Sumei Chen

Production and characterisation of the intergeneric hybrids between Dendranthema morifolium and Artemisia vulgaris exhibiting enhanced resistance to chrysanthemum aphid (Macrosiphoniella sanbourni)

Aphids represent the most destructive of chrysanthemum pests to cultivation. Reliable variety sources of resistance and control methods are limited, so development of highly resistant breeding lines is desirable. An intergeneric hybrid between Dendranthema morifolium (chrysanthemum) variety ‘Zhongshanjingui’ and Artemisia vulgaris (mugwort) ‘Variegata’ was attempted. Most of the hybrid embryos aborted at an early developmental stage. Embryo rescue allowed the generation of hybrid plants, whose hybridity was confirmed by a combination of morphological, cytological and GISH analysis. The hybrids were vigorous, flowered normally, and their flower and leaf shape resembled those of the chrysanthemum more than those of the mugwort parent. The hybrids showed much higher resistance to chrysanthemum aphid (Macrosiphoniellasanbourni) than maternal chrysanthemum by inoculation test. The leaves of the hybrid developed a higher density of trichomes and secretory glands compared to the maternal chrysanthemum. GC–MS analysis revealed that ~51% of the essential oil in the hybrid leaves were monoterpenoids and sesquiterpenoids, while the proportion in the chrysanthemum was ~37%, and in the mugwort was ~90%. It is inferred that higher aphid resistance in the hybrid mainly owed to the leaf micromorphology and bioactive essential oil content.

Molecular phylogeny of Chrysanthemum, Ajania and its allies (Anthemideae, Asteraceae) as inferred from nuclear ribosomal ITS and chloroplast trnL-F IGS sequences

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, ChrysanthemumArctanthemum 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.

Isolation and characterisation of Chrysanthemum crassum SOS1, encoding a putative plasma membrane Na+/H+ antiporter

A full-length cDNA homologue of SOS1 (salt overly sensitive 1) was isolated from the salinity-tolerant species Chrysanthemum crassum and found to encode a Na(+) /H(+) antiporter, using degenerate PCR and RACE-PCR. The 3752-bp sequence comprised a 3438u2003bp open reading frame, encoding a 127-kDa protein with 12 transmembrane domains within its N terminal portion, and a hydrophilic cytoplasmic tail in its C-terminal portion. CcSOS1 appears to be a plasma membrane protein, and shares ∼62% identity at the peptide level with its Arabidopsis thaliana homologue. Expression of CcSOS1 in the roots of C.xa0crassum was sensitive to salinity stress, while in the leaves CcSOS1 was down-regulated in the presence of abscisic acid. CcSOS1 transcript abundance was reduced in both roots and leaves of plants exposed to low temperature, while it was increased in leaves (but not in roots) after drought stress. CcSOS1 expression was not regulated in the presence of CaCl2 . A heterologous complementation assay in yeast suggested that CcSOS1 directs Na(+) efflux, mimicking the function of the endogenous NHA1 protein. Thus CcSOS1 appears to encode a salinity-inducible plasma membrane Na(+) /H(+) antiporter. This gene may be useful in transgenic approaches to improving the salinity tolerance of related ornamental species.

Interspecific hybrids between Dendranthema morifolium (Ramat.) Kitamura and D. nankingense (Nakai) Tzvel. achieved using ovary rescue and their cold tolerance characteristics

Ovary rescue was employed to create six interspecific hybrids from the cross between Dendranthema morifolium (Ramat.) Kitamura ‘rm20-12’ (2nxa0=xa054) and its wild diploid relative D. nankingense (Nakai) Tzvel. (2nxa0=xa018). The morphology of the hybrids differed from that of either parent. The leaf length and width of all three D. morifoliumxa0×xa0D. nankingense hybrids exceeded that of the parents, as did the plant height of two and the inflorescence diameter of another of the hybrids. One of the reciprocal hybrids was heterotic for leaf length and width. All the hybrids bore yellow flowers. The cold tolerance of five hybrids was significantly superior to that of their D. morifolium parent. Interspecific hybridization clearly provides an effective means of cultivar improvement in chrysanthemum.

Intergeneric hybridization and relationship of genera within the tribe Anthemideae Cass. (I. Dendranthema crassum (kitam.) kitam. × Crossostephium chinense (L.) Makino)

An intergeneric cross has been made between Dendranthema crassum (kitam.) kitam. (2nxa0=xa090; ♀) and Crossostephiumchinense (L.) Makino (2nxa0=xa018; ♂). Most of the hybrid embryos aborted at an early developmental stage. Using ovule rescue, it was possible to establish a single intergeneric hybrid plant showing 2nxa0=xa054 chromosomes. The leaf length, leaf width and epidermal hair density of the hybrid were all intermediate between those of the parents. However the flower diameter, number of tubular florets, epidermal hair height and epidermal hair length exceeded those of both parents. A genomic in situ hybridization approach was able to distinguish between the parental genomes in the hybrid plant.

Analysis of Expressed Sequence Tags (ESTs) Collected from the Inflorescence of Chrysanthemum

The expressed sequence tags (ESTs) described in this report were obtained from the inflorescence of chrysanthemum. A complementary DNA (cDNA) library was constructed from the inflorescence of the anemone-type chrysanthemum ‘Zhongshanzigui’. In total, 7,307 cDNA clones were sequenced, representing 4,563 unique sequences and consisting of 3,567 singletons and 996 contigs. Comparison to the GenBank nonredundant (nr) database revealed 57.2% (2,608/4,563) chrysanthemum sequences with homology to genes of known function of other organisms. Approximately 26.67% (1,217/4,563) of the unigenes were clustered into 23 categories by the clusters of orthologous group analysis: Most of the identified transcripts were genes related to metabolism, subcellular localization, protein biosynthesis, and cell wall structure. The ESTs presented here will be a valuable addition to floral development transcriptional database.

The identification of flavonoids and the expression of genes of anthocyanin biosynthesis in the chrysanthemum flowers

In order to provide additional information on the coloration of chrysanthemum flowers, the flavonoid composition and the expression of six structural genes involved in anthocyanin pathway in the ray florets of a pink flowering (cv. H5) and two white flowering (cvs. Keikai and Jinba) Chrysanthemum grandiflorum cultivars were examined. HPLCDAD/ESI-MSn analysis showed that cyanidin 3-O-(6″-O-malonylglucoside) and cyanidin 3-O-(3″,6″-O-dimalonylglucoside) were the two major flavonoids presented in H5, while white flowering cultivars contained flavones instead of anthocyanins. Nine flavone derivatives were detected in the three cultivars, the amount of each flavone varied upon cultivars, and seven of these were identified as luteolin 7-O-arabinosylglucuronide, apigenin 7-O-glucoside, luteolin 7-O-malonylglucoside, apigenin 7-O-malonylglucoside, chrysoeriol 7-O-malonylglucoside, acacetin 7-O-rutinoside and acacetin 7-O-malonylglucoside. The two white flowering cultivars showed similar total flavonoid content, which was about two fold higher than that in H5. A high expression of the genes encoding dihydroflavonol 4-reductase and 3-O-glucosyltransferase was detected only in H5 but not in Keikai or Jinba. Chalcone synthase, chalcone isomerase, flavanone 3-hydroxylase, and flavonoid 3′-hydroxylase were expressed in all flowers, suggesting that the lack of anthocyanin in white flowering cultivars cannot be due to any blockage of their expression.

The embryo rescue derived intergeneric hybrid between chrysanthemum and Ajania przewalskii shows enhanced cold tolerance

Five intergeneric hybrids between the chrysanthemum cultivar ‘Zhongshanjingui’ (as female) and Ajania przewalskii (as male) were obtained with the help of embryo culture. While ‘Zhongshanjingui’ bears a standard anemone type flower and A. przewalskii a non-anemone type one, the inflorescence type of the hybrids varied. The diameter of the hybrids’ flowers was intermediate between those of the parents. The chromosome number of the hybrids was 2nxa0=xa045, of which GISH analysis was able to establish that 27 were inherited from ‘Zhongshanjingui’ and the other 18 from A. przewalskii. A combination of various assays was used to show that the cold tolerance of the hybrids was equivalent to that of the highly tolerant A. przewalskii parent. Enhanced cold tolerance was correlated with an increase in free proline and a decrease in malondialdehyde content.

The Lateral Suppressor-Like Gene, DgLsL, Alternated the Axillary Branching in Transgenic Chrysanthemum (Chrysanthemum × morifolium) by Modulating IAA and GA Content

The lateral suppressor-like gene DgLsL was transformed by agroinfection into chrysanthemum in both the sense and antisense directions. Sense transformants branched more profusely than the wild-type nontransformant, while branching in the antisense transformants was significantly suppressed. An analysis of DgLsL transcript abundance in the shoot tips revealed that expression was enhanced in the sense transformants and suppressed in the antisense ones. The shoot tip content of indole-3-acetic acid (IAA) was reduced in the sense transformants but enhanced in the antisense ones. The sense transformants had a lower content and the antisense transformants had a higher content of gibberellic acid (GA). Cytokinin content was not affected by the variation in DgLsL expression. We conclude that DgLsL controls shoot branching through its effect on IAA and GA levels.

Reproductive barriers in the intergeneric hybridization between Chrysanthemum grandiflorum (Ramat.) Kitam. and Ajania przewalskii Poljak. (Asteraceae)

In order to reveal the causes of low seed set in the intergeneric cross between Chrysanthemum grandiflorum (Ramat.) Kitam. ‘Zhongshanjingui’ (female parent) and Ajania przewalskii Poljak. (male parent), we systematically investigated megasporogenesis and megagametogenesis of female parents, pollen germinability of male parents, pollen–pistil interaction and hybrid embryo development using paraffin section and light, fluorescence and scanning electron microscopy. The results indicate that development of megagametophyte of female parent belongs to Polygonum type and 84.6% ovules developed to normal 8-nucleate embryo sac at the stage of pollination; the pollen germinability in vitro of male parent was 39.3%; a large number of pollen grains germinated normally and no callose deposited on the female stigmas within 24xa0h after pollination. Furthermore, about 75% ovules were fertilized, whereas only 17.2% ovules developed to normal maturing embryos at 15xa0days after pollination due to abortion at various developmental stages. Taken together, these results suggest that sterile ovules of female parent, pollen viability and pollen–pistil interaction have no significant influence on seed set in the cross. A high percentage of embryo abortion or degeneration, i.e. post-fertilization barrier, may be the main factor for low seed yield.