We investigated the resistance to stem blight disease (Phomopsis asparagi (Sacc.)) in the progeny of two combinations of interspecific crosses between Asparagus officinalis (sensitive) and Asparagus A. kiusianus (resistant) in an effort to produce resistant cultivars. The progeny showed different degrees of disease severity, depending on the combination of crosses. Most of the hybrids derived from AO0060 (A. officinalis) × AK0501 (A. kiusianus) showed high disease resistance comparable to that of A. kiusianus. The results indicate that disease resistance could be introduced from A. kiusianus into A. officinalis, and that the selection of an appropriate cross combination is important for the production of disease-resistant cultivars. We analyzed the parents and hybrids of reciprocal crosses between A. officinalis and A. kiusianus using derived cleaved amplified polymorphic sequence markers to investigate the inheritance of the chloroplast genome, whose inheritance and genetic characteristics are not yet known. The chloroplast DNAs were inherited from the maternal parent, indicating that no major genes related to stem blight resistance were found in the chloroplast DNA.

The origin of a spontaneous triploid asparagus plant from crosses of 2x × 2x was investigated by SSR and flow cytometric analyses. One hundred and twenty-four progeny were obtained from crosses between a diploid female 'Gold Schatz' and a diploid male 'Hokkai 100'. SSR analysis proved that two and one genes were transmitted from the maternal and paternal parents, respectively, at each SSR locus of one progeny, 07M-61, whereas one gene each was from the female and male parents in the other diploid progeny. Triploidy of 07M-61 was confirmed by flow cytometric analysis. It was suggested that the triploid plant was derived from fertilization between an unreduced egg and reduced sperm nuclei, given its SSR genotypes. It was also suggested that the unreduced maternal gamete was derived from first division restitution (FDR) or second division restitution (SDR) with chiasma occurrence during meiosis. There were no noticeable morphological differences between the triploid and diploid progeny.