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Chrysanthemum morifolium is one of the most significant multipurpose crops with ornamental, medicinal, and edible value. Terpenoids, an essentials component of volatile oils, are abundant in chrysanthemum. However, the transcriptional regulation of terpenoid biosynthesis in chrysanthemums remains unclear. In the present investigation, we identified CmWRKY41 , whose expression pattern is similar to that of terpenoid content in chrysanthemum floral scent, as a candidate gene that may promote terpenoid biosynthesis in chrysanthemum. Two structural genes 3 -hydroxy-3-methylglutaryl-CoA reductase 2 (CmHMGR2) and farnesyl pyrophosphate synthase 2 (CmFPPS2), play key role in terpene biosynthesis in chrysanthemum. CmWRKY41 can directly bind to the promoters of CmHMGR2 or CmFPPS2 through GTGACA or CTGACG elements and activate its expression to promote sesquiterpene biosynthesis. In summary, these results indicate that CmWRKY41 targets CmHMGR2 and CmFPPS2 to positively regulate sesquiterpene biosynthesis in chrysanthemums. This study preliminarily revealed the molecular mechanism of terpenoid biosynthesis in chrysanthemum while enriching the secondary metabolism regulatory network. • Revealed CmWRKY41 regulates the biosynthesis of sesquiterpenes. • CmWRKY41 directly activates the expression of CmHMGR2 and CmFPPS2. • CmWRKY41 binds GTGACA and CTGACG elements, but not the classical W-Box (TTGACC). [ABSTRACT FROM AUTHOR]

Members of the B Box (BBX) family of proteins are known to be important for directing the growth and development of the Arabidopsis thaliana plant. Here, an analysis of a newly isolated chrysanthemum gene encoding a BBX family member implied that it was a likely ortholog of AtBBX13. The gene (designated CmBBX13) was most actively transcribed in the leaves and stem apex. CmBBX13 transcription was arrhythmic under either continuous darkness or continuous light, so the observed diurnal variation in its transcription appeared not to respond to the circadian clock. The outcome of transiently expressing CmBBX13 in onion epidermal cells suggested that the CmBBX13 protein localized to the nucleus. Both a yeast- and a protoplast-based assay showed that the protein has transactivational activity. When CmBBX13 was constitutively expressed in A. thaliana , flowering was delayed under both short and long day conditions. The presence of the transgene also down-regulated a number of genes known to promote flowering, including APETALA1 (AP1), SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1), FLOWERING LOCUS T (FT) and FD , while simultaneously up-regulating the floral inhibitor-encoding genes FLOWERING LOCUS C (FLC) and TARGET OF EAT 2 (TOE2). The data suggested that CmBBX13 regulates flowering time independently of the photoperiod pathway. • The isolation of a BBX transcription factor CmBBX13 from Chrysanthemum was described. • CmBBX13 over-expression in Arabidopsis delays flowering independent of day length. • The floral inductors were reduced, but the floral inhibitors were induced by CmBBX13. [ABSTRACT FROM AUTHOR]

RNA-Seq was applied to capture the transcriptome of the leaf and root of non-treated and salinity-treated chrysanthemum cv. ‘Jinba’ plants. A total of 206,868 unigenes of mean length 849 nt and of N50 length 1363 nt was identified; of these about 64% (> 132,000) could be functionally assigned. Depending on the severity of the salinity stress, differential transcription was observed for genes encoding proteins involved in osmotic adjustment, in ion transport, in reactive oxygen species scavenging and in the regulation of abscisic acid (ABA) signaling. The root stress response was dominated by the up-regulation of genes involved in ion transport, while that of the leaf reflected the plant's effort to make osmotic adjustments and to regulate Ca 2+ transport. An array of known transcription factors (WRKY, AP2/ERF, MYB, bHLH and NAC) were differentially transcribed. [ABSTRACT FROM AUTHOR]

The diploid species Chrysanthemum nankingense (Anthemideae, Asteraceae) is closely related to the commercially important hexaploid ornamental species Chrysanthemum morifolium and is well adapted to poor environments. In this study, phenotypic variants of C. nankingense were first identified by morphological traits. Using EST-SSR (simple sequence repeat) analysis, we detected some absent EST-SSRs. The percentage of AFLP (amplified fragment length polymorphism) polymorphic fragments was 78.2%, indicating high genetic diversity. To evaluate the genome methylation level and methylation polymorphism, we used the MSAP (methylation-sensitive amplification polymorphism) technique to analyze the 30 C . nankingense lines. The total DNA methylation level ranged from 54.6% to 62.6%. Most of the MSAP-methylated fragments (97%) were polymorphic in the lines. The U -values associated with hemi-methylation were larger than those associated with full methylation in four of the 30 lines, and six individual values were statistically significant ( U > 1.96). The high genomic diversity as well as the high methylation polymorphism may be responsible for the morphological polymorphism. There was no significant correlation between the phenotypic and genetic diversity among the lines. [ABSTRACT FROM AUTHOR]

The nitrogen nutrition index (NNI) plays a critical role in improving crop nitrogen (N) diagnosis and predicting crop yield. Proximal sensing chlorophyll meters (CMs) have been widely used in precision agriculture, but few studies have focused on its utilization for estimating the NNI of chrysanthemum (Dendranthema morifolium Ramat.). This study aimed to develop a model for NNI estimation in chrysanthemums using CM readings. Field experiments were conducted with five N fertilization treatments during two growing seasons (in 2019 and 2020). Chrysanthemum canopies were sampled across multiple days after planting (DAP) to determine plant N concentrations (PNC) and plant dry matter (PDM). CM measurements were recorded at defined DAP at different leaf layer positions (L1, L2, and L3 represent leaves that were 1/3, 1/2, and 2/3 apart from the top of the plant, respectively), and the normalized CM index (NCMI 1 , NCMI 2 , and NCMI 3) was calculated. All PNC and PDM data from the two seasons were then applied to fit the critical N (N c) dilution curve using a Bayesian statistical model to estimate the NNI. Regression models were established to predict chrysanthemum NNI using CM readings and the NCMI as predictor variables. This study determined the N c of chrysanthemum to be N c = 2.318 ×PDM−0.204. L1 was found to be the optimal leaf layer position for NNI estimation. Additionally, the NCMI-based prediction of NNI was found to be more reliable than that from the CM readings. NCMI 1 was the best predictor of chrysanthemum NNI across multiple DAP (NNI = 0.0741 ×e2.6285NCMI1, coefficient of determination = 0.59***, root mean square error = 0.110 NNI). The findings of this study can be applied to accurately predict chrysanthemum NNI from CM readings to provide technical support for N nutrition diagnosis in chrysanthemums. • This is the first study establishing the critical N dilution curve in chrysanthemum. • The upper leaf layer is optimal for chrysanthemum N nutrition index (NNI) estimations. • The normalized chlorophyll meter index showed to be the best predictor of chrysanthemum NNI. [ABSTRACT FROM AUTHOR]

• The heredity of four intrinsic qualities, i.e., total flavone, chlorogenic acid, luteoloside, and isochlorogenic acid A, is first investigated in a segregating F1 population. • Transgressive individuals in both directions are observed for all quality traits, and a moderate-high heritability is at 0.57 ∼ 0.84. • Three improved hybrids of superior quality are identified for breeding use. • The findings are conducive to the breeding success of high-quality tea chrysanthemums. The active compounds in the dry head-like capitulum of tea chrysanthemums are essential contributors to human health. Therefore, increasing the internal quality is a critical aim of tea chrysanthemum breeding programs, and knowledge of the inheritance of the quality traits and accurate identification of elite hybrids is vital for breeding success. The heredity of four intrinsic qualities, i.e., total flavone, chlorogenic acid, luteoloside, and isochlorogenic acid A, were investigated in a segregating F 1 population. We implemented the principal components analysis (PCA), the membership function method, and hierarchical cluster analysis (HCA) to identify hybrids of superior quality. The quality traits were widely segregated, with the coefficient of variation ranging from 0.29 to 0.88. Transgressive individuals in both directions were observed for all investigated traits. Genotypes, environments, and genotype × environment interaction significantly affected the investigated compounds, and a moderate-high heritability was at 0.57 ∼ 0.84. Total flavone, luteoloside, and isochlorogenic acid A showed highly positive heterosis (P < 0.01), while chlorogenic acid demonstrated negative heterosis, and the heterosis ratio was separately estimated at 17.11%, 127.14%, 14.51%, and -9.10%. Moreover, three elite hybrids with a comprehensive evaluation value (D) larger than 0.8 were selected for breeding use. The current study's findings add a new understanding of the inheritance pattern of the investigated active compounds, and the production of improved hybrids represents an essential step towards developing high-quality tea chrysanthemums. [ABSTRACT FROM AUTHOR]

Members of the large WRKY transcription factor family are responsible for the regulation of plant growth, development and the stress response. Here, five WRKY members were isolated from chrysanthemum. They each contained a single WRKY domain and a C 2 H 2 zinc finger motif, so were classified into group II. Transient expression experiments demonstrated that all five were expressed in the nucleus, although CmWRKY42 was also expressed in the cytoplasm. When expressed heterologously in yeast, the products of CmWRKY22 and CmWRKY48 exhibited transactivation activity, while those of CmWRKY21 , CmWRKY40 and CmWRKY42 did not. The transcription of the five CmWRKY genes was profiled when the plants were challenged with a variety of abiotic and biotic stress agents, as well as being treated with various phytohormones. CmWRKY21 proved to be markedly induced by salinity stress, and suppressed by high temperature exposure; CmWRKY22 was induced by high temperature exposure; CmWRKY40 was highly induced by salinity stress, and treatment with either abscisic acid (ABA) or methyl jasmonate (MeJA); CmWRKY42 was up-regulated by salinity stress, low temperature, ABA and MeJA treatment and aphid infestation; CmWRKY48 was induced by drought stress, ABA and MeJA treatment and aphid infestation. The function of CmWRKY48 was further investigated by over-expressing it transgenically. The constitutive expression of this transcription factor inhibited the aphids' population growth capacity, suggesting that it may represent an important component of the plant's defense machinery against aphids. [ABSTRACT FROM AUTHOR]

With water shortage worldwide, seeking drought resistance genes are of great value for molecular breeding. Here, we isolated a homologous AtSCL4/7 subfamily gene of GRAS transcription factor family from chrysanthemum and designated it as CmSCL4. CmSCL4 was responded to 20% PEG6000 treatment and its heterologous expression improved drought tolerance by up-regulating ABA signaling genes AtABI3 and AtABI4 in Arabidopsis. Moreover, the cotyledon greening rate, early seedling development and stomatal aperture of transgenic Arabidopsis are hypersensitivity to external ABA treatment. Meanwhile, overexpression and chimeric repression of CmSCL4 in chrysanthemum also conferred the increased or decreased drought tolerance and corresponding changes of the expression of CmABI4. Yeast two-hybrid screening of the cDNA library of chrysanthemum by CmSCL4 identified a MYB transcription factor as an important candidate partner, which was named as CmR1MYB1 hereafter. The interaction between CmSCL4 and CmR1MYB1 was further verified by in vitro pull-down, in vivo BiFC and Co-IP assays. CmR1MYB1 and CmSCL4 had similar expression patterns under 20% PEG6000 treatment. Heterologous expression of CmR1MYB1 in Arabidopsis also facilitated the expression levels of AtABI3 and AtABI4 , resulted in the improved drought tolerance. These results demonstrated that CmSCL4 cooperates with CmR1MYB1 to modulate the dehydration tolerance of chrysanthemum, at least partially through the regulation of ABA-responsive genes. • This study describes the identification of a GRAS transcription factor CmSCL4 in chrysanthemum. • Overexpression of CmSCL4 improves drought resilience in both chrysanthemum and Arabidopsis by regulating ABA signaling pathway. • CmSCL4 interacts with the MYB transcription factor CmR1MYB1 to synergistically modulate drought adaptation in chrysanthemum. [ABSTRACT FROM AUTHOR]

We showed the effect of aphid infesting on the volatile organic compounds (VOCs) emitted by the infested Artemisia annua and Chrysanthemum morifolium cultivar ‘Nan nong hong feng’ plants by using headspace solid-phase microextraction (HS-SPME) method combined with gas chromatography mass spectrometry (GC–MS). In olfactometer bioassay experiment, aphids showed a preference for the odour of both healthy and infested chrysanthemum, while we found an opposite result in A. annua . Aphids tend to healthy plants compared with the infested, and the phenomenon became obvious with time. Different extracts were tested with the healthy plants and aphid infested plants. Eucalyptol, β-caryophyllene, (E)-β-farnesene, and germacrene D were released as the major constituents in both species. After aphid infesting, we observed a great increase in artemisia ketone and (E)-β-farnesene and a decrease in germacrene D in A. annua ; comparatively, eucalyptol, isoborneol and β-caryophyllene increased in chrysanthemum. Combined with the GC–MS data and olfactometer bioassay results we concluded that (E)-β-farnesene and artemisia ketone emitted from A. annua might act as a potential volatile compound to resist aphids, and the two compounds would be useful for future ecological control of aphid in chrysanthemum cultivation. [ABSTRACT FROM AUTHOR]

Aphids have caused great damage to chrysanthemum production, and it's crucial to breed new chrysanthemums with strong aphid resistance. However, little information is available regarding the inheritance of aphid resistance in chrysanthemum. The inheritance pattern of chrysanthemum aphid resistance within an F 1 segregating population was dissected with the major gene plus polygene mixed inheritance model and molecular markers. The result showed that aphid resistance of chrysanthemum is a quantitative trait with a moderate coefficient of variation >50%. The mixed inheritance model based on a single segregating generation suggested the inheritance of aphid resistance was controlled by two pairs of major genes with additive effect 0.68 and 0.39, respectively. The heritability of major gene was calculated at 89.21%. Marker-trait analysis based on one-way variance analysis uncovered 11 markers significantly associated with phenotype, cumulatively explaining ∼74% variation. Bulked segregant analysis (BSA) based on the gene bulks of high resistant and susceptive genotypes in F 1 population identified two SSR markers, SSR145-93 and SSR197-205, linked to high aphid resistance ( r > 0.4). The QTL analysis detected 5 putative QTL for aphid resistance in two successive years, with individual QTL explaining the phenotypic variation of 14.30–28.00%. The inheritance model and molecular markers identified for aphid resistance facilitate the ongoing breeding activities in chrysanthemum. [ABSTRACT FROM AUTHOR]

Abstract: Various abiotic stresses downgrade the quality and productivity of chrysanthemum. A construct carrying both CcSOS1 (from Chrysanthemum crassum) and CdICE1 (from Chrysanthemum dichrum) was constitutively expressed in the chrysanthemum variety ‘Jinba’. The transgenic plants were superior to the wild type (WT) ones with respect to their sensitivity to low temperature, drought and salinity, as measured by visible damage and plant survival. Salinity stressed transgenic plants accumulated more proline, and their level of superoxide dismutase and peroxidase activity was higher than in WT plants. At the physiological level, they suffered less loss of viable leaf area, maintained a lower leaf electrolyte conductivity and retained more chlorophyll (a+b). The ratio between the K+ and Na+ content was higher in the root, stem and median leaves of salinity stressed transgenic plants than in those of WT plants. [Copyright &y& Elsevier]

• Little research has been done on the effects of grafting on growth and flowering. • Grafting can not only promote plant growth and increase plant biomass, and the total inflorescences per plant of spray chrysanthemum but also lengthen the ornamental period of spray chrysanthemum by advancing flowering and delaying the final flowering period. • The budding period can be advanced by 13 d, the final flowering period can be delayed by 4 d, and the ornamental period can be increased by 10 d To study the effect of grafting on the growth and flowering of spray chrysanthemum, Artemisia annua was used as the rootstock and eight spray chrysanthemum varieties 'Zhongshan Jinyang' ('ZSJY'), 'Zhongshan Xinmolian' ('ZSXML'), 'Zhongshan Xuerong' ('ZSXR'), 'Zhongshan Yinggui' ('ZSYG'), 'Zhongshan Zaohong' ('ZSZH'), 'Zhongshan Zhiying' ('ZSZY'), 'Zhongshan Zisongguo' ('ZSZSG'), and 'Zhongshan Ziwei' ('ZSZW') were used as the scions. The plant survival ratio, growth index (crown width, crown circumference, and biomass), and flowering characteristics (total inflorescences per plant, flower diameter, fresh and dry weight of single flowers, and flowering period) were studied after grafting. We found that for variety 'ZSYG', the grafted plants showed a 58.4% increase in crown width, a 68.7% increase in crown circumference, a 61.8% increase in the dry weight of the scion, a 108.4% increase in the dry weight of root, a 72.3% increase in the total dry weight, a 28.3% increase in root/shoot, and a 135.2% increase in the total inflorescences per plant compared to those in the own-rooted plants. Grafting can not only promote plant growth and increase plant biomass, and the total inflorescences per plant of spray chrysanthemum but also lengthen the ornamental period of spray chrysanthemum by advancing flowering and delaying the final flowering period. The budding period can be advanced by 13 d, the final flowering period can be delayed by 4 d, and the ornamental period can be increased by 10 d. Therefore, grafting facilitates the growth of spray chrysanthemums, advances flowering, and prolongs the ornamental period. [ABSTRACT FROM AUTHOR]

Highlights: [•] Drought inhibited the root/rate ratio of drought sensitive chrysanthemum cultivar. [•] Drought tolerant cultivar has denser trichomes and more wax contents. [•] Drought tolerant chrysanthemum has higher SOD, POD, and CAT activities under drought. [•] Drought induces the expression of SOD, POD and CAT genes in tolerant cultivar. [•] Drought tolerant cultivar has higher photosynthesis capacity under drought. [ABSTRACT FROM AUTHOR]

Abstract: The drought tolerance of the chrysanthemum (Chrysanthemum morifolium Ramat.) ‘Zhongshanjingui’, Ajania przewalskii Poljakov and two independent hybrid lines of ‘Zhongshanjingui’× A. przewalskii were compared. The intergeneric hybrids and paternal parent (A. przewalskii) showed higher tolerance to drought than the maternal parent (Zhongshanjingui) during continuous drought stress conditions. After 10 days of drought treatment, when the water content of the growth medium decreased to 0.8%, the female parent exhibited the most severe wilting (the maximum index value of 3.0), whereas the male parent and two hybrid lines showed moderate wilting (wilting indices of 1.9, 2.2 and 2.4, respectively). Twelve hours after rewatering of the drought-stressed plants, the chrysanthemum leaves failed to recover, whereas leaves of the hybrids and A. przewalskii recovered turgor. Under drought conditions, the hybrids and A. przewalskii showed superior root growth to that of chrysanthemum with respect to both the rate of relative root growth and root dry weight per plant. Enhanced drought tolerance was also correlated with an increase in free proline and a decrease in malondialdehyde contents. The results indicated that the hybrids showed morphological and physiological responses to drought conditions inherited from A. przewalskii, and that intergeneric hybridization is a favorable means to introduce multiple resistance characters of relative germplasm into chrysanthemum. [Copyright &y& Elsevier]

Abstract: The drought and salinity tolerances of a creeping ground-cover chrysanthemum variety ‘Yuhuaxunzhang’ were compared to the performance of its two derived transgenic lines carrying a drought-responsive element binding (DREB) factor from chrysanthemum designated as CgDREBa. The over-expression of CgDREBa conferred a measure of tolerance to both stresses. The transgenic lines showed a higher survival rate and were better able to retain fresh weight in the presence of stress. Activities of superoxide dismutase and peroxidase and the proline content were all higher in the leaves of the transgenic plants after a prolonged period of stress, but they accumulated less malondialdehyde. CgDREBa appears to function as a transcription activator of genes within the oxidative and osmotic homeostasis transduction pathways, and represents a promising candidate for a biotechnological approach to improve the level of abiotic stress tolerance in plants. [Copyright &y& Elsevier]

Abstract: The spray cut chrysanthemum (Chrysanthemum grandiflorum (Ramat.) Kitamura) is a popular cut flower species. As pedicel rigidity is a key component of its postharvest quality, the morphology, anatomy and physiology of the pedicel at various stages of flower bud development were compared in two contrasting chrysanthemum cultivars. The pedicel of the cultivar with the better vase life (‘H5’) showed a higher proportion of vascular elements throughout all floral stages, and higher lignin and relative water contents during stages II and III. A cDNA encoding caffeic acid 3-O-methyltransferase (CgCOMT) was isolated from chrysanthemum. It comprises a 1065bp opening read frame, predicted to encode a 355 residue polypeptide. The deduced peptide sequence of the CgCOMT product is very similar to that of COMT proteins isolated from other plant species, and shares the S-adenosylmethionine substrate binding motif LVDVGGGXG. Expression analysis by qRT-PCR showed that CgCOMT was expressed throughout the plant, but was particularly prominently in the stem. Its transcription increased with the development of the pedicel, and was higher in ‘H5’ than in ‘QX101’, the cultivar with the lesser vase life. This observation was consistent with the differences in rigidity of their pedicels. [Copyright &y& Elsevier]

Abstract: Artificial aphid infestation experiments on the three chrysanthemum cultivars ‘Keiun’, ‘Han6’ and ‘Jinba’ showed that the three cultivars vary markedly in their resistance. Of the three cultivars, the most resistant (‘Keiun’) produced the longest, highest and densest trichomes, the largest and fullest gland cells, and the most wax on the lower leaf epidermis. Superoxide dismutase (EC 1.15.1.1), peroxidase (EC 1.11.1.7), ascorbate peroxidase (EC 1.11.1.11), polyphenol oxidase activity (EC 1.14.18.1) and phenylalanine ammonia lyase (EC 4.3.1.5) were enhanced by aphid herbivory. In the two more resistant cultivars (‘Keiun’ and ‘Han6’), the activity of superoxide dismutase and ascorbate peroxidase enzymes rapidly increased following infestation, and their levels remained high from seventy-two to one hundred and sixty-eight hours after inoculation. We suggest that these two antioxidant enzymes contribute to aphid resistance of these chrysanthemum cultivars. All three cultivars showed quick responses to aphid infestation by increasing polyphenol oxidase and phenylalanine ammonia lyase activities during the early period after inoculation. Activities of these two defense enzymes were higher in the two resistant cultivars after 72h after inoculation, suggesting involvement of these two enzymes in aphid resistance. [Copyright &y& Elsevier]

Abstract: Anther wall development, microsporogenesis and microgametogenesis were compared between a normal male fertile chrysanthemum cultivar ‘NJAU04-29-2’ and the two male sterile selections ‘rm20-11’ (anther indehiscent) and ‘NJAU05-52-2’ (anther aborted). In both of the two male sterile types, the tapetum enlarged abnormally and showed signs of disorganization of walls at the onset of meiosis, the pollen was aborted, the anthers appeared shrunken, and the anther vascular bundle and connective tissue were degenerated by anthesis. In ‘rm20-11’, the two smaller pollen sacs began to degenerate at the microsporogenesis stage, so that only one or two microsporangia developed, while in ‘NJAU05-52-2’, only one or two microsporangia were formed following the archesporial cell stage, and most of the microspore mother cells degenerated during the course of meiosis. [ABSTRACT FROM AUTHOR]

Abstract: A genetic linkage map of chrysanthemum (Chrysanthemum morifolium) was constructed by genotyping 142 F1 progeny of the bi-parental cross ‘Yuhualuoying’בAoyunhanxiao’ with a combination of RAPD, ISSR and AFLP markers in a double pseudo-testcross mapping strategy. A total of 567 polymorphic markers, including 153 RAPDs, 61 ISSRs and 353 AFLPs, were used in linkage mapping. 336 of 567 (60%) markers were grouped on the two parental maps, leaving 231 (40%) markers unlinked. In the ‘Yuhualuoying’ linkage map, 210 markers including 116 testcross and 94 intercross markers were placed in 12 major and 32 minor (8 triplets and 24 doublets) linkage groups, covering 1034cM with an average map distance of 6.2cM between adjacent markers. In ‘Aoyunhanxiao’ linkage map, 190 markers consisting of 113 testcross and 77 intercross markers were resolved into 9 major and 24 minor linkage groups, with genome coverage of 1095cM and a mean inter-marker separation of 6.9cM between adjacent markers. Six pairs of homologous linkage groups were established on the basis of 64 intercross markers shared by the two parental maps. The maps lay a foundation for further quantitative traits loci (QTL) mapping and marker-assisted breeding of chrysanthemum. [Copyright &y& Elsevier]

Abstract: The responses to waterlogging of the two Dendranthema species D. nankingense (Nakai) Tzvel. and D. zawadskii (Herb.) Tzvel. contrast considerably. Although the stress induced wilting and leaf chlorosis in both species, symptoms were more apparent and appeared earlier in the intolerant D. nankingense. In the more tolerant D. zawadskii, adventitious roots formed above the flooding level, and aerenchyma developed in the root, stem and leaf. The D. zawadskii palisade parenchyma was thicker, and larger intercellular spaces developed in the spongy mesophyll. The activities of alcohol dehydrogenase, pyruvate decarboxylase and lactate dehydrogenase were enhanced in roots of both species following the imposition of stress. In D. zawadskii the rise in ADH activity was more pronounced, while D. nankingense showed a significantly higher LDH activity. The activities of superoxide dismutase, ascorbate peroxidase and catalase were all higher in the leaves of D. zawadskii than in D. nankingense, and the leaves of D. nankingense showed a higher content of malondialdehyde throughout the period of waterlogging. Photosynthesis was decreased in both species, and there was a significant fall in the intercellular CO2 concentration in D. zawadskii. These data suggested that the greater relative waterlogging tolerance of D. zawadskii appears to depend on a combination of metabolic and morpho-anatomical responses. [Copyright &y& Elsevier]

Abstract: Responses to waterlogging of a tolerant chrysanthemum cultivar (‘53-4’) were compared with those of a susceptible one (‘13-13’). Just 4 days of waterlogging were enough to induce wilting and leaf chlorosis in ‘13-13’, but there was no visual damage to the leaves of ‘53-4’ after 8 days of treatment. After 20 days, only a small number of adventitious roots had emerged from ‘13-13’ stems, but many vigorous adventitious roots had formed in ‘53-4’. Waterlogging induced increases in the activity of alcohol dehydrogenase (EC 1.1.1.1), pyruvate decarboxylase (EC 4.1.1.1) and lactate dehydrogenase (EC 1.1.1.27) in both cultivars, but the increases in ‘13-13’ were more pronounced than in ‘53-4’. On the other hand, the activity of superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11) and catalase (EC 1.11.1.6) was higher in ‘53-4’ than in ‘13-13’. Leaves of ‘13-13’ had a higher content of malondialdehyde, and the amount of this stress indicator in ‘53-4’ was stable throughout the waterlogging period. Ethylene production was enhanced by waterlogging in both cultivars, but peak ethylene production occurred 2 days earlier in the tolerant cultivar, and was 3-fold higher than in the susceptible one. [Copyright &y& Elsevier]

• We draw the transcriptomic immune model of how chrysanthemum responded to dodder invasion and explored the difference between chrysanthemum stems and leaves responding to dodder invasion. • When the vascular connections were formed through haustoria between chrysanthemum and dodder, chrysanthemum recognized and fended off pathogens by the two layers of immune systems (PTI and ETI). Six membrane bound receptors RLKs were identified as hub genes and reactive oxygen species (ROS), calcium signal, and MAPK-related pathways were activated during the interaction between chrysanthemum and dodder. • In stems of chrysanthemum, ET and SA signal transduction pathways played vital roles and had strong regulatory relationship with each other in response to dodder invasion, which were different from the leaves. Chrysanthemum (Chrysanthemum morifolium), as one of the most commercially important ornamental crops, is threatened by dodder (Cuscuta spp.) during cultivation. When chrysanthemum was parasitized by dodder, growth of chrysanthemum slowed down and the leaves became dry and yellow. In the study, RNA sequencing assays were used for elucidating the immune response of chrysanthemum after dodder invasion and a total of 20,789 genes were differentially expressed. KEGG enrichment analysis revealed that these differentially expressed genes were involved in multiple pathways, "plant hormone signal transduction", "cutin, suberine and wax biosynthesis", and "plant-pathogen interaction", etc. Combined with weighted gene co-expression network analysis (hereafter named WGCNA), we found that when the vascular connections were formed through haustoria, chrysanthemum recognized and fended off pathogens by the two stages of plant immune systems (PTI and ETI). Membrane bound receptors RLKs and the intracellular NLR proteins perceived pathogen-derived proteins and delivered the defense signals to trigger a series of defense responses in chrysanthemum. Reactive oxygen species (ROS), calcium, and MAPK-related pathways were triggered and a series of defense genes were up‐regulated. Besides, in stems of chrysanthemum, ET and SA signal transduction pathways played vital roles and had strong regulatory relationship with each other in response to dodder invasion. Our study provides an understanding of how chrysanthemum responds to dodder's invasion, which could lay the basis for further revealing the interaction mechanism between chrysanthemum and dodder. [ABSTRACT FROM AUTHOR]

• Inheritance of branching traits in chrysanthemum was dissected by QTL mapping under two contrasting densities. • Twelve and eight additive QTLs were uncovered under the low and high planting density regime conditions, respectively. • Two joint QTLs and four epistatic QTLs were detected. • Only one QTL, TsbnE1 × 4 or TsbnE2 × 4, was stable across two environments. The architecture of chrysanthemum plants raised for cut flowers is strongly influenced by their ability to form branches. The genetic basis of branching was revealed through a quantitative trait locus (QTL) analysis of an F 1 population generated by crossing the varieties 'Nannong Xuefeng' and 'Monalisa' grown under contrasting planting densities. Under the low planting density regime (E1), 12 additive QTLs involving seven branching-associated traits were detected, while under the high planting density regime (E2), the number of QTL detected was only eight. One of the individual QTL accounted for over 10% of the phenotypic variance. Of the 20 QTLs, only one was expressed under both high and low planting densities. A joint QTL analysis across the two environments identified two QTLs which were separately detected in E1. A set of four QTLs exhibiting additive × additive epistasis was identified, few of which had interaction with environments. [ABSTRACT FROM AUTHOR]