**7. Genetic diversity of apricot based on molecular markers**

Apricot is a temperate and subtropical zones fruit. China, the Irano-Caucasian region (Turkey and Iran), Central Asia, Europe and North America are the main producer regions in the world. The Central Asia is the oldest and the primary genetic source of apricot group is the Central Asian accessions are self-incompatible; the Irano-Caucasian apricots which are mostly the cultivated ones are mostly self-incompatible, with large fruits and low chilling requirements. The European and the North American apricots are originated from Irano-Caucasia has relatively narrow genetic diversity and are self-compatible with large fruits (Mehlenbacher et al. 1991). For a long period, genetic diversity in apricot was studied with pomological, morphological and phenological characteristics (Guerriero & Watkins, 1984). DNA-based markers that have been used in the last decade clarify the relationship among the apricot accessions.

For breeding and commercialization of promising apricot cultivars, a precise characterization and discrimination of the cultivars are prerequest. Different types of marker such as morphological, molecular, biochemical systems have been used for genetic analysis in horticultural plants. However, due to the effects of environmental factors, asessment of morphological and pomological traits may be ambiguous. Therefore, markers independent from the environment are necessary for reliable identification and discrimination of genotypes and cultivars. DNA markers are well known independent from environmental interactions and they show high level of polymorphism. Therefore, they are considered invaluable tools for determining genetic relationships/diversity. Various types of DNA markers are now available. Among them, RAPD developed by Williams et al. (1990) has been commonly used method in apricot to assess genetic variability and relationships among cultivars (Takeda et al. 1998; Zhebentyayeva et al. 2000; Hormaza, 2001; Mariniello et al. 2002; Ercisli et al. 2009). More recently, ISSR (Chenjing et al. 2005; Yilmaz, 2008), RFLP (De Vicente et al. 1998), AFLP (Hurtado et al. 2001, 2002; Hagen et al. 2002; Panaud et al. 2002; Geuna et al. 2003; Krichen et al. 2006; Yuan et al. 2007), SSR (Hormaza, 2002; Romero et al. 2003; Zhebentyayeva et al. 2003; Maghuly et al. 2005; He et al. 2006; Maghuly et al. 2006; Ali Khan et al. 2008) and SRAP (Uzun et al. 2010) techniques has also been used in apricot to characterize different cultivars belongs to diverse eco-geographical groups.

The diversity determined between apricot cultivars was probably due to crosses between wild and cultivated apricots and cultivars from different eco-geographic origin (Uzun et al. 2010). Microsatellite analyses suggested that European cultivars might have originated through hybridization among Irano-Caucasian genotypes and also most of the European cultivars have originated by hybridization with genotypes from the Irano-Caucasian group (Maghuly et al. 2005; Faust et al. 1998; Kostina, 1969). The heterozygosity of the apricot genotypes narrowed while apricot transfer from China to Europe. Pedryc et al. (2009) show that Middle European and Chinese apricot are distantly related.

Molecular markes have created new era in genetic diversity researches since early nineties. Restriction fragment length polymorphism (RFLP), and PCR based markers such as randomly amplified polymorphic DNA (RAPDs), sequence-related amplified polymorphism (SRAP), single nucleotide polymorphism (SNPs), micro-satellites or simple sequence repeats (SSRs) are mostly used marker systems in plants and also in apricot genetic divesity researches. Microsattelites among all is a very useful tool for apricot diversity studies, and most promising to cleary genetic relation among the apricots and travel routes of apricots (Romero et al. 2003; Maghuly et al. 2005).

Amplified fragment length polymorphism (AFLP) molecular markers assesment for the genotyping of 118 commercial apricot accessions and some related apricot species (Geuna et al. 2003). The researchers clustered the apricots into four groups corresponding to their geographic distribution; (1) Mediterranean apricots, (2) Chinese apricots, (3) apricots of continental Europe and (4) Europe-North American apricots. Their data confirmed that the migration of apricot from the East to West. They also showed with molecular markers that *Prunus sibirica* and *Prunus mandshurica* are different from *Prunus armeniaca*, but they group together with Chinese accessions (Geuna et al. 2003). In anohter study Romero et al. (2003) studied apricots by using of SSR markers to determine the genetic relationships among genotypes from different eco-geographical groups. They observed that Western European and North American subgroups clustered together in aggrement with their common origins from ancient European cultivars (Kostina, 1969; Bailey & Hough, 1975; Badanes et al. 1996). However their study placed Hungarian cultivars closer to the Central Asian group than to the other European cultivars.

Hayashi et al. (2008) studied Japanese apricot (*Prunus mume*) germplasm and reported that the genetic diversity and relationships among 127 Japanese apricot germplasms assessed by SSR markers. Their study supported the two hypotheses that Japanese apricot cultivated in Japan had been introduced from China and that fruiting cultivars had been selected from flower-ornamentals.

Turkish germplasm was studied by Yilmaz (2008) and Uzun et al. (2010) and genetic diversity and relationships among the accesessions were determined using RAPD, ISSR, SRAP and SSR markers. The researchers reported the high genetic diversity in Turkish apricots. Four high chilling requiring cultivars originated from Eastern Turkey clustered apart from the rest. European, South African, North American and other Turkish cultivars were not clearly grouped regarding to their geographic districts. Therefore the researchers suggested that these cultivars, despite their different geographic origins, have similar genetic background.
