Clark H. Livingston

Eradication of potato virus X from potato by ribavirin treatment of cultured potato shoot tips

Ribavirin treatment of cultured potato shoot tips was tested as a means of eradicating potato virus X (PVX) from two potato cultivars. Shoot tips were cultured on liquid medium containing 0, 1, 10 or 100μg/ml ribavirin. Cultures were evaluated periodically for viability, and scored for vigor on a relative growth scale. Developed plantlets were assayed for PVX by transmission tests toGomphrena globosa.Ribavirin treatment was phytotoxic at all tested concentrations, and lethal to all cultivars treated at 100 μg/ml. Treatment also delayed plantlet development by up to 2 months at 1 and 10 μg/ml as compared with nontreated controls. PVX assays indicated that 80 and 83% of the plantlets were free of PVX following treatment with 10 μg/ml for cultivars Russet Burbank and Red McClure, respectively. Five and 6% of the plantlets developed from the 1 μg/ml treatment were PVX-free, whereas 0 and 2% of the controls were PVX-free for the same cultivars. Six to 8 months were required to develop plants from shoot-tip cultures treated with 10 μg/ml ribavirin.ResumenTratamiento con Ribavirin de ápices de brotes de papa “in vitro” fue probado como un medio de erradicar al virus X de la papa (PVX) de dos cultivares. Apices de brotes fueron cultivados en medio liquido conteniendo 0, 1, 10 ó 100 μg/ml de Ribavirin. Los cultivos fueron evaluados periodicamente para determinar su viabilidad y calificados con relación a su vigor en una escala relativa de crecimiento. Las plántulas que desarrollaron fueron analizadas para PVX por pruebas de transmisión aGomphrena globosa.El tratamiento con Ribavirin fue fitotóxico en todas las concentraciones probadas y letales a todos los cultivares a 100 μg/ml. El tratamiento también redujo el desarrollo de las plántulas hasta en 2 meses a 1 y 10 μg/ml en comparación con los testigos no tratados. Las pruebas para PVX indicaron que 80 y 83% de las plántulas estuvieron libres de PVX con el tratamiento de 10 μg/ml para los cultivares Russet Burbank y Red McClure, respectivamente. Cinco y 6% de las plántulas que desarrollaron del tratamiento con 1 μg/ml estuvieron libres de PVX, mientras que 0 y 2% de los testigos estuvieron libres para los mismo cultivares. Se necesitaron 6 a 8 meses para desarrollar plantas a partir de ápices de brotes tratados con 10 μg/ml de Ribavirin.

Epidemiology of potato early blight in Colorado 1. Initial infection, disease development and the influence of environmental factors

SummaryThe dissemination of primary inoculum ofAlternaria solani and the infection of potato plants in the field was shown to occur early in the season under Colorado conditions. Secondary spore dispersal was easily detected by spore traps. The use of such measurements may serve as a basis for timing initial spray applications.Temporary resistance of young potato foliage and the relationship of plant senescence and other factors to primary symptom development and secondary spread ofA. solani under field conditions were explored. These phenomena are important factors in the epidemiology of the disease in certain areas and may have direct bearings on control practices.Early primary symptom development and secondary spread was initiated simultaneously in early, medium and late-maturing potato varieties; symptom development was, however, more rapid and more spores were produced following the beginning of secondary spread in the early maturing varieties than in the later maturing ones. Early varieties planted near later varieties may contribute inoculum to the latter and increase plant infection.Low temperatures and relatively dry conditions in Colorado appeared to influence the extent of losses due to early blight. More spores per unit area were trapped in 1963 than in 1964. This was closely related to lower temperatures and relative humidities which prevailed in 1964.Sumario en españolLa diseminación del inóculum primario deAlternaria solani y la infección de la planta de patata se demostró que ocurre al principio de temporada bajo las condiciones de clima de Colorado. La difusión secundaria de esporos fué fácilmente determinada con el uso de la trampa de capturar esporos.La resistencia temporal de la hoja de la planta joven y la relación de la evolución de la planta y otros factores relacionados con el desarrollo de los sintomas primarios y difusión secundaria delA. solani fueron explorados bajo las condiciones del campo. Estos fenómenos son factores importantes en la epidemiología de la enfermedad en ciertas zonas y tienen infiuencia directa en las prácticas de control. El uso de tales medidas puede servir de base para la elección del debido tiempo del tratamiento inicial.El desarrollo de los síntomas primarios y difusión secundaria fué iniciado simultáneamente en variedades de patatas temprana, media y tardía; el sesarrollo de síntomas fué mas rápido y se produjeron mas esporos seguido de la iniciación de la difusión secundaria en las variadades de patata temprana que en las variedades tardías. Variedades tempranas sembradas junto a variedades mas tardias pueden contribuir a la contaminación e incremento de la infección de las plantas.Temperaturas bajas y condiciones atmosféricas relativamente secas parecen influenciar la extensión de las pérdidas debidas al tizón temprano en Colorado. En 1963 se atraparon mas esporos por unidad de zona que en 1964. Esto se consideró relacionado con las temperaturas mas bajas y humedades relativas existentes en 1964.

Control of potato early blight in Colorado. I. Fungicidal spray schedules in relation to the epidemiology of the disease

SummarySpray schedules for early blight in which fungicidal applications were initiated or terminated at various periods during the growing season have demonstrated that as few as two to three applications timed properly can control early blight infection in potatoes equally as well as five to seven applications. Early sprays were shown to be of little importance in the overall blight control program. Effective spray schedules were those which happened to begin at or near the time of secondary spread, as measured by spore trapping techniques. This timing proved superior to schedules begun earlier or later than this date in that equal or better blight control was attained at reduced cost. The possible role of spore traps as guides for timing initial applications of fungicides on a commercial scale is suggested by these and other studies.Sumario en EspañolLos programas de aplicación de fungicida para el control del tizón temprano de la papa, iniciados y terminados durante varios períodos de crecimiento de la planta, demostraron que con la aplicación del fungicida a su debido tiempo, dos o tres tratamientos controlan la enfermedad tan eficazmente como cinco o siete tratamientos. En general, las aspersiones demasiado tempranas resultaron de poca importancia en el control del tizón. Los programas de aspersiones más efectivos fueron aquellos en que la aspersión inicial coincidió con el desarrollo de la infección secundaria, estimada por técnicas de capturas de esporas. La elección del tiempo oportuno se tradujo en resultados superiores a los obtenidos en programas iniciados más temprano o más tardiamente, puesto que se obtuvo igual o mejor control del tizón a un costo más reducido. Por estos estudios se sugiere el posible papel de las trampas de esporas como guías para la elección del tiempo oportuno para las aplicaciones de fungicida en escala comercial.

Control of potato early blight in Colorado. II. Spore traps as a guide for initiating applications of fungicides

SummaryThe use of weather-vane spore traps with vaseline coated slides is an effective means of timing initial fungicide applications for potato early blight control in Colorado. This technique is simple and more reliable than some methods currently being used. Effective control of early blight was achieved with fewer sprays by using this system rather than plant growth stage as the basis for initiating fungicide applications. The method promises to be most useful in areas where crops with diseases caused by fungi that produce spores similar to those ofA. solani are not grown in close association with potatoes.Sumario en españolEl uso de la veleta-trampa para atrapar las esporas de hongos en placas de vidrio cubiertas de vaselina, es un medio efectivo para determinar el momento oportuno para la aplicación inicial del fungicida en el control del tizón temprano de la papa en Colorado. Esta técnica es más simple y segura que algunos de los métodos usados comúnmente. El control efectivo del tizón temprano de la papa se obtuvo por este método, con menos aspersiones que cuando se usa el sistema que toma como base para la aplicación inicial del fungicida el estado de crecimiento de la planta. Este método parece tener más posibilidades en zonas donde las plantas se cultivan aisladas de aquellas que padecen enfermedades causadas por hongos que producen esporas similares a las deAlternaria Solani.

Protein content and specific gravity of Red McClure potatoes increased by 2,4-D treatment

SummaryTreatment of growing Red McClure potato plants with 2,4-D at a rate of one-half pound per acre produces tubers with significantly higher protein content and with a significantly higher specific gravity.

The effects of antiviral chemicals on potato virus X-I

SummaryThe antiviral properties of Malachite green and thiouracil with regard to potato virus X were studied using tissue culture technique. Stem nodal tissues of Russet Burbank potatoes were grown in culture using modified Whites medium enriched with gibberellin and containing Malachite green at the rate of 2, 4, 6, 10 and 15 ppm or thiouracil at the rate of 5 and 10 ppm. Stem tissues grew well with no evidence of phytotoxicity due to the presence of antiviral chemicals. Antiviral properties of these chemicals were evaluated by inoculating the leaves ofG. globosa with the extract of the apical portion of the newly developed shoots. As the concentration of Malachite green was increased, the detectible amounts of virus activity was generally reduced, and the number of apparently virus-free tips was increased. Thiouracil treatment at 5 ppm reduced the detectible virus activity present in the new shoots, but there were no antiviral effects at a concentration of 10 ppm.The effects of soaking stem nodal segments in thiouracil solution on virus X was studied using Red McClure potatoes. Stem segments were immersed in thiouracil solution at the rate of 50 and 100 ppm for periods of 1,2 and 3 hours and then maintained on modified Whites solid medium. The detectible virus activity of the new young shoot tissues was reduced following the soaking treatment of stem segments in solution at the rate of 50 ppm. Concentration of 100 ppm exhibited antiviral properties only with 1 hour treatment.

Cytology of flower necrosis in cattleyas infected by Cymbidium mosaic virus.

Abstract Ultrastructural changes in a non-limited virus-induced necrotic lesion are described. Necrotic and symptomless areas of a Cattleya flower infected with Cymbidium mosaic virus were examined by electron microscopy. In symptomless areas virus-like particles were aggregated in paracrystalline inclusions similar to those found in other PVX-type viral infections. Most pronounced cytopathic effects occurred in plastids bordering necrotic areas in which starch disappeared and osmiophilic globules and phytoferritin accumulated. Neither cell wall modifications nor plasmolysis were associated with the non-limited lesions in this disease.

The effects of dihydroquercetin on the cut surface of seed potatoes

The purpose of this study was to determine the effects which dihydroquercetin (DHQ) has on the natural healing process of suberization and wound periderm initiation in cut seed potatoes. Dihydroquercetin is a phenolic compound extracted from the bark of Douglas Fir,Pseudotsuga menziesii (Mirb.) Franco.Anatomical studies of treated seed potato tissue showed that treatment with bark-383, the cork-rich fraction of the whole bark containing approximately 2% pure DHQ, increases the thickness of the suberized layer formed below the cut surface. Treatment with 4% bark fraction I, which is blended to that concentration with the inert carrier dust Pyrax and contains approximately the same amount of DHQ as does the bark-383, also promoted the formation of a thicker layer of suberized cells.The thickness of the wound periderm did not significantly vary as a result of the use of any treatments containing DHQ. The use of Captan (Orthocide 50W) as a cut seed treatment in these studies was found to inhibit the formation of a suberized layer and subsequently the initiation of a wound periderm. The combination of bark-383 and Orthocide 50W in a treatment mixture reversed the inhibitory affect of the Orthocide 50W alone and therefore allowed for the formation of a well suberized layer and a wound periderm.It was found that wound healing on the cut surface of seed potatoes is largely dependent on the type of tissue present at any given point on that cut surface. Therefore, the response to treatment of the stolon end, center, and blossom end tissues was related to the type of tissue which was present in each of those tuber regions.The fungal mold growth on treated seed pieces incubated in a controlled environment was adequately retarded when Orthocide 50W was combined with bark-383 in a mixture ratio of 1:9 respectively. The longer the treatment material was allowed to remain on the seed piece, the greater was the protection against mold growth afforded by the mixture.

Terraclor as a control for various levels of Rhizoctonia inoculum in potato soils

Rhizoctonia disease is common throughout the potato growing areas of Colorado and is particularly dmnaging in some years. Soil treatment with Terraclor (pentachloronitrobenzene) ( P C N B ) has been used in Colorado as an effective control measure for Rhizoctonia (2) . To provide growers with more reliable information regarding rates of application, it was necessary to understand the relation of a particular rate of Terraclor application to a measured inoculnm level in a given field soil. Boosalis, et al (1) reported a technique for measuring the potential inoculum of Rhizoctonia solani Kuehn in field soils. These workers demonstrated a correlation between the incidence of sugar, beet crown rot in a field and the percent of plant debris fragments from the soil yielding Rhizoctonia solani when plated on a culture medium. Papavizas, et al (3) employed a trapping method in which buckwheat stem segments were buried in soil to isolate R. solani. The purpose of this study was to measure the effects of Terraclor applied to the soil at various rates on Rhizoctonia inoculum densities in the soil, disease incidence and yield of potatoes.

Effect of benomyl on shoot-tip cultures from PVX-and PVS-infected potatoes

Benomyl (50% WP) at 25 and 50 ώg ai/ml was tested as a constituent of potato shoot-tip culture medium. Both concentrations increased shoot-tip growth rate when compared to a nontreated control. The 25 ώg/ml benomyl treatment significantly reduced the amount of time required for plantlet regeneration. Benomyl had no eradicative effect on potato virus X, but it appeared to exhibit a weak eradicative effect on potato virus S.