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  • Author or Editor: D. Donnelly x
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The relative salinity tolerance of three potato cultivars, including `Russet Burbank', `Kennebec', and `Norland', were compared using three in vitro bioassays (single node cuttings, root tip segments, and microtuberization) and yield data from field lysimeters irrigated with salinized water. The single-node cutting bioassay was simpler to perform than the root tip segment and microtuberization bioassays. The single-node cutting bioassay can be recommended as a substitute for more laborintensive and costly field assessments of salinity effects on yield.

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In vitro bioassays for screening and selection of salinity (NaCl)-tolerant potato have primarily focused on nodal cuttings. However, the relative tolerance of the microtuberization stage to salinized medium may be more relevant. A two-step microtuberization protocol was used in which in vitro layering was followed by microtuber induction in salinized media. `Norland', `Russet Burbank', and `Superior' shoots were layered in liquid Murashige and Skoog (1962) basal salt medium with 20 g sucrose/liter and incubated for 4 weeks at 25C with 50 μmolm–2·s–1 photosynthetic photon flux density and 16-h day/8-h night period. Medium was replaced with liquid medium containing 80 g sucrose/liter and NaCl at 0, 80, or 160 mM. Cultures were incubated for 4 weeks at 15C with 50 μmolm–2–s–1 photosynthetic photon flux density and 8-h day/16-h night period. Relative salinity tolerance of cultivars differed during the microtuberization stage. Low salinity (80 mM) stimulated, but high salinity (160 mM) depressed, microtuber yields compared with controls.

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The potato (Solanum tuberosum L.) is considered moderately sensitive to salinity stress. Yields can be adversely affected by salinity at EC levels of 2 to 3 dS·m–1. In vitro screening and selection for salinity tolerance may be faster and more reliable than traditional field assessment. A modified nodal cutting bioassay was developed based on that of Morpurgo (1991) and used to rank the salinity tolerance of several potato cultivars, wild Solanum species, and their hybrids. Nodal cuttings were cultured in Murashige and Skoog (1962) basal medium which included NaCl at 0, 40, 80, and 120 mM. After 4 weeks at 25C and 16/8 h day/night period, vegetative growth parameters were assessed. Hybrids derived from S. chacoense outperformed hybrids of other wild species, their wild parents, and S. tuberosum cultivars. `Russet Burbank' and `Kennebec' were more salinity-tolerant than the three other cultivars tested.

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Globally, salinization of agricultural soils is an increasing problem. At least 25% of the world's cultivated land area is now salt-affected. Although the potato (Solanum tuberosum L.) is among the most important of crops plants, little is known of the range of salt tolerance among cultivars of S. tuberosum, wild Solanum sp., or their hybrids. The objective of this work was to rank the salinity (NaCl) tolerance of 200 North American and European cultivars, 13 hybrids of S. chacoense, S. tuberosum, and primitive cultivated diploids (S. phureja and/or S. stenotomum) and their progenies, and 14 accessions of S. chacoense from different collection sites. This was done in vitro, using a modified nodal cutting bioassay. The parameters evaluated included shoot and root lengths, and fresh and dry weights. Extreme variation for salinity tolerance was noted among the cultivars, the hybrids, and the wild species.

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Minituber production was investigated using ex vitro `Norland' plantlets in a rockwool-based hydroponic system. Productivity was evaluated for 12- and 16-h photoperiod pre-treatment, planting density (two, four, and six plantlets/slab), vertical or horizontal orientation, pinching, and hilling. Total yield differences did not result from photoperiod pre-treatments, but 12-h pre-treatment increased the number of minitubers in the desirable 10- to 40-g size range. Increased planting density reduced yield per plant but caused small increases in yield per slab. Planting orientation, pinching, or hilling had no effect on overall fresh weight yield, number, or size distribution. Short photoperiod pre-treatment, and planting densities of four to six plantlets/slab, oriented vertically, are recommended.

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Textile fiber residues spun into small (2 to 5 mm), soft pellets (Flocagro®), through a patented process, were evaluated for horticultural use. Pellets alone and in mixtures with other substrates, were assessed using standard criteria including cation exchange capacity (CEC), aeration porosity, bulk density, and water-holding capacity. The physical and chemical properties of these textile pellets were acceptable as a horticultural growing medium when mixed with substrates such as peat; it was light-weight, had a high water-holding capacity, moderately high aeration porosity, neutral pH, low inherent fertility, low buffering capacity, and mixed easily with other substrates. The potential of Flocagro® in potting mixtures for radish and tomato seedlings and micropropagated potato plantlets was demonstrated.

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The relative salinity tolerance of 130 North American and European potato cultivars were assessed in vitro using nodal cuttings micropropagated in salinized medium. Each cultivar was evaluated twice, using five single-node cuttings, at each salt level (0, 40, 80, and 120 mM NaCl). After 1 month in culture, plantlets were destructively harvested for shoot and root lengths, fresh and dry weights, and the data corrected for differences in cultivar vigor. Multivariate cluster analysis was used to partition this population, based on the six relative growth parameters. Six cultivars were top-ranked at all salinity levels.

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Abstract

The leaf anatomy of an aseptically cultured red raspberry clone (Rubus idaeus L.) was studied before and after transfer to soil under controlled environmental conditions. Leaves of plantlets formed in culture were smaller, thinner, had a less compact arrangement of palisade and mesophyll cells, and an altered palisade cell shape compared to leaves formed on plants in soil. The number of epidermal hairs, especialy the filiform type, was lower in vitro and the distribution of colleters was affected. Trichome number was greater in new leaves formed after transplantation and greatest in greenhouse- and field-grown control plant leaves. Calcium oxalate crystals were present in the leaves of in vitro plantlets and more numerous in the leaves formed on plants in soil. Stomata were fixed open, slightly raised, and occurred on the upper leaf surface of in vitro plantlets with many on the periphery of the leaf. Amphistomatous and the peripheral stomatal condition persisted in new leaves formed during the first month when cultured plantlets were transferred to soil at 3 or 6 klx. However, new leaves, like all greenhouse and field-control plant leaves, had few adaxial stomata at 9 klx and peripheral leaf stomata were rare. Anatomy of new leaves formed during the first month after transplanting in soil at 3, 6, or 9 klx was similar to those in culture. Parenchyma tissue was less compact than in control plant leaves and palisade cell shape remained abnormal. More than half the leaves from culture died within the first month of transferring plantlets to soil. Some survived for almost 3 months. Reduced trichome numbers, almost complete lack of filiform trichomes, and presence of peripheral and adaxial as well as unprotected, open, abaxial stomata would all contribute to transplant shock and water loss in cultured plantlets transferred to soil. New leaves of transplants, formed during the first month in soil, had transitional leaf anatomy and surface features. With time, in the soil environment, the appearance of subsequently formed leaves approached that of controls.

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Abstract

CO2 uptake and various leaf parameters were examined including photosynthetic pigment content (chlorophyll a, b, and total carotenoids), fresh/dry weight, percentage of water content, gram dry weight/area, and total plantlet leaf areas of an aseptically cultured clone of red raspberry (Rubus idaeus L.) incubated at 5 light intensities, from 2 to 6 klx. Cultured plantlets demonstrated relatively low levels of CO2 uptake, averaging 2.5 mg CO2 dm–2hr–1 and rarely exceeding 4 mg CO2 dm–2 hr–1 at saturating light intensities. Pigment content was higher in plantlets incubated at lower light intensities (2 to 4 klx). Cultures incubated at 3 klx were evaluated both at the time of transfer to soil and 1 month later. Plantlet leaves retained from culture could be distinguished from new leaves by tagging all plantlet leaves prior to soil transfer; both were assessed separately 1 month after transplantation. Leaves retained from culture, 30% of the total leaf area of transplants, contributed less than 10% of the CO2 uptake at 3 klx. These leaves accounted for 10% to 30% of the total leaf area at higher light intensities but were net respirers. There was an increase in dry matter accumulation at 6 and 9 klx in these tagged leaves, but not at 3 klx. Continued accumulation of dry matter by the tagged leaves can be only at the expense of photosynthetic activity of the newly formed leaves. New leaves of transplants had a greater dry matter accumulation at 9 klx and a pigment content greater than the tagged leaves. Their pigment content was similar to that of young, control plant leaves. Transplants were capable of uptake rates of 5–7 mg CO2 dm–2 hr–1 or 50% of field control rates. The photosynthetic contribution of the leaves from culture was small or negative. The first new leaves formed in soil were transitional with intermediate capability. Acclimatization to the soil environment was time dependent and required the production of new leaves initiated in the new environment.

Open Access

The effect of successive harvests on potato microtuber yield (fresh weight and number) and size distribution in stationary liquid cultures was evaluated in cultivars Norland, Bintje, and Shepody. Harvesting microtubers successively at both 33 and 65 days, compared with a single harvest at 65 days, increased the total number of microtubers but decreased the number of larger microtubers (>0.75 g). Selective removal of Shepody microtubers >8 mm (>0.5 g) at 33 days increased the combined total number of microtubers from both harvests, but decreased the number of very large microtubers (>1.5 g). Successive harvest had no effect on total fresh weight yield, but increased overall microtuber numbers and skewed the size distribution downwards.

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