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  • Author or Editor: C. Jack Hearn x
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Citrus rootstocks resistant to decline induced by citrus tristeza (CTV) have been developed using resistance found in Poncirus trifoliata (L.) Raf. A breeding line with resistance to CTV infection, US119 [Citrus paradisi Macf. cv. Duncan × P. trifoliata (L.) Raf. × C. sinensis cv. Succory], was developed and crossed with `Ambersweet' orange [C. reticulata Blanco × (C. paradisi × C. reticulata) × C. sinensis] to develop scions resistant to CTV infection. Fifty-one progeny were tested for CTV resistance by grafting each to rough lemon [C. limon (L.) Burm. f.] seedlings infected with CTV. These propagations were assayed repeatedly by ELISA. Seventeen progeny consistently tested negative for CTV (resistant), 24 were consistently positive (susceptible), and 10 gave weak or inconsistent reactions. These results confirm the feasibility of developing CTV-resistant scions by use of US119 to solve the stem pitting disease caused by CTV.

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Fresh pollen from Citrus tachibana Macf. was oven-dried (37C), freeze-dried, or placed into anhydrous acetone, and stored at -20C over silica gel. Pollen freeze-dried or stored in anhydrous acetone did not germinate 24 hours after treatment; oven-dried pollen germinated in 1 hour and was comparable to fresh pollen. Pollen that was oven-dried for 12 hours and stored for 1 year was used to pollinate a monoembryonic hybrid of `Temple' (origin unknown) × `Orlando' (C. paradisi Macf. `Duncan' ×C. reticulata Blanco `Dancy'). Glutamate-oxaloacetate transaminase (GOT) isozyme profiles verified progeny hybridity.

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leaf and seed glycoproteins were detected after sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and electroblotting onto polyvinylidene difluoride (PVDF) membrane when probed with biotinylated lectin at 1 μg·ml-1. Four lectins representing three carbohydrate-binding groups were used as probes. A preformed avidin-biotin-complex (ABC) was used to detect the glycoprotein-bound lectins and resulted in dark bands and little background staining. Concanavalin A (ConA) and wheat germ agglutinin (WGA) resulted in the darkest-staining bands. The four Citrus spp. and one related species studied had unique seed glycoprotein profiles when probed with ConA and WGA. This procedure might be useful in clarifying citrus taxonomy, providing genetic markers, and in physiological studies involving glycoproteins.

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Abstract

Leaf extracts from 58 cultuvars of citrus were examined by thin-layer chromatography and the methoxyflavones, flavanones and coumarins in the extracts used to show the relationships between parents and offspring as well as to indicate possible relationships for cultivars of unknown genetic origin.

Open Access

Abstract

Nearly all commercial citrus trees are grafted, and the rootstock has a major effect on the performance of the scion cultivar. A citrus tree’s resistance to or tolerance of disease, nematodes, salt, cold, and other factors may be influenced by the rootstock. Also, the rootstock affects the tree’s adaptability to various environmental factors, as well as the quantity and quality of fruit that it produces. No available rootstock possesses all of the desirable traits needed by the citrus industry. Also, changes in culture and production problems create new demands.

Open Access

Abstract

In an assessment of natural hazards on world crop production, an average of more than $ 100 million per year is lost in the continental United States due to freeze damage to 22 major crops. The greatest loss is in citrus production and amounts to about one-third of the national average. A severe freeze occurred in 1962 which cost Florida more than one-third of its total production, in excess of 10 million boxes (41 kg.) of fruit and onefourth of its 52 million trees. Similar losses occurred again in 1977 and, most recently, in 1981 and 1982. These losses impact negatively not only on the present and future economic stability of an industry, but also in meeting the dietary needs (supply and nutrition) of an expanding world population, which is facing ever-increasing uncertainties in adequate nutrition and subsistence levels.

Open Access