Two separate samples of DNA were prepared for RAPD analysis, one from ten homozygous dominant resistant plants and the other from ten homozygous recessive susceptible plants. In total, only 300 PCR reactions were required to obtain three markers linked to Dm, illustrating the efficiency of RAPDs for gene tagging (Michelmore et al., 1991) (iii) Use of RFLPs flanking a DNA segment.
In tomato, high density linkage map was used to select two intervals (one 15 cM long and the other 6.5 cM long), each containing the gene responsible for pedicel abscission and fruit ripening. Each interval was flanked by RFLP markers. Individual plants having alternative alleles of flanking markers were classified in two groups, and DNA samples obtained from the two groups of bulked plants, were screened with 200 random primers for PCR products.
It was assumed that polymorphism in PCR products should be derived from either within the defined interval or from a segment very close to it. Using this approach, three polymorphic products were identified linked to the selected intervals and to the gene of interest (Giovannoni et al., 1991).