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In our earlier study, pre-fertilization barrier was one of the main factors causing the failure of the wide hybridization between Chrysanthemum grandiflorum 'Yuhuaxingchen' and C. nankingense, and seriously restricted the utilization of the excellent chrysanthemum germplasm, C. nankingense. In order to overcome the pre-fertilization barrier and obtain some hybrids, we carried out wide hybridization between them again in this study, and tentatively adopted three pollination techniques including mentor pollen, delayed pollination, and gibberellic acid treatment. The average number of pollen grains germinating on stigma at 24 h after pollination and the percentage of embryo were investigated with a temporary mount method and the technique of fluorescence microscopy. It was found that, compared with the control, delayed pollination, gibberellic acid treatment, and mentor pollen significantly increased the average number of pollen grains germinating on each stigma at 24 h after pollination by approximately 152, 235, and 182%, respectively. In addition, all the three pollination techniques significantly increased the percentage of normal embryos at different periods after artificial pollination in comparison to the control. Furthermore, seed sets of the crosses using the three special pollination techniques were 1.1, 1.4, and 2.0%, respectively, whereas we did not obtained any seeds in the control. Taken together, these results suggest that delayed pollination, gibberellic acid treatment, and mentor pollen are three useful pollination techniques for overcoming pre-fertilization barriers and increasing seed set in the wide hybridization between C. grandiflorum 'Yuhuaxingchen' and C. nankingense, and they may be widely applied for increasing breeding efficiency in other chrysanthemum wide hybridization facing similar pre-fertilization barriers. [ABSTRACT FROM AUTHOR]

Chrysanthemum grandiflorum ‘Yuhuaxingchen’ is an important commercial chrysanthemum cultivar with excellent ornamental quality but low drought tolerance, whereas C. indicum has exceptional drought tolerance. In our earlier study, many hybrid seeds between them were obtained through interspecific hybridization. In the present study, we selected six putative hybrid lines with most drought tolerance from all the hybrid lines by withholding water, indentified their facticity by chromosome counting, and then evaluated their drought tolerance through determining foliar electrolyte leakage (EL), contents of malondialdehyde (MDA) and proline, and plant survival rate after 20% polyethylene glycol 6000 treatment. It was found that 155 out of 282 seeds germinated and only 132 seedlings survived. In addition, chromosome and morphological analysis showed that the six putative hybrids were real hybrids and their morphological features were intermediate between their parents. Furthermore, the density of leaf epidermal hair, proline content, and plant survival rate were the highest in C. indicum and the lowest in C. grandiflorum among the six hybrids and their parents. In contrast, EL value and MDA content were the highest in C. grandiflorum and the lowest in C. indicum. These results suggest that some true hybrids with improved drought tolerance can be obtained through interspecific hybridization in chrysanthemum breeding. Therefore, interspecific hybridization between chrysanthemum cultivars and their wild species may become a promising way to improve their biotic and abiotic resistance in the future breeding. [ABSTRACT FROM AUTHOR]

To better understand the evolutionary history, intergeneric relationships and circumscription of Chrysanthemum and Ajania and the taxonomic position of some small Asian genera (Anthemideae, Asteraceae), the sequences of the nuclear ribosomal internal transcribed spacer (nrDNA ITS) and the chloroplast trnL-F intergenic spacer (cpDNA IGS) were newly obtained for 48 taxa and combined with those already deposited in GenBank. Phylogenies with an emphasis on Chrysanthemum, Ajania and its allies, by both maximum parsimony and Bayesian analysis, were constructed using either the ITS sequence alone, the IGS sequence alone or combined sequences. The IGS sequence was low phylogenetically informative, but some deletions and insertions were informative for interspecific and intergeneric delimitations. The ITS and the ITS/IGS phylogenies both suggested the presence of two major clades. The monophyly of subtribe Artemisiinae (clade A) could be retrieved when the phylogenetic positions of some ambiguous taxa were renewedly considered. Subtribe Artemisiinae was chiefly divided into two groups, (1) one corresponding to Chrysanthemum, Arctanthemum, Ajania, Opisthopappus and Elachanthemum (the Chrysanthemum group), (2) another to Artemisia, Crossostephium, Neopallasia and Sphaeromeria (the Artemisia group). Within the Chrysanthemum group, Chrysanthemum Arctanthemum and Ajania were closely related to each other, and the generic circumscription was ambiguous; Phaeostigma was excluded from this group that was also confirmed by the 6-bp insertion in the IGS sequence; radiate or rare discoid Brachanthemum was excluded, and discoid Elachanthemum without ray florets was added to this group; at the same time, Opisthopappus in subtribe Tanacetinae should be transferred to subtribe Artemisiinae and became one of the components of the Chrysanthemum group. Based on the molecular phylogenetic framework, the evolution of pollen and capitulum characters was inferred. [ABSTRACT FROM AUTHOR]

Reproductive barriers often exist in the crosses between Dendranthema grandiflorum (Ramat.) Kitamura and its wild species and seriously result in low seed set, consequently reducing breeding efficiency. For the purpose of revealing the factors leading to low seed set, we investigated pollen viability, germination behavior of pollen grains on stigmas and embryo development in the crosses between D. grandiflorum and three wild species, D. nankingense (Nakai) Tzvel., D. indicum (L.) Des Moul. and D. zawadskii (Herb.) Tzvel. using technique of paraffin section, and light, fluorescence and scanning electron microscopy. The results indicated pollen viability of three wild species ranged from 20 to 25%. In the cross between D. grandiflorum and D. nankingense, very few pollen grains germinated on stigmas after pollination and most of them germinated abnormally. In addition, normal embryos were observed in 12% ovaries at 8 days after pollination and thereafter all the embryos aborted. In other two crosses, many pollen grains germinated on stigmas and pollen tubes penetrated stigmas normally after pollination. Moreover, normal embryos were observed in over 50% ovaries from 8 to 15 days after pollination in the cross between D. grandiflorum and D. indicum, and seed set was 59%. In the cross between D. grandiflorum and D. zawadskii, normal embryos were observed in 52% ovaries at 8 days after pollination. After that, however, most embryos degenerated and seed set was only 9%. These data suggest that pollen viability has no significant effects on seed set of the three crosses. Very few germinated pollen grains on stigmas and abnormal growth of most pollen tubes before fertilization, and embryo abortion are the main factors causing failure of the cross between D. grandiflorum and D. nankingense, whereas only embryo abortion is a main factor resulting in low seed set in the cross between D. grandiflorum and D. zawadskii and no barriers occur in the cross between D. grandiflorum and D. indicum. [ABSTRACT FROM AUTHOR]

Meiotic behavior in pollen mother cells and in vitro pollen germination were examined in a sample of small-flowered anemone type chrysanthemum cultivars. Bivalent formation predominated at metaphase I in all the cultivars although some univalents and multivalents (mainly quadrivalents) were observed. Lagging chromosomes, chromosome bridges, micronuclei and polyads were observed at anaphase I/telophase I and anaphase II/telophase II. Pollen germinability ranged from 0.3 to 25.6% and was below 10% in 15 of the 22 cultivars. A significant positive correlation was established between disk floret length (tube + lobe)/style length and the frequency of chromosome bridges at anaphase II/telophase II, and negative ones both between disk floret length/style length and pollen germinability, and between the frequency of univalents at metaphase I and pollen germinability. [ABSTRACT FROM AUTHOR]

The karyotypes and meiotic behaviour of six Chrysantheminae species are investigated. Pyrethrum coccineum (Willd.) Worosch. is a tetraploid, while the other five species ( Argyranthemum frutescens (L.) Sch.-Bip., Opisthopappus taihangensis (Ling) shih, Crossostephium chinense (L.) Makino, Tanacetum vulgare L. and P. parthenium (L.) Sm.) are all diploids. Their karyotypes consist mainly of median centromere and submedian centromere chromosomes, although C. chinense also has two terminal centromere chromosomes, and P. parthenium two subterminal centromere chromosomes. No satellited chromosomes are observed in any of the six species. All the species have a 2A type karyotype, except for P. coccineum which is 3A. The meiotic behaviour in the pollen mother cells (PMCs) of all six species is essentially normal, with metaphase I chromosome pairing configurations in the diploid species predominantly showing 9II, while P. coccineum shows 18II. A low frequency of quadrivalents (and trivalents) and chromosome bridges/lagging chromosomes is observed. [ABSTRACT FROM AUTHOR]