49 Genetic Diversity of Grapefruit and Pummelo Accessions Based on SRAP Markers A. Uzun 1 , T. Yesiloglu 2 , Y. Aka Kacar 2 , O. Tuzcu 2 , O. Gulsen 1 , G. Kafa 3 , B. Yildirim 2 and S. Anıl 4 1 Erciyes University, Faculty of Agriculture, Department of Horticulture, 38039 Kayseri, Turkey 2 Cukurova University, Faculty of Agriculture, Department of Horticulture, 01330 Adana, Turkey 3 Alata Horticultural Research Institute, Genetics and Breeding, 33740 Erdemli, Mersin, Turkey 4 General Directorate of Agricultural Research of Ministry of Agriculture and Rural Affairs, Ankara, Turkey Keywords: Citrus paradisi, Citrus maxima, germplasm, mutation Abstract Genetic diversity was evaluated by sequence related amplified polymorphism (SRAP) markers among 27 grapefruit (Citrus paradisi Macf.), 5 pummelo (Citrus maxima (Burm.) Merr.) accessions and 4 pummelo hybrids. Twenty-one SRAP primer combinations produced a total of 90 polymorphic fragments with an average of 4.3 per primer combinations. The mean polymorphism information content (PIC) was 0.34. The unweighted pair group method arithmetic average (UPGMA) analysis demonstrated that the accessions had a similarity range from 0.73 to 1.00. Accessions were separated into two main clusters and one of them included 5 pummelos whereas the other one included grapefruits. In the pummelo cluster all pummelos were distinguished whereas in the grapefruit cluster most of grapefruits did not clearly separate from each other probably due to their mutation origin. INTRODUCTION The grapefruit (Citrus paradisi Macf.) is believed to be a natural hybrid between pummelo [Citrus maxima (Burm.) Merr.] and sweet orange (C. sinensis L. Osb). It is originated from Barbados islands in the Caribbean and was first named as ‘Citrus paradisi Macf’ in 1837 by James Macfedyan (Scora et al., 1982; Scora, 1988). Grapefruits are highly polyembryonic so many cultivars originated as selected nucellar seedlings or bud sport mutations. Genetic variation among common grapefruit cultivars was reported to be very low due to their origin by mutation (Fang and Roose, 1997; Corazza-Nunes et al., 2002). After being introduced into Florida, grapefruit became an economically important Citrus species and since then many grapefruit cultivars have been developed (Hodgson, 1967). The United States is the major producer country in the world. Turkey’s grapefruit production is nearly 160 thousand tonnes and 78% of this production is exported, so grapefruit is economically important for Turkey (FAO, 2007). The pummelo is native of tropical and subtropical regions in Asia and has been cultivated for over 2000 years in China (Corazza-Nunes et al., 2002; Yong et al., 2006). Barrett and Rhodes (1976), reported that pummelo one of three ‘true citrus species’ and most subsequent studies are in agremeent with this thesis (Federici et al., 1998; Nicolosi et al., 2000; Barkley et al., 2006; Uzun et al., 2009). Pummelo has played important role as a parent of several cultivated citrus groups including sweet orange and sour orange. Molecular studies on pummelo genetic diversity has been limited. Simple sequence repeats (SSR) and random amplified polymorphic DNA (RAPD) (Barkley et al., 2006; Corazza-Nunes et al., 2002; Yong et al., 2006) markers have been used to determine pummelo genetic diversity. Sequence related amplified polymorphism (SRAP) is a PCR based marker system as described by Li and Quiros (2001). The SRAPs is a simple and efficient marker system that can be adapted for a cultivar of purposes in different crops, including map Proc. II nd IS on Citrus Biotechnology Eds.: A. Gentile and S. La Malfa Acta Hort. 892, ISHS 2011