Notes on Descriptions and Data of Accelerated Release Selections

These notes provide information on evaluation procedures, observations and rating scales referred to in describing the characteristics and performance of the Accelerated Release selections. The short descriptive text of each selection is based on limited data and observations and as such provides a guide to performance rather than a definitive description.

Most selections have been evaluated at the Benton Ridge Potato Breeding Substation, New Brunswick, in 50 hill and 100 hill non-replicated plots. Selections have also been evaluated in replicated plots in a National Trial with locations at Bloomfield, New Brunswick (New Brunswick trial location varies with the year), Charlottetown, Prince Edward Island, Elora, Ontario, Brooks, Alberta, Carberrry, Manitoba, Winkler, Manitoba and Outlook, Saskatchewan. The Tables provide the specific locations, years and the standard cultivars for each selection. Within row spacing varied with standard cultivar and selection, otherwise all entries at each location have been evaluated under the standard management practices for that location.

Performance Evaluation

Plant vigour and haulm maturity are both scored on a 1-9 scale which is related to standard cultivars. Atlantic and Shepody are considered to have moderate vigour and Kennebec to have strong vigour. Superior and Yukon Gold are considered to have midseason maturity, Kennebec to have late maturity and Russet Burbank to have late to extremely late maturity.

Tuber size is rated on the average size of the field run tubers on a scale of 1 to 9 where 5 = typical Atlantic or Superior (medium size), 6 = typical Russet Burbank, 7 = typical Kennebec or Shepody.

Tuber length to width ratios (L:W) used to describe tuber shape are calculated from measurements of 10-12 representative tubers.

Tuber number notes are based on general observations plus counts from one trial location, and are reported relative to Kennebec (medium), Chieftain (medium-high) and Russet Burbank (high).

Eye depth is recorded at grading on a 1-9 scale which is related to standard cultivars. Kennebec and Russet Burbank are considered to have intermediate depth eyes and Atlantic and Superior to have deep eyes.

Colours: In addition to a descriptive designation for skin and flesh colour, standard colour charts published by the Royal Horticultural Society (RHS) are used to describe colours as viewed under a north light.

Grades are based on the Agriculture Canada Products Standards Act, Fresh Fruit and Vegetable Regulations and yields are reported in metric tonnes per hectare:

Grade Round Long
Canada #1 57.2 - 88.9 mm
(2.25 - 3.5 in)
50.8 - 88.9 mm
(2.0 - 3.5 in)
Canada #1 large 88.9 - 114.3 mm
(3.5 - 4.5 in)
88.9 - 114.3 mm
(3.5 - 4.5 in)
Small 38.1 - 57.2 mm
(1.5 - 2.25 in)
38.1 - 50.8 mm
(1.5 - 2.0 in)

Tabulated Marketable Yield = Canada No. 1 + Large
Culls include tubers smaller than and greater than marketable grade, plus defects.

Defects, including greening, growth cracks, shatter cracking, bruising, skinning, hollow heart and sensitivity to herbicide, are recorded when they are observed in evaluation plots. When observed across several evaluation sites, or are severe at a single site, such defects are reported in these notes. Tubers are cut and internal defects noted at the Benton, Charlottetown, Elora and Winkler evaluation sites; a total of about 40 tubers are cut.

Skinning and bruising are evaluated at Benton Ridge using a standard procedure to damage tuber samples in a rotating barrel. Skinning and shatter cracking are recorded immediately after the treatment. Bruising is evaluated following about seven days storage when a tuber sample is peeled and the number and size of the bruises recorded. A randomly selected 5 tuber sample is assessed for bruise injuries and grouped into three classes according to the size of injuries (< = 1/4 inches (") is mild, 1/4 - 1/2" is moderate and >1/2" is severe). Each class is given a score number as follows: 1 = mild; 3 = moderate and 5 = severe. The percentage bruise score index is then estimated as the sum for all classes of [(the number of tubers in that class × the class number) × 100]÷(5× total number of tubers rated). The maximum (if all tubers are classed in the severe category) is 100.

Dormancy is assessed on a 20 tuber sample stored at 10°C and rated weekly for the number of tubers having apical sprouts greater than 3 millimeters (mm). These values are compared to standard cultivars. In most cases performance is based on results of two years.

Quality Testing

The majority of the quality tests are from the potato breeding program quality laboratory at the Potato Research Centre. Sample tubers are selected with specific gravities similar to the sample mean. Samples are evaluated by trained panelists.

Specific gravities are determined by the weight-in-air, weight-in-water method.

Boil scores combine evaluations of sloughing, appearance, texture, off-flavour, and discolouration; bake scores combine evaluations of appearance, texture, off-flavour and discolouration. Scores have a maximum value of 100 and are interpreted according to the scale:

Boil Bake Score Rating
Boil Bake Quality
<50 <55 Unacceptable
50-60 55-65 Fair
60-70 65-75 Good, relatively moist texture
>70 >75 Good, relatively dry texture

The French fry tests are conducted on a small sample and should be interpreted as showing potential performance only. Samples include slices from the outside and inside areas of the tubers. The preparation involves a hot water blanch, par fry, quick freeze and final fry. Samples are fried from storage at 13°C in December and February, and from storage at 7°C without reconditioning in December and February. Scores combine evaluation of the overall appearance of the entire sample, the external colour of the slices, the internal colour of the slices, and the texture of outside and inside slices. Scores have a maximum value of 100 and are interpreted according to the scale below. Scores of these clones are considered to be generally similar to or better than those of the check varieties.

French Fry Tests
Score Quality
<55 Poor
55-65 Moderate
65-80 Good
>80 Excellent

Chip tests are also conducted on a small sample and should be interpreted as showing potential performance only. For the New Brunswick trial sites, slices are fried from storage at four storage regimes (December at 7°C and 13°C, and February at 7°C reconditioned at 21°C for 4 weeks, and at 13°C). They are scored against Agriculture and Agri-Food Canada chip colour cards on a 100 point scale where scores of 60 and above are generally acceptable.

New Brunswick Chip Tests
Score Quality
<50 Poor
50-70 Moderate
70-80 Good
>80 Excellent

For the Ontario, Alberta, and Manitoba sites, samples consist of 5-8 average sized marketable tubers stored at 10°C for up to 2 months. Slices (1.0 mm thickness ) from five tubers were mixed and fried in vegetable oil (canola) at 190°C (375°F setting) and chips removed when bubbling ceases. After frying, chips cooled and colour measured using Agtron-Model E15FP, on 0-100 scale (higher value indicates lighter colour).

Total Glycoalkaloids: All selections have been tested for glycoalkaloids and all fall below the threshold of 20 milligrams (mg)/100 gram fresh weight as required for registration in Canada.

Disease and Pest Resistance Evaluations

All Accelerated Release selections have been evaluated for resistance to Common Scab. For other diseases and the golden nematode, resistance has been evaluated for only some of the selections. In some cases testing is decided on the basis of the known characteristics of the parents. All disease and pest resistance information should be considered preliminary since it is based on limited evaluation.

Common scab observations are based on 2 or 3 years of results from a severe test in a field with high inoculum levels. The index score is a value on a 1-9 scale with 9 being extremely susceptible. The susceptible check, Green Mountain, usually has a value of 8. The maximum surface covered by scab is recorded.

Wart tests are conducted in Newfoundland and Labrador. Selections are grown in soil infested with a mixture of races of Synchytrium endobioticum. At harvest the stolons and tubers are examined for the presence of wart. Arran Victory in the susceptible check.

Golden nematode resistance. Selections are also assessed for the presence or absence of a molecular marker associated with resistance to Ro1.

Late blight foliar test. Three whole plants per selection are inoculated with an aqueous solution of sporangia and zoospores of A2 mating type 5-6 weeks after planting. Disease development is estimated at 7 and 10 days post inoculation. Standard checks are used for comparison of disease progression.

Potato virus Y, O strain (PVYO), Potato virus X (PVX). Three plants are subjected to mechanical inoculation of the viruses in a greenhouse test conducted at the Potato Research Centre. Symptom expression and Enzyme-linked immunosorbent assay (ELISA) tests are used to detect infection. Selections that test negative twice by mechanical inoculation are subjected to graft inoculation. Those that remain free from virus in graft inoculations are designated extremely resistant. Entries, such as Kennebec, that usually resist mechanical inoculations are designated resistant.

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