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  • Author or Editor: G. Yelenosky x
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Ten-month-old seedlings, grown from seed extracted from 22 individual pummelo [Citrus grandis (L.) Osbeck] × trifoliate orange [Poncirus trifoliata (L.) Raf.] citrus hybrid trees that survived -15C freezes near Monticello, Fla., were cold-acclimated in controlled-environment rooms and freeze-tested at -6.7C for 4 h. Freeze damage to open-pollinated progeny was ranked by the number of uninjured seedlings and percentage of leaves killed and wood dieback. Morphological segregation was not associated with differences in freeze survival, and the dominant trifoliate gene was readily evident. Progeny from one tree, identified as 98-71, are considered the most likely candidates for further study in developing cold-hardy citrus trees.

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Abstract

Four-year-old ‘Marsh’ grapefruit (Citrus paradisi Macf.) trees on trifoliate orange [Poncirus trifoliata (L.) Raf.] rootstock were temperature acclimated to 5°C in controlled environment facilities with approximately 400 μeinsteins m−2s−1 PAR. Total soluble carbohydrates and proline increased in both leaves and fruit flavedo as temperatures were progressively decreased. Maximum accumulation of carbohydrates occurred in leaves and flavedo at 10° ambient air. Both sucrose and reducing sugars increased in leaves at all acclimating temperatures, but only reducing sugars increased in the flavedo at temperatures below 15°. The concentration of proline was the greatest in the leaves and flavedo at 5°. Both total soluble carbohydrates and proline decreased during temperature deacclimation at 25°.

Open Access

Abstract

Initial growth and development of ‘Valencia’ orange [Citrus sinensis (L.) Osbeck] shoots from buds grafted on 7 different rootstocks were determined during cold-hardening and nonhardening temperature regimes for the 1st 4 months after budbreak. Cold hardening included 12 hr each of 15.6°/4.4°C day/night (D/N) in controlled-environment rooms, where 80% fluorescent and 20% incandescent light averaged 450 μmol m-2s-1. Nonhardening included 32.2°/21.1° D/N as well as greenhouse conditions with natural daylight. Rootstocks influenced growth of ‘Valencia’ during cold-hardening temperatures. Cold-hardening temperatures, however, did not stop ‘Valencia’ growth on any of the rootstocks. Total growth was less than 1/20 of the dry weight accumulated during the warm temperatures. During the cold-hardening treatment, ‘Valencia’ grew the most on the relatively cold-tender volkamer lemon [C. volkameriana (Ten. and Pasq.)] rootstock. The least growth was on the more cold-hardy Swingle citrumelo (C. paradisi Macf. × Poncirus trifoliata (L.) Raf.] rootstock. The amount of growth during cold-hardening temperatures generally coincided with the cold hardiness of the rootstocks, but statistical separation was poor. Trees grown at the warm temperatures started to freeze at higher temperatures than trees grown at cold-hardening temperatures. Rootstocks did not influence freeze avoidance, and no differences were apparent in freeze (ice) tolerance. Three layers of palisade cells were found in leaves that were grown at the cold temperatures.

Open Access

Abstract

In the article “Growth Capacity of ‘Valencia’ Orange Buds on Different Rootstocks during Cold-hardening Temperatures” by G. Yelenosky and H.K. Wutscher [J. Amer. Soc. Hort. Sci. 110(1):78–83. 1985.], the figure captions for Figures 2 and 3 were reversed.

Open Access

Abstract

Available young hybrid trees of Eremocitrus glauca with ‘Valencia’ orange (Citrus sinensis (L.) Osbeck), Sicilian sour orange (C. aurantium L.), ‘Nagami’ kumquat (Fortunella margarita (Lour.) Swing.), and Koethen sweet orange (C. sinensis) were more cold hardy than the Citrus or kumquat parent in natural and controlled freezes. Eremocitrus may be a useful source of cold hardiness for breeding cold-hardy citrus hybrids.

Open Access

Abstract

Polyclonal antibodies against the major soluble glycoprotein of trifoliate orange [Poncirus trìfoliata (L.) Raf.] were produced in rabbits. The antisera were used to detect the glycoprotein in foliar protein extracts from a hybrid of Poncirus and Citrus genotypes by immunoblotting. One of the sera was found to be highly specific and was suited to indicate trifoliate gene expression. Cross-reacting bands in protein extracts from citrus callus tissue and in the medium of suspension cell cultures suggest that tissue culture systems can be used for biochemical studies of glycoproteins, but not for genotype characterization.

Open Access

Abstract

CO2 exchange rate (CER), stomatal conductance (Cs), and transpiration in mature attached leaves of ‘Valencia’ orange [Citrus sinensis (L.) Osbeck] were determined outdoors from predawn to 1100 EDT. The maximum values of CER and Cs, which were about 7 μmol CO2·s−1m−2 and 0.27 cm·s−1, respectively, at solar photosynthetic photon flux density (PPFD) of 500-700 μmol·s−1m−2, remained at these levels as PPFD, temperature, and vapor pressure deficit (VPD) between leaf and air continued to increase. Transpiration rates, with maximum values ranging from 1 to 4 mmol H2O·s−1m−2, increased throughout the measurement periods of the morning as leaf-air VPD increased. Thus, photosynthetic water use efficiency decreased with increasing VPD.

Open Access

Abstract

Four-year-old ‘Marsh’ grapefruit (Citrus paradisi Macf.) trees on trifoliate orange [Poncirus trifoliate (L.) Raf.] were subjected to temperature regimes of 25° to 5°C over 11 weeks in controlled environment facilities. Levels of total fatty acids in the flavedo of tree fruit decreased over this period by ≈50%, regardless of temperature. After 5 weeks, the level of linoleic acid in the flavedo of grapefruit that had been kept at progressively cooler temperatures from 25° to 5° was 76% greater than the level in control fruit at 25°. On rewarming and cooling, the differential for linoleic acid in flavedo was 41%. Increases of linoleic acid in the flavedo of fruit on trees that were treated with lower temperatures occurred in six lipids, with the greatest increases in phosphatidyl choline and wax-sterol esters. Chilling injury in harvested fruit during cold storage occurred slightly earlier in fruit from trees exposed to low temperatures, but was most severe in nonacclimated fruit.

Open Access

Abstract

In the paper, Distribution of l4C Photosynthetic Assimilates in ‘Valencia’ Orange Seedlings at 10° and 25°C by C. L. Guy, G. Yelenosky, and H. C. Sweet (J. Amer. Soc· Hort. Sci. 106(4):433–437. 1981) the title for Table 1 should read: l4C-labeled fractions extracted from ‘Valencia’ orange seedlings exposed to l4CO2 (50 μCi for 3 hours) at 25° and 10°C and maintained at those temperatures for 28 days in controlled temperature light rooms.

Open Access

Abstract

The distribution of 14C-photosynthate was determined in 8-month-old potted ‘Valencia’ orange seedlings [Citrus sinensis (L.) Osbeck] during 25° and 10°C temperature regimes. Seedlings were pulse-labeled with 14CO2 for 3 hr after equilibration with ambient air. Radioactive assimilates were extracted at selected intervals, from leaves, stems, and roots and separated into several biochemical fractions. Low-temperature (10°) exposure resulted in a greater retention of 14C in the sugar fraction of leaves and a lower rate of 14C incorporation into organic and amino acid fractions. Data indicate a lower rate of metabolism of photosynthate and a reduced distribution of 14C in citrus seedlings at 10° than at 25°C.

Open Access