Search Results

You are looking at 61 - 70 of 153 items for :

  • "sour orange" x
  • Refine by Access: All x
Clear All
Free access

Zhan'ao Deng, Fred G. Gmitter Jr., Shunyuan Xiao, and Shu Huang

Citrus tristiza virus (CTV) is the most-significant viral pathogen of citrus in the world. Rapid decline of trees on sour orange and stem pitting of grapefruit and sweet orange, two diseases induced by CTV, severely jeopardize citrus production worldwide. It is recognized that all future rootstocks should be resistant to this virus, and scion resistance to stem pitting stains is desirable. To facilitate introgression of the CTV resistance gene from Poncirus trifoliata and development of CTV-resistant varieties in citrus, gene mapping projects have been initiated and more than a dozen RAPD markers have been identified with tight linkage to the resistance gene. As part of our efforts to use marker-assisted selection with a large number of crosses, and ultimately to accomplish map-based cloning of the CTV resistance gene, we have been converting the most tightly linked RAPD markers into SCAR (sequence characterized amplified region) markers by cloning, sequencing the marker fragments, and designing locus-specific primers. One codominant and several dominant SCARs have been developed thus far. The updated progress and utilization of these SCARs in marker-assisted selection and possibly in characterization of a BAC library will be presented and discussed.

Free access

Francesco Loreto, Harold H. Burdsall Jr., and Alfio Tirro'

The effect of inoculating seedlings of Mediterranean cultivated trees grown under greenhouse conditions with North American isolates of Armillaria mellea (Vahl: Fr) Kumm. and A. ostoyae (Romagn.) Herink on net photosynthesis (A), stomatal conductance (gs), and water potential was examined. The effect of water stress was determined also on the same plant species independently and in combination with Armillaria infection. Red oak (Quercus rubra L.) was used as a control to indicate Armillaria virulence on North American trees. Carob (Ceratonia siliqua L.) was resistant to infection. Infection was successful in sour orange (Citrus aurantium L.), but A, gs, and water potential were unchanged over the 60-day experiment. In olive (Olea europea L.) and oak, A and gs were reduced following inoculation with A. mellea. A and gs of all species but carob were reduced under water stress. Olive and oak responses to water stress and Armillaria infection were quantitatively similar; however, the two stresses combined did not reduce A and gs further. Red oak was strongly susceptible to A. ostoyae infection, but Mediterranean trees were not infected by the same Armillaria isolate. Our results show that Armillaria infection may reduce A and gs in susceptible species.

Free access

Jim Syvertsen, J. Lloyd, and G. D. Farquhar

Four to six-yr-old `Red Ruby' grapefruit trees on either `Volkamer' lemon (VL) or sour orange (SO) rootstocks were fertilized with 3 rates of nitrogen (N) over a 3 year period. We studied the effects of leaf N concentration on stomatal conductance (gs), net assimilation (A) of CO2 (Li-Cor portable gas exchange system), carbon isotope discrimination (δ 13C) of tree tissues, root growth, canopy development and fruit yield. Using springtime measurements of net gas exchange during the fifth year, gs, A and leaf tissue δ 13C were positively correlated with leaf N. The faster growing trees on VL had larger canopy volumes and fruit yields but lower leaf N, A and δ 13C than those on SO. Thus δ 13C was positively correlated with A but negatively related to tree size and yield. By the sixth year, δ 13C was still related to N but tree growth had apparently obscured any rootstock effects on leaf N, water use efficiency, A and δ 13C. Leaf and trunk bark tissue δ 13C did not differ but root bark had lowest δ 13C regardless of rootstock species.

Free access

Robert E. Rouse

Juice quality from 4-year-old `Valencia' sweetorange (C. sinensis (L.) Osbeck) nucellar seedling clones VS-F-55-28-X-E, VS-SPB-1-14-19-X-E, old-line clones V-10-12-7-X-E, V-51-3-3-(STG-64G-4)-X-E, and `Rohde Red Valencia' RRV-472-3-26-(STG-31-18)-X-E, RRV-472-11-43-(STG-19-2)-X-E were compared for percentage juice per fruit, “Brix, acid, °Brix/acid ratio, soluble solids per standard 40.9 kg field box, and juice color score. Rootstocks were sour orange, Smooth Flat Seville, Cleopatra mandarin, Sun Chu Sha, calamandarin, Valencia seedling, P. myoliare × Ridge Pineapple X73-26, Duncan grapefruit, Carrizo, Benton and C-35 citranges, Swingle and F-80-18 citrumelos, Rangpur lime × Troyer citrange, P. trifoliata, and Vangasay lemon. V-10-12-7 had the most juice. RRV-472-11-43 had less acid than the other clones. VS-SPB-1-4-19 had highest ratio and RRV-472-3-26 the lowest. Soluble solids per box were lowest for RRV-472-3-26. Juice color score was highest for the two `Rohde Red Valencia' clones and lowest for V-10-12-7. Rootstock affected all juice quality factors except juice color score.

Free access

Mani Skaria and Zhang Tao

High-density or ultra-high-density orchards have had positive economic return up to 12 years after planting. However, an initial higher investment on more number of trees needed is a limiting factor for high-density planting. Our preliminary studies have shown that a microbudding technique that we had developed would produce less-expensive, budded citrus trees. In June 1997, several hundred microbudded citrus trees were planted in a field, under drip irrigation. The planting continued monthly until Dec. 1997. The cultivars planted were: `Marrs' orange, `Rio Red' grapefruit, `Meyer' and `Ponderosa' lemon, and satsuma mandarin. All plants were microbudded on sour orange rootstock grown in 5′′ long “conetainers.” Our objectives were to study the growth performance of small, microbudded trees planted in the field. The plants grew normally and even out-performed the conventionally budded trees in a field nursery next to the test plot. In Dec. 1999, tree height reached 60 inches. Five percent of the trees produced fruit and they were normal in shape, color, and quality.

Free access

Bhimanagouda S. Patil

Two-year field studies at three sites in the Lower Rio Grande Valley of Texas were conducted to evaluate the effects of location, rootstock, and irrigation on sheepnosing of `Rio Red' grapefruit (Citrus paradisi Macf.,) on sour orange (Citrus aurantium L.) rootstock. Based on the equatorial/polar diameter ratio, grapefruit grown in Weslaco had significantly higher percentage of sheepnosed fruits (62.66) than fruit grown in Mission (57.32), while Bayview had a negligible percentage of sheepnosed fruit (4.07). In a second study, `Rio Red' grapefruit grown on Carrizo [C. sinensis (L.) Osbeck × Poncirus trifoliate (L.) Raf.] had significantly higher percentage of sheepnosed fruit (59.46), compared to `Rio Red' grown on Swingle (C. paradisi × P. trifoliata) (47.83). In a third experiment, grapefruit with microjet irrigation had a significantly higher percentage of sheepnosed fruit (53.40), compared to flood irrigation (42.68). Although sheepnosed fruit had significantly greater peel thickness and a lower juice content, fruit quality was better because of higher soluble solids: titratable acidity ratio compared to normal shaped fruits. While significant, the irrigation and rootstock appear have a minor effect on sheepnosing less than growing location.

Free access

Victor Medina-Urrutia, Karla Fabiola, Lopez Madera, Patricia Serrano, G. Ananthakrishnan, Jude W. Grosser, and Wenwu Guo

No presently available rootstock combines all the available rootstock attributes necessary for efficient long-term citriculture (production and harvesting) of Mexican limes and other commercially important scions. In the present study, somatic hybridization techniques were used to combine the widely adapted Amblycarpa mandarin (also known as Nasnaran mandarin) with six different trifoliate/trifoliate hybrid selections: Benton, Carrizo, and C-35 citranges; Flying Dragon and Rubidoux trifoliate oranges; and a somatic hybrid of sour orange + Flying Dragon. The ultimate goal of this research is to generate polyploid somatic hybrids that express the complementary horticultural and disease resistance attributes of the corresponding parents, and have direct potential as improved tree-size controlling rootstocks. Somatic hybrids from all six parental combinations were confirmed by a combination of leaf morphology, flow cytometry, and randomly amplified polymorphic DNA (RAPD) (for nuclear hybridity) and cleaved amplified polymorphic sequence (CAPS) analyses (for mtDNA and cpDNA). This is the first report of citrus somatic hybridization using Amblycarpa mandarin. Unexpected hexaploid somatic hybrid plants were recovered from the fusion of Amblycarpa mandarin + C-35 citrange. Hexaploid hybrids should be very dwarfing and may have potential for producing potted ornamental citrus. Resulting somatic hybrid plants from all six combinations have been propagated by tissue culture and/or rooted cuttings and are being prepared for commercial field evaluation for their potential as improved rootstocks for Mexican lime and other important scions.

Free access

F.S. Davies, M.W. Fidelibusa, and C.A. Campbell

Gibberellic acid (GA) applied in late summer or fall delays subsequent loss of peel puncture resistance (PPR) and development of yellow peel color in many citrus cultivars. Our objective was to determine the optimal time to apply GA for increasing juice yield of `Hamlin' sweet orange [Citrus sinensis (L.) Osb.]. Mature trees on sour orange (Citrus aurantium L.) rootstock were sprayed with ≈24 L of a solution of GA (45 g a.i./ha) and organo-silicone surfactant (Silwet, 0.05%). Trees were sprayed on 26 Aug., 9 Sept., 2 Oct. (colorbreak), or 13 Oct. 1997, or nonsprayed (control). Peel puncture resistance, peel color, and juice yield were evaluated monthly between Dec. 1997 and Mar. 1998. Fruit from trees sprayed with GA had peels with higher PPR and less yellow color than fruit of control trees for most of the harvest season. The effect of GA on PPR and peel color lasted about 5 months. Juice yield was usually numerically greater for GA-treated fruit than for nontreated fruit. Fruit treated with GA at color break had significantly greater juice yield when harvested in late February than fruit from control trees. Thus, GA applied at color break appears to be the most effective time for enhancing peel quality and juice yield of `Hamlin' oranges.

Free access

Richard J. Crawford and David M. Eissenstat

The relationship of genotypic variation in root hair development with root proliferation, mycorrhizal colonization, and specific root length (length / dry mass) was studied in sixteen field-grown citrus relatives. The species varied widely in hair development, root length and mass density, and specific root length. No correlation was found between hair development, mycorrhizal colonization, root proliferation, and specific root length. However, there was a significant correlation (r=.55) between the percentage of total root length with hairs and the percentage of hairs with adhered soil. In a second experiment, the phenotypic plasticity in root hair development was studied in four-citrus rootstooks: Swingle citsumelo, Sour orange, Trifoliate orange and Volkamer lemon. Roots were grow” in either mineral soil or high organic matter media. After eight weeks, root length density and percentage of root length with hairs averaged over all four rootstocks was 232 % and 85 % greater in the organic media than in the mineral soil. Similar to the first experiment the percentage of total root length with hairs was significantly correlated (r=.99) with the percentage of hairs with adhered soil.

Free access

J.P. Syvertsen, M.L. Smith, and B.J. Boman

Effects of salinized irrigation water on tree canopy and root growth, water use, foliar nutrition, and leaching losses below the rootzone were studied during a 2-year period using single tree lysimeters. Eighteen 6-year-old `Valencia' orange trees on either Carrizo citrange (CC) rootstock or sour orange (SO) rootstock were each transplanted into 7.8 m3 drainage lysimeters and irrigated with water having an electrical conductivity of 0.3, 1.6, or 2.5 dS m-1 from a 3:1 ratio of NaCl:CaCl2. Six additional trees (3 on each rootstock) were transplanted into soil without tanks. Trees outside the tanks were smaller, but nutritionally similar to the low salinity trees in lysimeters. Trees on CC were larger, had greater root densities, and were associated with less leaching of ions and nutrients into drainage water from the tanks than trees on SO. High salinity irrigation water reduced canopy growth and ET, but increased fibrous root dry weight. Trees on CC accumulated more Cl in leaves and in fruit juice than those on SO. Leaching loss of total N varied from 2-8% of that annually applied to trees, but up to 70% of the applied N and up to 80% of the applied K were leached from the blank tank with no tree. Salinized trees lost more N and K to drainage water, especially those on SO. Tree size, root density, and irrigation water quality can influence leaching losses beyond the rootzone.