Genetic Variability Assessment of a Diploid Pre-Breeding Asparagus Population Developed Using the Tetraploid Landrace 'Morado de Huetor'

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 Huetor' (A. officinalis x A. maritimus). With this purpose, a diploid pre-breeding population (n = 1000) carrying introgressions of 'Morado de Huetor' 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 Huetor' 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 Huetor'. 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 Huetor' (0.83). Twenty-two alleles (52.4%) detected in the new diploid population were specific from 'Morado de Huetor'. 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.

Automated summary

This study aimed to develop new diploid plant material using a tetraploid landrace 'Morado de Huetor' to widen the genetic base of garden asparagus. The results showed that the new population had higher genetic diversity compared to diploid cultivars and could be used to expand the genetic base of current diploid asparagus cultivars.