S-genotyping in Japanese Plum by PCR and Capillary Gel Electrophoresis Detection M. E. Guerra and M. López-Corrales Departamento de Hortofruticultura. Centro de Investigación Agraria ‘Finca La Orden-Valdesequera’. A-V. Km 374, Guadajira, 06187 Badajoz Spain. J. Rodrigo and A. Wünsch Unidad de Fruticultura, Centro de Investigación y Tecnología Agroalimentaria de Aragón (CITA). Av. Montañana 930, 50059 Zaragoza, Spain Keywords: Prunus salicina Lindl., S-allele, SFB, S-RNase, gametophytic self- incompatibility Abstract In this work a PCR S-genotyping method using capillary electrophoresis detection was assayed in Japanese plum. Sweet cherry primers designed for S-RNase and SFB intron length polymorphism detection by capillary electrophoresis were assayed in Japanese plum cultivars. Amplification of both genes was successful and amplified sizes were correlated with Japanese plum S-alleles. The S-RNase genotype of 58 Japanese plum type cultivars previously determined by other methods was confirmed using this technology and the SFB alleles of these cultivars were also determined. Allele sizes of both genes are reported for 13 different S-alleles found in Japanese plum and will allow efficient S-genotype characterization in the species. INTRODUCTION Japanese plum (Prunus salicina Lindl.) type cultivars exhibit gametophytic self- incompatibility and hence cross-compatible pollinator trees have to be interplanted in most cultivars to ensure fruit set. There are several techniques available to determine cross-compatibility among different cultivars. Cross pollinations in the field and/or in the laboratory followed by pollen tube growth observation or the estimation of fruit set can be used. PCR-based-typing is also often used for S-genotype determination and to establish cross-compatibility and Incompatibility Groups. First S-RNases in Japanese plum were cloned by Yamane et al., (1999), identifying alleles Sa and Sb. Since then, other authors have identified the S- genotype of a great number of Japanese plum type cultivars using molecular techniques. Today 36 S-alleles have been described in cultivated Japanese plum; 19 have been labelled using letters (Sa to Ss) and further 17 have been labelled using numbers (S 7 , S 8 , S 10 , S 11 and S 15 to S 27 ) (Beppu et al., 2002, 2003; Sapir et al., 2004; Halász et al., 2007; Guerra et al., 2009). In this work, a PCR S-genotyping method using capillary electrophoresis detection was assayed, and the S-RNase genotype of 58 Japanese plum type cultivars previously determined by other methods was confirmed using this methodology. MATERIALS AND METHODS Fifty-eight Japanese plum-type cultivars of known S-genotype were analyzed (Table 1). Genomic DNA from these cultivars was isolated from young leaves and used for S-allele typing by PCR amplification (Guerra et al., 2009) of the S-locus genes S-