Asparagus macrorrhizus Pedrol, Regalado et López-Encina, an endemic species from Spain in extreme extinction risk, is a valuable genetic resource for asparagus breeding

Abstract

Asparagus maritimus is a species distributed in sandy soils along the Mediterranean coast. It has been reported as salt tolerant and resistant to rust. The wild asparagus species are a very important genetic resources for asparagus breeding because the current commercial cultivars have a narrow genetic base. Until recently, the only population of A. maritimus catalogued in Spain was a small population, which is at high extinction risk, located around the coastal lagoon “Mar Menor” in the region of Murcia. Different studies carried out in the current work support the recent description of this population as a new species named Asparagus macrorrhizus. Plants from three populations of A. maritimus were used to carry out studies of characterization and the results were compared with plants of A. macrorrhizus. The morphological studies showed clear differences between the populations of A. maritimus and A. macrorrhizus. One of the differences found between these populations was at the ploidy level. The plants of A. maritimus were hexaploid (2n = 6x = 60), while the plants of A. macrorrhizus were dodecaploid (2n = 12x = 120). Also, the flavonoid composition showed that A. maritimus contains six different flavonoids while in A. macrorrhizus 90 % of the flavonoid content corresponds to only one flavonoid (Nicotiflorin) followed by minor quantities of other two. Another difference between these populations was supported by the principal coordinate analysis (PCoA) using data from 4 EST-SSRs markers amplified in plants of A. maritimus and A. macrorrhizus, and clearly separates the two species. The differences found in this work highlight the importance of A. macrorrhizus as a possible genetic resource for asparagus breeding. The distribution of A. macrorrhizus is limited to the area surrounding the “Mar Menor” lagoon. The prospections carried out in the last years indicated the high risk of extinction of this species due to the urbanization of this natural habitat. Therefore, we have included A. macrorrhizus in our germplasm bank in vivo and in vitro as well as in the breeding programs.