Genetic diversity among melon accessions from Iran and their relationships with melon germplasm of diverse origins using microsatellite markers

Mahmoud Raghami 0 1 2 Ana Isabel Lopez-Sese 0 1 2 Mohamad Reza Hasandokht 0 1 2 Zabihollah Zamani 0 1 2 Mahmoud Reza Fattahi Moghadam 0 1 2 Abdolkarim Kashi 0 1 2 0 M. R. Hasandokht Z. Zamani M. R. F. Moghadam A. Kashi University of Tehran , Tehran, Islamic Republic of Iran 1 A. I. Lopez-Sese Instituto de Hortofruticultura Subtropical y Mediterranea 'La Mayora' (UMA-CSIC) , Malaga, Spain 2 M. Raghami (&) Vali-e-Asr University of Rafsanjan , Rafsanjan, Iran Melon is one of the most important horticultural crops in Iran. There are a few studies on the genetic structure of Iranian melon. A set of 18 simple sequence repeat (SSR) primer pairs were used to assess the genetic diversity in a collection of 24 melon accessions representing different botanical groups of Iranian cultivated melons (vars. inodorus, cantalupensis and dudaim), along with 28 reference accessions from diverse geographic origin. All studied SSR loci were polymorphic that confirmed their usefulness for genetic analysis of melons. A total number of 141 alleles were detected, with an average of 7.8 alleles per locus for reference genotypes and 4.38 alleles per locus for Iranian accessions. The low variability within Iranian melon accessions is reflected by the low values of the observed heterozygosity (with an average of 0.119), indicating lack of intercrossing between accessions or a high rate of self-pollination. Values of observed homozygosity for ''Suski-e-Sabz'' and ''Khatouni'', as the most cultivated melon in Iran, were 0.98 and 0.99, respectively. Cluster analysis divided Iranian accessions into two major groups. The highest level of polymorphism was detected among the dudaim group. The analysis of molecular variance indicated that the majority of variation (87 %) was due to the difference within accessions. The average pairwise genetic distance among Iranian accessions was 0.674. - Genetic distance Melons, Cucumis melo L., are important horticultural crops in tropical and subtropical regions, which are also grown extensively in temperate climates. Worldwide, more than 25 million tons of melons were produced in 2010, where China, Turkey and Iran were the major producers (FAO 2010). In Iran, more than 50 % of total vegetable production is related to cucurbits. Among them, melon is the most important crop. In 2010, Iranian farmers grew almost 75,000 ha of melon with a total production of 1.31 million tons (FAO 2010). Historical records indicate that melon was already cultivated in Persia (Iran) during the third millennia BC, and was imported to Europe from Iran and the Caucasus approximately 3,000 years ago (Walters 1989). Melons or muskmelon are native to Iran and adjacent countries toward the west and east. In fact, Musk is a Persian word for a kind of perfume and melon is derived from Greek words (Robinson and Decker-Walters 1997). The origin of diversity for melon was traditionally believed to be in Africa (Robinson and Decker-Walters 1997), although recent molecular systematic studies, suggested that it may be originated from Asia and then reached to Africa (Renner et al. 2007). Central Asia, Iran, Afghanistan, India, Transcaucasia, Turkmenistan, Tajikistan, and Uzbekistan, as well as Afghanistan and China (Robinson and DeckerWalters 1997) are considered primary diversity centre for melon (Tzitzikas et al. 2009). Two formal infraspecific taxa within C. melo were recognized by Kirkbride (1993) subsp. melo and subsp. agrestis. Subsp. melo comprises the large-fruited and sweet dessert melons of commerce originating mostly in western Asia and Europe (Nesom 2011). Nesom proposed that no wild forms are represented within subsp. melo. Cultivated forms of C. melo have long been known to be similar to morphologically distinct wild and feral races generally identified as subsp. agrestis. The forms comprising subsp. melo are known strictly as cultivars and almost certainly have arisen from subsp. agrestis, thus their taxonomic treatment as conspecific subspecies is appropriate (Nesom 2011). The high polymorphism of cultivated melons has led botanists to propose different infraspecific classifications (Pitrat et al. 2000) and several infra-specific classifications have been proposed for melon. Recently, classification focused mainly on central Asian diversity (Pitrat 2008). An overview of infra-specific nomenclature by Pitrat et al. (2000) proposed 16 botanical varieties: conomon, makuwa, chinensis, acidulus and momordica within the subsp. agrestis, and cantalupensis, reticulatus, adana, chandalak, ameri, inodorus, flexuosus, chate, tibish, dudaim and chito within subsp. melo. Nesom (2011) noted that molecular data have not supported the apportionment of the groups among the two subspecies in this classification. Recently, a simplified system is summarized by Nesom (2011) with four varieties [melo (including var. cantalupo], inodorus, reticulatus and flexuosus) within subsp. melo and seven varieties (agrestis, chito, conomon, texanus, dudaim, chate and momordica) within subsp. agrestis. In Iran, various groups of melon cultigens are grown. The main commercial ones are the sweet type melon of vars. inodorus and cantalupensis. The Inodorus type Iranian accessions differ from other melons belonging to the var. inodorus in their netted skin surface and in occasional rugby ball-shaped fruits. Some researchers suggest that these melons should be considered in other group called iraniansis (Lotfi and Kashi 1999). Var. Cantalupensis are less important in Iran. There are two types of melons in this group: globular-shaped fruits with meridian stripes and soft, spongy flesh, and the other ones are larger, less sweet, always have orange flesh and do not have stripes. Var. dudaim is also cultivated in various areas of Iran. It is characterized by small reddish yellow fruits with ochre stripes, and a round or slightly oval shape with a velvety skin. It has a unique fragrant and musky aroma, and a whitish and insipid pulp that is barely edible. They are originated from Persia (Nesom 2011) and generally cultivated for ornamental or aromatic uses from Turkey and the Caucasus to Afghanistan (Aubert and Pitrat 2006). Some Iranian accessions of var. dudaim are edible, sweet, with typical aroma and big size. A high level of molecular and morphological variability in leaf, plant, and fruit characteristics has been described in melon species (Akashi et al. 2002; Monforte et al. 2003; Stepansky et al. 1999). C. melo is, therefore, considered the most diverse species in Cucumis (Stepansky et al. 1999). Genetic diversity studies have used isozymes (Staub et al. 1997; Akashi et al. 2002), RFLPs (Zheng et al. 1999), RAPDs (Garcia et al. 1998; Stepansky et al. 1999; Mliki et al. 2001; Lopez-Sese et al. 2003; Staub et al. 2004; Sensoy et al. 2007; Tanaka et al. 2007), AFLPs (GarciaMas et al. 2000), ISSR and simple-sequence repeat (SSR) (Katzir et al. 1996; Staub et al. 2000; Daning-Poleg et al. 2001; Lopez-Sese et al. 2002; Mon (...truncated)