Morphological characteristics and chromosome behaviour in F1, F2 and BC1 progenies between Chrysanthemum × morifolium and Ajania pacifica

Abstract

The garden chrysanthemum (Chrysanthemum x morifolium) variety 'Aoyunhuoju' (2n = 6x = 54) was crossed as female with Ajania pacifica (2n = 10x = 90) to produce an intergeneric F1 hybrid, which was used both as a source ofF2 progeny and as a parent for a first back-cross with 'Aoyunhuoju'. The morphology of all of the F1 hybrids and hybrid derivatives was intermediate with respect to the two parents, although the BC1 progenies resembled 'Aoyunhuoju' more closely than any of the F1 and F2 progenies did. In the F1 hybrid, the density of silvery hairs on the lower leaf surface and along the margin of the leaf was lower than in A. pacifica, while that in the BC1 generation, this trait was less prominent than in the F1. The somatic chromosome number of the F1, F2 (with an exception of F2-6 of a mainly 63) and BC1 generations was 2n = 8x = 72, 2n = 8x = 72 and 2n = 7x = 63 respectively, as expected. The hybrids and their derivatives retained a variable degree of fertility. There was a low frequency of meiotic chromosome pairing failure in all three hybrid generations, with most of the chromosomes involved as bivalents. Some BC1 individuals show potential for commercialization thanks both to their flower shape and the inheritance of the silvery leaf trait from A. pacifica.