Search Results (9)

Peelability, a crucial commercial trait for fresh-eating citrus, has received limited research attention regarding its underlying mechanisms. This study investigated three late-maturing citrus cultivars, namely ‘Qingjian’ (QJ), ‘Mingrijian’ (MRJ), and ‘Chunjian’ (CJ), analyzing their peelability development using texture analysis and exploring the physiological and biochemical factors influencing peeling difficulty. The results showed that peelability improved with fruit maturation, reaching its peak at full ripeness, with the following order of peeling difficulty: QJ (hardest) > MRJ (intermediate) > CJ (easiest). At full maturity, QJ (the most difficult to peel) exhibited more regularly shaped peel cells with fewer intercellular spaces, lower intracellular organic matter accumulation, and higher levels of cell wall polysaccharides, calcium (Ca), and abscisic acid (ABA). These characteristics may be linked to the lower relative expression of soluble sugar (TS)-related genes (CCR4A, SPP1) and the titratable acid (TA)-related gene (CsCit1), as well as the higher relative expression of ABA biosynthesis genes (NCED1, NCED2). Correlation analyses demonstrated that citrus peel firmness and adhesion strength are significantly associated with multiple growth and developmental characteristics, including fruit morphometric parameters, peel cellular architecture, intracellular organic compound content, cell wall polysaccharide levels and related degradative enzyme activities, calcium concentrations, and endogenous phytohormone profiles. These findings provide valuable insights for studying peelability mechanisms and improving fruit quality in citrus breeding. Full article

Late-maturing hybrid citrus is a significant fruit that combines the best traits of both parents and is highly prized for its unique flavor. Not only can organic acids alter the flavor of citrus pulp, but they are also essential for cellular metabolism, energy conversion, and maintaining the acidbase balance in plant tissues. Although organic acids play a key role in the quality formation of citrus fruits, there is still insufficient research on the metabolic processes of organic acids in late-maturing hybrid citrus varieties. In this study, three late-maturing citrus varieties with different acidity levels, namely ‘Huangjinjia’ (HJ), ‘Kiyomi’ (QJ), and ‘Harumi’ (CJ), were selected to systematically investigate the metabolic regulation mechanism of organic acids in late-maturing citrus through transcriptome sequencing technology, combined with physiological and biochemical analyses. This study revealed gene expression differences related to organic acid synthesis and degradation. Through gene expression profiling, several genes closely associated with organic acid metabolism were identified, and a preliminary gene network related to the regulation of organic acid metabolism was constructed. The results showed that there were significant differences in the organic acid metabolic pathways between different varieties and growth stages of the fruit. Specifically, HJ had a higher TA content than QJ and CJ, primarily due to the significantly higher citric acid and malic acid contents in HJ compared to the other two varieties. Further analysis revealed that four gene modules showed a high correlation with the levels of major organic acids in the fruits. The genes involved in these modules are closely related to organic acid synthesis, degradation, and transport. Additionally, we also identified several key genes (AS1, BZP44, COL4, TCP4, IDD10, YAB2, and GAIPB) that might be involved in the regulation of organic acid metabolism. The functions of these genes could have a significant impact on the expression levels changes of enzymes related to organic acid metabolism. This study provides a foundation for exploring the intrinsic mechanisms regulating the organic acid content in late-maturing hybrid citrus fruits and contributes to the functional research of organic acids in late-maturing hybrid citrus and the molecular design of high-quality varieties. Full article

Immature citruses are an important resource for the pharmaceutical industry due to their high levels of metabolites with health benefits. In this study, we used untargeted liquid chromatography–mass spectrometry (LC-MS) metabolomics to investigate the changes associated with fruit size in immature citrus fruits in the first weeks of growth. Three orange cultivars (Citrus sinensis ‘Navel’, Citrus sinensis ‘Valencia’, and Citrus sinensis ‘Valencia Late’) and a mandarin (Citrus reticulata Blanco ‘Fremont’) were separated into eight fruit sizes, extracted, and analyzed. Statistical analyses revealed a distinct separation between the mandarin and the oranges based on 56 metabolites, with an additional separation between the ‘Navel’ orange and the ‘Valencia’ and ‘Valencia Late’ oranges based on 21 metabolites. Then, metabolites that evolved significantly with fruit size growth were identified, including 40 up-regulated and 31 down-regulated metabolites. This study provides new insights into the metabolite modifications of immature Citrus sinensis and Citrus reticulata in the first weeks of growth and emphasizes the significance of including early sampled fruits in citrus maturation studies. Full article

Sichuan Province is the largest inland area for late-maturing citrus fruit production in China, and its climate conditions are a primary consideration for the cultivation of late-maturing citrus fruits. Based on meteorological data from 2010 to 2020 for the 18 prefecture-level cities and autonomous prefectures in Sichuan Province that cultivate late-maturing citrus fruits, along with the traditional method of dividing the advantages of citrus and the calculation of comparative advantage using factor endowment coefficients, we identified the annual average temperature, annual accumulated temperature ≥ 10 °C, average temperatures in July and January, annual precipitation, and annual sunshine hours as input indicators. We selected the resource endowment coefficient as the output indicator and used the DEA–Malmquist index model to evaluate the climate adaptability of Sichuan’s late-maturing citrus fruit industry. The analysis results indicate that the overall climate conditions in Sichuan are suitable for the growth of late-maturing citrus fruits. However, extensive cultivation of similar varieties has led to a decline in resource endowment across different regions. The use of arable land for cultivating late-maturing citrus fruits has also reduced climate adaptability. Policies that contradict climate adaptability do not support sustainable development within Sichuan’s late-maturing citrus fruit industry. Full article

The use of different rootstocks has a significant effect on the content of flavor components and overall fruit quality. However, little information is available about the metabolic basis of the nutritional value of citrus plants. In this study, UPLC-MS/MS (ultra-performance liquid chromatography-tandem mass spectrometry) was performed to analyze the metabolites of three late-maturing hybrid mandarin varieties (‘Gold Nugget’, ‘Tango’ and ‘Orah’) grafted on four rootstocks (‘Trifoliate orange’, ‘Carrizo citrange’, ‘Red tangerine’ and ‘Ziyang Xiangcheng’). A total of 1006 metabolites were identified through OPLS-DA (Orthogonal Partial Least Squares-Discriminant Analysis) analysis. KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis revealed the most critical pathways among the different pathways associated with genes grafted on the four rootstocks that were differentially activated, including tryptophan metabolism and sphingolipid metabolism in ‘Gold Nugget’; tryptophan metabolism, phenylpropanoid biosynthesis and sphingolipid metabolism in ‘Tango’; and pantothenate and CoA biosynthesis- and photosynthesis-related biosynthesis in ‘Orah’. A considerable difference between the different rootstocks was also observed in the accumulation of lipids, phenolic acids and flavonoids; further analysis revealed that the rootstocks regulated specific metabolites, including deacetylnomylinic acid, sudachinoid A, amoenin evodol, rutaevin, cyclo (phenylalanine-glutamic acid), cyclo (proline-phenylalanine), 2-hydroxyisocaproic acid, and 2-hydroxy-3-phenylpropanoic acid. The results of this study provide a useful foundation for further investigation of rootstock selection for late-maturation hybrid mandarin varieties. Full article

The use of natural-based coatings is an eco-friendly approach that can be applied in citrus postharvest to preserve fruit quality and to prolong shelf life. Additionally, the study of antioxidant capacity of obtained by-products from fruits is of great value to mitigate better practices to manage the residues left from the juice processing industry. Under this context, the aim of this study was to investigate the use of carnauba wax/wood resin-based coating and cold storage on postharvest life of Valencia Late and Natal IAC sweet oranges, as well as the physicochemical quality and antioxidant capacity of its by-products. Mature fruits were harvested in 2019 and 2020 seasons. Initially, fruits were assessed for physicochemical quality and antioxidant capacity. Then, fruits were treated with carnauba wax and wood resin mixture and stored for 0, 15, 30, 45 and 60 days in a cold chamber. Fruit color index, weight loss, physicochemical quality and sensory profile of the fruits were monitored at harvest and during each cold storage period. Evaluations were performed in triplicates of 10-fruit. Valencia Late and Natal IAC fruits had proper quality in both years, attending the requirements of the fresh market and processing industry. Flavedo and albedo section displayed the highest concentration of bioactive compounds such as phenolics, flavonoids and antioxidant activity. The coating treatment associated with cold storage was efficient to preserve fruit color and to retard weight loss for both varieties up to 60 days. The sensory profile and quality of the carnauba wax/wood resin treated fruits were preserved all over the cold storage period, while uncoated fruits ranked low for most of the sensory attributes. Together, Valencia Late and Natal IAC fruits contain a high level of healthy beneficial compounds, which may be exploited as a natural source of low-cost antioxidants. Further, carnauba wax/wood resin coating associated with cold storage effectively reduce weight loss and color progression in sweet orange fruits, in addition to preserving overall physicochemical and sensory quality. Full article

Intra-specific variation in seed storage behaviour observed in several species has been related to different maternal environments. However, the particular environmental conditions and molecular processes involved in intra-specific variation of desiccation tolerance remain unclear. We chose Citrus sinensis ‘bingtangcheng’ for the present study due to its known variability in desiccation tolerance amongst seed lots. Six seed lots of mature fruits were harvested across China and systematically compared for drying sensitivity. Annual sunshine hours and average temperature from December to May showed positive correlations with the level of seed survival of dehydration. Transcriptional analysis indicated significant variation in gene expression between relatively desiccation-tolerant (DT) and -sensitive (DS) seed lots after harvest. The major genes involved in late seed maturation, such as heat shock proteins, showed higher expression in the DT seed lot. Following the imposition of drying, 80% of stress-responsive genes in the DS seed lot changed to the stable levels seen in the DT seed lot prior to and post-desiccation. However, the changes in expression of stress-responsive genes in DS seeds did not improve their tolerance to desiccation. Thus, higher desiccation tolerance of Citrus sinensis ‘bingtangcheng’ seeds is modulated by the maternal environment (e.g., higher annual sunshine hours and seasonal temperature) during seed development and involves stable expression levels of stress-responsive genes. Full article

Kirkwood Navel and Ruby Valencia are two spontaneous bud-mutations of the ordinary Washington Navel and Valencia late oranges characterized by the red coloration of their flesh. The purpose of this study was to analyze the physiological features, internal fruit quality, contents of relevant bioactive compounds and antioxidant capacity in the pulps of the red-fleshed fruits compared with the ordinary oranges during late development and maturation. In general, the content of sugars, organic acids, vitamin C, tocopherols, total phenolics and flavonoids, the hydrophilic antioxidant capacity and their changes during maturation were similar in the red-fleshed oranges and in the corresponding blond oranges. However, the mature Ruby fruits contained lower concentrations of sugars, malic and succinic acid and higher levels of citric acid than the ordinary Valencia. The major difference between the pulps of the Kirkwood and Ruby oranges and those of the ordinary oranges was the higher lipophilic antioxidant capacity and SOAC (singlet oxygen absorption capacity) of the former. Together, the high and unique content and composition of carotenoids in Kirkwood and Ruby may contribute to an enhanced antioxidant capacity without any detrimental effects on other fruit-quality attributes, making these varieties good sources of phytochemicals for the fresh-fruit and juice-processing citrus industries. Full article

Harvesting makhwaen (Zanthoxylum myriacanthum Wall. ex Hook. f) fruits at the appropriate maturity is the key to ensure that the essential oil quality meets the need of consumers. In common practice, the fruits are usually harvested when their pericarps start to open and fruits are greenish-red in colour depending on the judgment of the farmers. This leads to inconsistencies in the essential oil quality. This research aims at characterising the aromatic profiles of makhwaen essential oil thereby for consumers to choose the quality that best fits their need and eventually identify the optimum harvesting index of the fruits. The effects of maturity states viz. 15, 36, 45 and 60 (MK15-60) days after fruiting on chemical and sensorial quality of the essential oil was evaluated. Fruit sizes ranged from ~3.3–3.7 mm and fruits appeared to dry initially when they reached 45 days. Essential oils were extracted from these fruits after they had been oven dried (60 °C) to the same moisture content, about 10%. The chemical profiles of the essential oil were different. L-limonene and sabinene were evaluated as key components for good quality essential oil and they were found to be higher in MK45 and MK60 (max = 139.04 µg·mL⁻¹ and max = 146.27 respectively). NIR spectral patterns of pure extracted oil for every different harvesting time (of every different harvesting time of MK60 and MK36) were similar. Sensorial descriptive analysis by semi-trained panellists defined six terms for characteristics (woody, citrus, herb, sweet, pine and spice). The panels provided the highest rating score (15 numeric scale) of citrus and pine scents at MK45, while sweet and woody aromas were the highest at MK15. The spice scent was maximum when the fruits were harvested at 36 days after fruiting. From this study we suggest that the optimum harvesting index for the distinctive aroma of essential oil ought to be at late harvesting (45–60 days after fruiting). The findings contribute to our understanding of the harvesting maturity, which can also provide significant benefit for the perfumery industry, i.e., the optimum harvesting stage that imparts the essential oil with highest quality. Full article