Andromonoecious outcrossing: a novel method of generating males suitable as parents of male asparagus cultivars

N.K. Stone, M.L. Roose
Plants homozygous at the sex locus for the dominant male allele (supermales) are valuable as parents of all-male asparagus hybrids, which are generally higher yielding and more homogeneous than mixed-sex hybrids. A novel method is described that uses outcrossed andromonoecious plants to generate supermales. Previous work by J. Sneep reports the undesirable expression of andromonoecy in the progeny of plants fathered by supermales generated from repeated selfing of andromonoecious plants. In this study, outcrossing highly andromonoecious plants descended from Sneep's germplasm with a pollen donor lacking andromonoecy appears to have been successful in producing supermales capable of producing offspring that express andromonoecy rarely or not at all. Two populations were produced using one andromonoecious female outcrossed with two different males. The female:male ratios of 20:65 and 14:36 observed in these populations were not significantly different than the 1:3 ratio expected from a Mm × Mm cross. However, one population had a significantly higher number of MM males in the progeny of test crossed males (11:13 Mm:MM) than would be expected from such a cross, while test cross progeny from the other population were not significantly different than the expected 2:1 Mm:MM ratio (32:14 Mm:MM). Two years' observations have identified a total of 22 supermales from these two populations that appear to transmit acceptably low levels of andromonoecy to their progeny. An additional two individuals may be useful supermale parents in some crosses, but require more testing. A higher frequency of skewed sex rations and/or andromonoecy occur in the progeny of some females. For example, test crosses performed with one male (MM4.256.9) and 14 females, resulted in 284 progeny. Only one of these 14 females produced female or andromonoecious progeny (2 female:2 andromonoecious:15 normal male). The other 13 crosses produced 264 normal male progeny.
Stone, N.K. and Roose, M.L. (2020). Andromonoecious outcrossing: a novel method of generating males suitable as parents of male asparagus cultivars. Acta Hortic. 1301, 75-82
DOI: 10.17660/ActaHortic.2020.1301.11
breeding, andromonoecy, supermales, Asparagus officinalis L

Acta Horticulturae