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  • Author or Editor: Herbert C. Barrett 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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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.

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