Citrus Fruit Production Research Articles

Facultative apomixis and chromosome doubling are sources of heterogeneity in citrus rootstock trials: Impact on clementine production and breeding selection

All commercial citrus rootstocks are polyembryonic and propagated by seeds. Although these seeds produce uniform plant material most of the time, zygotic or polyploid citrus seedlings may arise. The aim of this study was to understand how zygotic or tetraploid rootstock could affect a citrus rootstock selection field trial. A trifoliate orange selection field trial, which was planted in 1974 and grafted with clementine, was re-investigated with respect to the presence of rootstocks that were not true-to-type. Among the 288 trees investigated, flow cytometry identified 2.4% of rootstocks as tetraploid and SSR markers indicated that 6.6% were zygotic. Yield data showed that the presence of tetraploid rootstock dramatically decreased (by about 45%) clementine fruit production. However, zygosity did not always affect fruit production and a range of effects were observed, from a slight increase in production to a 24% decrease. Exclusion of non-true-to-type genotypes from the production analysis indicated that the best candidate for rootstock was a clone previously ranked in the middle of the 32 rootstocks under evaluation. However, the presence of zygotic rootstock did not appear to cause any significant differences in fruit quality during the first 5 years of the investigation, which suggests that non-true-to-type plants cannot be identified by fruit quality parameters. This study indicates that tetraploid and zygotic rootstocks have a strong impact on citrus fruit production in orchards, and removal of off-type seedlings is required prior to planting in any agronomic trial.

‘Garbí’ Mandarin: A New Late-maturing Triploid Hybrid

Citrus is the most extensively produced fruit tree crop in the world (FAO, Food and Agriculture Organization, 2009). There are two clearly differentiated markets: fresh fruit and processed juice. In 2007, the main citrus fruit-producing countries were China (17.9%), Brazil (17.8%), the Mediterranean countries (17.1%), and the United States (8.5%) (FAO, Food and Agriculture Organization, 2009). These areas account for more of two-thirds of the total production of citrus fruits. In the Mediterranean area, citrus fruits are primarily produced for the fresh fruit market. Spain is the principal producer in the area with a total planted area of 330,000 ha and a production 6.3 million tons. Seedlessness is one of the most important characteristics for mandarin on the fresh fruit market, because consumers do not accept seeded fruits. Parthenocarpy is an essential trait for seedless fruit production, and this characteristic is present in citrus germplasm. Triploidy gives rise to seedless commercial cultivars. However, triploid plants have very low fertility, are generally sterile, and do not induce seeds in other cultivars by crosspollination (Frost and Soost, 1968). Several methods have been developed to obtain triploid citrus (Navarro et al., 2002; Ollitrault et al., 2008). One exploits natural events of polyploidization such as 2n gametes using embryo rescue and flow cytometry to select triploids in 2x · 2x crosses. Second meiotic division restitution has been proposed for diploid megagametophyte development in clementine (Luro et al., 2004), whereas Chen et al. (2008) proposed first meiotic division restitution in sweet oranges. In Spain, the structure of mandarin cultivars poses several problems. Mandarins include satsumas, clementines, and mandarin hybrids. Satsumas are harvested from the beginning of September until the beginning of November. They are cultivars with a high degree of parthenocarpy and have sterile pollen and ovules. Clementines are the most representative cultivars of mandarin in Spain. They are picked from mid-September until mid-February. They are self-incompatible, but pollen and ovules are viable, being able to pollinate and to be pollinated by other cultivars. Mandarin hybrids, like ‘Nova’ [C. clementina · (C. paradisi · C. tangerina)], ‘Fortune’ (C. clementina · C. tangerina), and ‘Ortanique’ tangor (natural hybrid between mandarin and C. sinensis), were introduced in the Spanish citriculture to cover the demand of late-season mandarins by international markets. They enable the harvesting period to be extended until May. These hybrids are also self-incompatible, but pollen and ovules are viable and cross-pollinate with clementines, producing fruits with seeds in both groups of cultivars. A triploid breeding program has been carried out in Spain since 1996 based on sexual hybridization, embryo rescue, and ploidy analysis by flow cytometry (Navarro et al., 2002). The objective is to produce new high–quality, late-season and seedless triploid mandarin hybrids. In this article, we describe ‘Garbi’ mandarin, a new triploid hybrid developed within this program characterized by its high-quality, late-season ripening and seedless fruits.

Improvement of mobile citrus fruit grading machine

A mobile grading machine was earlier developed to establish precision citrus fruit production. This machine could travel in citrus orchards and measure appearance and internal qualities of fruit harvested by humans on-site. In addition, it could record harvesting date and fruit locations. It consisted of a mobile mechanism, a differential global positioning system, a fruit conveyor system, two machine vision systems (one for fruit inspection, the other for trees monitoring), a sugar content measurement system using a near-infrared (NIR) spectrometer, and a personal computer for control and database. The color, size, and sugar content of each fruit and leaf color of each tree were measured by the machine vision devices and the NIR inspection system. As fruit features were extracted based on image analysis by the machine vision system, it was observed that the result of size had a correlation with actual citrus size and the result of color was accurately compared with human eyes. However, it was considered that the lighting device positions should be changed for higher quality images, because the edges of the fruit were dark due to radiation angles. This paper reports on moves of the lighting device position and to obtain lower light radiation angles so that the estimate of fruit size could get higher correlation with the actual fruit size. Furthermore, the earlier results of sugar content measurement had a low correlation with the actual brix values because the sensing head of NIR inspection system was pressed to each fruit from the top. The pressing direction was changed to from the side to obtain higher performance of the system. The improvements caused higher correlations of the sensor outputs to the fruit size and sugar content.

カンキツのマルチ・点滴かん水同時施肥システムの開発と普及

カンキツのマルチ・点滴かん水同時施肥システムの開発と普及

Le cooperative canadesi e i loro lavoratori: questioni spinose nella gestione delle risorse umane

- Social conflict and cooperation. The case of Valencian citrus fruit cooperatives The production of Valencian citrus fruit, besides being the most traditional and representative cultivation of the region, was an important source of wealth during the first three quarters of the XX century, not only for the Valencian region but also, for the whole national economy. During this period of splendour, the agrarian cooperatives played an important role in the promotion of the citrus fruit production. Nevertheless, they have not succeeded in developing a cooperative model which could be sustainable in the long term and suitable to the new needs and problems of the sector. This article offers an overview of the situation of the citrus fruit sector in the Valencian region, and, in particular, it analyzes the weaknesses of the current cooperative model, presenting some suggestions for addressing future and necessary restructurings of the Valencian citrus fruit cooperatives.

BAZI PORTAKAL ÇEŞİTLERİNDE IN VİTRO SÜRGÜN UCU AŞILAMA TEKNİĞİNDE FARKLI ANAÇLARIN AŞILAMA BAŞARISINA ETKİLERİ

Virus and virus-like diseases are one of the main reason for low citrus fruit production in Turkey. In citrus nursery propagation use of infected budwood is primarily cause for distributing diseases. The success of the in vitro shoot–tip grafting techniques used for sanitation of viruses and virus-like diseases of citrus is affected by the rootstock and cutting variety, rootstock age, size of the shoot–tip, light and the talent of the grafter. In this study to determine the effect of rootstocks on the shoot-tip grafting, Troyer citrange, Carrizo citrange, Rusk citrange, and Flying Dragon was used as rootstocks and grafted with some orange varities. The most successful grafting was obtained with Troyer citrange.

Thermomechanical process intensification for oil extraction from orange peels

Abstract The study investigated the intensification and improvement of oil extraction from orange peel through a thermomechanical process: the instantaneous controlled pressure drop (briefly D.I.C. process). This process involves subjecting orange peel for a short time to steam pressure, followed by an instantaneous decompression to a vacuum at 50 mbar. Central composite design was used to study the combined effects of processing steam pressure (1–7 bar; which corresponds to a temperature ranging between 100 °C and 162 °C respectively), processing time (0.3–3.7 min) and initial moisture content of orange peel before thermomechanical oil extraction (9.8–60.2% on dry material basis). The quantitative analysis, have been undertaken on oil present in orange peels, after processing. Correlation analysis of the mathematical regression model indicated that quadratic polynomial model could be employed to optimize the extraction of oil from orange peel. From response surface plots, the three variables exhibited a linear effect with the strongest effect for the processing pressure. The optimum reaction conditions selected with response surface analysis were as follows: steam processing pressure: 6.6 bar, processing time: 3.68 min, initial moisture content: 53.6% d.m. basis. Under these conditions, experimental yield of orange peel oil was close to predicted value (99%) calculated from the polynomial response surface model equation. A kinetic study indicated that extraction performed by D.I.C. process is clearly quicker than conventional steam distillation method. Industrial relevance World production of citrus fruit has experienced continuous growth in the last decades of the XX century. Total annual citrus production was estimated at over 105 million tons in the period 2000–2004 ( http://www.unctad.org/infocomm/anglais/orange/market.htm ). Oranges constitute the bulk of citrus fruit production, accounting for more than half of global citrus production in 2004. Thus, the quantities of generated by-products are very important. In this study, extraction of oil from orange peel was performed through a thermomechanical process developed in our laboratory. We report on some results obtained using this process as well as others comparing extraction kinetics when using a conventional steam distillation process and the proposed extraction process. One of the advantages of the described method is the short contact of extracted oil with the heated zones in the apparatus resulting in a lower heating period of the product compared to steam distillation. At industrial scale, this is interesting regarding oil quality and energy saving.

1A2-B15 カンキツ生産の情報化のための移動型選果機の試作

1A2-B15 カンキツ生産の情報化のための移動型選果機の試作

Comparisons of qualitative and quantitative issues in the fruit supply industries in The Netherlands, Poland, Greece, and Spain

SummaryThis paper presents an overview of the fruit supply chains in Poland, Spain, Greece, and the Netherlands. The roles of the different participants in the functioning of the fruit supply chains are presented, along with their quantitative characteristics. Although apple production was most popular in northern countries (i.e., Poland and The Netherlands), while in southern countries (i.e., Spain and Greece) citrus fruit (especially orange), grape, and peach production were most important, the participants along the fruit supply chains were the same in all cases: namely, research centres and seed companies, nurseries, fruit producers, co-operatives, fruit processors, wholesalers, retailers, and the food service sector. Any differences lay mainly in the level of concentration among participants at each stage of the fruit supply chains. Despite an ongoing process of consolidation, the fruit processing sector remains fragmented. There were only a small number of large enterprises that had a considerable position in multi-national markets, alongside a large number of much smaller entities that served local, regional, and national markets. With respect to product distribution in the fruit supply chains, the most characteristic feature was the increasing concentration of the retail trade.

Bioassay directed identification of natural aryl hydrocarbon-receptor agonists in marmalade

Citrus fruit and citrus fruit products, like grapefruit, lemon and marmalade were shown to contain aryl hydrocarbon receptor (AhR) agonists, as detected with the DR CALUX ® bioassay. This is of interest regarding the role of the Ah-receptor pathway in the adverse effects of dioxins, PCBs and other aromatic hydrocarbons. So far it is unclear which compounds in citrus fruit are responsible for the AhR-mediated activity and whether regular exposure to these compounds can cause effects comparable to, e.g. dioxins. The present study aimed at developing a method for identifying unknown Ah-receptor agonists in citrus products based on bioassay directed analysis, using marmalade as a first target. Following extraction with hexane and purification on an aluminium oxide-column, the extract was fractionated by HPLC using a C-18 semi-preparative column. Fractions were extracted, solvent-exchanged into dimethylsulfoxide and subsequently tested with DR CALUX ®. Extracts were shown to contain primarily coumarins, furocoumarins (FCs) and polymethoxyflavones (PMFs). Identification of fractions most active in the bioassay via LC/MS revealed that bergapten (an FC) is the most important Ah-receptor agonist in marmalade. The approach and method developed resulted in the successful identification of the bioactive component. However, potential pitfalls of the procedure will be discussed.

Greywater reuse: A strategy for water demand management in Harare?

Greywater is wastewater from baths, sinks and washing machines, accounting for about 60% of the outflow from homes. It contains little pathogens and 90% less nitrogen than toilet water, so does not require the same treatment process. With the increasing demand for freshwater, its use may reduce irrigation water needs, increasing its availability of freshwater for other primary uses. Agriculture is the main water consumer in Africa, which cannot be compromised due to its role in domestic food security and export supplies. The purpose of this paper is to demonstrate findings of the research done on benefits of greywater reuse in some countries, applicable to African countries. In Australia, greywater reuse has reduced freshwater demand, strain on wastewater treatment plants and energy consumption. Aquifer recharge has improved due to increased infiltration flows from greywater uses. In Lebanon, greywater is a valuable resource for encouraging plant growth from nutrients that may otherwise have been wasted. Palestine shares similar climate and water scarcity conditions with most arid sub-Saharan African countries, yet utilizes grey water in production of crops and citrus fruits. Thus use of grey water should be possible in African cities such as Harare, where nearly two thirds of the population rely on agriculture for livelihoods. The problem of blue green algae in sewerage ponds and water reservoirs is significantly reduced by household reuse of grey water in Mexico. Water savings are increased and expenses reduced, as illustrated by the reduction in consumption of municipality freshwater supplies in South African urban areas. Rural communities and schools in Namibia and Egypt have raised funds from grey water reuse in banana plantations. A possible constraint to this strategy could be the unavailability of appropriate technology for primary treatment of grey water before reuse. This strategy may pose health risks where water quality tests are unknown or unavailable but can be overcome through educational campaigns. Supporting data and evidence on safety and benefits of grey water is required to achieve regulatory approval of grey water use.

Orange Empire: California and the Fruits of Eden (review)

Reviewed by: Orange Empire: California and the Fruits of Eden Anthea M. Hartig (bio) Orange Empire: California and the Fruits of Eden. By Douglas Cazaux Sackman . Berkeley: University of California Press, 2005. Pp. xv+386. $45. Those who can remember a time before and just after World War II in Southern California recall pastoral acres of trees in neat rows—"It was all groves as far [as] the eye could see." What they visualize is the landscape of the highly complex and influential citrus industry, here dubbed in Douglas Cazaux Sackman's masterful new book the "orange empire." An empire it was, carefully planned and scientifically managed. By 1910, Southern California's citrus-fruit production spread over a hundred thousand acres throughout Los Angeles, Orange, Riverside, San Bernardino, and Ventura counties. Representing nearly ten thousand farms and employing over twenty thousand laborers, it attained hegemony by the 1920s, and in 1930 the highly organized citrus empire grossed more than $100 million. In flowing, lyrical prose, Sackman powerfully lays bare the imperial transformation of the Los Angeles basin at the hands of citrus industrialists, and details subsequent challenges to the order. Sackman presents Orange Empire in a tripartite narrative form. First, in "Fabricating Eden," he chronicles the creation of the citrus belt, populated by growers who colonized the land and established a race- and place-based hierarchy. Luther Burbank and scientists from the U.S. Department of Agriculture transformed citrus fruits for market, and their desires to alter and control nature are here nicely exposed by Sackman, as are their eugenics-based hopes to perfect the human race. Sackman reveals these so-called sun-kissed fruits, promoted as pure products of nature, to be mass-market commodities resulting from a high degree of scientific manipulation. "Work in the Garden," Sackman's second section, reveals whose hands did the work that made the citrus empire, and just what backbreaking labor it was. His detailed depiction of actual citrus production is top-notch, although he occasionally misses an opportunity to engage the topic from the vantage point of labor. Rather, he sticks to his organizing thesis, empha-sizing the orange as artifact as he details its journey from tree to market: "Between the packing house and the grocery store, the magical transformation of nature into commodity had been laboriously accomplished. Workers put their bodies on the line to make the oranges' journey out of nature as smooth as possible, . . . they helped make the orange that would match consumers' fantasy" (p. 152). Sackman then turns to the defenders of labor and of a more socialized form of agriculture, first to Upton Sinclair and then to activists, writers, and artists he dubs "agrarian partisans" in the last and longest "Reclaiming Eden" section. Delving into Sinclair's 1934 gubernatorial campaign in California, the author recounts his framing and defeat by Republicans banded [End Page 215] together and led by none other than the Orange "Emperor" C. C. Teague, long-time president of the California Fruit Growers Exchange (known by the trademark "Sunkist"). But the agrarian partisans succeeded where Sinclair failed in publicizing the violence and moral bankruptcy of the large growers, symbolized by the soulful though pointedly political photographs of Dorothea Lange and the activist pens of Paul Taylor, Carey McWilliams, and of course John Steinbeck, whose 1939 The Grapes of Wrath, that "gut-wrenching, myth-breaking novel," depicted the wanton destruction of surplus oranges while people starved (p. 262). Orange Empire joins the work of other historians who have shone their investigative light on the citrus belt, most notably in monographs by Matt Garcia and Gilbert González, and others of us who have produced shorter pieces in journals and anthologies such as the spring 1995 citrus issue of California History. Sackman provides a rewarding blend of cultural and agricultural history, but expect an emphasis on the former. One caveat: for historians whose interest lies in particular locales, when Sackman crosses the Tehachapi range and travels north in the great Central Valley for the last portion of Orange Empire, the argumentative force wanes as the narrative drifts away from the landscape he so eloquently depicts earlier in the book. This does not diminish the brilliance...

Isolation of cytoplasts from Satsuma mandarin (Citrus unshiu Marc.) and production of alloplasmic hybrid calluses via cytoplast–protoplast fusion

Cytoplasm of Satsuma mandarin (Citrus unshiu Marc.) is known to influence seedlessness. Transfer of cytoplasm to a seedy cultivar could possibly lead to the production of seedless citrus fruits. In the present paper cytoplasts were isolated from cell suspension-derived protoplasts of Satsuma mandarin via ultra-centrifugation in a discontinuous gradient. No nucleus could be detected in the cytoplasts by DAPI (4', 6-diamidino-2-phenylindole) staining compared with normal protoplasts. The cytoplasts, with high viability and small size, did not divide during solid embedding culture. Cytoplasts of Satsuma mandarin were electrically fused with embryogenic protoplasts of Murcott tangor (C. reticulata x C. sinensis), which led to regeneration of several cell lines. Flow cytometry (FCM) indicated that the cell lines were diploids. Simple sequence repeats (SSR) and cleaved amplified polymorphism sequence (CAPS) showed that the cell lines got their nuclear DNA from the protoplast parent, whereas the cytoplast parent donated the mtDNA, confirming transfer of mtDNA from Satsuma mandarin into Murcott tangor via cytoplast-protoplast fusion though no polymorphism was detected in chloroplast DNA between the fusion partners. This is the first report on isolation and characterization of cytoplasts, together with cytoplast-protoplast fusion in Citrus, which has a potential for citrus cultivar improvement involving cytoplasm transfer via cytoplast-protoplast fusion.

New technologies and systems for high quality citrus fruit production, labor-saving and orchard construction in mountain areas of Japan

Novel technologies have been necessary for improving fruit quality and productivity of citrus, labor-saving and orchard conservation on steep slope lands since aging of growers and decrease in the number of successors is remarkable in mountain areas of southwestern Japan. The purpose of this paper is to introduce new technologies for improving citrus production that have been developed in recent years. A new fruit quality control system using drip irrigation and liquid fertilization technique combined with year-round plastic mulching was developed, and it enables high quality and stable citrus fruit production. Water and/or nutrient solution is automatically su:lied through drip tubes that are laid under the mulching sheets to give adequate water stress, so as to improve sugar and acid content of fruit. A new transportation system for steep sloping citrus orchards, which is a combination of the monorail system and contour narrow paths, was suggested. A small walking cultivator was developed to explain the procedure of narrow path excavation. After introducing the narrow path, working hours for fertilizer and chemical herbicide a:lication were reduced. Disaster prevention ma:ing of citrus orchards on slope lands was developed based on computer-aided seepage estimation and topographic data. The ma:ing can show zones of both ascending flow and descending flow of underground water during heavy rains in citrus orchards. The ma:ing is considered to be effective for the management of orchards and prevention of erosion on slope lands.

Energy requirement and economic analysis of citrus production in Turkey

The aim of this research was to examine the energy requirements of the inputs and output in citrus production in the Antalya province of Turkey. Data for the production of citrus fruits (orange, lemon and mandarin) were collected from 105 citrus farms by using a face to face questionnaire method. The research results revealed that lemon production was the most energy intensive among the three fruits investigated. The energy input of chemical fertilizer (49.68%), mainly nitrogen, has the biggest share in the total energy inputs followed by Diesel (30.79%). The lemon production consumed a total of 62 977.87 MJ/ha followed by orange and mandarin with 60 949.69 and 48 838.17 MJ/ha, respectively. The energy ratios for orange, mandarin and lemon were estimated to be 1.25, 1.17 and 1.06, respectively. On average, the non-renewable form of energy input was 95.90% of the total energy input used in citrus production compared to only 3.74% for the renewable form. The benefit–cost ratio was the highest in orange production (2.37) followed by lemon. The results indicate that orange production in the research area is most remunerative to growers compared to lemon and mandarin.

High Application Rates of Reclaimed Water Benefit Citrus Tree Growth and Fruit Production

Conversion of wastewater to reclaimed water for crop irrigation conserves water and is an effective way to handle a growing urban problem: the disposal of wastewater. Water Conserv II is a large reclaimed water project developed by Orlando and Orange County, Fla., that presently irrigates ≈1900 ha of citrus. The project includes a research component to evaluate the response of citrus to irrigation using reclaimed water. Citrus trees in an experimental planting responded well to very high application rates of reclaimed water. Irrigation treatments included annual applications of 400 mm of well water, and 400, 1250, and 2500 mm of reclaimed water. The 2500-mm rate is excessive, and since disposal was of interest, this rate was used to determine if citrus could tolerate such high rates of irrigation. The effects of these treatments were compared on `Hamlin' orange [Citrus sinensis (L.) Osb.] and `Orlando' tangelo (C. paradisi Macf. × C. reticulata Blanco) combined with four rootstocks: Carrizo citrange [Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.], Cleopatra mandarin (C. reticulata Blanco), sour orange (C. aurantium L.), and Swingle citrumelo (C. paradisi × P. trifoliata). Growth and fruit production were greatest at the highest irrigation rate. Concentration of soluble solids in the juice was usually lowered by the highest irrigation rate, but total soluble solids per hectare were 15.5% higher compared to the 400-mm rate, due to the greater fruit production. While fruit soluble solids were usually lowered by higher irrigation, the reduction in fruit soluble solids observed on three of the rootstocks did not occur in trees on Carrizo citrange. Fruit peel color score was lower but juice color score was higher at the highest irrigation rate. Crop efficiency (fruit production per unit of canopy volume) was usually lower at the 2500-mm rate and declined as trees grew older. Weed cover increased with increasing irrigation rate, but was controllable. Irrigation with high rates of reclaimed water provided a satisfactory disposal method for treated effluent, benefited growth and production of citrus, and eliminated the need for other sources of irrigation water. Reclaimed water, once believed to be a disposal problem in Florida, is now considered to be one way to meet irrigation demands.

Evaluation of auraptene content in citrus fruits and their products.

Auraptene quantities in Tanaka's 77 Citrus species (including 14 varieties and cultivars), 5 Fortunella species, one Poncirus species, 27 hybrids between Citrus species, and 51 intergeneric hybrids between Citrus and Poncirus have been evaluated. The genus Citrus has been divided into eight groups. Auraptene is found in all of the species of Cephalocitrus group, a part of the species of Aurantium group, and most of the species of Osmocitrus group. The Citrus species contain a small amount of auraptene in the juice sacs compared with in the peels except for Henka mikan (C. pseudo-aurantium), Ichang lemon (C. wilsonii), and a Hassaku (C. hassaku)-pummelo hybrid (Okitsu No. 39), which contain large quantities of auraptene in their juice sacs (0.23, 0.52, and 0.14 mg/g, respectively). The Hong Kong wild kumquat (F. hindusii) alone contains auraptene in Fortunella species. All of the Citrus-trifoliate orange (P. trifoliata) hybrids as well as the trifoliate orange contain a large quantity of auraptene in both the peel (16.57-0.51 mg/g) and the juice sac (10.32-0.15 mg/g). These hybrids are almost inedible. The Iyo (C. iyo)-trifoliate orange hybrid (IyP269) is edible and contains auraptene in the peel (1.49 mg/g) and in the juice sac (1.73 mg/g). Citrus fruit products, for example, brand-named grapefruit juice and marmalade, retain about 0. 1 mg and 0.3 mg/100 g of auraptene, respectively.

Nitrate concentrations in drinking water and the relation to different crop types production in the province of Valencia (Spain)

The aim of the present study was to investigate the evolution of nitrates contamination of public drinking water in the province of Valencia, where is concentrated most fertilizer consumption of Spain, between 1968 and 1991, and its relation to the different types of crops found in this municipalities. Correlation analysis and factorial analysis was made of the between nitrate concentrations in public drinking water in the years 1968, 1981 and 1991, in all the municipalities of the province of Valencia, the percentage of different crop types studied and the nitrogen fertilizer employed per hectare annually. Positive correlations were noted between nitrate levels and the cultivation of citrus fruits, vegetables and cereals, and the use of nitrogen fertilizers. Negative correlations were derived with the rest of dry‐land crops. The greatest correlations were obtained between fertilizer utilization and citrus crops (R2 = 0.82). Factorial analysis reveals, the relationship between the presence of nitrates in underground water layers, the surface dedicated to citrus fruit production, and the presence of nitrates in soils and the minimum influence of cereals with respect to the presence of nitrates both in water and in soil.

Drug interactions with grapefruit juice.

Some drugs demonstrate a significantly greater (up to 3-fold) mean oral bioavailability on coadministration with grapefruit juice. With some calcium antagonists, the benzodiazepines midazolam and triazolam and the antihistamine terfenadine, changes in bioavailability are accompanied by altered drug action. Study design factors possibly contribute to the magnitude of changes in drug bioavailability; they include the source of the citrus, its intake schedule, drug formulations and individual metabolising capacity. The components of citrus juice that are responsible for clinical drug interactions have yet to be fully determined. Based on the flavonoid naringin's unique distribution in the plant kingdom, abundance in grapefruit and ability to inhibit metabolic enzymes, naringin is likely to be one of the grapefruit components influencing drug metabolism. Other components present in citrus fruit, such as furanocoumarins, may be more potent inhibitors than flavonoids and are under investigation. Conclusions drawn from clinical drug interaction studies should be considered specific to the citrus fruit products evaluated because of the variation in their natural product content. The predominant mechanism for enhanced bioavailability is presumably the inhibition of oxidative drug metabolism in the small intestine. The consistent findings across studies of diverse cytochrome P450 (CYP) 3A substrates support the mechanistic hypothesis that 1 or more grapefruit juice components inhibit CYP3A enzymes in the gastrointestinal tract. The evaluation of the need to avoid the concomitant intake of grapefruit products with drugs is best done on an individual drug basis rather than collectively by drug class. Based on the narrow therapeutic range of cyclosporin and research experience in organ transplant recipients, its interaction with grapefruit juice is likely to be clinically significant.

Essential Oil of Two New Pigmented Citrus Hybrids,Citrus clementina × Citrus sinensis

The chemical composition of the essential oils of two new Citrus hybrids, obtained by crossbreeding the diploid clementine Citrus clementina Hort. ex Tan. and the tetraploid orange Citrus sinensis (L.) Osbeck cv. Tarocco, was studied by GC/MS. In all, 42 components were fully characterized and grouped into four classes (monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpenes, and aliphatic aldehydes and alcohols) for an easier comparison with the oils of the parents. Since limonene is by far the main component of all the essential oils examined, representing generally ca. 95% of the total, significant hybrid-hybrid and parent-hybrid differences can be observed only within the remaining 5%. These new hybrids are the first example of a mandarin-like hybrid with a red pigmentation, a feature inherited from the Tarocco orange. These new fruits, therefore, add further to the very high production of pigmented citrus fruits, which are an almost exclusive patrimony of Sicilian citrus production. This pigmentation is due to the presence of anthocyanins, whose known antioxidant activity gives them an important biological role in the disease prevention of living systems.