The descriptive, cultural and utilisation characteristics given in the illustrated sheets are taken from the official sheets published by GEVES for varieties registered in France.

The cultural and utilisation criteria are evaluated by comparing them with control varieties, using trials in various locations over 2 years.

    - Earliness of tuber development
    - Earliness or maturity
    - Tuber characteristics
    - Dormancy period
    - Use-related characters
    - Susceptibility to diseases, pests and physiological disorders
    - Yield

Earliness of tuber development

The scores range between 5 (= BINTJE) and 9 (= SIRTEMA). Intermediate scores indicate that tuber development is earlier than BINTJE, but later than SIRTEMA.


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Earliness or maturity

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Tuber characteristics

Skin : according to the variety, the tuber skin colour can be white (Bl), clear yellow (Jc), yellow (J), red (R), or sometimes two-tone (Bic) = yellow skin, red or purple eyes.

Flesh : its colour can be white (Bl), yellowish white (Blj), pale yellow (Jp), yellow (J) or dark yellow (Jf).


Shape :

This is defined by the Length/Width ratio of the tuber, measured on samples of tubers in the size grade 50-60 mm.

Since the "Length/Width" ratio can vary rather strongly according to the year, in particular with the climatic conditions, as well as the locality and date of the crop, it is necessary each time to compare the varieties with the following reference controls :

In the case of the long and very long varieties, account is taken of the outline : claviform (Clav), reniform (Ren), pear-shaped.

The term "variable" (Var) is employed when there is a very great scattering in "Length/Width" for tubers of the same sample.


Eye depth :

Geometrical regularity of shape :

Size of tubers :

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Dormancy period

The dormancy is the period after the harvest, during which a tuber, even when placed in an environment favourable to germination (temperature 15-20 °C; humidity higher than 90 %), remains unable to germinate.

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Use-related characters

The varieties are classified into groups A, B, C and D by taking into account mainly their degree of disintegration on cooking, the firmness of their flesh and their floury texture. If necessary, they may be placed in the intermediate groups A-B, B-C or C-D.


Group A

Potatoes with fine-textured flesh, little or no flouriness, aqueous to moderately aqueous, and not disintegrating during cooking.

Group B

Potatoes with rather fine-textured flesh, a little floury and disintegrating slightly on cooking

Group C

Potatoes with floury flesh, dry, coarse and presenting a rather marked disintegration during cooking

Group D

Potatoes with very floury flesh, dry, disaggregating almost entirely during cooking.


The firm-fleshed ware potato varieties all belong to group A; the ware varieties belong mostly to group B, and more rarely to the groups A-B, B-C or C; the starchy varieties are almost entirely in group D.

The dry matter content of the ware varieties was determined by the densimetric method on 5-kg samples taken in different comparative trials. The values thus obtained made it possible to draw up a varietal classification from the dry matter content on a scale from 1 (=very low) to 9 (very high) with extreme values of 16.5 to 27 %. Although this character can vary strongly according to the environmental conditions and the techniques of production, the classification of the varieties is generally not disturbed. The content of dry matter of the tubers partly influences the culinary and processing characteristics of the varieties.

Blackening after cooking (greying of the flesh) appears especially when tubers are cooked in water or steam, and are then peeled or cut and left exposed to the air. The susceptibility of the varieties is mainly determined by comparison with ACKERSEGEN and CLAUSTAR controls (fairly well marked) and BINTJE (nil).

Discoloration during frying is judged more particularly according to the aptitude for crisping. For varieties having the best aptitude for frying, information is given on the respective page. For the others, NTR (nothing to report) indicates a low to medium aptitude.

The keeping quality (aptitude for storage) is graded from 1 to 9 (a score of 5 is allotted to BINTJE). high scores characterize those varieties with a good to very good keeping quality, i.e. a late germination, weak development of sprouts, reduced loss of weight and little deterioration of quality (absence of black spots and excessive sweetening). This character is particularly interesting in the mid-season varieties, especially if they cannot be kept in ventilated or refrigerating stores. More generally, however, the varieties with scores lower than 4 are often more difficult to maintain in long storage.

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Susceptibility to diseases, pests and physiological disorders

The susceptibility is graded by comparison with a range of control varieties exhibiting various degrees of susceptibility.

For black wart, a score of 9 is attributed to the varieties not attacked during infection tests; a score of 2 is given to varieties reacting by medium to large-sized scabs (BINTJE type). In this book, the varieties scored at 7 are described as slightly susceptible, while all the others are susceptible.

For the potato cyst nematode (Globodera rostochiensis), the codes R and (r) mean resistant and very slightly susceptible to the pathotype RO 1-4.

NTR (nothing to report) means absence of information.

The susceptibility to blight is a character likely to evolve, particularly in varieties possessing type-R monogenic resistance, by the appearance of parasite strains able to overcome this resistance. The scores allotted to certain rather old and intensely cultivated varieties are probably over-estimated.

The susceptibility to desprouting (= susceptibility to incubation and/or speed of incubation) is graded, just like the diseases, on a scale from (1 = very susceptible) to 9 (very slightly susceptible). A strong susceptibility to desprouting characterizes certain varieties that, in practice, are qualified as delicate. More than others, these require great care in the storage and preparation of their seed potatoes, as well as with the soil preparation before plantation.

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Yield

The yield is evaluated for each class of maturity and in each category of varieties compared to the reference controls chosen from the most cultivated or most representative varieties. It is then expressed in the following way:

Varieties registered before 1995

For the early, medium-early, medium and medium-late varieties, the yield is expressed compared to the reference control BINTJE (index = 100); the late varieties are compared to the control KERPONDY (index = 100).

For the starch varieties, a starch yield index of 100 is given by the control KAPTAH VANDEL. The starch yield was obtained by multiplying the tuber yield by the average content of starch determined using the feculometer (densimetric method) in the same trials.


Varieties registered since 1995

On the illustrated pages, the yield is expressed as a percentage of the official control during the two years of CTPS experimentation preceding the year of registration (example: 107 % of (SIRTEMA+ OSTARA)/2 - Years 1999 and 2000 for an early to medium-early ware variety registered in 2001). In the summary tables, the index compared to the controls BINTJE and KAPTAH VANDEL corresponds to a value estimated by the ITCF.

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