Abstract:

Seeds are seldom obtained in the crosses between chrysanthemum cultivars and diploid wild species in Dendranthema, which seriously influences utilization of excellent genes from those wild speices. In the present study, with an aim to reveal the factors leading to infertility in the crosses between chrysanthemum cultivars and wild species, we carried out the interspecific hybridization between D. grandiflorum ‘JinlingHuangyu’and D. avandulifolium, tested pollen viability of male parent, examined germination behavior of
pollen grains on the stigmas after pollination, and observed embryo development. It was found that pollenviability of D. lavandulifolium was 11.2% just before pollination, no pollen grains germinated on the stigmas during 4 h after pollination and only 7.5 pollen grains germinated on each stigma at 8 h after pollination. At 12 h after pollination, the number reached the highest value, 16.1. At 24 h and 48 h after pollination, the number was quickly decreased to 3.2 and 2.4, respectively. In addition, most pollen grains germinated abnormally on the stigmas and many pollen tubes stayed on the stigmaspsurface and failed to enter ovaries. At 8 d after pollination, normal globular embryos were observed only in 12.0% ovaries. Thereafter, only
abnormal embryoswere observed in some ovaries, and as a consequence, no seedswere obtained in the cross. However, seed set of female parent under open pollination conditions was as high as 42.3%. These results suggest that both pre- and post-fertilization barriers, i. e. only a few germinated pollen grains on the stigmasand abnormal germination ofmost pollen grains before fertilization aswell as degeneration of a large number of embryos after fertilization, may be the main factors resulting in infertility in the cross.

Key words: Dendranthem agrandiflorum, artificial crossing, seed set, pollen viability, embryo abortion