Janet E. A. Seabrook

Effect of photoperiod on in vitro tuberization of potato (Solanum tuberosum L.)

Single-node cuttings of potato cultivars ‘Jemseg’, ‘Katahdin’, ‘Russet Burbank’ and ‘Superior’ were cultured on a multiplication medium containing MS salts and no growth regulators. Cultures were exposed to 8 h (SD) and 16 h (LD) photoperiodic regimes. The subsequent plantlets were excised and single node cuttings from each photoperiodic regime were placed under SD or LD on a second medium containing growth regulators which promoted tuberization. Production of microtubers was strongly influenced by genotype and by photoperiodic treatments. ‘Superior’ produced stunted plantlets and some microtubers under SD conditions in the multiplication medium. The number of microtubers formed by ‘Jemseg’ was not influenced by photoperiod. However, ‘Katahdin’ and ‘Russet Burbank’ formed fewer microtubers under LD-LD conditions compared to LD-SD, SD-SD and SD-LD regimes. Compared with the other regimes, LD-SD photoperiod generally promoted microtuber formation with larger diameters and significantly (p<0.05) greater fresh weight. The intensity of the tuberization stimulus was affected by daylength, and this was characterized by microtubers with secondary tubers, the growth of more than one axillary microtuber, and microtubers subtended by stolons. The maturity group of the potato cultivars and photoperiodic regime in vitro strongly influenced the production of microtubers. These results can be employed to adapt light regimes for multiplication and tuberization to the specific requirements for cultivars from different maturity groups, and thus increase the efficiency of potato multiplication protocols.

Microtuberization of layered shoots and nodal cuttings of potato: the influence of growth regulators and incubation periods

A protocol is presented for the rapid induction of microtubers on micropropagated, layered potato shoots of ‘Kennebec’, ‘Russet Burbank’ and ‘Superior’ in medium devoid of growth regulators. Layered shoots microtuberized more rapidly and produced significantly larger microtubers compared with nodal cuttings. The addition of coumarin or (2-chloroethyl)-trimethylammonium chloride and benzyladenine to microtuberization medium, either had no effect or significantly reduced microtuber weight per shoots compared with medium containing only 80 g × 1-1 sucrose and minimally affected the number of microtubers per shoot. Increasing the incubation period from 28 to 56 days did not affect the number but significantly increased the weight of microtubers per shoot and substantially increased the proportion, up to 20%, of microtubers heavier than 1 gram.

Light effects on the growth and morphogenesis of potato (Solanum tuberosum) in vitro: a review.

Growth, morphogenesis, and tuberization of potato tissuesin vitro are affected by light. Measurements of the various aspects of light that control development and growth of potato are outlined. Physical parameters like light sources, delivery of the light source, and the degradation of culture media by light are discussed. Irradiance, photoautotrophic growthin vitro, spectral wavelength, and photoperiod modify the responses of potato tissues in culture. Acclimatization of tissue culture plantlets, vegetative growth, and the production, quality, and dormancy of microtubers are modified by light. New light sources such as light-emitting diode (LED) lamps are becoming available forin vitro research and for micropropagation of potato. Pulsed or chopper light has the potential to save energy costs. Light effects on potato protoplasts, anther culture, virus eradication, andin vitro conservation are discussed. Potential new research areas are the effect of the spectral quality of light on regeneration of shoots and somatic embryosin vitro, end-of-day red and far-red light treatments, axillary shoot formation in cultured plantlets, and the use of LEDs. The influence of monochromatic spectral filters on growth and development of potatoes in tissue culture could potentially lead to improvements in productivity. The relationship between daily quantum light integral and photoperiod and their effects on growth and morphogenesis of the potato will provide some useful areas of research.ResumenLos procesos de crecimiento, morfogénesis y tuberización de los tejidos de papain vitro son afectados por la luz. Mediciones de los varios aspectos de la luz que controlan el crecimiento y desarrollo de la papa son delineadas. Parámetros físicos tales como la fuente de luz, difusión y su efecto en la degradación del medio de cultivo son discutidos. La irradiación, el crecimiento foto-autotróficoin vitro, la longitud de onda espectral y el foto período modifican las respuestas de los tejidos de la papa en cultivo. La aclimatación de las plántulas de cultivo de tejidos, crecimiento vegetativo y producción, calidad y dormancia de los microtubérculos son modificadas por la luz. Nuevas fuentes de luz como aquella emitida por las lámparas de diodo (LED) están siendo disponibles para la investigaciónin vitro y la micropropagación de la papa. La luz intermitente tiene el potencial de ahorrar los costos de energía. Los efectos de la luz sobre los protoplastos de papa, cultivo de anteras, erradicación de virus y conservaciónin vitro son discutidos. Nuevas áreas potenciales de investigación son, el efecto de la calidad espectral de la luz sobre la regeneración de los brotes y los embriones somáticosin vitro, tratamientos con luz roja del final del día y del lado lejano del espectro infrarrojo, formación axilar de brotes en plántulas cultivadasin vitro y el uso de LEDs. La influencia de los filtros espectrales monocromáticos sobre el crecimiento y desarrollo de plántulas de papa en cultivo de tejidos podría potencialmente conducir a un mejoramiento en la productividad. La relación entre la cantidad diaria de luz integral y foto período y sus efectos sobre el crecimiento y morfogénesis de la papa proporcionarán algunas áreas útiles de investigación.

Segregation for somatic embryogenesis on stem-internode explants from potato seedlings

Differences in productivity for somatic embryos (SEs) in vitro among 18 potato cultivars and three wild Solanum species in an earlier study led to the hypothesis that regeneration of SEs may be under genetic control. To examine this possibility, three test crosses were initiated; Coastal Russet×AF 186-2; Costal Russet×Lenape; AF 186-2×Lenape. True potato seedlings from these crosses were germinated in vitro. Five stem internode explants from each seedling were excised and cultured on two successive media to promote the formation of SEs. Seedling explants Costal Russet×AF 186-2 cross produced more SE than the other two crosses, and explants from the AF 186-2×Lenape cross generally only produced <10 SEs per explant. SEs were produced on the stem-internode explants from the three crosses at different rates. Data for the number of explants producing SEs and numbers of SEs per explant were highly significant. Regeneration of SEs is probably under nuclear control and the inheritance for regeneration may be quite straightforward.

Prevention of stem growth inhibition and alleviation of intumescence formation in potato plantletsin vitro by yellow filters

Potato (Solanum tuberosum L.) cvs. AC Brador and Shepody grownin vitro exhibit plantlets with a short, rosette-type growth habit, and restricts multi plication rates. In contrast, Russet Burbank develops into plantlets with adequate internode lengthin vitro. Cool-white fluorescent lamps provided irradiation for wooden boxes fitted with yellow plexiglass filters. The resultant irradiation lacked wavelengths from 380 to 525 nm. A box fitted with clear plexiglass was the control. Internode length of plantlets was ca.1.0 cm for all three cultivars when grown in boxes with yellow filters, and was 0.5 cm when clear filters were used. The number of nodes, haulm area, stem length, haulm fresh and dry weight of cvs. AC Brador and Shepody were significantly greater in boxes with yellow filters. Potato cvs. AC Belmont, Eramosa, Hunter, Huron, Mirton Pearl, Raritan and York all have a short growth habitin vitro and stem length was increased by the use of a yellow filter. The incidence of intumescences or oedemas on leaves of potato plantletsin vitro was reduced from 60 to seven percent for AC Brador and from 70 to 10% for Shepody with the use of yellow filters. Blue-green light is therefore putatively involved in the occurrence of intumescences on potato tissuesin vitro.

Photoperiodin vitro affects subsequent yield of Greenhouse-grown potato tubers

In vitro potato plantlets of cultivar (cv.) Shepody (Solatium tuberosum L.) were exposed to 12-or 16-hr photoperiods for 8 weeks. Plantlets were acclimatized to the greenhouse and grown under 14-hr photoperiods until they senesced, and minitubers were harvested. Greenhouse-grown potato plants developed from tissue-culture plantlets exposed to a 16-hr photoperiod were taller and had more nodes than plants developed from plantlets exposed to 12-hr photoperiods. However, yield data of minitubers from greenhousegrown plants indicated that the 12-hr photoperiodic treatment increased the numbers, dry weight and specific gravity of minitubers. A further advantage of the 12-hr photoperiodic treatment was the greater numbers of minitubers in the 15–40 g size class compared with tubers in the <15 g and >40 g size classes. Thus, for the cv. Shepody, plant height and node number of greenhouse-grown plants were not good indicators of minituber yield from that crop. Seed potato nuclear stock facilities producing minitubers should investigate the possibility of optimizing minituber production by exposing multiplication cultures to shorter daylengths.CompendioPlantitas in vitro de papa del cultivar (cv.) Shepody (Solatium tuberosum L.) fueron expuestas a fotoperiodos de 12 o 16 hr, por ocho (8) semanas. Las Plantitas fueron aclimatadas al invernadero y crecieron bajo fotoperiodos de 14 hr hasta su senescencia, cosechándose sus tuberculillos. Las plantas que crecieron en el invernadero, desarrolladas de plantitas procedentes de cultivos de tejidos expuestos a fotoperiodos de 16 hr, fueron mas altas y tuvieron más nudos que las plantas desarrolladas de plantitas expuestas a fotoperiodos de 12 hr. Sin embargo, la información sobre el rendimiento en tuberculillos de las plantas que crecieron en el invernadero indicó que el tratamiento fotoperiódo de 12 hr incrementó el número, el peso seco y la gravedad específica de los tuberculillos. Una ventaja adicional del tratamiento fotoperiódico de 12 hr fue el mayor número de tuberculillos en la clase del tamaño de 15–40 g, en comparación con los tubérculos en la clase de los tamanos <15 y >40 g. Por lo tanto, para el cv. Shepody, la altura de planta y el número de nudos de las plantas mantenidas en invernadero no fueron buenos indicadores del rendimiento en tuberculillos de ese cultivo. Las instalaciones de existencias nucleares de semilla de papa produciendo tuberculillos deben investigar la posibilidad de optimizar la producción de tuberculillos exponiendo los cultivos de multiplicación a longitudes de día más cortas.

Screening diploidSolarium genotypes responsive to different Anther culture conditions and ploidy assessment of Anther-derived roots and plantlets

Twenty-three diploid (2n=2x=24) potato clones were screened for response to four different anther culture media. Anther derived tissues (calli/embryos) were obtained from seven of the clones in liquid culture media. Anther culture response of these seven clones was further quantified on five additional media. Since clonal responses are specific to culture conditions (Tiainen, 1992), the seven genotypes somewhat differed from each other in the magnitude of the response to each of the media. In agreement with Heberle-Bors (1985) a more realistic assessment of the responsiveness was possible when pollen counts per anther were used to express the yield of anther-derived material. A relatively higher level of exogenous cytokinin (6-benzyladenine) to that of auxin (3-indoleacetic acid) proved to be favourable for the inducton of calli/embryos. Use of a semi-solid medium saved space and was convenient for culture observations therefore it was found more conducive for the genotypic screening. Anther derived tissues that regenerated to produce root tissue and/or plantlets were further multiplied on a root culture medium and a plantlet medium. Liquid culture conditions on orbital shakers were conducive for the growth of root explants. Anther derived material (roots and plantlets) originating from clone 9507–04 revealed differences in growth vigor. Flow cytometric estimation of ploidy in regenerated roots and plantlets, revealed that clone 9507–04 produced 44% monoploid roots and 77% monoploid plantlets. Seventy-three percent anther-derived plantlets from clone 6028–02 were monoploids.

Reduction in vigour of leafless potato cuttings in vitro

SummaryRemoving the leaves from single node potato cuttings in vitro allows propagules to be placed in culture vessels at increased densities with the intent of saving resources and space. Under light intensities of 22 wattsm−2, the removal of the subtending leaf resulted in fewer nodes, shorter plantlets, smaller leaf area, and lower fresh and dry weights of 4-week-old plantlets of cvs Atlantic, Kennebec, Russet Burbank and Shepody. Fewer nodes and reduced plantlet height may result in inefficient multiplication protocols because fewer propagules are available and shorter internodes make dissection more difficult. The coefficient of variation for the various growth parameters was greater when propagules lacked leaves, indicating that the variability of the plant material for propagation was increased. A reduction of vigour and growth was still evident when plantlets of cv. Shepody were grown for 6–8 weeks.

Effect of leaves on microtubers produced from potato single-node cuttingsIn Vitro

Microtubers are used to propagate, to store, and to transport potato clones. Culturing single-node explants from potato plantletsin vitro without subtending leaves was reported to result in plantlets with lower vigor and a higher coefficient of variation. The effect on microtuber productionin vitro of leaf area and the presence or absence of leaves on potato single-node cuttings was investigated as an extension of the above study. Stock plantlets of potato cvs Atlantic, Kennebec, Russet Burbank, and Shepody were cultured under a 16-h photoperiod. Single-node cuttings were excised and grown in a high-sucrose tuberization medium in darkness. Leaf area did not affect the frequency, size, or weight of microtubers of cvs Katahdin and Russet Burbank. The absence of leaves reduced microtuber diameter for Russet Burbank; whereas Atlantic, Kennebec, and Shepody were unaffected. Mean fresh weight of microtubers was reduced when leaves were removed for all cvs except Atlantic. No effect of the removal of the leaf was observed for mean dry weights of microtubers from all cvs, although microtubers from single-node cuttings without leaves accumulated significantly more percent dry matter than those with leaves. Rapid multiplication facilities may therefore wish to consider conserving resources such as media, vessels, and growth room space by culturing explants without leaves for the production of microtubers.ResumenLos microtubérculos se usan para propagar, almacenar y transportar clones de papa. Se ha reportado que cultivando explantas de un solo nudo, a partir de plántulas de papain vitro sin hojas subtendidas da como resultado plántulas con poco vigor y un alto coeficiente de variación. Como una extensión del estudio anterior se investigó el efecto sobre la producción de microtubérculosin vitro, de área foliar y la presencia o ausencia de hojas en esquejes de un solo nudo. Plántulas de papa de los cultivares Atlantic, Kennebec, Russet Burbank y Shepody se cultivaron a 16 horas de fotoperiodo. Se cortaron esquejes de un solo nudo y se pusieron a crecer en un medio de tuberización con alto contenido de sucrosa y en oscuridad. El área de hoja no afectó la frecuencia, tamaño o peso de los microtubérculos en los cultivares Katahdin y Russet Burbank. La ausencia de hojas redujo el diámetro de los microtubérculos en Russet Burbank, mientras que Atlantic, Kennebec y Shepody no fueron afectados. Cuando se eliminaron las hojas no se observé reducción en el promedio de peso seco de los microtubérculos en ninguno de los cultivares, aunque los microtubérculos provenientes de esquejes de un solo nudo y sin hojas acumularon mayor porcentaje de materia seca que aquellos con hojas. Por lo tanto, para una multiplicación rápida es deseable considerar los recursos de conservación, tales como medios, envases y cámara de crecimiento para el cultivo de explantas sin hojas para producción de microtubérculos.

Optimizing the propagation of potato (Solanum tuberosum L.) by stem cuttings

Stem cuttings from potato plants are frequently used in multiplication programs for disease-free cultivars. The survival of these leafy cuttings is often very poor, and thus various techniques were investigated which were designed to increase rooting and cutting survival. Stock plants of cultivars “Caribe,” “Jemseg,” “Keswick,” “Russet Burbank,” “Sable,” “Sebago” and “Shepody” were grown in the greenhouse under long days. Promoting growth of the axillary shoots was successfully achieved by shading the shoot apex with aluminum foil. Trimming the outer leaves of the cuttings was deleterious to both survival and rooting. A rooting hormone improved root initiation and development, and the use of shade cloth or intermittent mist increased survival by reducing wilting. A rooting substrate of vermiculite: perlite (1:1) provided sufficient aeration, support and drainage for the cuttings. Antitranspirants sprayed on the stock plants prior to the excision of cuttings and also on the excised cuttings did not improve rooting or survival. The addition of activated charcoal (1% w:w) increased rooting of the cuttings and improved vigor of potted plants obtained from the cuttings.