Genetic characterization of Asparagus officinalis doubled-haploid collection and wild relatives

The genus Asparagus is very large consisting of around 150 species found as herbaceous perennials, tender woody shrubs and vines. The cultivated species (Asparagus officinalis L., diploid) is a highly prized vegetable,
grown in different environments ranging from cool temperate zones to deserts, Mediterranean climates and tropical areas. As a consequence, Asparagus breeders have developed different cultivars that
differ for their morpho-agronomic traits, habit and ploidic status (few triploid and tetraploid cultivars
are used). Several breeding methods are used for developing cultivars, among which a well developed in vitro anther culture technique produces homozygous clones useful for F1 hybrids constitution. A fluorescent
based AFLP (amplified fragment length polymorphism) technique were applied with the aim to assess genetic diversity among a collection of 173 doubled haploid (DH) androgenetic clones, five Asparagus wild species and interspecific hybrids obtained among the cultivated species and two wild relatives. The average number of AFLP fragments generated per primer set was 105, varying in size from 50 to 550 bp. A total of 1054 AFLP fragments were detected, 20% of which were polymorphic.
Genetic similarity based on DNA polymorphisms, showed that a few number of AFLP primer combinations are able to distinguish the cultivated DH clones from the wild species. Indeed, from one DH clone
for each anther donors and the wild species were used to construct a dendrogram using Dice’s coefficient and the unweighted pair group method with the arithmetic mean (UPGMA). Genetic distances among all DH clones were calculated using the C.S. Chord distance; and a neighbour-joining (NJ) consensus tree was constructed in order to support the breeder for parental genotype choice for asparagus hybrid
constitution.
These results represent the first study on the genetic relationships among several DH clones from a large collection useful for supporting breeding programs as well as among cultivated DH clones group,
wild species and interspecific hybrids.