MOLECULAR MARKERS IN TROPICAL AND SUBTROPICAL HORTICULTURE

Various classes of DNA markers have been used in several species including human, animals and plants. The two main purposes for applying DNA markers are identification and linkage analysis. This manuscript will describe some classes of DNA markers, discuss their applications and present data obtained from the application of DNA markers to avocado and mango. Three kinds of DNA markers were mostly used: AFLP, Minisatellites and Microsatellites. The polymorphism of AFLP results from the absence or presence of restriction enzyme sites. Mini and microsatellites are based on a Variable Number of Tandem Repeats (VNTR) and result in a higher level of polymorphism. Minisatellites create multi-band patterns which are quite useful for identification purposes but rather unsuitable for linkage analysis. Microsatellites or Simple Sequence Repeats (SSRs) are single locus markers, quite polymorphic and suitable for linkage analysis but expensive to generate and to genotype. AFLP and minisatellites were used to identify mango cultivars and rootstocks and to assess genetic relatedness between them. Minisatellites were applied to avocado to study genetic relatedness between cultivars and races and to assess the level of heterozygosity. Microsatellites were applied to avocado in order to generate a linkage map and to identify linkages between DNA markers and genes coding for agriculturally important traits.