Molecular techniques such as PCR have become a key tool for researchers and plant
breeders, allowing for faster identification of resistant/susceptible or homozygous/heterozygous
plants. This knowledge allows breeders to minimize the time for developing disease resistant
hybrids. PCR fragments produced with the REXF1/R2 primers were sequenced from a variety of
Solanum (Lycopersicum) species. The REX-1 locus sequences of 13 different plants were aligned
and from areas of conserved sequences, four primer pairs were designed that would amplify
single fragments of different sizes (300, 400, 500, and 600 bp) at annealing temperatures of 53-
57°C. These primers gave the expected fragment sizes with over 70 samples. Thus, it is
anticipated that these four pairs of primers could be used in multiplex-PCR reactions as internal
controls for evaluation of the quality of the sample DNA. This would allow researchers to rely
on one set of internal controls that could be used in a wide range of reactions.