Genetic Similarity Among Broccoli Inbreds “Essentially Derived” from Commercial Cultivars

Abstract

DNA markers can assess close genetic relationships between individuals of a crop as when one variety is developed (i.e., “essentially derived”) from another. An acceptable threshold, based on empirical results, should be established for a crop to indicate what constitutes an “essentially derived” variety in the absence of clear pedigree information. Empirical data could help settle infringements of intellectual property rights, but appropriate data are not being generated for most crops. Thus, our objectives were to characterize genetic relationships among broccoli varieties “essentially derived” from known parents using random amplified polymorphic DNA (RAPD) markers as a measure of genotype and to provide an empirical basis for threshold levels in this crop. Six F1 broccoli hybrids and three inbred lines (doubled-haploids) developed from each of the hybrids (24 entries) were evaluated by RAPD analysis. RAPD assays were conducted using 23 different oligonucleotide 10-mers. Of 179 RAPD bands scored, 94 were polymorphic among the entries. Similarity indices were computed from RAPD data, and a multi-dimensional scaling (MDS) plot was constructed. Similarity indices for all pairwise comparisons ranged from 0.40 to 0.90. `High Sierra' and it's derived lines were the most closely related group with indices from 0.81 to 0.90. With `High Sierra', `Sultan', and `Marathon', the three derived lines were more closely related to their respective parental hybrids than were any other entries. The hybrids `Futura', `Everest', and `Viking' were more genetically similar to other entries than to their derived lines. A threshold level based on data from `High Sierra', `Marathon', `Sultan', and their derived lines would not identify “essentially derived” lines developed from other hybrids.