Fertility and chromosome number in interspecific Impatiens hybrids

Abstract

The effects of chromosome number on female fertility of interspecific hybrids among Impatiens from Java (I. platypetala Lindl.), New Guinea (I. hawkeri Bull.), and Celebes (I. aurantiaca Teysm.) and the role of unreduced gametes in determining chromosome number and fertility were investigated. Two 24-chromosome interspecific hybrids were used as parents, 'Tangeglow' and 1 7851-1'. The F 1 offspring from this cross had chromosome numbers ranging from 28 to 36. Because 'Tangeglow' is seed-propagated and has normal meiosis, '7851-1' must have produced some male gametes that were incompletely unreduced and other gametes that were completely unreduced. The female fertility of interspecific hybrids with 36 chromosomes and 29 chromosomes was compared. The hybrids with 36 chromosomes exhibited greater fertility than the hybrids with 29 chromosomes. These results indicate that completely unreduced gametes provide for greater female fertility in the hybrid progeny because of the pre sence of complete genomes of Java and New Guinea Impatiens.