Star Ruby Research Articles

Seasonal Dynamic of NO3− and K+ in a Citrus Crop Irrigated by Different Water Qualities

This study evaluated the effect of (i) irrigation water source: transfer (TW) and reclaimed water (RW), and (ii) crop phenological stage: winter rest (WR), flowering-sprouting (FS), and fruit growth (FG), on NO3− and K+ dynamics in soil and leaf of a citrus crop. The experiment was carried out during the 2018 and 2019 growing seasons on adult ‘Star Ruby’ grapefruit trees (Citrus paradisi Macf.). The concentration of both nutrients was periodically measured in soil and leaf samples and continuously monitored in the soil soluble fraction with nutrient sensors. Moreover, soil NO3− leaching was indirectly estimated by the periodic measurement of the leaf enrichment in 15N isotope (15Nleaf). The two water sources showed a different nutrient loading. Thus, NO3− and K+, were approximately 5 and 7 times higher, respectively, in the RW. Furthermore, the average contents of NO3− and K+ in the soil samples from the RW treatment were 10.1 and 19.7%, respectively, higher than in TW, with the highest soil NO3− leaching observed in RW treatment. In line with this, the mean contents of NO3− and K+ in the leaves from the RW treatment were 106.9 and 30.4% higher than the TW ones. As for the different phenological stages, in the FG stage, the lowest concentrations of NO3− in the soil samples and the highest in the leaf tissue were observed after a high soil leaching event. In this study the nutrient sensors measurements varied according to the dynamic of NO3− and K+ in the soil samples. The use of RW promoted an accumulation of NO3− and K+ in the soil and leaves of grapefruit trees, but also enhanced soil NO3− leaching, indicating that the proper management of this water source is necessary to avoid soil contamination. The mobilization of NO3− and K+ from soil to leaf was the highest in the FG stage, to ensure fruit development and vegetative growth.

Bitterness and flavanone composition of ‘Redson’ fruit: A new red-fleshed pomelo × grapefruit hybrid

‘Einat’ (‘Redson™’) is a new triploid, red-fleshed pomelo × grapefruit hybrid. We examined the quality, flavor, bitterness and flavanone composition of ‘Redson’ fruit, as compared to 'Oroblanco', another pomelo x grapefruit hybrid, 'Star Ruby' grapefruit, 'Goliath' pomelo and 'Newhall' navel orange. ‘Redson’ fruit are seedless with a yellow peel and red flesh and have unique quality characteristics. Descriptive sensory tests revealed that ‘Redson’ fruit are bitterer than other citrus fruit, but earned a high consumer acceptance score and ranked first for preference among all bitter citrus fruits, including pomelo, grapefruit and their hybrids. ‘Redson’ fruit contained the highest amount of the bitter flavanone naringin, but had low levels of other bitter flavanones (neohesperidin and poncirin) and non-bitter flavanones (hesperidin and narirutin). Furthermore, we detected a high correlation (R2 = 0.957) between naringin levels and the sensation of bitterness among citrus fruit, featuring the importance of naringin in determining citrus bitterness.

The Combination of Citrus Rootstock and Scion Cultivar Influences Trioza erytreae (Hemiptera: Triozidae) Survival, Preference Choice and Oviposition.

Trioza erytreae (Del Guercio, 1918) (Hemiptera: Triozidae) is a citrus pest which produces gall symptoms on leaves and transmits bacteria associated with the citrus disease Huanglongbing, 'Candidatus Liberibacter' spp. In the present work, the biology and behaviour of T. erytreae were studied in different rootstock-cultivar combinations. Six rootstocks were used, Flying dragon (FD), 'Cleopatra' mandarin (CL), Carrizo citrange (CC), Forner-Alcaide no.5 (FA5), Forner-Alcaide no.517 (FA517) and Citrus macrophylla (CM), and six scion cultivars: 'Star Ruby', 'Clemenules', 'Navelina', 'Valencia Late', 'Fino 49' and 'Ortanique'. Survival and oviposition were evaluated in a no-choice trial, and preference in a choice trial, all of them under greenhouse conditions. Trioza erytreae did not show a clear settle preference for any citrus combination. However, it was able to lay more eggs in 'Fino 49' grafted on CC than on FD. In terms of survival, 'Ortanique' grafted onto FA5 was more suitable than when grafted onto FA517, and in the case of 'Valencia Late', when it was grafted onto CM rather than CC. Our results showed that T. erytreae behave differently depending on the citrus combination.

Involvement of Phytophthora citrophthora and Phytophthora nicotianae in severe decline and gummosis of grapefruit (Citrus x paradisi Macfad.) in southern Türkiye

AbstractSince the summer of 2020, severe decline and gummosis were observed on 20‐ to 30‐year‐old grapefruit trees cv. Star Ruby in Antalya province in the Western Mediterranean region of Türkiye. Grapefruit trees were examined in affected commercial orchards in Aksu, Manavgat, Muratpaşa and Serik counties, located near the coast of the Mediterranean Sea. Symptomatic trees exhibited leaf discoloration, defoliation and severe dieback, as well as dark, water‐soaked lesions with gum exudates, characteristic of Phytophthora infections, formed on the bark of the main stem and major limbs. No Phytophthora species could be isolated from these bark tissues, while two were obtained from soil samples taken from around symptomatic trees. Based on morphological characteristics, isolates were identified as P. citrophthora and P. nicotianae. Identifications were confirmed by sequencing of the internal transcribed spacer (ITS) and the cytochrome oxidase I (cox1) gene regions. Pathogenicity tests, carried out by inoculations of the main stems and branches of grapefruit seedlings cv. Star Ruby indicated that both species were pathogenic. All P. citrophthora and P. nicotianae isolates obtained in this work were sensitive to mefenoxam. EC50 values of P. citrophthora isolates were between 0.284 and 0.285 μg mL−1, whereas those of P. nicotianae were between 0.288 and 0.291 μg mL−1. Phytophthora citrophthora was previously known to cause disease on citrus in Türkiye, but this is the first report of P. nicotianae causing citrus gummosis in the country. Because P. nicotianae is more widespread than P. citrophthora, it should be considered a threat to citrus cultivation in this region of Türkiye.

Oviposition by the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), on five citrus types in a laboratory

AbstractFrugivorous insects use visual, chemical and tactile cues to find a suitable host for oviposition. However, these cues can vary greatly among fruit cultivars and condition, changing their susceptibility to fruit fly oviposition. The aims of this study were to (1) determine the effects of ripeness stage and damage on oviposition propensity by sexually mature, mated female oriental fruit flies, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), on five citrus types (species and cultivars) under choice and no‐choice conditions and (2) describe the oviposition behaviour of B. dorsalis on ripe fruit of the same five citrus types that were either damaged or undamaged under no‐choice conditions. All tests were conducted in the laboratory. The citrus types tested were Citrus sinensis (L.) Osbeck cv Delta Valencia orange, Citrus sinensis (L.) Osbeck cv Glen Ora Late navel orange, Citrus limon (L) (Burm.f.) cv Eureka lemon, Citrus paradisi (Macfad.) cv Star Ruby grapefruit and Citrus reticulata (Blanco) cv Nadorcott mandarin. Peel physical properties and essential oil composition were determined for each citrus type and stage. Oviposition propensity of B. dorsalis was significantly greater on damaged citrus but was not correlated with fruit diameter, peel thickness, oil gland density or oil gland size. A total of 45 aromatic compounds were found to be significant between the five cultivars investigated, and 6 of 11 compounds were significantly associated with over‐ripe fruits. Bactrocera dorsalis spent a significantly greater proportion of time ovipositing in damaged citrus and showed higher aggression when oviposition occurred in undamaged citrus. These results suggest that the removal of damaged and fallen fruit is important for controlling this pest in citrus orchards.

First report of grapefruit rot caused by Colletotrichum gloeosporioides and C. karsti in France.

The grapefruit (Citrus paradisi) is a citrus hybrid tree (C. maxima & C. sinensis). Due to nutritional value and its bioactive compounds, the fruits are recognized as a functional food, valued as promoting health. French grapefruit production is low (7.5 Kt/year) but is confined to a restricted area in Corsica and benefits from a quality label, the economic impact of its cultivation being therefore locally significant. Since 2015 previously unreported symptoms have been repeatedly observed on grapefruits in more than half of the orchards in Corsica, with an incidence of 30% of fruits altered. Brown to black circular spots were observed on fruits and leaves, surrounded by chlorotic halos on the latter. On the mature fruit, lesions were round, 4 to 10 mm in diameter, brown and dry (e-Xtra 1). Although the lesions are superficial, the fruits cannot be marketed due to constraints linked to the quality label. 75 fungal isolates were obtained from symptomatic fruits or leaves collected in Corsica (in 2016, 2017, and 2021). Cultures obtained after 7 days on PDA at 25°C, were white to light grey in colour, forming concentric rings or dark spots on the agar surface. We did not observe any notable difference among the isolates except some evolved towards a more marked grey. Colonies tend to form a cottony aerial mycelium and orange conidial masses appear with age. The conidia were hyaline, aseptate, cylindrical with ends rounded, and measured 14.9 ± 0.95 µm length and 5.1 ± 0.45 µm width (n = 50). Cultural and morphological characteristics were similar to those described for C. gloeosporioides s. lat. or C. boninense s. lat. (Weir et al. 2012 ; Damm et al. 2012). Total genomic DNA was extracted from all isolates, and the ITS region of rDNA was amplified with ITS 5 & 4 primers, then sequenced (GenBank Accession Nos. OQ509805-808). For 90% of isolates GenBank BLASTn results were 100% identical to C. gloeosporioides isolates sequences, whereas for other isolates the resulting sequences were 100% identical to C. karsti or C. boninense isolates sequences. Four strains (three C. gloeosporioides with light colour differences, in order to see if there was diversity among isolates of C. gloeosporioides s. lato ; and one C. karsti) were further characterized by sequencing partial actin [ACT], calmodulin [CAL], chitin synthase [CHS-1], glyceraldehyde-3-phosphate dehydrogenase [GAPDH], β-tubulin 2 [TUB2], for all strains ; glutamine synthetase [GS], Apn2-Mat1-2-1 intergenic spacer and partial mating type (Mat1-2) gene [ApMAT] for C. gloeosporioides s. lat., and HIS3 for C. boninense s. lat. (Weir et al. 2012 ; Silva et al, 2012) (GenBank Accession Nos. OQ509805-808 & OQ507698-724). Multilocus phylogenetic analyses carried out with the obtained and Genbank available sequences confirmed that 3 isolates (UBOCC-A-116036, -116038, & -116039) clustered within C. gloeosporioides s. s., while the other (UBOCC-A-116037) clustered within C. karsti (e-Xtra 2) 'Star ruby' grapefruits were surface sterilized then wound-inoculated with 20 μl of a conidial suspension (105 conidia ml-1) of UBOCC-A-116036 & 116037 isolates or 20 μl sterile water for control (ten fruits for each isolate or control). After 10 days incubation at 20°C, symptoms, identical to those initially observed, developed around the inoculation point, while controls inoculated with water remained symptomless. Fungal colonies re-isolated from the lesions were morphologically like the original isolates. Recently, various infections caused by some Colletotrichum sp. have strongly compromised citrus production in different Mediterranean countries: ie Italy (Aiello et al. 2015), Portugal (Ramos et al. 2016), Tunisia (Ben Hadj Daoud et al. 2019), Turkey (Uysal et al. 2022). In these studies, C. gloeosporioides s. s. and C. karsti were identified as the causal agents. These two species were the predominant Colletotrichum sp. associated with Citrus and allied genera in Europe (Guarnaccia et al. 2017). To our knowledge, our study is the first report of C. gloeosporioides and C. karsti causing anthracnose on grapefruit in France, which confirms the incidence of these two pathogens on the Mediterranean rim. Given the economic importance of citrus cultivation in the Mediterranean region, the presence of Colletotrichum spp. should deserves to be monitored, and a control strategy should be considered.

A method for gel grade determination and application evaluation of two citrus pectins

Citrus paradisi Macf. cv. Changshanhuyou and Citrus paradisi Macf. cv. Star Ruby are two emerging processed citrus fruits. The processing produces lots of peel wastes rich in pectin. While more attentions were paid on pectin's functional properties, the quality about commercial application like gel grade was little investigated. In this study, we established a method for gel grade determination based on texture analyzer, the new method is economical and can be used on a large scale in the laboratory. The commercial application related qualities of two citrus pectins were also studied in detail. The results showed that the yields of Changshanhuyou and Star Ruby pectins (CHP and SRP) were 20.23 % and 18.33 %, respectively. The indexes of CHP and SRP mostly were in line with the commodity standards, except the dry weight loss. The gel grades of CHP and SRP determined by the new method were 109.9 and 96.8, respectively. The CHP aqueous solution exhibited higher apparent viscosity and better performance in stabilizing acidified milk drink (AMD) compared with commercial pectin. From the view of commercial application related qualities and functional properties, CHP could be a good potential commercial pectin.

Phytochemical characterisation of two news blood grapefruits by means of HPLC-MS

In this study, the main flavanones, polymethoxyflavones, anthocyanins and furanocoumarins were evaluated in two blood grapefruits (CQP 31 and CQP 32), in their juice, peel, and leaves, by means of HPLC-DAD analysis and identified by HPLC-MS-MS. They are compared with the contents of these secondary metabolites in three commercial grapefruits: Star Ruby, Marsh, and Duncan; a blood orange, cv. Sanguinelli and with the parents of both cultivars Citrus grandis cv Azimboa and cv. Violeta de los valles. The flavonic profile in cultivars CQP 31 and CQP 32 revealed the presence of the characteristic flavanones of grapefruit, naringin being the most abundant. The ripe fruits of cultivars CQP 31 and 32 showed a red coloring due to the presence of anthocyanins with a total juice content of 145 and 136 ppm. The levels of furanocoumarins in juices of cultivar CQP 31 were well below the values quantified in Star Ruby, Marsh and Duncan. These furanocoumarins were not detected in the juice of the cultivar CQP 32. These results indicate that CQP 31 and 32 can be classified as blood grapefruits with a high content of bioactive compounds and low content or absence of furanocoumarins.

Effectiveness of Ozonated Water for Preserving Quality and Extending Storability of Star Ruby Grapefruit

The aim of this study was to explore the impact of aqueous ozone technology on maintaining grapefruit flavor and freshness by minimizing the occurrence of postharvest deterioration. During the 2018 and 2019 seasons, Star Ruby grapefruit fruits were treated with 0.3 and 0.6 ppm aqueous ozone for 5 and 10 min after harvest at water temperatures of 5 °C and 15 °C, respectively. The fruits were stored for 40 days at 8 ± 1 °C with 85–90% relative humidity. The results revealed that all the ozonated water treatments reduced physiological weight loss, disease infection, and decay, as well as providing long-term protection to the fruits throughout storage. The best treatment for preserving the postharvest quality was 0.6 ppm ozonated water at 5 °C for 5 min, which successfully delayed ripening while concurrently preserving the TSS/acid ratios, total phenolics, and antioxidant activity. Overall, aqueous ozone treatment is a promising example of a treatment that is beginning to be utilized on a commercial scale. In accordance with the findings of this study, it can be deduced that aqueous ozone can be used to maintain fruit quality, reduce postharvest diseases, and extend storage life.

Impact of citrus species on the biological characteristics and life table parameters of Eutetranychus orientalis (Klein) (Acari: Tetranychidae)

Biological characteristics and life table parameters of Eutetranychus orientalis (Klein) were revealed on four different citrus species: grapefruit (Citrus paradisi Macf. cv. Star Ruby), lemon (C. limon (L.) Burm. f. cv. Meyer), mandarin (C. reticulata Blanco cv. Okitsu) and orange (C. sinensis L. cv. Washington Navel) under laboratory conditions. Results show that oviposition period, fecundity, and life table parameters varied significantly depending on the host plant species. Furthermore, host plant species had little effect on immature development, except for the teleiochrysalis and total developmental period, which was significantly shorter on lemon (13.77 days for females, 12.67 days for males). Total mean numbers of eggs laid by E. orientalis was 15.92 on mandarin and 29.78 on lemon. In addition, intrinsic rate of increase (rm), net reproductive rate (R0), finite rate of increase (λ) and doubling time (DT) are 0.12 day–1, 10.41 ♀/♀, 1.13 day–1 and 5.59 days for lemon, 0.17 day–1, 22.36 ♀/♀, 1.19 day–1 and 4.04 days for grapefruit, respectively. However, shortest and longest mean generation times (To) were obtained at 18.26 days on orange and 19.37 days on grapefruit. Our results demonstrate that intergeneric differences of Citrus should be considered when determining E. orientalis population abundance and dynamics in field conditions.

Evaluating the hydrophilic antioxidant capacity in different citrus genotypes

Antioxidants are the body's defense system against the damage caused by reactive oxygen species, formed naturally during many physiological activities. In vegetables and fruits, various antioxidant compounds such as vitamin C, polyphenols, flavonoids, and carotenoids have been identified. Because fruits and vegetables are the primary antioxidant sources in our daily diet, it is necessary to determine their antioxidant capacity. Citrus fruit consumption per capita has steadily increased over the world over the last 30 years. Citrus fruits are high in vitamin C as well as other active ingredients like phenols and flavonoids that are beneficial to human health. Using carotenoid complement and pigmentation genetic diversity, the objective of this research was to see how vitamin C and carotenoids contributed to the capacity of hydrophilic antioxidants of the citrus fruits’ pulp. Six citrus cultivars were chosen for this purpose: two sweet orange genotypes, Valencia Ruby and Valencia Late; two grapefruit genotypes, Star Ruby and Marsh; and two mandarin genotypes, Nadorcott and Clemenules. In proportion to their color singularity, total carotenoid composition and content in fruit pulp differed dramatically. A good and clear connection was found between hydrophilic antioxidant capacity and vitamin C concentration in the pulp of various fruit species, as measured by DPPH and ABTS tests. The proportion of vitamin C to the total HAC was calculated to be between 15% and 30%.

Analysis and Potential Value of Compounds Extracted From Star Ruby, Rio Red, and Ruby Red Grapefruit, and Grapefruit Juice Processing Residues via Steam Explosion.

Culled whole grapefruit (WG) and grapefruit juice processing residues (GP) are currently incorporated into low-cost animal feed. If individual chemical components found within these side streams could be recovered as high-value coproducts, this would improve the overall value of the grapefruit crop. In this study, pectic hydrocolloids, sugars, volatiles, phenolics, and flavonoids were extracted from Star Ruby, Rio Red, and Ruby Red GP and WG using a continuous pilot scale steam explosion system. Up to 97% of grapefruit juice oils and peel oils could be volatilized and contained 87–94% d-limonene. The recovery of pectin, as determined by galacturonic acid content, was between 2.06 and 2.72 g 100 g−1. Of the phenolics and flavonoids analyzed in this study, narirutin and naringin were extracted in the amounts of up to 10,000 and 67,000 μg g−1, respectively.

Effect of fruit shading and cold storage on tocopherol biosynthesis and its involvement in the susceptibility of Star Ruby grapefruit to chilling injury

The aim of this study was to investigate the role of tocopherols in the susceptibility of Star Ruby grapefruit to postharvest chilling injury (CI). Fruit exposed to normal sunlight (NC, non-covered) and deprived of light (C, covered) in the last stages of development were used. Tocopherol contents increased in the flavedo of both NC and C fruit during development, concomitantly with the up-regulation of TAT1 and most genes of the tocopherol-core pathway. Fruit shading reduced total contents by repressing γ-tocopherol accumulation, associated to a down-regulation of GGDR and VTE1 and, to a lesser extent, of VTE2, VTE3a and VTE4. During cold storage, total and α-tocopherol contents increased in NC and C fruit, and no direct relationship between tocopherol accumulation and CI tolerance was found. Cold stress up-regulated most genes involved in the synthesis of tocopherol precursors and down-regulated those of the tocopherol-core pathway, but changes seemed to be cold-mediated and not related to CI development.

Transcriptional Analysis of C-Repeat Binding Factors in Fruit of Citrus Species with Differential Sensitivity to Chilling Injury during Postharvest Storage.

Citrus fruit are sensitive to chilling injury (CI) during cold storage, a peel disorder that causes economic losses. C-repeat binding factors (CBFs) are related to cold acclimation and tolerance in different plants. To explore the role of Citrus CBFs in fruit response to cold, an in silico study was performed, revealing three genes (CBF1, CBF2, and CBF3) whose expression in CI sensitive and tolerant cultivars was followed. Major changes occurred at the early stages of cold exposure (1–5 d). Interestingly, CBF1 was the most stimulated gene in the peel of CI-tolerant cultivars (Lisbon lemon, Star Ruby grapefruit, and Navelina orange), remaining unaltered in sensitive cultivars (Meyer lemon, Marsh grapefruit, and Salustiana orange). Results suggest a positive association of CBF1 expression with cold tolerance in Citrus cultivars (except for mandarins), whereas the expression of CBF2 or CBF3 genes did not reveal a clear relationship with the susceptibility to CI. Light avoidance during fruit growth reduced postharvest CI in most sensitive cultivars, associated with a rapid and transient enhance in the expression of the three CBFs. Results suggest that CBFs-dependent pathways mediate at least part of the cold tolerance responses in sensitive Citrus, indicating that CBF1 participates in the natural tolerance to CI.

Flavedo and albedo of five citrus fruits from Southern Italy: physicochemical characteristics and enzyme-assisted extraction of phenolic compounds

Peels are major byproducts of the juice processing industry. Citrus peels are composed of two tissues, namely the flavedo (outer layer) and the albedo (inner layer). Here, flavedo and albedo were obtained from the peel of grapefruit cv. ‘Star ruby’, lemon cv. ‘Akragas’, and sweet orange cvs. ‘Tarocco’, ‘Sanguinello’ and ‘Moro’. Freeze dried flavedo and albedo were investigated for their functional properties, and subjected to enzyme-assisted extraction with pectinase and cellulase (concentration of 6 U g−1 DW) to extract the phenolic compounds. Albedo showed superior physicochemical characteristics than flavedo. Albedo from ‘Tarocco’ exhibited the maximum water holding capacity (10.9 ± 0.48 g/g). Grapefruit albedo revealed the highest water swelling (13.4 ± 2.62 mL/g) and oil binding (6.31 ± 2.62 g/g) capacities. As regards the enzyme-assisted extraction of phytochemicals, both enzymes enhanced the extraction of phenolics (p < 0.05) compared to the controls. In flavedo, pectinase and cellulase increased the recovery of phenolics by approx. 30%, whereas in albedo the yields were increased above 60%. Results from this investigation suggest that albedo might be used by the food industry as a novel raw material, due to its superior physicochemical properties. Moreover, results provide evidence that the enzyme-assisted extraction is advantageous to recover phenolics from the citrus peels.

Screening of citrus scion-rootstock combinations for tolerance to water salinity during seedling formation

Arid and semiarid regions are vulnerable to water deficits and salinity. Citrus plants are sensitive to saline stress and require the use of tolerant scion-rootstock combinations. Thus, this study aimed to evaluate and classify citrus scion-rootstock combinations with respect to their tolerance to salinity during seedling formation in a protected environment. An experiment was conducted in a randomized block design with a 5 x 12 x 2 factorial scheme corresponding to five levels of water salinity (0.8, 1.6, 2.4, 3.2, and 4.0 dS m-1) applied in 12 citrus rootstocks grafted with two scion varieties: ‘Tahiti’ acid lime and ‘Star Ruby’ grapefruit. The scion-rootstock combinations were evaluated for accumulated dry matter and survival index at 330 days after sowing the rootstocks. Salinity exerted different effects on the dry matter formation of scion-rootstock combinations. ‘Star Ruby’ was less sensitive to salinity, particularly when the rootstocks were the hybrids from ‘Sunki of Florida’ mandarin (TSKFL) with ‘Troyer’ citrange (CTTR) – 013 (TSKFL x CTTR – 013), common ‘Sunki’ mandarin (TSKC) with ‘Argentina’ citrange (CTARG) – 019 (TSKC x CTARG – 019), TSKC with ‘Swingle’ citrumelo (CTSW) – 031 (TSKC x CTSW – 031), and the trifoliate hybrid (HTR) - 069, as well as the varieties Volkamer lemon and Santa Cruz Rangpur lime. When grafted with ‘Tahiti’ acid lime, the rootstocks displaying the less sensitive to salinity were TSKFL x CTTR - 013 and TSKC x CTARG - 019.

Comparative studies on pigmented grapefruit (Citrus paradisi Macf.) cultivars under climatic conditions of Sahiwal, Punjab

Four pigmented grapefruit cultivars viz. Shamber, Flame, Star Ruby and Rio Red were evaluated at Horticultural Research Station, Sahiwal (Pakistan) for their production features encompassing growth, yield and fruit characteristics. The cultivars significantly differed for the studied physical parameters i.e. yield per plant (kg), fruit weight (g), fruit length (cm), fruit breadth (cm), peel thickness (mm), peel, juice and rag contents (%)], and biochemical traits i.e. TSS (°Brix), acidity (%) and ripening index. The highest fruit yield (84.28 kg/plant) was recorded for Star Ruby and the minimum (75.00 kg/plant) was recorded for Rio Red. The maximum fruit weight (338.92 g/fruit) was noted in Rio Red, while the maximum fruit length (9.14 cm) was found in Shamber. The highest TSS was noted for Rio Red (8.32 °Brix) followed by Shamber (7.94 °Brix). The maximum fruit acidity was observed for Star Ruby (1.00%), while the minimum for Shamber (0.94%). It was concluded that four grapefruit cultivars under consideration were divergent in their performance under prevailing conditions.

Grapefruit Field Trial Evaluation of Citrus Tristeza Virus T68-Strain Sources.

Determination of virus genomes and differentiation of strains and strain variants facilitate the linkage of biological expression to specific genetic units. For effective management of stem pitting disease of citrus tristeza virus (CTV) by cross-protection, an understanding of these links is necessary. The deliberate field application of a biological agent such as a virus first requires a thorough assessment of the long-term impact before it can be applied commercially. Three CTV sources were genetically characterized as different variants of the T68 strain, and their long-term effects on stem pitting and production were investigated. The different CTV sources were inoculated to 'Star Ruby' grapefruit trees and evaluated for a number of biological parameters in a field trial in the Limpopo Province of South Africa over a 10-year period. Significant differences were observed in stem pitting severity, impact on tree growth, yield, and the percentage of small fruit produced. These T68 variants were also associated with different stem pitting phenotypes. The variants differed in only 44 nucleotide positions across their genomes, and these minor genetic differences can therefore be used to identify possible genome regions affecting stem pitting.

Antioxidant capacity in fruit of Citrus cultivars with marked differences in pulp coloration: Contribution of carotenoids and vitamin C.

The purpose of this study was to evaluate the specific contribution of carotenoids and vitamin C to the lipophilic and hydrophilic antioxidant capacity, respectively, of the pulp of citrus fruits using the genetic diversity in pigmentation and in the carotenoid complement. To this end, six citrus varieties were selected: two mandarins, Clemenules (Citrus clementina) and Nadorcott (C. reticulata); two grapefruits (C. paradisi), Marsh and Star Ruby; and two sweet oranges (C. sinensis), Valencia late and Valencia Ruby. Total carotenoid content and composition in the pulp of fruits were very different, in relation to their color singularities. Valencia Ruby and Nadorcott had the highest carotenoid content, accumulating the former large amounts of linear carotenes (phytoene, phytofluene, and lycopene) and Nadorcott of β-cryptoxanthin. Orange fruits contained the highest amount of vitamin C while in Nadorcott mandarin it was substantially lower. Analysis of antioxidant capacity, evaluated by 2,2'-azino-di-(3-ethylbenzthiazoline sulfonate) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays, in the pulp of the different fruit varieties indicated a high and positive correlation between vitamin C content and hydrophilic antioxidant capacity. Nevertheless, a weak correlation was observed between carotenoids content and lipophilic antioxidant capacity in the pulp extracts assayed by ABTS. Overall, vitamin C in the pulp of citrus fruit had an important contribution to the hydrophilic antioxidant capacity, whereas that of carotenoids to lipophilic antioxidant capacity was very variable, being the highest that of Valencia Ruby orange, with large concentrations of lycopene and phytoene, followed by Nadorcott mandarin, with high β-cryptoxanthin content.

Biological Control of Star Ruby Grapefruit to Maintain Fruit Quality During Cold Storage

Biological Control of Star Ruby Grapefruit to Maintain Fruit Quality During Cold Storage