Polyploidy and Aneuploidy in the Tamarillo, Cyphomandra betacea (Cav.) Sendt. (Solanaceae).

Abstract

AbstractThe occurrence of spontaneous polyploidy was quantified in the tamarillo (Cyphomandra betacea [Cav.] Sendt.), a diploid (2n = 2x = 24) solanaceous fruit crop cultivated in New Zealand. Polyploids of this species were recognized by their small, almost seedless fruit, these types occurring at a frequency of 0.24 % in seedling orchards. Parallel spindles were seen on rare occasions during meiotic anaphase II in diploid tamarillos and were the probable cause of spontaneous polyploidy in this crop. Pollen volume and viability, seed number per fruit, seed weight, fruit size, stomatal length and guard cell chloroplast number were measured in diploids and polyploids. The polyploids typically showed the manifestation of the gigas effect, with thicker leaves and larger flowers. Pollen volume, stomatal length and guard cell chloroplast number also increased with higher ploidy. Pollen viability was markedly lower in the polyploids compared to the diploids and in combination with post‐zygotic abnormalities caused a reduction in seed set and hence fruit size. Improvements in fertility and thus fruit size would be needed if the polyploids were to have commercial potential.