Varietal purity evaluation in sesame (Sesamum indicum L.) seeds by means of RAPD markers in Venezuela.

Sesame (Sesamum indicum L.) is an important crop in tropical countries. Its grain is used mainly as source of an excellent quality oil, but it has also applications in confectionery. As any other crop, the seed used as initial input in the agricultural process, is the first warranty of success for the farmer, therefore concept of seed quality is very important. Quality seed must be evaluated during multiplication process, to be sure that this multiplication does not affect varietal purity, which is one of the components of genetic quality of seed. To determine ability of RAPD markers to evaluate varietal purity, two objectives were defined: to evaluate ability of RAPD markers to detect seeds of another cultivar that is not being evaluated (seed contaminants), for that seeds of cultivar UCLA-1 were mixed with seeds of one accession of the Germplasm Bank of Universidad Centroccidental Lisandro Alvarado, in different proportions: 99:1, 98:2, 97:3 and 95:5. RAPD markers were performed on these different proportions, and band pattern of each proportion were compared to UCLA-1 and to the other accessions band pattern. Every band was reported when RAPD were performed for every sample in each proportion, either bands of UCLA-1 and bands of the other accession. It means, that RAPD was able to identify seed contaminant in proportion as low as 1%. The other objective was to evaluate the ability of RAPD to detect troubles in the step of multiplication seed. For that, RAPD was performed on samples from genetic seed, and seeds of the two following multiplication cycles. RAPD identified the three samples from genetic seed with the same band pattern, but it was different to band pattern of the other two kinds of seed. Therefore, RAPD had the ability to identify that multiplication of seed was not totally suitable, because some non-target seeds appeared as source of DNA, as source of contamination. RAPD proved to be an effective tool to monitor genetic quality, specifically varietal purity, in sesame seed.