Camellia flowers are highly prized for their beauty worldwide and are strongly symbolic in many cultures. A new interspecific hybrid cultivar, Camellia ‘Maozi’, generated by crossing Camellia pubipetala with C. japonica ‘Dahong Mudan’, exhibits strong hybrid vigor and has small flowers with a rare light tone of purple. In southwest China with a subtropical monsoon climate, young Camellia ‘Maozi’ trees flush shoots three times in spring, summer, and autumn, with an average annual growth of 12.9 cm. Adult trees flush once a year. Floral bud formation occurs in late April and early May. Camellia ‘Maozi’ flowers are sterile with no fruits and seeds produced. While an individual flower wilts 4–8 days after opening, the blossom can last 1–3 months. Frost damage can be found in young leaves when temperature drops to 4–7 °C. Under direct sunlight with temperatures of 37–39 °C lasting for more than 2 days, young leaves can turn yellow on their edges. Its primary diseases include sooty mold, shoot tip blight, and peony leaf tip blight. Its primary insect pests are tea green leafhopper (Jacobiasca formosana) and tea aphid (Toxoptera aurantii). Rooting of stem cuttings occurs directly from stems, mostly without callus development. Two hours of treatment with 500 mg·L−1 indole-3-butyric acid and rooting in a mix of latosolic red soil and vermiculite (2:1 v/v) resulted in high rooting rate and quality of aboveground growth. Grafting can be carried out from May to September, while survival rate and new shoot length are highest in July. The most compatible rootstock is C. oleifera, followed by C. polyodonta. The results of this study are of value for understanding the reproductive biology of Camellia ‘Maozi’ and further disseminating it as a new cultivar for camellia collection.
Xiao-Juan Wei, Xiao-Jing Liang, Jin-Lin Ma, Kai-Xiang Li, and Haiying Liang
Xiao-Juan Wei, Jinlin Ma, Kai-Xiang Li, Xiao-Jing Liang, and Haiying Liang
The flowers of Camellia chrysantha, commonly named as golden camellia, are treasured for their unique yellow color and are popularly used for tea. Compared with common camellia flowers that are either red, purple, pink, or white, golden camellia flowers are rare and are in high market demand. Our study was aimed to induce flowering in juvenile C. chrysantha grafted plants with urea and paclobutrazol (PBZ), a growth retardant. Generally, it takes 6–8 years for C. chrysantha seedlings and 5–6 years for grafted plants to set flower buds. With a 4 × 4 factorial design, four dosages of urea (1, 3, 5, or 8 g/plant) and four concentrations of PBZ (50, 150, 350, and 750 ppm) were tested on 4-year-old C. chrysantha grafted plants. Significant interaction between urea and PBZ was observed, and nine of the 16 combinations produced significantly more flower buds than the control, although not all flower buds could open because of abscission. High concentrations of PBZ and high dosages of urea were generally associated with severe defoliation and slow growth of basal stem diameter. When taking bud abscission into account, combinations of 150 ppm PBZ with 1 g urea and 350 ppm PBZ with 3 g urea resulted in significant flowering in juvenile C. chrysantha grafted plants without negative effects on vegetative growth and flower bud size and severe defoliation. This is the first report on flowering induction in a golden camellia species using juvenile plants. Our results suggest that application of optimized PBZ and urea doses can be a potential means for manipulation of early flowering in golden camellia species.
Xiaojuan Wei, Siyu Wu, Xiaojing Liang, Kun Wang, Yuejuan Li, Baocai Li, Jinlin Ma, and Haiying Liang
Golden camellia flowers are treasured for their unique yellow color and bioactive chemical compounds. Because of its high market demand, there is strong interest in inducing early flowering in golden camellias for earlier harvest. Previously, we have successfully induced flowering in Camelia chrysantha (Hu) Tuyama juvenile grafted plants and seedlings with paclobutrazol (PBZ). During this study, we investigated the efficacy of PBZ on C. tamdaoensis juvenile rooted cuttings. C. tamdaoensis is a yellow-flowering camellia species that is native to Vietnam and valued by the local population. It was found that applications of 100 and 200 ppm PBZ generated an average of 13 and 30 flowers per 5-year-old plant, respectively. None of the control plants flowered. The average flower diameter was 17.2 cm for 100-ppm-induced flowers and 26.0 cm for 200-ppm-induced flowers. The dynamics of various phytohormones (indoleacetic acid, abscisic acid, salicylic acid, and jasmonic acid) were altered by PBZ treatment. It is suggested that low indoleacetic acid, high abscisic acid, and jasmonic acid and a gradual increase in salicylic acid benefit floral initiation of golden camellias. The study provided the first insight regarding the action mechanism of PBZ for the initiation of camellia flowering.
Kai-Xiang Li, Kai Liu, Yingying Chen, Xiaolu Huang, Wenhui Liang, Baocai Li, Yingbai Shen, and Haiying Liang
Lithocarpus polystachyus is a unique medicinal tree species that is valued for its abundant flavonoids in leaves. Currently, genes and metabolites involved in the flavonoid biosynthesis pathway remain largely unknown. To elucidate the flavonoid biosynthesis pathways, transcriptome and metabolome analyses of young, mature, and old leaves were conducted. A total of 86,927 unigenes were obtained, and 51.4% of them were annotated in eight public databases. The majority of the 44 candidate genes in the flavonoid biosynthesis pathway were downregulated as leaves aged. Metabolome profiling revealed a set of 427 metabolites in leaves. Consistent with the transcriptome results, 15 of the 19 metabolites in the flavonoid pathway decreased during the development of leaves. The data indicate that young leaf is the optimal stage for tea harvest. This is the first report of integrated transcriptome and metabolome profiling of L. polystachyus. This study demonstrates the correlation of gene expression and metabolites related to flavonoid biosynthesis and reveals the key genes responsible for flavonoid accumulation in young leaf. The information can be applied to future studies performed to elucidate and manipulate flavonoid biosynthesis in L. polystachyus.
Haiying Liang, Bing-Qing Hao, Guo-Chen Chen, Hang Ye, and Jinlin Ma
Camellia is one of the four main oil-bearing trees along with olive, palm, and coconut in the world. Known as “Eastern Olive Oil,” camellia oil shares similar chemical composition with olive oil, with high amounts of oleic acid and linoleic acid and low saturated fats. Camellia was first exploited for edible oil in China more than 1000 years ago. Today, its oil serves as the main cooking oil in China’s southern provinces. Introduction of camellia oil into the Western countries was delayed until the recognition of its many health benefits. Although popularity for the oil has yet to grow outside of China, interest has emerged in commercial production of camellia oil in other countries in recent years. Unlike seed-oil plants that are grown on arable land, oil camellias normally grow on mountain slopes. This allows the new crop to take full usage of the marginal lands. To facilitate promoting this valuable crop as an alternative oil source and selecting promising cultivars for targeted habitats, this paper reviews the resources of oil camellias developed in China, use of by-products from oil-refining process, as well as the progress of developing camellias for oil production in China and other nations.
Haiyan Zhao, Haiying Liang, Yibing Chu, Congcong Sun, Ning Wei, Mengnan Yang, and Caixia Zheng
Ginkgo biloba L. (ginkgo) is generally regarded as a tolerant species to environmental stresses. However, its tolerance mechanisms are not well understood, particularly for salt stress. To evaluate the species’ physiological responses to salt stress, 3-year-old ginkgo seedlings were exposed to a range of salinity levels (0% to 1.0% NaCl). A significant reduction in maximum (F v/F m) and actual (ΦPSII) quantum yields of photosystem II (PSII) photochemistry and the nonphotochemical quenching (qN) coefficient only occurred in late treatment stages at the salinity levels of 0.6% to 1.0%. As salt concentration increased, the response time and chlorophyll (Chl) fluorescence indices decreased. Overall, the activities of superoxide dismutase (SOD) and peroxidase (POD); contents of catalase (CAT), reduced glutathione (GSH), and flavonoids; and scavenging rate of free radicals enhanced under salinity stress. These data indicate that ginkgo seedlings are tolerant to low salt stress, and enzymatic and nonenzymatic antioxidant systems seem to work synergistically to reduce lipid oxidation under NaCl stress because malondialdehyde (MDA) content did not increase. Correlation and principal component analyses determined that water potential, Chl fluorescence parameters, activities of POD and SOD, contents of CAT and flavonoids, and hydroxyl (•OH) and diphenyl picrylhydrazyl (DPPH) free radical scavenging capability were sensitive to salt stress. These parameters can be used for in vitro or rapid and nondestructive monitoring of the responses of ginkgo seedlings to salinity stress. It is of significance to understand the tolerance mechanisms of ginkgo to salt stress, reduce the harm of NaCl and other snow-melting agents to ginkgo as shade trees, and develop new salt-tolerant varieties.
Yihua Chen, Peng Jiang, Shivegowda Thammannagowda, Haiying Liang, and H. Dayton Wilde
We investigated the FT/TFL1 family of peach (Prunus persica), a gene family that regulates floral induction in annual and perennial plants. The peach terminal flower 1 gene (PpTFL1) was expressed in a developmental and tissue-specific pattern that, overall, was similar to that of TFL1 orthologs in other woody Rosaceae species. Consistent with a role as a floral inhibitor, ectopic expression of PpTFL1 in arabidopsis (Arabidopsis thaliana) delayed flowering and prolonged vegetative growth. Other members of the peach FT/TFL1 family were identified from the sequenced genome, including orthologs of flowering locus T, centroradialis, brother of ft, and mother of ft and tfl. Sequence analysis found that peach FT/TFL1 family members were more similar to orthologous genes across the Rosaceae than to each other. Together these results suggest that information on genes that regulate flowering in peach could be applied to other Rosaceae species, particularly ornamentals.
Xiao-Juan Wei, Jinlin Ma, Kun Wang, Xiao-Jing Liang, Jin-Xuan Lan, Yue-Juan Li, Kai-Xiang Li, and Haiying Liang
Camellia chrysantha flowers are in great market demand as a result of their high ornamental and medicinal values. To induce early flowering in 4-year-old juvenile C. chrysantha seedlings, three levels of paclobutrazol (PBZ) concentration (100, 200, and 300 ppm) were applied to the roots. PBZ is a triazole-type cytochrome P450 inhibitor that was found successful in inducing flowering in juvenile C. chrysantha grafted plants in a prior report. The current study shows that all three PBZ concentrations were equally effective in induction of floral buds, resulting in an average of 20 floral buds per treated plant. In comparison, none of the untreated plants flowered. Although the induced flowers were smaller than the ones from mature trees, PBZ treatment did not affect C. chrysantha flowers’ medical values, because there was no significant change in the content of pharmacologically active compounds (polysaccharide, polyphenols, flavonoids, and saponins). None of the PBZ treatments had a negative effect on the current year’s growth in height and basal diameter, photosynthesis, and levels of water-soluble sugars and nutrients [phosphorus (P), nitrogen (N), potassium (K), and carbon (C)]. It is concluded that PBZ is an effective flowering inducer for juvenile C. chrysantha plants. It was also found that PBZ-treated plants experienced defoliation, and there existed a strong correlation between severity of defoliation and PBZ concentration. This might be attributed by the stress induced by PBZ, as demonstrated by the increased activities of some of the stress-related enzymes [ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD)], and the level of malondialdehyde (MAD). Considering that severe defoliation can cause stunted or malformed plants and reduce aesthetic value, 100 ppm is the optimal PBZ concentration for flowering induction in C. chrysantha seedlings.
Ke-peng Che, Chun-yang Liang, Yue-guang Wang, De-min Jin, Bin Wang, Yong Xu, Guo-bing Kang, and Hai-ying Zhang
Amplified fragment length polymorphism (AFLP) analyses were used to assess genetic diversity among 30 genotypes of watermelon [Citrullus lanatus (Thunb.) Mansf.] representing a broad genetic base, including breeding lines and commercial germplasm. Eight AFLP primer combinations selected from 64 primer combinations were polymophic. The polymorphism was 13.0% to 31.9% within the 28 cultivars examined, and 45.3% to 64.2% among all the genotypes. Each genotype could be successfully distinguished based on AFLP scoring. Cluster grouping of accessions based on the AFLP analysis was consistent with that from classification by pedigrees and ecotypes.