Development of microsatellite (SSR) marker multiplexes for future construction of a genetic linkage map for pear (Pyrus communis L.)
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Recent advances in the field of plant genetics and application of molecular technologies has lead to greater understanding of various crop genomes and their organization.The applications of these techniques include molecular markers which have been used to examine DNA variation within crop species. This allows for the creation of further genetic variation for new and favourable traits.Molecular markers or DNA markers are short fragments of DNA that can be used to locate desirable genetic traits in the genome or show specific genetic differences. The Maloideae subfamily includes fruit species such as pear. Pears (Pyrus communis L.) are large edible fruit that are grown in cool climates, native to coastal regions in Africa, Asia and Europe. The external appearance of this fruit plays a vital role on its rate of sale potential. Thus it is important for the appearances of the pear to meet the expectations of the consumer.External factors affecting the appearance of fruit, such as shape and colour, can have a large influence on the consumer’s first impression and opinion of what the fruit may taste like(Jaeger and MacFie, et al., 2001). The South African pear industry is the fourth largest in the fruit industry after apple, citrus and grape, exporting 3.8% to Europe (Ferrandi, et al., 2005).Increase in production and export of the pear is dependant on the variety of cultivars with desired traits. New cultivars, especially ranges of new cultivars, with harvest dates from early to late in the season, can fill gaps in the marketing strategy of exporters and in the local markets (Human, et al., 2005) Therefore, development of molecular markers allows for their possible use in maker-assisted selection and for the construction of a genetic linkage map thus leading to the location of favourable traits and ultimately the improvement of the quality of the pear.In this study high throughput genomic DNA extractions were performed. The Cetyltrimethyl ammonium bromide (CTAB) method was employed as the results proved to be most promising. Furthermore the screenings of molecular markers were conducted in order to obtain DNA variation. Molecular markers were used to locate specific genetic differences.Multiplexing PCR was conducted using fluorescent primers for further screening and results proved to be useful as many variations could be observed.