Sixty-eight percent of the `Pineapple', 52% of the `Navel', 46% of the `Valencia', 38% of the `Hamlin', and 0% of the `Ambersweet' orange [Citrus sinensis (L.) Osh.] trees in five Florida citrus nurseries were infected with severe strains of citrus tristeza virus (CTV), as demonstrated by reaction with a monoclinal antibody specific for severe strains of the virus. Severe strains of CTV infected 4%, 46%, 76%, 30%, and 48% of the trees at each of the five nurseries, respectively, indicating a considerable difference in severe strain prevalence among the nurseries. Thirty-five percent of the trees in the scion blocks (budwood source) of the nurseries also contained severe strains of CTV.
Charles A. Powell and Robert R. Pelosi
Charles A. Powell, Robert R. Pelosi, and Phyllis A. Rundell
None of 4190 sweet orange [Citrus sinensis (L.) Osb.] nursery trees of `Hamlin', `Midsweet', `Navel', and `Valencia' sampled from five Florida citrus nurseries were infected with a decline-inducing isolate of citrus tristeza virus (CTV) as judged by enzyme-linked immunosorbent assay (ELISA) using isolate-specific monoclonal antibodies. Two of the nurseries had a relatively high level of infection (37% to 100% of composite samples containing tissue from 10 trees) with nondecline-inducing (mild) isolates of CTV, depending on the cultivar. Three of the nurseries had a lower incidence of mild CTV (0% to 22% of 10 tree composite samples). No nursery was CTV-free. ELISA of individual trees used as budwood sources by the nurseries revealed that one tree out of 260 tested contained decline-inducing CTV, and 83 contained mild CTV. These results suggest that the budwood certification program adopted in 1997 has virtually eliminated decline-inducing CTV from commercial budwood supplies.
Dale E. Kester and Ale E. Kester
The term “clone” is a key biological term that designates a number of horticultural situations. In breeding, many cultivars are designated as clones, originating from consecutive vegetative propagation from individuals within a seedling population, from individual plants of a clone exhibiting “bud mutations,” and, more recently, from genetic engineering and biotechnology. Extensive vegetative propagation of a limited numbers of clones in modern horticultural systems has been accompanied by systemic incorporation by serious pathogens (viruses, viroids, phytoplasmas, etc.), and in some cases by horticultural deterioration (e.g., noninfectious bud-failure in almonds). Control of these problems in clonal propagation is achieved by 1) propagation source selection 2) maintenance of the source in a registered foundation block under protected conditions and 3)multipli-cation in controlled “mother blocks” or “increase blocks” from which commercial material is distributed after a minimum of consecutive generations of vegetative propagation. This system is the basis for Registration and Certification programs and “clean stock” in general. In many crops the selected propagation source is a single plant, its progeny constitutes a “clone,” and the new entity is given a unique name or number. To distinguish this “new” clone from the “original” clone, the designation of FOUNDATION CLONE is suggested. Biological and horticultural significance is illustrated in almond (Prunus dulcis).
Jenna Sicuranza and Nathaniel A. Mitkowski
rhododendron varieties for use in the production of clean stock plants or potentially for the production of saleable plants. Materials and Methods Flower buds were collected from 25-year-old rhododendron plants growing outdoors at the University of Rhode
David J. Norman and Jianjun Chen
. Res. 48 329 335 Patel, M.K. Bhatt, V.V. Kulkarni, Y.S. 1951 Three new bacterial diseases of plants from Bombay Indian Phytopathol. 4 144 151 Raju, B.C. Olson, C.J. 1985 Indexing systems for producing clean stock for disease control in commercial
Nathan J. Jahnke, John M. Dole, and H. David Shew
stations need to maintain clean stock, allow air movement around plant materials, and keep leaf surfaces dry during growth and before shipping. These practices will limit infection occurrences, sporulation, and spore dispersal. If gray mold does develop and
Dong Sub Kim, Mark Hoffmann, Steven Kim, Bertha A. Scholler, and Steven A. Fennimore
ambient temperatures. Literature Cited Baker, K.F. (ed.). 1957 The U. C. system for producing healthy container-grown plants through the use of clean soil, clean stock, and sanitation. Univ. CA Div. Agricultural Sci. Agricultural Expt. Sta. Ext. Serv
Christopher A. Clark, Tara P. Smith, Donald M. Ferrin, and Arthur Q. Villordon
meristem-tip culture and indexing to generate VT tissue culture plantlets, but the methods for subsequent increase and dissemination of clean stock to growers differ from state to state ( Dangler, 1994 ). In Louisiana, VT tissue cultures are increased by
Jennifer L. Parke, Neelam R. Redekar, Joyce L. Eberhart, and Fumiaki Funahashi
for producing healthy container-grown plants: Through the use of clean soil, clean stock, and sanitation. Univ. California, Agr. Expt. Sta., Ext. Serv., Berkeley Baker, K.F. Cook, R.J. 1974 Biological control of plant pathogens. Freeman, San Francisco
Kim D. Bowman and Ute Albrecht
through research, such as using clean stock ( Vidalakis et al., 2010 ) and nutritional management ( Bernardi et al., 2015 ; Maust and Williamson, 1994 ). Supplemental light to increase daylength and accelerate plant production is one component of the