Genetic Variability Assessment of a Diploid Pre-Breeding Asparagus Population Developed Using the Tetraploid Landrace ‘Morado de Huétor’

Different studies have reported a narrow genetic base for garden asparagus (Asparagus officinalis L.) due to its common origin, a diploid population (‘Purple Dutch’). The present study focused on the development of new diploid plant material that may be useful to widen the genetic base of the crop by using a tetraploid landrace ‘Morado de Huétor’ (A. officinalis × A. maritimus). With this purpose, a diploid pre-breeding population (n = 1000) carrying introgressions of ‘Morado de Huétor’ has been obtained. This new population derived from crosses under open pollination of a parental collection (n = 77) that was developed in a previous study. The parental collection derived from the first backcrossing using different diploid cultivated plants as a recurrent parent and ‘Morado de Huétor’ as a donor. The genetic diversity of the pre-breeding population was assessed using a set of EST-SSR markers (AG7, AG8, TC1, TC3, TC7, TC9) in a collection of plants (n = 57), which was randomly sampled in the pre-breeding population. The results were compared to previous data obtained from the parental collection, a set of current diploid asparagus cultivars and the landrace ‘Morado de Huétor’. The average of PICm (Polymorphic Information Content) values obtained in the pre-breeding population (0.75) resulted higher than the value obtained in the diploid cultivars (0.63) but lower than in ‘Morado de Huétor’ (0.83). Twenty-two alleles (52.4%) detected in the new diploid population were specific from ‘Morado de Huétor’. Principal Coordinate Analyses (PCoA) revealed that the new population had a genetic diversity distribution different from the current cultivars. This new population was also evaluated for different morpho-agronomic traits (earliness, stalk number, branching height and stalk thickness) for two years. Significant differences among plants (p < 0.001) were found for these five traits and, therefore, a genotype variation is suggested. As a result, 71 plants were selected to develop a breeding base population. The genetic variability of those selected plants was also analyzed and similar genetic variability to the pre-breeding population was obtained. The results obtained in this study show that this new population could be used to enlarge the genetic base of the current diploid asparagus cultivars.