Kenneth B. McRae

An efficient in vitro shoot propagation of cranberry (Vaccinium macrocarpon ait.) by axillary bud proliferation

SummaryCultures of two eranberry (Vaccinium macrocarpon Ait.) cultivars, ‘Ben Lear’ and ‘Pilgrim’, and three eranberry clones from natural stands in Newfoundland were established in a nutrient medium containing N6[2-isopentenyl]adenine (2iP) from nodal and/or shoot-tip explants obtained under aseptic conditions. The cultivars differed in shoot regeneration in terms of shoot number per explant with various concentrations of 2iP over two culture periods. Best total shoot production was obtained when nodal segments were cultured in the medium supplemented with 2.5–5.0 mg 2iP l−1 (12.3–24.6 μM). With higher 2iP levels, shoots did not expand and had a high mortality rate. Nodal explants of the three clones cultured in the same nutrient medium supplemented with 2.5 mg 2iP l−1 (12.3 μM) produced three to five healthy axillary shoots per explant. In another experiment, nodal explants were more productive than shoot tips. In all experiments with subculture, there was an increase in shoot multiplication rate for all genotypes. Shoots were rooted in vitro in the same media used for shoot proliferation, but without any growth regulators. After their transfer to potting medium, almost all of the rooted plants survived. Cranberry genotypes can be efficiently propagated and maintained through nodal culture in a nutrient medium without auxin that contains 2.5–5 mg 2iP l−1 (12–25 μM).

Reduction in potato growth at high temperature: role of photosynthesis and dark respiration

The relationship of photosynthesis and dark respiration to reduced potato growth at temperatures above 20°C was determined. Ten potato clones were propagated in vitro from sterile plandets and grown in a growth chamber at 20/15°C and 30/25°C (day/night) with an 18 hr. daylength. Plants were harvested 26 to 30 days after transplanting. Daylength was decreased to 12 hrs. to induce tuberization and plants were harvested at 45-51 and 75-79 days after transplanting. At each harvest one plant from each cultivar was chosen from each of five blocks and selected growth (tuber number and dry weight of leaves, stems, roots and stolons, and tubers) and physiological variates [leaf area, net photosynthesis, maintenance dark respiration, and chlorophyll fluorescence parameters 0 (Initial), P (Peak), T (Terminal), P-O (Variable fluorescence) and P-T (Fluorescence quenching)] were measured. The high temperature decreased root and stolon, tuber and total dry weight and increased stem dry weight. Amongst physiological variates, the higher temperature decreased leaf area, net photosynthesis and maintenance dark respiration. The chlorophyll fluorescence parameter 0 significantly increased, which also increased the P and T parameters. Variable fluorescence (P-O) and fluorescence quenching (PT) were not significantly affected by the growth temperature. The analyses of covariance, in which physiological variates were used as covariates to remove significant differences in growth variates, indicated that the most effective covariate was the T chlorophyll fluorescence parameter. The least effective covariates were leaf dark respiration and the chlorophyll fluorescence parameters P-O and P-T. The changes in 0 fluorescence suggest that reduced photosynthetic efficiency, particularly in Photosystem II, plays a major role in reduced potato production at high temperatures.

In Vitro Culture of Lingonberry (Vaccinium vitis-idaea L.)

Abstract Shoots of three lingonberry (Vaccinium vitis-idaea L.) cultivars, ‘Regal’, ‘Splendor’, and ‘Erntedank’ and two clones from natural stands in Newfoundland were initiated in vitro from shoot tip and nodal explants on modified Murashige and Skoog (MS) medium containing the plant growth regulators N6-[2-isopentenyl]adenine (2iP) (12.3 μM) or zeatin (5.7 μM). Zeatin was more effective than 2iP, and induced proliferation of 2 to 3 times as many shoots in ‘Regal’ as 2iP. Out of four media tested for shoot proliferation, modified MS medium was found more effective than the Woody Plant Medium for shoot multiplication. With all three cultivars, a reasonable balance in terms of shoot multiplication rate and desirable growth characteristics was attained in a new medium. Nodal explants of the two clones cultured on the modified MS medium with 12.3 μM 2iP produced 4 to 6 healthy axillary shoots per explant in clone 1 and 2 to 4 shoots in clone 2. Shoots rooted well ex vitro directly on a 2 peat: 1 perlite (v/v) medium after dipping in 39.4 mM indole-3-butyric acid. The new protocol proposed from this study is expected to be adapted for propagating a wide range of lingonberry germplasm.

Gaseous ozone treatment inactivates Listeria innocua in vitro

Aims:  To investigate the effects of ozone on inactivation of Listeria innocua on solid media.

Lowbush blueberry quality changes in response to prepacking delays and holding temperatures

The quality of stored wild lowbush blueberries (Vaccinium angustifolium Ait. and V. myrtilloides Michx.) was examined with different prepacking temperatures (5, 12, 19, and 26°C), delay times (3, 9, 21, and 45 h), and subsequent storage times (7, 14, and 21 d) at 0°C. All factors were considered both individually and in combination. Quality after storage was defined by changes in ten attributes: split berries, bloom, firmness, weight loss, moisture, soluble solids, titratable acids, pH, microbial counts, and marketable berries. We concluded that when there is minimal impact damage during packing and berries are stored at 0°C, cooling before packing is beneficial only when the delay time exceeds 21 h. Precooling creates severe condensation problems during the subsequent packing at ambient temperatures. Minimizing delays is the best option for maximizing fresh lowbush blueberry quality.

An efficient adventitious shoot regeneration system on excised leaves of micropropagated lingonberry (Vaccinium vitis-idaea L.)

Summary An efficient system to regenerate shoots in vitro on excised leaves of lingonberry (Vaccinium vitis-idaea L.) was developed. Leaf explants from shoot-proliferating cultures produced multiple shoots without an intermediary callus phase on zeatin (ZN)-containing shoot induction media within 3–4 weeks of culture initiation. Cultivars Regal and Splendor, and one clone from a natural stand in Estonia (ECL1), were used in the first experiment. Young expanding leaves with the adaxial side touching the culture medium, and maintained for 7 d in darkness, produced the best results. There were significant genotypic differences in adventitious shoot formation. A second experiment studied the effects of ten concentrations of three cytokinins: ZN at 5, 10, 20, 30 and 40 μM; 1-phenyl-3-(1,2,3-thiadiazol-5-yl) urea (thidiazuron, TDZ) at 0.1, 1, 5 and 10 μm; and 6-(γ-γ-dimethylallylamino) purine (2ip) at 25 μM were compared with leaf segments of different polarity in ‘ECL1’. Zeatin was found to be more effective than TDZ or 2iP as an inductive signal for regenerating many vigorous shoots. Zeatin induced multiple shoot formation at all concentrations tested, but maximum morphogenic response was observed at 20 to 30 μM. The media containing TDZ generally promoted more callus formation and suppresed shoot elongation. In a third experiment with the lingonberry cultivar Erntedank and the clone ‘ECL1’, a new medium developed for lingonberry shoot culture proved more effective than the modified Murashige and Skoog medium for regenerating shoots on leaf explants. Elongated shoots were excised and rooted directly on a 2 peat:1 perlite (v/v) medium after dipping in 0.8% indole-3-butyric acid. Rooted plantlets were acclimatized under greenhouse conditions to evaluate somaclonal variation.

Comparison of a new apple firmness penetrometer with three standard instruments

Abstract The performance of a newly developed firmness penetrometer (fruit quality tester — FQT), was evaluated over two growing seasons with poststorage apples against the Effegi, Magness-Taylor (MT) and electronic pressure tester with the speed control engaged (EPT-SC). The FQT was operated in the: (a) standard (FQT-Std); (b) MT (FQT-MT); and (c) EPT (FQT-EPT) modes with the latter two simulating the operation of the MT and EPT-SC devices, respectively. ‘Cortland’, ‘McIntosh’ and ‘Northern Spy’ fruit were stored for 3–14 months in controlled atmosphere (CA) conditions and were then held at room temperature for 1–7 days, following which firmness was measured by four operators with each of the six instruments or modes. The ten cultivar/storage/poststorage fruit lots were designated as either hard or soft if the poststorage firmness average for the lot was ≥ or

A One-Step In Vitro Cloning Procedure for Cranberry (Vaccinium macrocarpon Ait.)

Abstract An in vitro cloning protocol that enables shoot proliferation and rooting of cranberry (Vaccinium macrocarpon Ait.) genotypes in the same medium was developed. Plantlets of four clones (NC197, NC201, NC216, and NC230) from natural stands in Newfoundland and Labrador and one cultivar, Stevens, were obtained in vitro from nodal explants on a nutrient medium containing the plant growth regulators, N6-[2-isopentenyl]adenine (2iP) or zeatin. Zeatin was more effective than 2iP for shoot proliferation and rooting. The genotypes differed in terms of shoot and root number per explant, length and vigor, number of leaves per shoot, and callus formation at the base of explants; this was manifested with various concentrations of 2iP and zeatin over two culture periods. Shoots proliferated and roots developed best when nodal segments were cultured in the medium supplemented with 2 μM to 4 μM zeatin. Subculturing improved the number of shoots and roots per responding explant, shoot height, root length, and root vigor. Changing the positioning of explants on the medium from vertically upright to horizontal increased shoot number and callus size, but decreased the rooting incidence, roots per explant, and root vigor. The protocol proposed from this study is expected to be applicable for propagating a wide range of cranberry germplasm.

Genetic variability of principal isoflavones in red clover

Isoflavones, known for their health benefits, are abundant in red clover (Trifolium pratense L.). Total isoflavone concentrations can be 30 times that of soybean, indicating that red clover is a good source of nutraceutical and functional food ingredients. In this study, tissue samples of 13 red clover cultivars were taken at two growth stages (late-bud stage and late-flowering stage) to determine the concentration of individual isoflavones using HPLC. Individual isoflavone concentrations and total isoflavone concentration differed significantly according to red clover cultivar. We found significant genetic variability for total isoflavone concentration and individual isoflavone concentrations; these differences were not related to ploidy level (diploid vs. tetraploid). Broad-sense heritability (H = genetic variance/total variance) ranged from 0 to 83% and was influenced by isoflavone type and sampling date. The results of this study suggest that there is significant genetic variability for isoflavone con...

Tapani red clover

Tapani is a 21-clone diploid synthetic cultivar of red clover (Trifolium pratense L.). It was developed by phenotypic selection at Agriculture and Agri-Food Canada, Crops and Livestock Research Centre, in Charlottetown, Prince Edward Island, and at the Soils and Crops Research and Development Centre in Quebec City, Quebec. The original material for this strain was selected from collections made in old stands of red clover in three Atlantic Provinces of Canada. Tapani is early flowering and winterhardy. In Atlantic Canada, Tapani yielded an average of 109% of the check cultivar Marino over three production years. This cultivar has superior re-growth potential with high second-cut herbage yield. Key words: Red clover, Trifolium pratense L., cultivar description