Clean Stock Research Articles

Occurrence and distribution of stone fruit viruses and viroids in commercial plantings of Prunus species in western Anatolia, Turkey.

Symptoms of virus and viroid infections have been observed during the last ten years in stone fruit crops, however, no relative incidences of virus and viroid diseases have been reported on stone fruit crops in western Anatolia, Turkey. Large-scale surveys were conducted from June to August between the years 2004 and 2006 in the main stone fruit growing orchards and mother blocks of western Anatolia to determine the seven most important virus and two important viroid affecting Prunus species. The results of serological (ELISA) and molecular (PCR and tissue-printing molecular hybridization) tests demonstrated the occurrence of Plum pox virus (PPV), Prune dwarf virus (PDV), Prunus necrotic ringspot virus (PNRSV), Apple chlorotic leaf spot virus (ACLSV), Apple mosaic virus (ApMV), Apricot latent virus (ApLV), Plum bark necrosis stem pitting-associated virus (PBNSPaV), Peach latent mosaic viroid (PLMVd), and Hop stunt viroid (HSVd) in tested 1732 specimens of stone fruits. The overall infection level with these graft-transmissible agents was 30%. The results showed that PDV is predominant in stone fruit crops. To our knowledge, PBNSPaV was reported for the first time in western Anatolia. The results obtained in this study illustrate a need for certification or clean stock program to prevent the occurrence and the spread of graft transmissible agents in western Anatolia.

Potential Risk of Commercial Geranium to Infection by Puccinia pelargonii-zonalis

Outbreaks of rust caused by the fungus Puccinia pelargonii-zonalis on geraniums can result in large losses due to the plants' reduced aesthetic value and eradication efforts. To assess the potential risk of a rust outbreak in geranium production facilities, 77 commercial varieties of geranium were inoculated with a mixture of two isolates of P. pelargonii-zonalis. All but one variety (98.7%) developed at least one sporulating lesion and 72.7% developed rust lesions on more than 20% of the leaves. Six varieties had lesions on fewer than 10% of the leaves and one variety did not develop visible lesions. These data indicate that the potential for geranium rust to spread throughout commercial greenhouses is very high if an accidental introduction should occur. While fungicides are available to manage the disease, including products with curative properties, minimizing risk by using disease-free cuttings, maintaining clean stock plants, and avoiding leaf wetness is essential to limit losses to geranium rust. Accepted for publication 16 July 2007. Published 31 October 2007.

Cleansing the long-term micropropagated triploid watermelon cultures from covert bacteria and field testing the plants for clonal fidelity and fertility during the 7–10 year period in vitro

The study was aimed primarily at cleansing the in vitro-decline displaying long-term micropropagated triploid watermelon ‘Arka Manik’ cultures from covert bacteria and their further field testing. Disinfectant treated shoots showed endophytic survival but to a lesser extent in shoot-tips. Culturing the NaOCl (5 min) treated shoot-tips on filter paper bridges in liquid watermelon medium containing single antibiotic (gentamycin (Gm), amoxycillin (Ax) or cefazolin (Cz) at 50, 250, 500 or 1000 mg l−1) for 1 month followed by repeated indexing of medium and tissue for two-four subculture passages facilitated the cleansing of cultures with 12.5% recovery as monitored for 2 years. Partial bleaching damage by NaOCl, phytotoxicity to higher levels of antibiotics, poor growth response in the initial sucrose-free medium and rampant hyperhydricity came in the way of a higher recovery. The effectiveness of the above approach was ascertained after back inoculating clean cultures with a mixture of Gram-positive and Gram-negative bacteria yielding 30, 45 and 35% clean cultures in Gm, Ax and Cz (250 mg l−1 for 1 month) treatments, respectively in modified medium compared with 10% recovery after mere HgCl2 surface sterilization. The results indicated that antibiotic treatment was essential but not its choice, and extended culture-indexing subsequent to disinfection or antibiotic treatment was crucial in identifying clean stocks. Cleansed cultures, showed restoration of growth but a drop in rooting. Most of the in vitro cultures appeared normal and true-to-type during the 7–10 year period in vitro but a small proportion of bacteria-harboring stocks displayed ‘epigenetic variations’. Acclimatized plants and those in the field also appeared true-to-type but for a minor proportion derived from bacteria-harboring stocks. Field-plants which originated from bacteria-freed stocks after 9 years of continuous culturing were normal and fertile validating the possibility of keeping treasured cultures in vitro for long periods if covert contaminants are checked.

Sanitary Status of Fruit Trees with Implementation of Clean Stocks

Sanitary Status of Fruit Trees with Implementation of Clean Stocks

Principles of Plant Health Management for Ornamental Plants

Economic, environmental, and technological influences complicate the task of achieving disease-free products in the ornamentals industry. Integrated pest management (IPM) is a cornerstone of floriculture and nursery crop production: strategies include sanitation, clean stock, host resistance, and control through biological, cultural, environmental, chemical, and regulatory means. Sanitation measures and cultural controls must keep pace with new production technologies. Clean stock programs are used for many crops that are propagated vegetatively. Breeding, selection, and biotechnology provide crops resistant to pathogens. Offshore production for economic competitiveness can introduce pathogens that make regulatory programs necessary. New biocontrol and chemical products continue to improve control while meeting the requirement for minimal environmental impact. Continual introduction of new crops and new production technologies creates new opportunities for pathogens to exploit, such that new disease management tactics must be discovered and old ones rediscovered to achieve optimum health management for ornamentals.

Evaluation of Clones, Container Types and Tissue Culture Media for Production of Calla Lilies as a Nursery Crop

Abstract Studies were designed to determine if colored callas (Zantedeschia sp.) can be successfully grown as a spring color crop under field conditions in the Southeastern United States without substantial modification of greenhouse culture protocols and if yield of clean stock from tissue culture can be improved. Results indicate colored calla lily production in containers in hardiness Zone 8B can be successful, without making significant modifications to either existing greenhouse production guidelines or the environment used for woody plant container culture. Neither fiber nor deeper containers improved overall calla performance over traditional plastic pots. ‘Garnet Glow’ and ‘Pink Persuasion’ produced the most blooms over 6 weeks of evaluation and would be better adapted for the spring color market than ‘Florex Gold’ or ‘Mango’ which bloomed heavily for only two weeks. The disease index developed for this study indicated ‘Mango’, ‘Florex Gold’, ‘Rubylite Pink Ice’ and ‘Majestic Red’ suffered the most soft rot damage while ‘Pink Persuasion’, ‘Garnet Glow’ and ‘Pot of Gold’ had the least when using field grown tubers. Tissue culture propagation efficiency was improved, as reflected in propagule size, by increasing sucrose levels in production media from 30 g/liter up to 120 g/liter, thus speeding production of larger clean microtubers. Proper cultivar selection and strict adherence to a disease control program, as in greenhouse production, allow production of high-quality colored callas in the Gulf South as an outside container crop for the spring color market.

Micropropagation of Achillea filipendulina cv. ‘Parker’

Achillea filipendulina (family Asteraceae) is widespread throughout temperate North America. In order to clean stock plants from endemic fungal and bacterial contaminations a method for large-scale propagation of A. filipendulina through meristem culture was sought and found and is described in this paper. The best conditions for propagating A. filipendulina was found to be MS (Murashige and Skoog) salt medium supplemented with 3% sucrose and 1 mg l−1 IAA (indole-3-acetic acid) plus 2 mg l−1 BA (6-benzyladenine) under 16 h of cool fluorescent light. Rooted plants were successfully acclimatized within a short time after propagating on this medium. The propagation via tissue culture did not affect plant's presentation. The use of clean stock plants made it possible to increased Israeli production of Achillea from about 150,000 stems a year to about 1,300,000 stems a year.

ASIAN CITRUS PSYLLIDS (STERNORRHYNCHA: PSYLLIDAE) AND GREENING DISEASE OF CITRUS: A LITERATURE REVIEW AND ASSESSMENT OF RISK IN FLORIDA

The Asian citrus psyllid, Diaphorina citri Kuwayama, was discovered in Florida in 1998. It can be one of the most serious pests of citrus if the pathogens that cause citrus greening disease (huanglongbing) are present. Citrus greening recently has been reported in Brazil by Fundecitrus, Brazil. The establishment of D. citri in Florida increases the possibility that the disease may become established. Diaphorina citri can be separated from about 13 other species of psyllids reported on citrus. The biology of D. citri makes it ideally suited to the Florida climate. Only two species, D. citri and Trioza erytreae (del Guercio), have been implicated in spread of citrus greening, a disease caused by highly fastidious phloem-inhabiting bacteria. The disease is characterized by blotchy mottle on the leaves, and misshapen, poorly colored off-tasting fruit. In areas where the disease is endemic, citrus trees may live for only 5-8 years and never bear usable fruit. The disease occurs throughout much of Asia and Africa south of the Sahara Desert, on several small islands in the Indian Ocean, and in the Saudi Arabian Peninsula. Transmission of citrus greening occurs primarily via infective citrus psyllids and grafting. It is transmissible experimentally through dodder and might be transmitted by seed from infected plants and transovarially in psyllid vectors. Citrus greening disease is restricted to Citrus and close citrus relatives because of the narrow host range of the psyllid vectors. Management of citrus greening disease is difficult and requires an integrated approach including use of clean stock, elimination of inoculum via voluntary and regulatory means, use of pesticides to control psyllid vectors in the citrus crop, and biological control of psyllid vectors in non-crop reservoirs. There is no place in the world where citrus greening disease occurs that it is under completely successful management. Eradication of citrus greening disease may be possible if it is detected early. Research is needed on rapid and robust diagnosis, disease epidemiology, and psyllid vector control.

The Concept of “Foundation Clones” in Source Selection for Vegetative Propagation of Almond

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).

Rapid and Sensitive Colorimetric Detection of Xanthomonas axonopodis pv. citri by Immunocapture and a Nested-Polymerase Chain Reaction Assay

We have developed a sensitive and specific assay for Xanthomonas axonopodis pv. citri, the causal agent of citrus bacterial canker. The assay is based on sequential nested amplification by polymerase chain reaction (PCR) of a region of plasmid DNA that is very highly conserved in X. axonopodis pv. citri. Specific amplification products were observed in reactions containing three or fewer target molecules, an improvement of 50- to 100-fold over single-stage PCR, and similar results were observed when beginning with purified DNA or living bacterial cells. Colorimetric detection of amplification products was performed with the DIANA (detection of immobilized amplified nucleic acids) method, which uses labeled primers to allow amplification product capture and detection in a microtiter plate. Predicted amplification products were produced from all strains of X. axonopodis pv. citri and from four of six strains of X. axonopodis pv. aurantifolii but not from other xanthomonads, including citrus epiphytes, except for X. axonopodis pv. vignicola and one strain isolated from Feronia elephantiacum, consistent with previous hybridization results. No amplification products were observed from strains of X. axonopodis pv. citrumelo that incite citrus bacterial spot disease in Florida citrus nurseries. Amplification was completely inhibited by copper hydroxide when present in the reaction mix at 13.6 μg/ml. Concentrated leaf extracts from tangelo and mandarin orange, but not similar extracts from other citrus varieties, also inhibited amplification. Immunomagnetic separation of target bacteria prior to amplification was used to concentrate and recover X. axonopodis pv. citri from samples containing compounds that inhibit amplification (i.e., copper and concentrated citrus extracts). Immunocapture, by concentrating target bacteria from dilute plant extracts, improved the sensitivity of the assay by 100-fold over nested-PCR alone. The combination of sensitivity, specificity, and speed of the assay could make this a widely used assay both in plant quarantine and in areas where X. axonopodis pv. citri is endemic and clean planting stock programs are to be initiated.

Propagation of Zingiberaceae and Heliconiaceae.

Increased interest in tropical cut flower export in developing nations has increased the emand for clean planting stock. The most popular items have been various gingers (Alpinia, Curcuma, and Heliconia) . This paper reviews seed and vegetative methods of propagation for each roup. Auxins such as IBA and NAA enhanced root development on aerial offshoots of Alpinia at the rate 500 ppm while the cytokinin, PBA, enhanced basal shoot development at 100 ppm. Rhizomes of Heliconia survived treatment in 4811 C hot water for periods up to 1 hour and 011 C up to 30 minutes in an experiment to determine their tolerance to tempera tures for eradicating nematodes. Pseudostems soaks in 400 mg/LN-6-benzylaminopurine improved basal bud break on heliconia rhizomes.[...]

Mycoplasma infection of cultured cells.

Mycoplasma contamination is tough to detect and even more difficult to eradicate. It is best to start over fresh from clean cell stocks, but several elimination options are available.

AIDES — an engineer's design process

The Automated/Interactive Design Engineering System (AIDES) is a system of computer-aided engineering design tools for electronic hardware development. AIDES gives the engineer tools for early design analysis, graphical schematic entry of design information, and quick model building. AIDES is fashioned to encourage the engineer to sit at the computer terminal, perform the analysis, and build files for modeling. Hard copy of clean schematics, physical layout, and stock lists are generated at any time for design reviews by engineering and manufacturing organizations. Once the design is tested and verified, the design file is transmitted for printed circuit layout.

An epidemiological study of Salmonella in a closed pig herd.

An epidemiological survey of salmonella infection in a closed herd of pigs is reported. The main cause of cross-infection resulted from the movement of animals, with subsequent mixing of infected and clean stock and exposure of non-infected animals to infected faeces. Pen-to-pen infection carried by farm attendants also proved important.An extended survey is at present being conducted to gain further information on the processes of cross-infection.

EPIDEMIOLOGY AND CONTROL OF DEAD-ARM OF GRAPES

Inoculation of pruning wounds on grape with spore suspensions of Phomopsis viticola Sacc. at different times of the year rarely resulted in more than 25% infection. In many cases, incipient lesions and even pycnidia developed shortly after inoculation, but infection did not progress further. Highest infection rates were obtained in the summer months with freshly cut wounds. Wounds that had dried out for several weeks were difficult to infect.Primary infections occurred on young, uninjured, succulent, green shoots. Their incidence and severity were dependent on the inoculum potential resulting from the previous year's infection and on the amount of precipitation in the latter half of May. Discrete primary lesions were nearly always superficial but coalescent ones were more deeply seated and often became perennial. Functional pycnidia were frequently observed in the mature layer of bark on the basal nodes and internodes of 1-year-old canes, the underlying tissues of which were not diseased. Green shoots are considered to be more important infection sites than the pruning wounds made during the dormant season in normal commercial practice.Control measures should include propagation and planting of clean nursery stock as well as a pre-bloom spray program. If the disease becomes established in arms or trunk it is more effective and economical to remove and renew the vine at ground level than to try to save part of an affected vine at a greater risk of reinfection.

Peppermint and spearmint production

A prescription for the production of peppermint based on the known data would be as follows. Mint requires a normally fertile soil with high water holding capacity or irrigation available if rainfall is not sufficient. It requires an area having a day length of 15 to 16 hours, as much sunlight as possible, clean planting stock, and disease control measures which have not yet been fully developed.

Hot-Water treatment of gladiolus cormels for the eradication ofFusarium oxysporumf.gladioli

does not appear. First page follows. Introduction An obstacle to the use of pathogen-free gladiolus corms as a primary disease control is the universal contamination of commercial varieties, which makes it very difficult to obtain such clean stock by simple selection. As Buxton (1955a)4 has pointed out, “Once the Fusarium has become established in a stock of corms by infection from the soil, eradication is almost impossible.” However, two alternative methods remain for obtaining clean stock: 1) New pathogen- and virus-free varieties may be developed from seed. This is a slow and expensive procedure, even when the factor of actual resistance is not involved. 2) Methods may be devised for commercially freeing present varieties from the major pathogens. Some studies with this promising approach are presented in this paper. Of course, with either method, it is necessary to protect the stock from reinfection. Of the available means for completely freeing planting stock of disease organisms, treatment with chemicals has not been effective because many of the pathogens are carried internally in deep lesions or in the vascular elements. Heat therapy has been investigated by several workers with little success. (Massey (1916)) found that tube cultures of the hard-rot fungus (Septoria gladioli Pass.) and dry-rot fungus (Stromatinia gladioli (Drayt.) Whet.) were killed at about 122° F for 10 minutes, and that medium-size corms were not materially harmed by dry heat of 122° F for 90 minutes, or by hot water of 122° F for 30 minutes. However, when corms with dry rot and hard rot were treated as above on the day they were dug, neither pathogen

Some Regulatory Problems

A brief discussion of some of the problems confronting regulatory officials at the present time, calling attention to the transportation of plants and plant materials by unregulated trucks over Federal-State highways; the use of clean planting stock in highway beautification projects; financing of regulatory services under present economic conditions and quarantines.