January 9-13, 2010
Town & Country Convention Center
San Diego, CA
Nimmakayala Padma1 , Nurul Islam-Faridi2 , Yan R Tomason1 , Satish K Ponnaiah1 , Umesh K Reddy1
Accessions of Citrullus spp. belonging to C. lanatus var. lanatus, C. lanatus var. citroids and Citrullus colocynthis and heirloom collections were subjected to molecular diversity analysis using AFLPs, methylated AFLPs and SSRs. Clustering pattern of principal coordinate analysis (PCA) with the shared polymorphisms using the subsets of data between any two taxon combinations helped to elucidate the introgression and interrelationships among the species. The current research explored additional insights such as extent of diversity at the methylation level that can cause epigenetic changes among the watermelon cultivars. We have undertaken Fluorescent in situ Hybridization (FISH) and observed two different organizational features in these two species. In lanatus, we have identified two major 18S-28S rDNA sites and these are located on two different homologous pairs of chromosomes. One 5S rDNA site, on the other hand, was observed and located on a pair of homologous pairs of chromosomes. In contrary, only one 18S-28S rDNA site and two 5S rDNA sites were observed in citroides accession. A dual FISH showed that all the three rDNA sites were on three different pairs of homologous chromosomes. To our knowledge, it is unusual in plant species, where the number of 18S-28S rDNA sites is always higher than the 5S rDNA site. Salient features pertaining to molecular and cytogenetic inferences will be presented.