Pomelo Research Articles

Selection and characterization of a yeast strain for the suppression of brown spot on Tru Long pummelo (Citrus maxima)

Tru Long pummelo is an endemic plant of Quang Nam province with high economic value. However, many different diseases, especially brown spot disease caused by Alternaria fungus on pummelos, have affected the quality of pummelos. Pesticides are overused and misused for the environment and human health. Therefore, there is an urgent need to reduce the use of synthetic chemicals. Biological control offers an alternative to the use of pesticides. Eight yeast strains have been isolated from healthy leaves, pummelo fruits, and healthy mulberries. They were screened for biological activity against Alternaria sp. by the dual culture method. The inhibitory potency ranged from 10.46% to 59.86%. The strain with the highest percentage (59.86%) was identified as Candida tropicalis using sequence analysis of the ITS region.

Qi Gong Wan ameliorates adipocyte hypertrophy and inflammation in adipose tissue in a PCOS mouse model through the Nrf2/HO-1/Cyp1b1 pathway: Integrating network pharmacology and experimental validation in vivo

Ethnopharmacological relevanceInitially recorded in Yifang Jijie (an ancient Chinese text), Qi Gong Wan (QGW) is used to treat obese women with infertility. QGW can help promote follicular development and maturation, regulate the balance of serum hormones between testosterone and estradiol, enhance endometrial receptivity, improve waist circumference, and ameliorate insulin resistance. It contains eight herbs: Pinellia ternata (Thunb.) Makino (Banxia), Citrus maxima (Burm.) (Juhong), Poria cocos (Schw.) Wolf. (Fuling), Atractylodes macrocephala Koidz (Baizhu), Cyperus rotundus L. (Xiangfu), Conioselinum anthriscoides 'Chuanxiong' (Chuanxiong), Massa Medicata Fermentata (Shenqu), and Glycyrrhiza uralensis Fisch. ex DC. (Gancao). However, the underlying mechanism of how QGW affects women with PCOS remains unclear.Aim of the study: QGW has been widely used to treat PCOS patients with obesity clinically. This study was designed to identify its chemical and pharmacological properties. Materials and methodsNetwork pharmacology was used to predict the active compounds, potential targets, and pathways of QGW. Female C57BL/6J mice were injected with letrozole and fed a high-fat diet to establish a PCOS-insulin resistance (PCOS-IR) model. Body weight, estrous cycles, ovarian pathology, and serum insulin resistance were measured. qRT-PCR was used to examine the inflammation-related and steroid hormone biosynthesis-related mRNA expression in adipose tissue. Western blotting was used to determine the protein levels of Nrf2, HO-1, and Cyp1b1 in adipose tissue. Molecular docking was used to reveal the key chemical compounds of QGW. ResultsNetwork pharmacology revealed a total of 91 active ingredients in QGW that were associated with 167 targets. QGW could potentially treat PCOS-IR via nitrogen metabolism, steroid hormone biosynthesis, and ovarian steroidogenesis pathways. In the PCOS-IR mouse model, we found that QGW decreased the mean diameter of adipocytes and the total adipocyte area. Furthermore, QGW was found to significantly lower the expression of inflammation-related genes including Tnfɑ and C4a/b and the steroid hormone biosynthesis-related gene Cyp1b1. QGW showed a tendency to improve cystic follicles, fasting insulin, and HOMA-IR index in the PCOS-IR mouse model. Combining these findings with the results of KEGG analysis, we conclude that QGW promotes the Nrf2/HO-1/Cyp1b1 pathway to protect adipose tissue under conditions of PCOS. Molecular docking revealed that rutin, nicotiflorin, and baicalein may be the key chemical compounds of QGW through which it improves adipocyte hypertrophy and inflammation. ConclusionsQGW improved adipocyte hypertrophy and inflammation in the PCOS-IR mouse model by activating the Nrf2/HO-1/Cyp1b1 pathway to protect adipose tissue. Our work thus provides a new research avenue for the study of traditional Chinese medicine in the treatment of PCOS.

Reducing Macronutrients and Increasing Micronutrient Fertilizers Are Key to Improving the Quality of Pomelo Citrus grandis (L.) Osbeck Cv. “Guanxi”

Due to long-term excessive fertilization, the fruit quality of the Guanxi pomelo (Citrus grandis) has been declining. The classification of fruit quality and its relationship with nutrients in soils and trees were studied to declaim the characteristics of nutrients in Guanxi pomelo orchards, ultimately guiding the fertilization for high-quality fruit production. By cluster analysis, 281 samples were grouped into four clusters. High-quality fruit (HF) showed a gourd shape with moderate weight size, high sweetness, edible rate (ER) up to 73%, and vitamin C content over 40 mg/100 g. Compared to sub-quality fruit (SF), common fruit (CF), and inferior fruit (IF), the content of magnesium (Mg) in the leaves of HF was 11.76, 11.76, and 18.75% higher, while the content of iron (Fe) was 6.45, 5.76 and 10.97% higher, respectively. Meanwhile, the contents of Zinc (Zn, 8.51, 6.44, and 11.22% higher than SF, CF, and IF, respectively) and Boron (B, 13.47, 13.83, and 25.40% higher than SF, CF, and IF, respectively) were also found to increase. However, the contents of Mn (35.34, 27.51, and 25.53% higher) and Cu (31.90, 31.99, and 5.64% higher) in IF were significantly higher than in HF, SF, and CF. Acid soils (4.24–4.40) with low OM content (23.00–26.71 g kg−1) led to an imbalance uptake of nutrients of citrus, ultimately resulting in poor quality. These results indicated that farmers should reduce the application of nitrogen (N), phosphorus (P), and K fertilizer and pesticides and increase micronutrient and organic fertilizer, which provides a theoretical basis for scientific fertilization to improve the fruit quality of Guanxi pomelo (Citrus grandis) of Pinghe County.

Pangenome-wide analysis of cyclic nucleotide-gated channel (CNGC) gene family in citrus Spp. Revealed their intraspecies diversity and potential roles in abiotic stress tolerance.

Cyclic nucleotide-gated channels (CNGC) gene family has been found to be involved in physiological processes including signaling pathways, environmental stresses, plant growth, and development. This gene family of non-selective cation channels is known to regulate the uptake of calcium and is reported in several plant species. The pangenome-wide studies enable researchers to understand the genetic diversity comprehensively; as a comparative analysis of multiple plant species or member of a species at once helps to better understand the evolutionary relationships and diversity present among them. In the current study, pangenome-wide analysis of the CNGC gene family has been performed on five Citrus species. As a result, a total of 32 genes in Citrus sinensis, 27 genes in Citrus recticulata, 30 genes in Citrus grandis, 31 genes in Atalantia buxfolia, and 30 genes in Poncirus trifoliata were identified. In addition, two unique genes CNGC13 and CNGC14 were identified, which may have potential roles. All the identified CNGC genes were unevenly distributed on 9 chromosomes except P. trifoliata had genes distributed on 7 chromosomes and were classified into four major groups and two sub-groups namely I, II, III, IV-A, and IV-B. Cyclic nucleotide binding (CNB) motif, calmodulin-binding motif (CaMB), and motif for IQ-domain were conserved in Citrus Spp. Intron exon structures of citrus species were not exactly as same as the gene structures of Arabidopsis. The majority of cis-regulatory elements (CREs) were light responsive and others include growth, development, and stress-related indicating potential roles of the CNGC gene family in these functions. Both segmental and tandem duplication were involved in the expansion of the CNGC gene family in Citrus Spp. The miRNAs are involved in the response of CsCNGC genes towards drought stress along with having regulatory association in the expression of these genes. Protein- Protein interaction (PPI) analysis also showed the interaction of CNGC proteins with other CNGCs which suggested their potential role in pathways regulating different biological processes. GO enrichment revealed that CNGC genes were involved in the transport of ions across membranes. Furthermore, tissue-specific expression patterns of leaves sample of C. sinensis were studied under drought stress. Out of 32 genes of C. sinensis 3 genes i.e., CsCNGC1.4, CsCNGC2.1, and CsCNGC4.2 were highly up-regulated, and only CsCNGC4.6 was highly down-regulated. The qRT-PCR analysis also showed that CNGC genes were highly expressed after treatment with drought stress, while gene expression was lower under controlled conditions. This work includes findings based on multiple genomes instead of one, therefore, this will provide more genomic information rather than single genome-based studies. These findings will serve as a basis for further functional insights into the CNGC gene family.

The draft genome and multi-omics analyses reveal new insights into geo-herbalism properties of Citrus grandis ‘Tomentosa’

Citrus grandis ‘Tomentosa’ (CGT) (Huajuhong, HJH) is a widely used medicinal plant, which is mainly produced in Guangdong and Guangxi provinces of South China. Particularly, HJH from Huazhou (HZ) county of Guangdong province has been well-regarded as the best national product for geo-herbalism. But the reasons for geo-herbalism property in HJH from HZ county remains a mystery. Therefore, a multi-omics approach was applied to identify the nature of the geo-herbalism in CGT from three different regions. The comprehensive screening of differential metabolites revealed that the Nobiletin content was significantly different in HZ region compared to other regions, and could be employed as a key indicator to determine the geo-herbalism. Furthermore, the high-quality genome (N50 of 9.12 Mb), coupled with genomics and transcriptomics analyses indicated that CGT and Citrus grandis are closely related, with a predicted divergence time of 19.1 million years ago (MYA), and no recent WGD occurred in the CGT, and the bioactive ingredients of CGT were more abundant than that of Citrus grandis. Interestingly, Nobiletin (Polymethoxyflavones) content was identified as a potential indicator of geo-herbalism, and O-methyltransferase (OMT) genes are involved in the synthesis of Polymethoxyflavones. Further multi-omics analysis led to the identification of a novel OMT gene (CtgOMT1) whose transient overexpression displayed significantly higher Nobiletin content, suggesting that CtgOMT1 was involved in the synthesis of Nobiletin. Overall, our findings provide new data resources for geo-herbalism evaluation, germplasm conservation and insights into Nobiletin biosynthesis pathways for the medicinal plant C. grandis ‘Tomentosa’.

The new exploration of pure total flavonoids extracted from Citrus maxima (Burm.) Merr. as a new therapeutic agent to bring health benefits for people.

The peel and fruit of Citrus varieties have been a raw material for some traditional Chinese medicine (TCM). Pure total flavonoids from Citrus maxima (Burm.) Merr. (PTFC), including naringin, hesperidin, narirutin, and neohesperidin, have been attracted increasing attention for their multiple clinical efficacies. Based on existing in vitro and in vivo research, this study systematically reviewed the biological functions of PTFC and its components in preventing or treating liver metabolic diseases, cardiovascular diseases, intestinal barrier dysfunction, as well as malignancies. PTFC and its components are capable of regulating glycolipid metabolism, blocking peroxidation and persistent inflammation, inhibiting tumor progression, protecting the integrity of intestinal barrier and positively regulating intestinal microbiota, while the differences in fruit cultivation system, picking standard, manufacturing methods, delivery system and individual intestinal microecology will have impact on the specific therapeutic effect. Thus, PTFC is a promising drug for the treatment of some chronic diseases, as well as continuous elaborate investigations are necessary to improve its effectiveness and bioavailability.

Localization of CgVPE1 in secondary cell wall formation during tracheary element differentiation in the pericarp of Citrus grandis 'Tomentosa' fruits.

CgVPE1 is important in the differentiation of TE cells in C. grandis 'Tomentosa' fruits as it may directly affects secondary cell wall construction while participating in PCD. The vacuolar processing enzyme (VPE) plays an important role in both developmental and environmentally inducible programmed cell death (PCD); it was originally identified as a cysteine protease localized in the vacuole to activate and mature vacuolar proteins in plants. Interestingly, we found a VPE called CgVPE1 to be associated with deposition of the secondary cell wall in tracheary element (TE) cells in the pericarp of Citrus grandis 'Tomentosa' fruits. We then used ultrathin sections and the TUNEL assay to verify that PCD is involved in TE development. Furthermore, CgVPE1 was found to be mainly expressed in secretory cavities and TEs in the pericarp of Citrus grandis 'Tomentosa' fruits. Immunolocalization of CgVPE1 in the pericarp indicated that CgVPE1 is mainly distributed in the central large vacuole, endoplasmic reticulum, Golgi vesicles, cytosol, and secondary wall before TE maturation. CgVPE1 appeared earlier in the endoplasmic reticulum and Golgi vesicles of TEs cells. The vesicles containing CgVPE1 near the large central vacuole and secondary wall were observed, respectively. CgVPE1 proteins content in the cytoplasm decreased sharply, while the CgVPE1 content in the secondary cell wall did not change significantly after vacuole rupture. CgVPE1 protein contents in the secondary cell wall were significantly reduced until the TE cells developed into hollow thick-walled cells. Furthermore, labeling of VPE homologues in Arabidopsis thaliana using immunoelectron microscopy with anti-CgVPE1 antibody revealed that VPE homologues were specifically distributed in the secondary cell wall of stem TEs. Overall, these results suggested that CgVPE1 is not only involved PCD during TE cell development; furthermore, it may directly participate in the construction of plant secondary cell walls.

Hair growth promoting effect of essential oil from grapefruit peel (citrus grandis) combine dried gleditsia sinensis's extract powder on a shaved white mice model

Background: Many people are experiencing hair loss problems such as excessive hair loss, thinning hair and especially baldness. There are many ways to overcome this, one of which is to use hair care products that help stimulate hair growth, reduce hair loss and make hair stronger.
 Objectives: To evaluate the hair growth promoting effect of Grapefruit essential oil product containing Citrus grandis peel essential oil combined with dried Gleditsia sinensis’s extract powder on a shaved white mice model. Materials and methods: 07-week-old male white mice were marked with dorsal skin and hair removed with a specialized hair removal tool. Grapefruit peel is extracted by steam distillation and is used to prepare grapefruit peel essential oil product. Minoxidil 5% and physiological saline were used as controls. Grapefruit essential oil product, minoxidil and physiological saline are applied daily on the shaved back skin after bathing with clean water.
 Results: Research show that the hair growth in mice using Grapefruit essential oil product is faster than that in mice without using, p<0.05. Hair length was also significantly improved in mice after using Grapefruit essential oil product (25% of the batch). With a significance level of 91%, it was found that using Grapefruit essential oil product or minoxidil increased the number of hairs significantly. Conclusions: The use of Grapefruit essential oil product on mice shows that Grapefruit essential oil product has the ability to improve hair condition, helping hair grow faster, more and longer.

Effects of Foliar Fertilization on Nutrient Uptake, Yield, and Fruit Quality of Pomelo (Citrus grandis Osbeck) Grown in the Mekong Delta Soils

Foliar application is a popular technique to supply mineral nutrients to crops. It also enhances nutrient use efficiencies, especially under limited soil fertility or restricted environmental conditions. This study aimed to evaluate the influence of foliar application of phosphorus (P) with potassium (K), magnesium (Mg), and zinc (Zn) on the nutrient uptake, yield, and fruit quality of pomelo. The experiments were conducted between 2018 and 2021 in three different sites of alluvial soils, including four treatments, namely, control (without foliar fertilization), FF1 (containing P, K, and Mg), FF2 (P, K, Mg, and Zn), and FF3 (Zn). The results indicated that the P, K, and Mg concentrations in leaves and fruits were significantly enhanced after the spraying of solutions FF1 and FF2 compared with the control and FF3. The application of FF1 and FF2 greatly improved the fruit quality, and the fruit yield response was as high as 4.0-5.0 t ha−1. Foliar Zn application (FF3) increased the Zn concentration in leaves, but there was no improvement in fruit Zn content, fruit quality, and yield compared to the control treatment. The results indicate that FF1 or FF2 could be used as a sustainable fertilizer strategy for pomelo trees because of its ability to improve the leaf and fruit nutrient concentration and enhance the fruit quality and productivity of pomelo.

Citrus aurantium 'Changshan-huyou'-An ethnopharmacological and phytochemical review.

Citrus fruits are composed of oil cells layer, white membrane layer, pulp and seeds. The cultivar Citrus aurantium ‘Changshan-huyou’ (CACH) is a hybridization of Citrus grandis Osbeck and C. sinensis Osbeck. It is a rutaceae plant, and mainly grows in Changshan, Zhejiang, China. With the exploration of its high traditional values, it has been paid more and more attention by the scientific community in recent years. At present, one hundred and two chemical constituents have been identified from the pulp and peel of CACH, including volatile oils, terpenoids, phenols, limonins, sugars, etc., As the representative active component of CACH, phenols have been widely investigated. Studies have shown that CACH shows a variety of significant pharmacological activities, such as anti-inflammatory, antioxidant, hepatoprotective activity, respiratory system protection and intestinal regulation activity. This review mainly introduces the chemical constituents and pharmacological activities of CACH, and discusses its future research and development directions. It will provide theoretical basis for further research of its pharmacodynamic substances, functional mechanism and rational utilization.

Phytochemistry, micronutrient composition, and antioxidant potentials of Citrus maxima (Shaddock) fruit juice

Citrus maxima fruit, the largest of all Citrus varieties has been observed to be less consumed compared to other Citrus fruits. Paucity of information/awareness about its nutritive/medicinal properties could be a reason for that hence an increased research on its nutritive potentials could boost its consumption. This study was designed to evaluate its phytochemistry, micronutrient composition and in vitro antioxidant potentials. Citrus maxima juice was obtained from its fruit using a manual screw juice extractor. Analysis was carried out using standard methods. Phytochemical analysis of fresh juice of C maxima fruit showed the presence of phenols, flavonoids, tannins, alkaloids, glycosides, steroids and terpenoids. Zinc, copper, iron, magnesium, Vitamins C and E were present in appreciable quantities. Citrus maxima juice scavenged 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and superoxide radical (O2). This study showed that Citrus maxima fruit juice possesses considerable amounts of phytochemicals, minerals, vitamins C and E, and relative antioxidant potentials.

Effectiveness of Pollinator Insects in Increasing Fruit Formation of Pummelo (Citrus maxima (Burm.) Merr.)

Pummelo (Citrus maxima (Burm.) Merr.) is a type of plant which have commercial value, and at least 24 cultivars are spread across various regions in Indonesia. Some cultivars have self-incompatibility (SI) mechanisms as genetic barriers to fertilization, but this can be reduced through cross-pollination by insects. Therefore, this study aims to measure the effectiveness of wild pollinator insects, as well as human and bee pollinations in pummelo. A total of six treatments were set up, namely closed pollination or control, open treatment, human pollination using pollen from the same tree (geitonogamy) or different trees (xenogamy), as well as supplementation colony of honey bee (Apis cerana), and stingless bee (Tetragonula laeviceps). The highest increase of pummelo fruit formation was found in human-pollination (xenogamy), followed by A. cerana, T. laeviceps, open treatment, and geitonogamy pollination with 63%, 54%, 48%, 41%, and 14%, respectively. Based on the results, bees (A. cerana, T. laeviceps, Ceratina sp., Xylocopa confusa, X. latipes), fly (syrphid species), as well as butterflies (Papilio demoleus, Catopsilia pyranthe, and C. pomona) are potential pollinating agents of pummelo

Photosynthetic Characteristics and Chloroplast Ultrastructure Responses of Citrus Leaves to Copper Toxicity Induced by Bordeaux Mixture in Greenhouse.

Bordeaux mixture (Bm) is a copper (Cu)-based pesticide that has been widely used for controlling citrus scab and citrus canker. However, frequent spraying of Bm is toxic to citrus. To our knowledge, few studies are available that discuss how the photosynthetic characteristics and chloroplast ultrastructure of citrus leaves are affected by Cu toxicity induced by excessive Bm. In the study, two-year-old seedlings of Citrus grandis (C. grandis) and Citrus sinensis (C. sinensis), which were precultured in pots, were foliar-sprayed with deionized water (as control) or Bm diluted 500-fold at intervals of 7 days for 6 times (4 times as recommended by the manufacturer) to investigate the leaf Cu absorption, photosynthesis, chloroplast ultrastructure and antioxidant enzymatic activities. Bm foliar-sprayed 6 times on citrus seedlings increased the leaf Cu content, decreased the photosynthetic pigments content and destroyed the chloroplast ultrastructure, which induced leaf chlorosis and photosynthetic inhibition. A lower Cu absorption, a higher light photon-electron transfer efficiency, a relative integrity of chloroplast ultrastructure and a promoted antioxidant protection contributed to a higher photosynthetic activity of C. grandis than C. sinensis under excessive spraying of Bm. The present study provides crucial references for screening and selecting citrus species with a higher tolerance to Cu toxicity induced by excessive Bm.

Optimization of Pb(II) Metal Adsorption on Pomelo Peel Biosorbent by Immobilization in Ca-Alginate

Industrial wastewater is a source of water pollution that dominates today. Wastewater is known to cause damage to the environment, health and threatens the availability of clean water. Industrial wastewater is a problem because it contains a lot of dangerous heavy metals, one of which is Lead or Pb(II).' Adsorption technology has become one of the most exciting technologies because of its good performance. Adsorption media currently popular for the study is adsorption using agricultural waste. One of the agricultural wastes that can be used as biosorbent is grapefruit peel (Citrus maxima). The functional groups in grapefruit peel are ether, pedophilic, carboxyl, carbonyl, and hydroxyl. These functional groups are essential in binding heavy metals from the aquatic environment. In this study, grapefruit peel was modified into a Ca-alginate immobilized biosorbent. The analyzes that will be carried out include the characteristics of the biosorbent, namely the water content and ash content test, the FTIR test to determine the functional groups contained in the biosorbent, the SEM-EDX test to assess the appearance of the biosorbent, as well as analysis of the initial and final levels of Pb(II). Based on the results obtained, the best percentage decrease in Pb(II) levels was obtained with operating conditions of pH 4.7, contact time of 90 minutes, and Pb(II) concentration of 100 mg/L with a percentage decrease in Pb(II) levels of 89%.

Optimization of Pb(II) Metal Adsorption on Pomelo Peel Biosorbent by Immobilization in Ca-Alginate

Industrial wastewater is a source of water pollution that dominates today. Wastewater is known to cause damage to the environment, health and threatens the availability of clean water. Industrial wastewater is a problem because it contains a lot of dangerous heavy metals, one of which is Lead or Pb(II).' Adsorption technology has become one of the most exciting technologies because of its good performance. Adsorption media currently popular for the study is adsorption using agricultural waste. One of the agricultural wastes that can be used as biosorbent is grapefruit peel (Citrus maxima). The functional groups in grapefruit peel are ether, pedophilic, carboxyl, carbonyl, and hydroxyl. These functional groups are essential in binding heavy metals from the aquatic environment. In this study, grapefruit peel was modified into a Ca-alginate immobilized biosorbent. The analyzes that will be carried out include the characteristics of the biosorbent, namely the water content and ash content test, the FTIR test to determine the functional groups contained in the biosorbent, the SEM-EDX test to assess the appearance of the biosorbent, as well as analysis of the initial and final levels of Pb(II). Based on the results obtained, the best percentage decrease in Pb(II) levels was obtained with operating conditions of pH 4.7, contact time of 90 minutes, and Pb(II) concentration of 100 mg/L with a percentage decrease in Pb(II) levels of 89%.

New insights into vesicle granulation in Citrus grandis revealed by systematic analysis of sugar- and acid-related genes and metabolites

Vesicle granulation is a common internal physiological disorder in citrus fruit, associated with excessive consumption of sugar and acid. Aside from cell wall metabolism, it remains largely unexplored how the sugar and acid metabolic pathways altered as vesicle granulation progressed. The present study performed systematic analysis of sugar- and acid-related genes and metabolites in vesicles during pomelo granulation. Eighty-one genes were identified from the pomelo genome, belonging to 19 families, including 37 and 44 genes for sugar and acid metabolism, respectively. Vesicle granulation was characterized by increasing expression levels of genes of sucrose and citrate degradation while decreasing expression levels of genes of sucrose and citrate synthesis, according to the genome-wide transcript analysis. Further, those genes of citrate degradation were mainly related to glutamine and acetyl-CoA pathways. Systematic analysis of metabolites suggested that various metabolites, including glutamine and other metabolites of the acetyl-CoA pathway, were accumulated dramatically upon granulation. Interestingly, the γ-aminobutyrate shunt, the pivotal pathway for citrate degradation in citrus fruit upon ripening, may not be activated during pomelo granulation. In conclusion, the present study discovered novel metabolic pathways underlying citrus granulation, including shifting citrate flux to the glutamine pathway and acetyl-CoA pathway, but not the γ-aminobutyrate shunt.

Pomelo Tree Detection Method Based on Attention Mechanism and Cross-Layer Feature Fusion

Deep learning is the subject of increasing research for fruit tree detection. Previously developed deep-learning-based models are either too large to perform real-time tasks or too small to extract good enough features. Moreover, there has been scarce research on the detection of pomelo trees. This paper proposes a pomelo tree-detection method that introduces the attention mechanism and a Ghost module into the lightweight model network, as well as a feature-fusion module to improve the feature-extraction ability and reduce computation. The proposed method was experimentally validated and showed better detection performance and fewer parameters than some state-of-the-art target-detection algorithms. The results indicate that our method is more suitable for pomelo tree detection.

Rhamnosyltransferases involved in the biosynthesis of flavone rutinosides in Chrysanthemum species.

Linarin (acacetin-7-O-rutinoside), isorhoifolin (apigenin-7-O-rutinoside), and diosmin (diosmetin-7-O-rutinoside) are chemically and structurally similar flavone rutinoside (FR) compounds found in Chrysanthemum L. (Anthemideae, Asteraceae) plants. However, their biosynthetic pathways remain largely unknown. In this study, we cloned and compared FRs and genes encoding rhamnosyltransferases (RhaTs) among eight accessions of Chrysanthemum polyploids. We also biochemically characterized RhaTs of Chrysanthemum plants and Citrus (Citrus sinensis and Citrus maxima). RhaTs from these two genera are substrate-promiscuous enzymes catalyzing the rhamnosylation of flavones, flavanones, and flavonols. Substrate specificity analysis revealed that Chrysanthemum 1,6RhaTs preferred flavone glucosides (e.g. acacetin-7-O-glucoside), whereas Cs1,6RhaT preferred flavanone glucosides. The nonsynonymous substitutions of RhaTs found in some cytotypes of diploids resulted in the loss of catalytic function. Phylogenetic analysis and specialized pathways responsible for the biosynthesis of major flavonoids in Chrysanthemum and Citrus revealed that rhamnosylation activity might share a common evolutionary origin. Overexpression of RhaT in hairy roots resulted in 13-, 2-, and 5-fold increases in linarin, isorhoifolin, and diosmin contents, respectively, indicating that RhaT is mainly involved in the biosynthesis of linarin. Our findings not only suggest that the substrate promiscuity of RhaTs contributes to the diversity of FRs in Chrysanthemum species but also shed light on the evolution of flavone and flavanone rutinosides in distant taxa.

Differential response of bacterial diversity and community composition to different tree ages of pomelo under red and paddy soils.

Rhizosphere soil microbial communities substantially impact plant growth by regulating the nutrient cycle. However, dynamic changes in soil microbiota under different tree ages have received little attention. In this study, changes in soil physicochemical properties, as well as bacterial diversity and community structures (by high-throughput Illumina MiSeq sequencing), were explored in pomelo trees of different ages (i.e., 10, 20, and 30 years) under red and paddy soils cultivated by farmers with high fertilizer input. Moreover, soil factors that shape the bacterial community, such as soil pH, AP (available phosphorous), AK (available potassium), and AN (available nitrogen), were also investigated. Results showed that pH significantly decreased, while AP, AK, and AN increased with increasing tree age under red soil. For paddy soil, pH was not changed, while AP was significantly lower under 10-year-old pomelo trees, and AK and AN contents were minimum under 30-year-old pomelo trees. Both soil types were dominated by Proteobacteria, Acidobacteria, and Actinobacteria and showed contrasting patterns of relative abundance under different tree age groups. Bacterial richness and diversity decreased with increasing tree age in both soil types. Overall, bacterial community composition was different under different tree ages. RDA analysis showed that soil pH, AP, and AN in red soil, and pH and AP in paddy soil showed the most significant effects in changing the bacterial community structure. A random forest model showed Sinomonas and Streptacidiphilus in red soil, while Actinoallomurus and Microbacterium in paddy soil were the most important genera explaining the differences among different age groups. The ternary plot further revealed that genera enrichment for Age_30 was higher than that for Age_10 and Age_20 in red soil, whereas specific genera enrichment decreased with increasing tree age under paddy soil. Co-occurrence network revealed that bacterial species formed a complex network structure with increasing tree age, indicating a more stable microbial association under 20 and 30 years than 10-year-old pomelo trees. Hence, contrasting patterns of changes in soil physicochemical properties and soil microbial communities were recorded under different tree ages, and tree ages significantly affected the bacterial community structure and richness. These findings provide valuable information regarding the importance of microbes for the sustainable management of pomelo orchards by optimizing fertilizer input for different ages of trees.

Metabolic Profiling and Transcriptional Analysis of Carotenoid Accumulation in a Red-Fleshed Mutant of Pummelo (Citrus grandis).

Citrus grandis ‘Tomentosa’, commonly known as ‘Huajuhong’ pummelo (HJH), is used in traditional Chinese medicine and can moisten the lungs, resolve phlegm, and relieve coughs. A spontaneous bud mutant, named R-HJH, had a visually attractive phenotype with red albedo tissue and red juice sacs. In this study, the content and composition of carotenoids were investigated and compared between R-HJH and wild-type HJH using HPLC–MS analysis. The total carotenoids in the albedo tissue and juice sacs of R-HJH were 4.03- and 2.89-fold greater than those in HJH, respectively. The massive accumulation of carotenoids, including lycopene, β-carotene and phytoene, led to the attractive red color of R-HJH. However, the contents of flavones, coumarins and most volatile components (mainly D-limonene and γ-terpinene) were clearly reduced in R-HJH compared with wild-type HJH. To identify the molecular basis of carotenoid accumulation in R-HJH, RNA-Seq transcriptome sequencing was performed. Among 3948 differentially expressed genes (DEGs), the increased upstream synthesis genes (phytoene synthase gene, PSY) and decreased downstream genes (β-carotene hydroxylase gene, CHYB and carotenoid cleavage dioxygenase gene, CCD7) might be the key factors that account for the high level of carotenoids in R-HJH. These results will be beneficial for determining the molecular mechanism of carotenoid accumulation and metabolism in pummelo.