Breeding of Polyploid Asparagus (Asparagus officinalis L.)

Abstract

Asparagus is especially suitable for polyploidy breeding. The aim is to develop clone-based hybrid varieties, in particular male 4x varieties. For this purpose, genetically divergent diploid idiotypes") are subjected to mitotic or meiotic polyploidization. In developing hybrid partners, special attention is paid to resistance in addition to yield and quality characters. Early diagnoses are apphed in selection so as to shorten breeding times. Somaclonal variations may occur relatively often on in vitro propagation; these need to be eliminated. Triplex and quadruplex type males are suitable for paternal hybrid partners. Strong inbreeding depressions need to be avoided in their production.

Second meiotic division restitution (SDR) 2n pollen formation in diploid and hexaploid species of Asparagus

“…In the Asparagus plants analyzed, 2n microspores developed into large size pollen grains (2n pollen) whose functionality in crosses was not determined . However, four tetraploid plants were identified among 200 field grown Skiebe et al (1991), working with the same species, obtained 42 triploid and four tetraploid plants from 1168 4x x 2x crosses. They also cite a previous report by Falavigna & Fantino (1985), on the production of polyploids from 4x-2x crosses.…”

“…Since these are related species belonging to a polyploid series, the results obtained are considered an indication that 2n pollen formation in them is not the result of accidental disturbances in meiosis but is, rather, under genetic control. On the other hand, no information is available on frequencies of 2n egg production or mode of formation in the genus, although polyploid plants have been obtained in 2x x 4x crosses in garden asparagus (Skiebe et al, 1991). 1 174 0 26 41 107 2 169 3 6 14 146 3 172 0 14 14 144 4 200 66 82 12 40 5 148 0 24 18 106 6 174 2 18 18 136 Most mutants which affect the meiotic process leading to the formation of numerically unreduced gametes have been found to be recessive.…”

“…Alternatively, a breeding program could be carried out at the polyploid level, as Skiebe et al (1991) have proposed, since the expression of relevant agronomic characters such as spear diameter and yield has a large heterotic component. With a maximum of four alleles per locus, the tetrasomic level is of greater productive potential than the disomic because it can harbor greater diversity per locus.…”

“…But, since they are formed by independent meiotic processes, the population of spores produced by a plant would present a high level of heterogeneity which could be of value to increase the genetic variability of polyploid populations for breeding purposes. Asparagus breeding at the polyploid level is still in an early stage of development (Skiebe et al, 1991). Further and intensive breeding work needs to be carried out to test the feasibility of this approach in contrast to conventional diploid breeding, and to assess the advantages of sexual vs. asexual polyploidization in the generation of polyploids.…”

Short communication. Employment of molecular markers to develop tetraploid “supermale” asparagus from andromonoecious plants of the landrace ‘Morado de Huétor’

“…In A. officinalis populations, it is possible to find plants with different ploidy levels, in spite of their diploid genome, which is a result of the formation of unreduced gametes (2n) (Camadro, 1992(Camadro, , 1994. The cross between these tetraploid and diploid plants could generate triploid hybrids (Hasegawa et al, 1987;Skiebe et al, 1991;Ozaki et al, 2004). Hybrids between diploid plants Employment of molecular markers to develop tetraploid "supermale" asparagus from andromonoecious plants of the landrace 'Morado de Huétor' from commercial cultivars and tetraploid 'Morado de Huétor' have been developed and can be used to widen the genetic pool of commercial asparagus cultivars (Moreno et al, 2010).…”