eight primer pairs for di-base polymorphisms (AC/GT and AG/CT) were used. The PCR products were analyzed on denaturing and non-denaturing polyacrylamide gels (9 and 30 SSRs respectively). The evaluation of SSRs for their screening ability was based on the number of alleles and the indices, PIC (polymorphism information content), DI (diversity index) and I (probability of identity) whereas the DNA fingerprint pattern for each genotype was obtained. Data indicated that all SSR loci were highly polymorphic. The average estimates for the indices, taking the two species together, were PIC = 0.805 ±0.125, DI = 0.844 ±0.048, I = 0.044 ±0.025. Primers were generally effective in discriminating among genotypes and were ranked according to their ability to identify genotypes within and between species. Either of the two primers, UDK 96-092 and UDK 96-141, were the most effective in discriminating among genotypes within A. chinensis. In contrast, two primers in combination, UDK 96-088 and UDK 99-168, were necessary for effective genotype identification within A. deliciosa. The primer UDK 96-035 by itself effectively discriminated between A. chinensis and A. deliciosa. Data obtained allowed the fingerprint pattern to be established for each genotype and will be helpful in cultivar maintenance and identification, estimating genetic similarities and/or in cultivar development programs.