Morphological characteristics and chromosome behaviour in F _1, F _2 and BC _1 progenies between Chrysanthemum × morifolium and Ajania pacifica

摘要

The garden chrysanthemum (Chrysanthemum × morifolium) variety "Aoyunhuoju" (2n = 6x = 54) was crossed as female with Ajania pacifica (2n = 10x = 90) to produce intergeneric F1 hybrids, which were used both as the source of F _2 generation and as the parent for a first back-cross with "Aoyunhuoju". The morphology of all of the F _1 hybrids and hybrid derivatives was intermediate with respect to the two parents, although the BC _1 progenies resembled "Aoyunhuoju" more closely than any of the F _1 and F _2 progenies did. In the F _1 generation, 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 F _1. The somatic chromosome number of the F _1, F _2 (with an exception of F _2-6 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 BC _1 individuals show potential for commercialization thanks both to their flower shape and the inheritance of the silvery leaf trait from A. pacifica.