Amphidiploids produced by natural chromosome-doubling in inter-specific hybrids between Dianthus × isensis Hirahata et Kitam. and D. japonicus Thunb.

Abstract

SummaryInter-specific crosses were carried out between two lines of Dianthus isensis Hirahata et Kitam., and one line of D. japonicus Thunb. Germinating seeds were obtained from only one line of D. x isensis used as the seed parent, and a total of 46 progeny from this cross were all confirmed to be hybrids by RAPD analysis and flow cytometry. The hybrids had intermediate characters of both parents with respect to leaf-width and flower-size, but flowered at the same time as each other with a uniform flower colour, purplish-pink. All 46 hybrids initially had sterile pollen and seeds, but two later produced some flowers of larger size with fertile pollen. Flow cytometric analysis revealed that flowers with restored pollen fertility originated from a chimaeric tetraploid branch induced by natural chromosome-doubling. Amphidiploid progeny were obtained from seeds produced by self-pollination of flowers with restored pollen fertility. Since these amphidiploids had some desirable characters, such as the early flowering of D. isensis, and the vigorous Summer growth, robust upright stems and broad leaves of D. japonicus, they can be used in carnation breeding programmes to incorporate useful traits from these two species such as disease resistance, heat tolerance and unique flower morphologies.