Salt solution treatment plays an important role in overcoming pre-fertilization barriers during Asiatic and Oriental lily crossbreeding

Abstract

Incompatibility between the stigma and pollen is the key factor limiting distant cross-breeding to produce Lilium Asiatic × Oriental hybrids (AO hybrids). To date, AO hybrids have not been available on the flower market. To produce AO hybrids, three pollination methods were applied to perform distant crosses between the Asiatic (A) hybrid ‘Pollyanna’ and the Oriental (O) hybrid ‘Siberia’ in this study. The seed-setting rate was significantly improved after a salt solution treatment. To clarify the mechanism by which the salt solution treatment allowed cross-incompatibility to be overcome, the effects of NaCl and KCl on the papilla cell morphology, pollen tube growth and seed setting rate were studied in the ‘Pollyanna’ × ‘Siberia’ crosses. After a salt treatment, the papilla cells at each stage swelled significantly, and the viscid exudates covering the papilla cell surface were diluted or dissolved. Furthermore, the pollen germination percentage increased, and the pollen tubes grew rapidly, causing more pollen tubes to enter the treated styles than the control styles. Hybridity of seedlings of ‘Pollyanna’ × ‘Siberia’ were confirmed by simple sequence repeat analysis, and their leaves showed intermediate traits between both the parents. These results suggest that salt solution treatments could be utilized for overcoming cross-incompatibility between A and O lilies to achieve AO hybrids, and that they provide insights into achieving other distant hybridizations in lilies.