Characterisation of multiple embryos in almond

Abstract

Multiple embryos within the same tegument occur spontaneously in certain almond [Prunus dulcis (Mill.) D.A. Webb]cultivars including Nonpareil and Mission. Seedlings from the same polyembryonic seed are frequently viable, thoughoften one of the seedlings shows weak growth and develops poorly. These dwarf seedlings have been characterised in aprevious work as haploid. In this work, we have characterised 450 seedlings from polyembryonic seeds of the Californiancultivar Nonpareil, and 100 seedlings from polyembryonic seeds of the Spanish selections D97396 and D97407,including their germination and later growth. Isozyme and Simple Sequence Repeat markers were used to geneticallyanalyse seedling genetic structure. In addition, individual mitotic karyotypes were determined following staining of roottips. The percentage of twin embryos showing aberrant growth was approximately 25% with mortality rates of about 90%.Results suggested the sexual origin of both embryos. Seedlings from the same seed are genetically identical with a similargrowth, though often one of the seedlings from the secondary embryo loses part of the genomic contents and becomesan aneuploid plant and showed a weak development. The use of this material in almond breeding is also discussed.