Isolation and characterization of ten microsatellite loci for wild Citrus japonica (Rutaceae)

Abstract

The genus of Citrus Linnaeus (Rutaceae) includes several widely cultivated species, such as C. sinensis (L.) Osbeck, C. limon (L.) Burm.f. and C. maxima (Burm.) Merr., which are top ranked among all the fruit crops (Mabberley 1997). Citrus is believed to be native to Southeast Asia (Scora 1975; Gmitter and Hu 1990) and has been cultivated for fruit for over 4000 years (Webber et al. 1967). The long cultivation history, together with a great number of intraspecific and interspecific hybrids in Citrus, makes the genetic background extremely complex. The C. japonica is native to South China, with wild populations distributed in broad-leaved evergreen forests and cultivated forms widely grown in warm parts of China (Zhang et al. 2008). It is a species complex, integrated from the formerly segregated genus Fortunella, consisting of F. hindsii (Champ. ex Benth.) Swingle, F. venosa (Champ. ex Benth.) Huang, F. margarita (Lour.) Swingle, F. japonica (Thunb.) Swingle and F. bawangica Huang (Zhang et al. 2008). Despite this taxonomic revision, a considerable amount of variation in fruit size within some wild populations still exists. Further comprehensive field and molecular studies throughout the complex are needed. Recently, due to human activities and environmental changes, wild populations of C. japonica have been dramatically declining (Huang et al. 2010). Evaluating the genetic structure of these wild populations is urgent for their conservation. Additionally, various cultivated forms of C. japonica have important ornamental and medicinal, as well as food values. However, their origins have never been identified. Microsatellites have been proven to be efficient genetic markers for taxon delimitation, genetic structure analysis and detection of origins of cultivars. In the present study, a set of polymorphicmicrosatellite markers for