Development of Pollen Parent Cultivar-Specific SCAR Markers and a Multiplex SCAR-PCR System for Discrimination between Pollen Parent and Seed Parent in Citrus.

This study discusses the challenge of distinguishing between two high-quality mandarin cultivars, 'Asumi' and 'Asuki', which have been introduced and cultivated in Korea after being developed through crossbreeding in Japan. Owing to genetic similarities resulting from crossbreeding between the same parent cultivars, it is challenging to differentiate them morphologically at the seedling stage. This difficulty poses challenges for cultivation and harvesting on farms. To address this issue, we developed a method using sequence characteristic amplification region (SCAR) markers for rapid and accurate differentiation between the two cultivars. We selected specific primer sets from random amplified polymorphic DNA-SCAR combinations and sequence-related amplified polymorphism contrast markers. The multiplex PCR system using these molecular markers was able to identify 16 mandarin cultivars, including 'Asumi' and 'Asuki', among 30 cultivars. The use of these SCAR markers is expected to enhance citrus cultivation by accurately identifying mixed cultivars and facilitating proper harvest timing for citrus distribution. Additionally, the markers can help identify the genetic traits of hybrid varieties at the seedling stage.

Comparative Analysis of Physicochemical Properties and Storability of a New Citrus Variety, Yellowball, and Its Parent.

Although numerous citrus varieties have recently been developed to enhance their quality, information on their quality characteristics is limited. We assessed the quality characteristics of Yellowball, a novel citrus variety, by evaluating its appearance, storability, sensory properties, functionality, and metabolite profiles and then comparing these characteristics with those of its parent varieties, Haruka and Kiyomi. The metabolite profiles between the citrus varieties differed significantly, resulting in distinct physicochemical and functional qualities. The storability of Yellowball was significantly increased compared with that of its parent varieties owing to its strong antifungal activity and unique peel morphology, including the stoma and albedo layers. While we did not investigate the volatile compounds, overall functional activities, and detailed characteristics of each metabolite, our data provide valuable insights into the relationship between citrus metabolites, peel morphology, physicochemical properties, and storability, and demonstrate the potential of Yellowball as a promising variety in the citrus industry.

Anther Culture-Derived Haploids of Citrus aurantium L. (Sour Orange) and Genetic Verification of Haploid-Derived Regenerated Plants.

Citrus plants are important fruit tree species; however, the breeding of high-quality varieties of citrus species is a time-consuming process. Using haploid-derived plants from anther culture may reduce the time required for obtaining purebred lines. This study aimed to genetically verify whether anther culture-derived sour orange (Citrus aurantium L.) plants developed from somatic embryos or haploid tissues. Sour orange anthers were cultured in N6 and MS media to induce calli and somatic embryos. N6 liquid medium supplemented with 1 mg·L-1 gibberellic acid and 200 µM spermidine resulted in a 10% increase in callus and embryo induction rates. Regenerated plants were validated using simple sequence repeat markers. Out of the 109 regenerated plants, ploidy analysis identified 99 diploids, two haploids, and eight putative aneuploids; out of the 99 diploid plants, 33 were haploid-derived homozygous diploids. The chromosomal analysis confirmed most plants as diploids, whereas some were identified as aneuploids (19-21 chromosomes). Furthermore, phylogenetic analysis confirmed that the resultant homozygous or heterozygous plants were haploid-derived. This is the first report of haploid-derived homozygous diploid and aneuploid sour orange plants obtained through anther culture. Moreover, the anther cultivation technique described herein can be applied to other citrus varieties.

Development of Molecular Marker to Detect Citrus Melanose Caused by Diaporthe citri from Citrus Melanose-like Symptoms.

It is difficult to distinguish melanose and melanoses-like symptoms with the naked eye because they appear similar. To accurately detect melanose symptoms caused by Diaporthe citri from melanose-like symptoms, we developed PCR-based specific primers Dcitri by aligning the internal transcribed spacer (ITS) region of D. citri with the ITS of Diaporthe cytosporella, Diaporthe foeniculina, Colletotrichum gloeosporioides, Botrytis cinerea, Alternaria citri, and Fusarium oxysporum found on citrus peel. PCR results showed that the specific product was amplified in D. citri but not in other isolates including, C. gloeosporioides, B. cinerea, A. citri, F. oxysporum. In addition, specific products were observed in melanose symptoms caused by D. citri but not in melanose-like symptoms, such as copper-injury, sunscald, damages by yellow tea thrips, and pink citrus rust mite. Using the Dcitri primers developed in this study, it is expected that melanose caused by D. citri could be accurately distinguished from melanose-like symptoms.

Comparative Metabolomics Analysis of Citrus Varieties.

Many citrus varieties are hybridized to improve their quality and to overcome the effects of climate change. However, there is limited information on the effect of the chemical profiles of hybrid varieties on their quality. In this study, we analyzed 10 citrus varieties and evaluated the correlation with their general characteristics and antioxidant activities. Chemical profiles, including the contents of sugars, organic acid compounds, flavonoids, limonoids, and carotenoids, which are related to taste, color, and health benefits, were significantly different depending on the citrus varieties, leading to different antioxidant capacities and general quality parameters. Based on these data, the correlations were investigated, and 10 citrus varieties were clustered into four groups-Changshou kumquat and Jeramon (cluster I); Setoka (cluster II-1); Natsumi, Satsuma mandarin, and Navel orange (cluster II-2); Kanpei, Tamnaneunbong, Saybyeolbong, and Shiranui (cluster II-3). Moreover, a metabolomic pathway was proposed. Although citrus peels were not analyzed and the sensory and functional qualities of the citrus varieties were not investigated in this study, our results are useful to better understand the relationship between citrus quality and metabolite profiles, which can provide basic information for the development and improvement of new citrus varieties.

Chemical composition and anti-inflammation activity of essential oils from Citrus unshiu flower.

Though many essential oils from citrus peels are claimed to have several medicinal functions, the chemical composition and biological activities of the essential oils of Citrus flowers have not been well described. Therefore, this study intended to investigate the chemical composition and anti-inflammatory potential of essential oils from C. unshiu flower (CEO) to support its purported beneficial health effects. The chemical constituents of the CEO, analyzed by gas chromatography-mass spectrometry (GC-MS), included y-terpinene (24.7%), 2-beta-pinene (16.6%), 1-methyl-2-isopropylbenzene (11.5%), L-limonene (5.7%), beta3-ocimene (5.6%), and alpha-pinene (4.7%). The effects of the CEO on nitric oxide (NO) and prostaglandin E2 (PGE2) production in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages were also examined. The results indicate that the CEO is an effective inhibitor of LPS-induced NO and PGE2 production in RAW 264.7 cells. Additionally, CEO was shown to suppress the production of inflammatory cytokines including interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, and IL-6. Based on these results, CEO may be considered a potential anti-inflammatory candidate with human health benefits.

Down-regulation of tyrosinase, TRP-1, TRP-2 and MITF expressions by citrus press-cakes in murine B16 F10 melanoma.

OBJECTIVE: To investigate the suitability of citrus-press cakes, by-products of the juice industry as a source for the whitening agents for cosmetic industry. METHODS: Ethylacetate extracts of citrus-press cakes (CCE) were examined for their anti-melanogenic potentials in terms of the inhibition of melanin production and mechanisim of melanogenesis by using Western Blot analysis with tyrosinese, tyrosinase-related protein-1 (TRP-1), TRP2, and microphthalmia-associated transcription factor (MITF) proteins. To apply the topical agents, citrus-press cakes was investigated the safety in human skin cell line. Finally flavonoid analysis of CCE was also determined by HPLC analysis. RESULTS: Results indicated that CCE were shown to down-regulate melanin content in a dose-dependent pattern. The CCE inhibited tyrosinase, TRP-2, and MITF expressions in a dose-dependent manner. To test the applicability of CCE to human skin, we used MTT assay to assess the cytotoxic effects of CCE on human keratinocyte HaCaT cells. The CCE exhibited low cytotoxicity at 50 µg/mL. Characterization of the citrus-press cakes for flavonoid contents using HPLC showed varied quantity of rutin, narirutin, and hesperidin. CONCLUSIONS: Considering the anti-melanogenic activity and human safety, CCE is considered as a potential anti-melanogenic agent and may be effective for topical application for treating hyperpigmentation disorders.

Chemical composition and anti-inflammatory effects of essential oil from Hallabong flower.

A number of essential oils derived from plants are claimed to have several medicinal functions, including anti-cancer and anti-inflammation effects. However, the chemical composition and biological activities of flower-derived components have not been sufficiently characterized. Therefore, we investigated the composition of essential oils from Hallabong flower [(Citrus unshiu Marcov × Citrus sinensis Osbeck) × Citrus reticulata Blanco] and their anti-inflammatory effects. Hydro-distilled essential oils (HEOs) were analyzed using gas chromatography-mass spectrometry (GC-MS). In total, 21 components were identified, representing more than 98 % of the oils, with sabinene (34.75 %), linalool (14.77 %), ß-ocimene (11.07 %), 4-terpineol (9.63 %), l-limonene (5.88 %), and γ-terpinene (4.67 %) as the main components. In the present study, we also investigated the anti-inflammatory effects of HEOs on lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. HEOs were found to inhibit nitric oxide (NO) and prostaglandin E2 (PGE2) production and to suppress the LPS-induced expression of cyclooxygenase-2 (COX-2) protein. In addition, HEOs downregulated the production of the inflammatory cytokines, tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1ß (IC50 values are 0.05 %, 0.02 %, and 0.01 %, respectively). On the basis of these results, we suggest that HEOs can be considered potential anti-inflammatory candidates for therapeutic use in humans.