Creating novel chrysanthemum germplasm via interspecific hybridization and backcrossing

The interspecific cross between Chrysanthemum x grandiflorum (Ramat.) Tzvel. 'rm20-12' (R, 2n = 54) and C. makinoi Matsum., and Nakai (M, 2n = 18) was achieved using embryo rescue, and a single backcross progeny using C. x grandiflorum 'rm20-12' as paternal parent was obtained. The morphology of the two independent F-1 hybrids (MR1 and MR2) differed from that of both parents. MR1 had a larger inflorescence diameter along with narrow leaves and a reduced number of ray and tubular florets. MR2 was shorter and its inflorescence developed fewer tubular florets than either M or R. The BC1F1 hybrid was similar to its maternal plant MR2 in terms of leaf length and width, inflorescence diameter and the number of ray florets, while it produced fewer tubular florets than either MR2 or R. The flower color in both F-1 hybrids was lavender, while the BC1F1 plant bore purple flowers. The aphid resistance and heat tolerance of MR1, MR2 and the BC1F1 hybrid were both significantly superior to that of C. x grandiflorum 'rm20-12'. Interspecific hybridization followed by backcrossing shows clear potential for cultivar improvement in chrysanthemum.