GENERATION AND APPLICATION OF VNTR DNA MARKERS TO FRUIT TREES

摘要

Multilocus and single locus variable number of tandem repeat (VNTR) DNA markers have been used to identify individuals and races as well as to detect genetic linkage with genes coding for the traits of interest. Multilocus VNTR markers are advantageous for identification, while single locus markers are suitable for linkage analysis. DNA fingerprint information was used to identify mango cultivars and to analyse the genetic relatedness of 20 mango cultivars. Individual specific patterns were obtained for each cultivar and the probability of obtaining a similar pattern for two different cultivars was found to be 9.4 × 10~(-6). Individual specific patterns were also obtained for the Carica species and for the tomato and avocado cultivars. Evolutionary trees, based on genetic distances, were established for mango cultivars, for tomato cultivars and accessions, and for several Persea species and avocado races. Genetic analyses aimed at detecting allelic and linked bands were carried out using VNTR multilocus probes in the family structures of avocado and mango. Using this tool, a very high level of heterozygosity was detected in these loci in avocado. By applying several methodologies of linkage analysis, a specific avocado DNA fingerprint band (p8) was identified as being genetically linked to a gene coding for avocado fruit skin colour. The complexity of linkage analysis of the multiband pattern led us to generate simple sequence repeat (SSR) single locus DNA markers to identify linkage with the traits of interest in avocado. Because of their characteristics, these SSRs are the markers of choice for human geneticists. The generation scheme for SSR markers, as well as their evaluation, are presented. The avocado SSR markers are now being mapped.