Orange Varieties Research Articles

Changes in the sugars and volatile compounds profiles associated with anthocyanin accumulation in oranges: Blood vs. blond varieties, and slightly pigmented vs. intensely pigmented blood fruit

The blood oranges accumulate anthocyanins in their peel and pulp, which give them their characteristic red colour. To investigate whether there is a specific volatile compounds profile for blood oranges, we compared the volatile composition of the blood varieties ‘Moro’, ‘Tarocco Rosso’ and ‘Sanguinelli’ to that of the blond ones ‘Cadenera’, ‘Salustina’ and ‘Hamlim’ using a non-targeted approach based on HS–SPME–GC–MS. Moreover, fruits from each blood orange variety were divided into slightly and intensely pigmented fruits, and individual sugars and anthocyanins were determined by liquid chromatography to investigate whether their profiles depend on the degree of pulp pigmentation. A total of 101 volatile compounds were identified in this study. Hierarchical Cluster Analysis, including all compounds, revealed that blood oranges have no unique volatiles profile that makes them more similar to one another than to the blond varieties. For blood orange varieties, our results corroborated that greater anthocyanin accumulation in the most intensely pigmented fruit is associated with higher sugar content (an increase of 0.8–2.3 % depending on the variety). Moreover, we reported for the first time that anthocyanin accumulation is also associated with changes in the volatiles profile. A Multifactor Analysis including data on volatiles, sugars and anthocyanin showed that sucrose is the sugar more strongly linked to anthocyanin accumulation. A group of volatile compounds, mainly esters (ethyl acetate, ethyl-2-methyl butanoate and ethyl-2-butenoate) along with ethanol, are present at increased levels, sometimes even doubling in the most intensely pigmented samples compared to the slightly pigmented ones. These results open the door to further investigate the possible metabolic link between sugars and anthocyanins accumulation and changes in volatile compounds.

Analysis of Technical Efficiency on Orange Fleshed Sweet Potatoes Production Among the Smallholder Farmers in Migori County Kenya

Sweet potatoes (<i>Ipomea batatas </i>L.), particularly the orange fleshed variety, have become increasingly popular due to their ability to thrive in various environmental conditions with minimal inputs. Orange fleshed sweet potatoes (OFSPs) show potential for productivity, yet smallholder farmers in Kenya still struggle to maximize their yields. The factors influencing OFSP production efficiency among these farmers in Western Kenya have not been thoroughly examined. This study evaluated the technical efficiency of OFSP production among smallholder farmers in Migori County. Using a descriptive research design, a sample of 225 OFSP farmers was randomly selected by a cluster sampling technique. Data was collected through a structured questionnaire on inputs and selected socio-economic factors. The data was analyzed using the frontier stochastic model in STATA. Smallholder farmers estimated mean technical efficiency was 77.82% significant variables were; size of the land, availability of planting vines, access to hired labour, gender of the household decision maker, farming experience, household size, land ownership status, participation in training programs and extension services, and proximity to markets, indicating a need to improve OFSP production by 22.18%. These findings suggest that to reduce inefficiencies among smallholder OFSP farmers, targeted training programs are needed to enhance farmers' agronomic knowledge specific to OFSP production. Further, policy interventions should prioritize the provision of extension services to support and improve the performance of OFSP smallholder farmers.

Bio-fortification with selenium (Se) improves quality and nutrient profile in citrus fruit

Selenium (Se) is an essential nutrient for the human body. Humans can enhance Se absorption by consuming horticultural plants, particularly fruits. Therefore, there is need for Se biofortification in fruits to meet the human demand for Se. The objective of this study was to determine the optimal Se application rate, application stage and method, and to assess their impacts on improving both the quality and nutrient profile of a sweet orange cultivar 'Hongjiangcheng' (Citrus sinensis (L.) Osbeck). 'Hongjiangcheng’ is a notable variety of mandarin orange, acclaimed for its large size, thin and smooth skin, orange-red flesh, tender and juicy texture, balanced sweetness and acidityand distinctive flavor. A field experiment was conducted at the Qiaotou Town Test Base in Chengmai County, Hainan Province, China. Biofortification of Se was done through foliar and soil application methods. Treatments were: Control (C) with no application of Se, foliar application of 25 (SeF1), 50 (SeF2), 100 (SeF3) and 200 (SeF4) mg/L and soil application of 100 mg/L (SeS1) as well as a combination of 100 mg/L Se in soil along with 50 mg/L Se on leaves (SeS1F2). At start of the experiment, 189 healthy, four-year-old citrus trees of similar size and normal growth were selected. The trees were divided into three groups of 63 each. Each group received the aforementioned treatments at the young fruit, expanding fruit and premature fruit stages. The Se was applied once during each stage before 9:00 am on sunny days. Treatments were arranged in a randomized complete block design with 9 biological replicates (7 treatments × 9 replicates = 63 citrus trees/ application stage). Foliar application of Se at rate of 200 mg/L (SeF4) enhanced total Se content in leaves by 105, 34 and 69 % at young fruit, expanding fruit and premature fruit stages compared to control (p≤0.05). Respective increments in fruits were 264, 22 and 21 %. The total Se content in leaves were 32 and 40 % higher in the SeF4 (foliar) compared to SeS1 and SeS1F2 (soil) treatments across all development stages (p≤0.05), respectively. The respective increments in fruits total Se content were 16 and 52 %. Only at the young fruit stage, the organic Se content in fruits was significantly higher in the SeF4 compared to soil application treatments (p≤0.05). Single fruit weight was enhanced by 16.61, 13.69 and 4.36 g by foliar than soil application at young fruit, expanding fruit and premature fruit stages, respectively. It was significantly higher (155.53 vs. 113.13 g) after application of SeF4 treatment at young fruit stage relative to all other treatments (p≤0.05). The application of SeF4 at the young fruit stage resulted in an increased seed rate (97 %), total soluble solids (28 %) and solid-to-acid ratio (75 %), while titratable acid decreased by 26 % compared to the control. Interestingly, Se application had non-significant effects on the fruit shape index, peel rate and residue rate across all stages (p>0.05). Additionally, a positive correlation was observed between fruit Se content and several quality indices like total soluble solids, solid acid ratio, fruit shape index and fruit weight at young fruit stage (p≤0.05). It is concluded that foliar application of Se at 200 mg/L (SeF4) during young fruit stage improved citrus Se content, its fruit weight and quality indices establishing these fruits as a valuable source of Se-rich food for human consumption.

A comparative analysis of the volatile profiles in the pulp of red-fleshed and standard orange varieties during fruit maturation

Kirkwood Navel and Ruby Valencia red-fleshed sweet oranges accumulate high concentrations of the carotenes phytoene, phytofluene and lycopene in the pulp. In order to gain insight into the parameters that influence fruit quality in these varieties, a comparative analysis of volatile organic compounds (VOCs) in the pulp of Kirkwood Navel and Ruby Valencia red-fleshed sweet oranges and their standard blond counterparts, Navel and Valencia, was performed during fruit development and ripening. A total of 95 VOCs were identified by HS-SPME/GC–MS during the ripening process. The observed differences in VOCs between red-fleshed and blond oranges were more closely related to the fruit ripening stage than to the genotype. However, two distinctive common features were identified in both red-fleshed oranges compared to their respective standard varieties. These were lower levels of sesquiterpenes and higher levels of the norisoprenoids 6-methyl-5-hepten-2-one and geranylacetone. These findings indicate that altered carotenoid metabolism in red-fleshed oranges not only affects flesh pigmentation but also leads to changes in specific VOCs that may influence flavor perception.

Identification of the sweet orange (Citrus sinensis) bHLH gene family and the role of CsbHLH55 and CsbHLH87 in regulating salt stress.

Salt stress is one of the primary environmental stresses limiting plant growth and production and adversely affecting the growth, development, yield, and fruit quality of Citrus sinensis. bHLH (basic helix-loop-helix) genes are involved in many bioregulatory processes in plants, including growth and development, phytohormone signaling, defense responses, and biosynthesis of specific metabolites. In this study, by bioinformatics methods, 120 CsbHLHgenes were identified, and phylogenetic analysis classified them into 18 subfamilies that were unevenly distributed on nine chromosomes. The cis-acting elements of the CsbHLH genes were mainly hormone-related cis-acting elements. Seventeen CsbHLH genes exhibited significant differences in expression under salt stress. Six CsbHLH genes with significant differences in expression were randomly selected for quantitative real-time polymerase chain reaction (qRT-PCR) validation. The qRT-PCR results showed a strong correlation with the transcriptome data. Phytohormones such as jasmonic acid (JA) are essential for biotic and abiotic stress responses in plants, and CsbHLH55 and CsbHLH87 are considered candidate target genes for sweet orange MYC2 transcription factors involved in the JA signaling pathway. These genes are the main downstream effectors in the JA signaling pathway and can be activated to participate in the JA signaling pathway. Activation of the JA signaling pathway inhibits the production of reactive oxygen species and improves the salt tolerance of sweet orange plants. The CsbHLH55 and CsbHLH87 genes could be candidate genes for breeding new transgenic salt-resistant varieties of sweet orange.

Transcriptome and weighted gene co-expression network analyses reveal key genes and pathways involved in early fruit ripening in Citrus sinensis

BackgroundThe fruit ripening period is an important target trait in fruit tree crop breeding programs. Thus, citrus tree breeders seek to develop extreme early ripening cultivars that allow optimization of citrus maturation periods. In this study, we explored the regulatory network involved in fruit ripening in Citrus sinensis using the ‘Newhall’ navel orange variety and its early-ripening mutant, ‘Gannanzao’. This research will provide a basis for further research on important signaling pathways, gene functions and variety breeding of Citrus sinensis related to fruit ripening period.ResultsPhysiological analyses suggested that early fruit ripening in ‘Gannanzao’ is regulated by early accumulation of abscisic acid (ABA), persistently high levels of jasmonic acid (JA), and higher sucrose content in the pericarp. Pericarp samples from ‘Gannanzao’ and ‘Newhall’ navel oranges were sampled for RNA sequencing analysis at 180, 200, and 220 days after flowering; 1430 differentially expressed genes (DEGs) were identified. Functional enrichment analysis indicated that these DEGs were mainly enriched in the plant hormone signal transduction and sugar metabolism pathways, as well as other pathways related to fruit ripening. Important DEGs associated with fruit ripening in ‘Gannanzao’ included genes involved in ABA and JA metabolism and signal transduction, as well as sugar metabolism. Weighted gene co-expression network analysis showed that the deep pink module had the strongest correlations with ABA content, JA content, and early ripening. Based on gene functionality and gene expression analyses of 37 genes in this module, two candidate hub genes and two ethylene response factor 13 (ERF13) genes (Cs_ont_5g000690 and Cs_ont_5g000700) were identified as key genes regulated by ABA and JA signaling. These findings will help to clarify the mechanisms that underlie early citrus fruit ripening and will lead to the development of excellent genetic resources for further breeding of extreme early-ripening varieties.ConclusionsThrough analyses of the ‘Newhall’ navel orange cultivar and its early-ripening mutant ‘Gannanzao’, we identified genes involved in ABA and JA metabolism, signal transduction, and sugar metabolism that were related to fruit ripening. Among these, two ERF13 genes were inferred to be key genes in the regulation of fruit ripening. These findings provide insights into the genetic architecture related to early fruit ripening in C. sinensis.

Implementing Internet of Things for Real-Time Monitoring and Regulation of Off-Season Grafting and Post-Harvest Storage in Citrus Cultivation: A Case Study from the Hilly Regions of Nepal

Citrus fruit cultivation, especially mandarin oranges, is crucial to the economy of Nepal’s hilly regions due to their ideal geoclimatic conditions. Despite its economic importance, the sector faces several challenges, such as inadequate grafting techniques, low-quality saplings, and ineffective post-harvest storage. This paper explores these issues and proposes innovative solutions through the use of Internet of Things (IoT) technology. To address these challenges, we identified key areas for improvement. First, we focused on extending grafting practices during the off-season to ensure a higher success rate and better-quality saplings. Second, we examined different post-harvest storage methods to determine their effectiveness in terms of shelf life, decay loss, and quality of fruit. In addition to exploring post-harvest strategies, this paper provides preharvest recommendations for farmers, emphasizing methods to enhance fruit quality and longevity through effective pre-storage practices. Our IoT-based approach introduces off-season grafting in polyhouses and advanced monitoring for post-harvest storage. The results are promising: We achieved grafting success rates of 91% for acid lime and 92% for local mandarin orange varieties. Additionally, our research compared different post-harvest storage methods for mandarin oranges, including room, cellar, and cold chamber. We assessed these methods based on shelf life, physiological weight loss, and the total soluble solids (TSS) to titratable acidity (TA) ratio. The cold chamber proved to be the most effective method, offering superior conditions for storing mandarin oranges. The IoT-based monitoring system played a crucial role in maintaining optimal temperature, humidity, and gas content within the cold chamber, resulting in reduced post-harvest losses and extended shelf life. These findings highlight the transformative potential of IoT technology in mandarin orange cultivation and post-harvest storage.

Comparative Antibacterial Effectiveness of Orange Peel Extracts from Five Varieties Against Strain of Multi Drug Resistance Escherichia coli

The purpose of this study was to investigate the antibacterial activity of orange peel extracts from five different orange varieties in North Sumatera against resistant Escherichia coli bacteria and compare it to the effectiveness of vancomycin and erythromycin. To assess antibacterial activity, orange peel extracts were prepared from five different orange varieties, namely Citrus aurantifolia, Citrus microcarpa Bunge, Citrus limon L., Citrus sinensis L., and Citrus hystrix. Antibacterial activities were evaluated using the microdilution method to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The best antibacterial activity was determined using the smallest MIC and MBC values. The research found that all five orange peel extracts exhibited significant antibacterial activity compared to the standard antibiotics vancomycin and erythromycin. The most potent inhibitory effect was observed with the Citrus hystrix peel extract, with the lowest MIC and MBC (125 and 250 µg/mL), followed by Citrus aurantifolia (250 and 500 µg/mL), and Citrus sinensis L. (500 and 500 µg/mL). The results showed significant antibacterial activity of orange peel extracts from five different orange varieties in North Sumatera against resistant Escherichia coli bacteria. Keywords: Antibiotic resistance, citrus peel extracts, Escherichia coli, MIC, MBC.

Focused Analysis of Changes in Bioactive Compounds and Antioxidant Potential of Sweet Orange Varieties throughout Developmental Stages

Focused Analysis of Changes in Bioactive Compounds and Antioxidant Potential of Sweet Orange Varieties throughout Developmental Stages

Effect of <i>Meloidogyne incognita</i> infection on the accumulation of phenolic compounds in plants of the genus Mint (Mentha L.)

The purpose of the research is to compare the accumulation of phenolic compounds of different species and varieties of mint, zoned in Central Russia against the background of plant infection by Meloidogyne incognita.Materials and methods. Plants were grown from cuttings in a growing experiment in open ground. Mentha × piperita L. (varieties: Tik-Tak, Orange, Minneola, Mojito, Mitchum, Chocolate), M. spicata L. (varieties Morocco, Crispa) and M. longifolia L. (Longifolia) were taken for the study. A month later, the rooted plants were infected at the rate of 1000 sp. infective larvae of M. incognita per plant. After 8 weeks leaves were fixed in ethanol. The total content of phenolic compounds (PC), phenylpropanoids, flavonoids and catechins was studied using a spectrophotometer. The determination of the total content of PС was carried out using the Folin-Cecolte reagent with measurement at 725 nm, phenylpropanoids – by direct measurement of optical density at 330 nm, flavonoids – by reaction with aluminum chloride at 415 nm, the total content of flavans (catechins - flavan-3-ols), their oligomeric forms – proanthocyanidins, as well as leukoanthocyanidins were assessed by reaction with vanillin at 500 nm.Results and discussion. It has been shown that the accumulation of phenols is related to the species of plants. The varieties Mentha × piperita L. in most cases contained more phenols than M. spicata L. and M. longifolia L. A significant number of PC was noted in the violet-colored varieties Mitchum, Chocolate and Orange. The total content of PC almost completely correlates with the content of their precursors – phenylpropanoids. In terms of the content of flavonoids, the Mitchum variety stands out noticeably, and in terms of the content of catechins, the Orange variety stands out. Nematode infection in most varieties causes a noticeable increase in the total accumulation of soluble PC, phenylpropanoids and flavans, but leads to a decrease in the content of flavonoids.

LC−MS/MS−based metabolite profiling and antioxidant evaluation of three Indonesian orange varieties

The orange peel contains bioactive components with health−promoting effects, a rich source of antioxidants, and could be used for functional food. However, due to many factors, the composition and concentration of bioactive compounds from orange peels differ because of their variety. This study aims to identify the metabolite and evaluate the antioxidant activity of peels from Indonesian orange varieties, i.e., Rimau Gerga Lebong (RGL, Bengkulu), Brastagi (JBM, North Sumatra), and Garut (JSG, West Java). The metabolite profile was analyzed using LC−MS/MS and discriminated based on orange variety using principal component analysis (PCA) and hierarchical clustering analysis (HCA). Antioxidant activity was measured using the 2,2 −diphenyl− 1 −picrylhydrazyl (DPPH), cupric ion−reducing antioxidant capacity (CUPRAC), and ferric−reducing antioxidant power (FRAP) methods. In this study, the metabolite profile of orange peel proved to be rich in flavonoids like hesperidin, rutin, nobiletin, polyphenol−organic acids like p − coumaric acid, citric acid, quinic acid, and other metabolites from the class terpenoids, amino acids, and sugars. PCA separated each variety and HCA heatmaps showed variations in the distribution of identified metabolites. In the RGL variety, 47 metabolites were identified, dominated by flavonoids and terpenoids. As many as 44 metabolites in the JBM variety contain many amino acids and flavonoids. In JBM, 44 metabolites were identified with carboxylic and amino acids as the main compounds. RGL orange peel extract had the highest antioxidant activity using the DPPH and CUPRAC methods, whereas the FRAP method did not show significant differences. Regarding metabolites and antioxidant activity, RGL, JBM, and JSG orange peels can be developed as alternative functional foods.

Assessment of Physicochemical Properties of Orange Juice Concentrate Formulated with Pectin, Xanthan, and CMC Hydrocolloids.

Orange concentrate (OC) is one of the main raw materials in the nonalcoholic beverage industry. Considering the difference in orange varieties, preserving its natural quality is essential to yield a product with favorable attributes and physical stability. Thus, the present study is aimed at assessing the effect of pectin, xanthan, and carboxymethyl cellulose (CMC) in a concentration range of 0-0.2% (w/v) along with mixing temperature on Brix, pH, acidity, density, turbidity, and viscosity of OC and at calculating the model equation for each attribute. The results showed that, except for CMC, the influence of concentration, type, and amount of hydrocolloid on pH changes was insignificant. Adding each hydrocolloid individually, in pairs, or threes reduced the density, and the measured density was lower at a mixing temperature of 4°C. Also, it was observed that mixing temperature was the only factor influencing turbidity, and the values were significantly lower at 80°C compared to 4°C. A significant interaction effect of xanthan concentration and mixing temperature on the Brix was observed. Adding hydrocolloids, except pectin, resulted in a significant (p < 0.05) increase in viscosity, and xanthan had the greatest effect on the viscosity. A suitable model was designed using pectin and xanthan, pectin and CMC, and all three gums, resulting in a final OC product with high stability and improved physical and chemical attributes. The optimized values for Brix, pH, acidity, density, turbidity, and OC viscosity were achieved using 0.08% pectin, 0.19% xanthan, and 0.08% CMC at 80°C mixing temperature.

A high-quality chromosome-scale genome assembly of blood orange, an important pigmented sweet orange variety

Blood orange (BO) is a rare red-fleshed sweet orange (SWO) with a high anthocyanin content and is associated with numerous health-related benefits. Here, we reported a high-quality chromosome-scale genome assembly for Neixiu (NX) BO, reaching 336.63 Mb in length with contig and scaffold N50 values of 30.6 Mb. Furthermore, 96% of the assembled sequences were successfully anchored to 9 pseudo-chromosomes. The genome assembly also revealed the presence of 37.87% transposon elements and 7.64% tandem repeats, and the annotation of 30,395 protein-coding genes. A high level of genome synteny was observed between BO and SWO, further supporting their genetic similarity. The speciation event that gave rise to the Citrus species predated the duplication event found within them. The genome-wide variation between NX and SWO was also compared. This first high-quality BO genome will serve as a fundamental basis for future studies on functional genomics and genome evolution.

Determination of ascorbic acid levels in oranges under different storage conditions using Redox Iodometric method

Ascorbic acid is one of the most important vitamins to the human body due to its potentially protective role as an antioxidant. Oranges by far the most important citrus species are an excellent source of ascorbic acid. The ascorbic acid in three varieties of Ghanaian local oranges was estimated after storage under four different storage conditions. The storage conditions were deep freezing, dark cupboard, open shelf and in the sun. The redox titrimetric method using potassium iodide as the titrant and starch as an indicator was employed to evaluate the ascorbic acid levels in the orange samples after two, four and six days. The result shows a decrease in the ascorbic acid content of oranges over the storage periods. The decrease was expressed as a percentage loss of ascorbic acid originally in oranges. Less ascorbic acid was lost with the refrigerated orange samples compared to the other storage conditions. A huge loss of ascorbic acid was however lost with the samples that were exposed to the sun.

Attributes of sensory and instrumental analysis that determine overall liking of fresh orange varieties with different maturity index.

Spain is the leading exporter of fresh citrus for consumption. In order to adapt to market needs, it is key to analyze the attributes that most influence each variety, the time of ripening and the color of the fruit. In this way, the producer can select the right fruit for each moment of the season. The main objective was to evaluate the fruit quality of three interesting orange tree varieties for fresh consumption: "Washington Navel," "Navelate," and "Lanelate" sweet orange. To achieve this goal, sensory analysis was combined with instrumental analysis. In Washington Navel, the maturity index provided a positive contribution to overall liking. Both herbaceous and fruity aroma have a negative influence on the overall liking score. In Navelina, the color and aromas (herbaceous and fruity) played an important positive role in overall liking. The importance of this smell could be related to the freshness of the oranges. In contrast, the maturity index provided a negative contribution. Lanelate is the only variety in which vitamin C provided a positive contribution to overall liking. However, L* value showed a negative contribution. Therefore, there were clearly different characteristics among varieties that were detected. So far, different orange varieties have not been compared according to their maturity index and using sensory analysis. Descriptive analysis and the variables that influence overall liking are fundamental to adapt to consumer expectations. The results obtained would help to select the fruit with better acceptability in the market.

Mandarin Variety Significantly Affects the Metabolites Present in the Leaves

Late-season varieties of mandarin (Citrus reticulata Blanco) have a high economic value, so their study, characterization, and comparison among different commercial varieties is of great interest for agriculture. Detailed metabolomic analysis of mandarin leaves can provide valuable information on agronomic characteristics, vegetative development, and tree response to abiotic and biotic stresses. In this study, an analysis of the main metabolites presents in the leaves of three late-season mandarin orange varieties (‘Afourer’, ‘Orri’ and ‘Tango’), cultivated under homogeneous conditions, was carried out using nuclear magnetic resonance (1H NMR) and multivariate statistical analysis techniques. The results show that organic acids and sugars are the metabolites with the highest presence in mandarin leaves, especially malate and sucrose. Ten amino acids and other metabolites such as choline and trigonelline were also detected. Metabolites such as asparagine and isoleucine were widely implicated in the metabolic pathways of the detected compounds. The ‘Orri’ variety showed significantly more differences in metabolite concentrations compared to the other two varieties studied. Malate and sucrose were shown to be the metabolites with the greatest significant differences between the varieties compared. From an agronomic point of view, the ‘Orri’ variety differs from the other two varieties because it has concentrations of metabolites that provide good resistance to abiotic and biotic stresses and fruits of higher quality and sweetness.

Identification and pathogenicity of Colletotrichum species associated with twig dieback of citrus in Western Australia

AbstractUp to 32 Colletotrichum species have been reported to be associated with pre‐ or postharvest diseases of citrus globally, while in Australia, six species have been reported to cause citrus leaf and fruit disease. Twig or shoot dieback has recently been observed as an emerging disease in citrus orchards in Western Australia. Colletotrichum species were isolated from diseased twigs showing dieback (withertip) or lesions, with or without gummosis, collected from 12 varieties of orange, mandarin and lemon. Colletotrichum gloeosporioides sensu stricto, Colletotrichum karstii and Colletotrichum novae‐zelandiae were identified using a polyphasic approach that included multigene phylogenetic analysis using sequences of internal transcribed spacer and intervening 5.8S nrDNA (ITS), glyceraldehyde‐3‐phosphate dehydrogenase (gapdh), β‐tubulin (tub2), actin (act) and histone (his3) for isolates in the boninense species complex, and Apn2–Mat1–2 intergenic spacer and partial mating type (Mat1–2) (ApMat) and glutamine synthetase (gs) for isolates in the gloeosporioides species complex, as well as morphological characteristics. C. gloeosporioides was the most prevalent species associated with twig dieback in Western Australia, while C. novae‐zelandiae was reported for the first time in Australia. Pathogenicity tests on shoot twigs from lemon and orange trees confirmed C. gloeosporioides, C. karstii and C. novae‐zelandiae as the cause of twig dieback, with C. gloeosporioides being the most aggressive species. Knowledge of the species causing twig dieback and their lifestyle will assist the development of integrated control methods.

Chemotaxonomic classification of closed-related sweet oranges (Citrus sinensis L.) using principal component and cluster analysis of color and bi-oactive compounds in the orange peels

Chemotaxonomy is a systematic approach to plant classification based on discernible variations and similarities in their biochemical compositions, with a particular emphasis on secondary metabolites that often exhibit specificity within taxonomically related plant species. In the context of our investigation, we conducted a comprehensive chemotaxonomic analysis of sweet oranges utilized in concentrated juice production. This involved a thorough examination of antioxidant activities, characterization of flavonoid and phenolic profiles, UV-visible spectra scanning, and the implementation of color analysis. The results from cluster analysis demonstrated the superior efficacy of color analysis in discerning subtle distinctions among orange varieties. Further refinement in the analytical process requires the application of supplementary techniques after an exhaustive and precise extraction facilitated by organic solvents. Notably, all employed methodologies successfully discriminated between distinct orange types. While the compilation of extensive datasets presents inherent challenges, the incorporation of Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) enhances the interpretability of the obtained results. Considering that existing methodologies for assessing fresh fruit quality rely on subjective human visual inspection or orange juice analysis by ratio, which may lack precision in quantifying chemical constituents, there exists a growing demand for expedited techniques that can reliably ensure the quality of orange juice within the industry.

К НАУЧНЫМ ОСНОВАМ СОЗДАНИЯ ЦИТРУСОВЫХ «ДЕРЕВЬЕВ САДОВ»

The main breeding techniques used in the 50s of the 19th century by breeder F.M. Zorin – creator of the Friendship Tree, candidate of agricultural sciences (1944), are considered. Fyodor Mikhailovich developed valuable varieties of mandarin oranges, grapefruits, lemons, plums, figs, and hazelnuts. Author of more than 40 scientific papers. He was awarded the State Prize for the creation of new varieties of fruit plants. This article shows theoretical research and practically used methods for breeding new varieties of citrus fruits. The basis of his research was vegetative hybridization (from Greek “hybris” – inbreeding) – the production of hybrids by grafting. Zorin F.M. paid a special role in the breeding work to “tree gardens”, which were of both scientific and industrial importance. Fruits from such a tree could change shape, size, color and ripening time. At the same time, he paid attention not only to the selection of the scion, but also the rootstock. As a result, such a tree had many trunks, and the crown consisted of numerous varieties and species of three genera – Citrus, Fortunella, Poncirus of the Rutaceae family. Almost the entire Pomeranian subfamily (Aurantioideae) grafts onto each other and is highly compatible. It is important to take into account varietal characteristics: timing of flowering and ripening, as well as their biology. The main advantages of citrus «tree-gardens» are the saving of garden space, the aesthetic appearance of the trees and originality, as well as the ability to obtain more varieties per unit area.

Selecting autotetraploids from a facultatively apomictic tree of the nonapomictic ‘Licheng’ sweet orange (Citrus sinensis) variety

Tetraploid plays major roles in the polyploid breeding and production of citrus plants. Autotetraploids of nonapomictic citrus varieties are desirable in citrus polyploid breeding due to their high frequencies of hybrid polyploid production, certain genotypes and some predictable phenotypes. However, it is difficult to obtain autotetraploids of nonapomictic citrus varieties. In the present study, the nonapomictic sweet orange variety ‘Licheng’, which is native to China, was used as the main material. A ‘Licheng’ tree, LCOYC-04, that produced polyembryonic seeds at a frequency of 34.96±2.88 % was selected. Plants that grew from self-pollinated polyembryonic seeds of LCOYC-04 were investigated by flow cytometry. Four tetraploids were selected from 550 plants and identified according to chromosome observation. Exonic single-nucleotide polymorphism (SNP) locus genotyping based on genome resequencing showed that 22.18 %-70.49 % of heterozygous loci in the genome of LCOYC-04 were homozygous in the genomes of plants grown from self-pollinated monoembryonic seeds. The proportions of homozygous loci were 2.07 %-2.45 % in the 4 selected tetraploids. These values were close to those in 7 asexual ‘Licheng’ relatives (1.97 %-2.71 %). Therefore, the 4 tetraploids were confirmed to be autotetraploids of LCOYC-04. Genome sequencing revealed a region of low sequencing depth (approximately 855 kb) on chromosome 4 of all ‘Licheng’ trees. The CitRWP gene, which is responsible for the occurrence of nucellar embryos in citrus plants, was located in the low sequencing depth region. It was confirmed by quantitative PCR that one of two allelic CitRWP gene was defective in genome of ‘Licheng’. The current study indicates that it is possible to induce nonapomictic citrus to mutate into facultatively apomictic citrus through chromosome segment deletion, and provides a reference for excavating autotetraploids which produce polyembryonic and monoembryonic seeds.