Potato evaluation methods

Summary of available evaluation results

incl. a description of data source & evaluation methods

Cyst and Root-knot Nematodes	VR	R	M	S	VS	total
Globodera rostochiensis: Ro1	1	45	6	514		566
Ro2		8	1	165		174
Ro3		3	2	11		16
Ro5		46	48	205		299
Ro1-5		15	11	56		82
G. pallida: Pa1		30	4	7		41
Pa2		121	118	290		529
Pa3	2	250	76	368	9	705
Pa2/3 (by INRA)		10	6	37		53
Meloidogyne chitwoodi	8	1	1	77		87
M. fallax	8	3	2	72		85
M. hapla		15	11	67		93
Fungal diseases	VR	R	M	S	VS	total
Late blight field test (Phytophthora infestans)	73	158	235	403	817	1686
Late blight laboratory test	103	82	103	120	849	1257
Wart R1 (Synchytrium endobioticum)		57	34	122		213
Wart R2		71	52	60		183
Wart R6		94	104	92		290
Wart R8		91	61	84		236
Gangrene (Phoma exigua var. foveata)		99	121	190		410
Dry rot (Fusarium coeruleum)		76	72	304		452
Rhizoctonia solani		3	4	5		12
Common scab (Streptomyces scabies)				20		20
Virus diseases		I	IS	S	VS	total
PVX		25	43	60	97	225
PVY		2	13	36	184	235
		R	M	S	VS	total
PVM		9	7	190		206
Bacterial diseases	VR	R	M	S	VS	total
Blackleg (Pectobacterium atrosepticum)		327	133	67	31	558
Softrot (P. atrosepticum)		3	12	66		81
Other	range					total
Reducing sugar content	35-2838 mg/100g tuber					337
Dry matter content	14 - 44.5 %					348
Starch content	9.2 - 37.1 %					195
Vitamin-C content	32 - 128 ppm					74
		T	M	S	VS	total
Salt tolerance		4	4	28	22	58
TOTAL number of evaluation results:						9806

Data source & evaluation methods

Results for cyst-nematodes (Globodera rostochiensis (Woll.) Stone, G. pallida Stone) have been obtained from the following sources:

• CPRO (incl. SVP, the former Stichting voor Plantenveredeling), Wageningen. Material tested 1966-1985 and 1997. Virulence groups Ro1, Ro2, Ro3, Ro5, Pa3 (Rookmaker population), and the mixture Ro1,2,3,4,5.
• Max-Planck-Institut für Züchtungsforschung (MPI), Köln-Vogelsang. Material tested 1969-1980. Virulence groups Ro1, Ro2, Ro3, Ro5, Pa1, Pa2, Pa3.
• Biologische Bundesanstalt für Land- und Forstwirtschaft (BBA), Institut für Nematologie, Münster. Material tested 1978-1989. Virulence groups Ro5 (Harmerz population), Pa2 (Winsen or Kalle population).
• INRA-Ploudaniel. Virulence groups Ro1 (Ecosse population), Pa2/3 (Chavornay population). Results published by Rousselle-Bourgeois & Mugniery (1995).

The procedure for testing the resistance was described by Huijsman (1957) and Ross & Huijsman (1969). Samples of 15-40 plants per accession are tested.

Screening methods used:

1. testing in infested soil
2. testing in pots including an inoculum of 25-30 "full" cysts
3. testing in pots in cluding an inoculum of 3 cysts wrapped in nylon mesh. The substrate is analysed with Kort's elutriator and females extracted by centrifugation. With more than 5 females the clone are scored susceptible. Resistant clones retested.

The second is a simple method and almost all screenings were conducted that way. However, some of the earlier testings were conducted in infested soil. INRA-Ploudaniel used the third method, the more reliable one. In Europe at present 5 virulence groups of G. rostochiensis and 3 of G. pallida are recognised. To obtain standardization the earlier results (from Ross & Huijsman, 1969; and Hermsen & Verdenius, 1971) had to be adapted to the scheme of Kort et al. (1977). For the more recent data, the number of plants with 0 cysts (Pa2) and 0-2 cysts (Pa3, 1981-1985) in relation to the total number of screened plants, is available too. In the root ball test only the outside of the root ball is screened on the presence of cysts, but when performed under sub-optimal growing conditions (winter season) also the inner root ball was visually examined.


Root-knot nematodes

Results on Meloidogyne hapla, M. chitwoodi and M. fallax were received from CPRO and published by Janssen et al. (1996). During the investigations a new Meloidogyne species was identified deviating from M. chitwoodi, which has been described as M. fallax (Karssen, 1996).
Screening method used: 3-5 weeks after sowing about 600 nematode juveniles were supplied around the base of the seedling. After 7 weeks the roots of the plants were stained and egg masses counted. When less than 6 egg masses were found, then the test was repeated using a stem cutting of the plant. A genotype is scored as resistant when it showes less than 6 egg masses on the roots.
Since 1 May 1997 M. chitwoodi and M. fallax are quarantine organisms in the EU. To prevent spread, any planting material needs to be free of these two root-knot nematode species.

Fungi

Late blight

In the screening for late blight (Phytophthora infestans) resistance one hopes to find non-specific (horizontal or partial) resistance. Evaluation results have been obtained from following sources:

• CPRO (incl. SVP, the former Stichting voor Plantenveredeling), Wageningen. Material tested in the field in 1974-1989 and 1996-1999.
• Biologische Bundesanstalt (BBA), Institut für Pflanzenschutz in Ackerbau und Grünland, Braunschweig. Material tested in the laboratory in 1977-1993.
• WAC inventory (Hermsen & Verdenius, 1971); subsp. andigena only, no resistance found.

Field test

In 3 field plots of 4-8 plants, the seedlings were inoculated early July. Until 1983 a mixture of the pathotypes 1.2.3, 1.3.4 and 1.4.11 was used; 1984 a mixture of the pathotypes 1.2.3.7, 1.3.4.7.10 and 1.4.10.11 was used; 1985 the pathotype 1.3.4.7.10 was mixed with a complex pathotype (P1) with unknown virulence genes; 1986 & 1987 the pathotype 1.2.3.4.5.7.10.11 was used, and from 1988 onwards the complex pathotype 1.2.3.4.5.6.7.10.11 with a concentration of 50 zoospores/mm³ was used. The latter pathotype originates from Gembloux (Belgium, 1982) and has good chances to break through (known) monogenic resistance genes. To obtain optimum inoculation conditions, the field was sprayed with a sprinkle system. All accessions are screened weekly for their percentage infected foliage. The results are reduced by the principle of the "weighted mean" (WM) and devided by 10 to get figures from 0-9 (van Soest et al., 1984).

For the import of the results into the GENIS database, the original WM values were multiplied by 10 to restore the unit PERCENTAGE (infected foliage). The WM values of the susceptible variety Bintje are: 59.8 (1975), 62.5 (1976), 55.2 (1977), 55.5 (1979), 62.4 (1981), 57.5 (1982), 52.2 (1983) and 52.1 (1984); those of Bildstar are: 55.1 (1986), 71.2 (1987), 65.6 (1988), 59.2 (1989), 55.8 (1997), 44.8 (1998) and 43.7 (1999); those of Eersteling are: 69.5 (1986), 78.6 (1987), 72.1 (1988), 66.5 (1989), 60.8 (1997), 60.6 (1998) and 51.0 (1999); and of Ostara: 59.2 (1989), 56.3 (1997), 44.4 (1998) and 45.3 (1999). The WM values of the more tolerant variety Pimpernel (without R-genes) are: 23.1 (1974), 28.6 (1975), 30.3 (1976), 21.6 (1981), 21.8 (1983), 27.6 (1984), 29.9 (1986), 41.8 (1987), 47.1 (1988), 27.3 (1989), 32.5 (1997), 23.4 (1998) and 17.2 (1999). Because of the too positive results of the standard varieties in 1998 and 1999, the results of these two years were adapted accordingly (WM values multiplied with factor 1.3 ). For the opposite reason the results of 1984 were multiplied with 0.77 .

Due to a simplification of the screening method no WM-values are available from 1985 (16 plants / accession were screened twice with a time interval of a week, in a phase with representative differences in susceptibility). The figures received from CPRO in 1985 were multiplied with 0.6 , to get figures that are 'in-line' with the usual WM results. 1997 also ADPC values were calculated. The WM and ADPC values are coded as follows:

Code	Level of susceptibility	WM-Index	ADPC
VR	very low	0.0 - 6.0	0.00 - 0.07
R	low	6.1 - 18.0	0.08 - 0.22
M	intermediate	18.1 - 30.0	0.23 - 0.36
S	high	30.1 - 42.0	0.37 - 0.49
VS	very high	> 42.0	> 0.49

Laboratory test

The method used was described by Hodgson (1961). The plant material used are leaves from up to 20 plants per accession, picked before flowering. Discs of 15 mm in diameter are cut from the leaves with a corkborer and 100 discs per accession are placed in moist trays. Each disc is inoculated with 1 drop of suspension containing zoospores of the pathotype 1.2.3.4.7.8.10.ll. The concentration of the suspension is 250 zoospores/0.05ml. Approximately 6 days later the percentage of the total disc surface that is sporulating is scored. This percentage is called the sporulation index (SI).
The codes for the resistance are obtained as follows:

Code	Level of susceptibility	Sporulation index
VR	very low	0 - 3.9
R	low	4 - 19.9
M	intermediate	20 - 39.9
S	high	40 - 59.9
VS	very high	> 60

Wart

Results for wart (Synchytrium endobioticum (Schilb.) Perc.) have been obtained from the Biologische Bundesanstalt (BBA), Institut für Pflanzenschutz in Ackerbau und Grünland, Braunschweig. Material tested in 1976-1994. Results were discussed by Langerfeld & Hoekstra (1992).

The test, called the Glynne-Lemmerzahl method, was described by Hille (1965). It is a laboratory method in which tuber-cuttings are contaminated with the fungus. After approximately 2-3 weeks the results can be scored. From the pathotypes found in Europe the following ones are used: 1 (Dahlem D1), 2 (Giessübel G1), 6 (Olpe O1) and 8 (Kohlhaus K2). 5-10 tubers per accession were used. The results are presented as follows:

Code	Meaning of code
R	resistant
M	intermediate
S	susceptible

Here you'll find the original evaluation data for Wart scored on BGRC accession numbers. Results from years: 1994-1980  (R2, R6 & R8, some R1), 1979-1976 (R1 only) as PDF. Scores obtained in a specific year used tubers produced the year before. Database fields used in those days for different wart pathotypes: AXS = R1, AXT = R2, BQG = R6, CEG = R8. The PDF also shows how the results were coded for the database. In a few cases observations from more than one year were available. Then a mean value was included in the database. Intermediate scores "RS" were later transformed in the database to "M".
More info on the quarantine status in the EPPO data sheet on this disease.


Gangrene

Virus diseases

Institute for Potato Research, Department of Genetics, Mlochow, Poland. 10-20 plants per accession were tested. Scions of each plant were grafted on tomato plants infected with PVM (isolate Uran) (Dziewonska & Ostrowska, 1978). The screening is based on the percentage of plants in which PVM was detected 6 weeks after grafting on infected tomato plants. Plants apparently not infected were retested. The results are presented as follows:

Code	Meaning of code
R	< 40 % of grafted plants infected
M	> 40 % of grafted plants infected
S	all grafted plants infected

Potato virus X

Stichting voor Plantenveredeling (SVP, later merged into CPRO, since 2000 Plant Research International), Wageningen. Material tested in 1978, 1979, 1982 - 1984. Preliminary screening for extreme resistance of samples of 50-100 seedlings, started 3 weeks after inoculation. The inoculation of the seedlings at the cotyledon stage with a spray-gun was described by Wiersema (1961). The final testing of seedlings by means of grafting on tomato stocks is not included in this test.

The results are presented as follows:

Code	Meaning of code
I	0 - 5 % of the plants with PVX symptoms
IS	6 - 30 % of the plants with PVX symptoms
S	31 - 70 % of the plants with PVX symptoms
VS	> 70 % of the plants with PVX symptoms

Potato virus Y

Material tested by the Stichting voor Plantenveredeling (SVP, later merged into CPRO, since 2000 Plant Research International), Wageningen in 1978, 1979, 1982 - l984. Preliminary screening for extreme resistance of samples of 50-100 seedlings, started 3 weeks after inoculation. The inoculation of the seedlings at the cotyledon stage with a spray-gun was described by Wiersema (1961). The final testing of seedlings by means of grafting on tomato stocks is not included in this test.

The results are presented as follows:

Code	Meaning of code
I	0 - 5 % of the plants with PVY symptoms
IS	6 - 30 % of the plants with PVY symptoms
S	31 - 70 % of the plants with PVY symptoms
VS	> 70 % of the plants with PVY symptoms

 

Bacterial diseases

Blackleg

Material tested on blackleg (Pectobacterium atrosepticum (van Hall) Gardan et al. {syn. Erwinia carotovora (Jones) Hol. subsp. atroseptica (van Hall) Dye.}) by the Bayerische Landesanstalt für Bodenkultur und Pflanzenbau (now Bayerische Landesanstalt für Landwirtschaft: LfL), Freising in 1977-1993. Results were discussed by Hoekstra & Munzert (1990). The method is described by Munzert (1975). Three weeks old tuber eye cuttings are inoculated with filter paper covered drawing-pins, previously dipped in a bacterial suspension of 5 x 10⁸ bact./ml. After approximately 10 days the first blackleg symptoms become visible. Three weeks after the inoculation the test is stopped and the plants are scored for presence of blackleg. 10-40 tubers per accession are tested.

The data are coded as follows:

Code	Level of susceptibility	% Blackleg
R	low	< 5.9
M	intermediate	6.0 - 20.9
S	high	21.0 - 40.0
VS	very high	> 40

Softrot

Results on softrot (Pectobacterium atrosepticum (van Hall) Gardan et al. {syn. Erwinia carotovora (Jones) Hol. subsp. atroseptica (van Hall) Dye.}) evaluations obtained from INRA-Ploudaniel, published by Rousselle-Bourgeois & Priou (1995). The aggressive strain Eca 86.20 from Brittany was used to inoculate the biggest tubers available just after harvesting. The test was adapted from Austin el al. (1988). Sterile pipette tips containing 10 µl of bacterial suspension (10⁸ cfu/ml) were pressed into the tuber to a depth of 1 cm. Incubation period: 6 days at 20 °C. Progeny of uninfected genotypes were retested the year after.

Other

Following 3 traits were evaluated by the Bundesanstalt für Getreide-, Kartoffel- und Fettforschung, Institut für Stärke- und Kartoffeltechnologie, Detmold, Germany (BAGKF; since 2008 Department of Safety and Quality of Cereals and part of the Max Rubner-Institut).

• Reducing sugar content (mg / 100 gram fresh tuber weight). The content was determined after storing the tubers during 6 weeks at 4°C. Differences in the results between years can be substantial. Results from 1990-1994. Reducing sugars are involved in non-enzymatic browning (the Maillard reaction).
• Dry matter content (%). Results from 1990-1994.
• Starch content (%), calculated from the under water weight. Because of the small tuber size the results are very preliminary. Results from 1992-1994.

Vitamin C content

Vitamin C content of some Solanum tuberosum subsp. andigena clones, data from the WAC inventory (Hermsen & Verdenius, 1971) expressed in ppm (parts per million). The mean vitamin C content of potato varieties is about 20 mg/100 g freshly harvested tubers, and it rapidly declines to about 8-10 mg/100 g tuber in storage (CIP, 1974). The contents scored range from 3,2 to 12,8 mg/100 g tuber.

Salt tolerance

Evaluation results from Elhag (1991) on 58 genbank accessions and 11 potato varieties. From each accession 1 genotype was multiplied in vitro. The in vitro test was carried out with 0, 40, 80 and 120 mMol NaCl in the growth medium (7 replications; 6 weeks; 16 hours 4000 lux; 20-23°C). Shoot length appeared to be a good parameter to determine the salt tolerance in the in vitro test. The results from the lower salt concentration (40 mM) were not used for the classification below


Classification:
The accessions were classified as follows, using the mean value of the relative shoot lengths (as % of untreated) from the 80 and 120 mM sodium chloride treatments.

Code	Mean shoot length (%)
T (tolerant)	60 - 66
M (interMediate)	51 - 58
S (susceptible)	26 - 44
VS (very susceptible)	8 - 24

The best clones:
The relative shoot lengths (as % of untreated) of the 8 best performing accessions and the control varieties in the treatments with 80 and 120 mM NaCl are:

BGRC Accession / Clone	CGN no.	80 mM NaCl	120 mM NaCl	Score
16979 chacoense	17898	72	60	T
24687 sparsipilum	18099	70	59	T
15451 vernei	17836	69	57	T
16837 gourlayi	17853	66	53	T
24717 tarijense	18107	64	52	M
18326 spegazzinii	18034	64	50	M
28043 TBR ssp.andigena	18233	59	48	M
7463 TBR ssp.andigena	17619	57	44	M
Desiree	-	62	49	M

The other varieties tested were susceptibel (Erntestolz: 43%, 36%; Roxy: 48%, 23%; Spunta: 38%, 30%; Marfona: 36%, 26%; Alpha: 35%, 22%; Draga: 34%, 18%) or very susceptible (Kennebec: 29%, 14%; Diamant: 19%, 16%; Culpa: 30%, 0%; Hansa: 17%, 0%) to the two salinity treatments: 80 mili mol and 120 mM of sodium chloride (NaCl).

In an additional test the best genotypes were compared with 5 clones from CIP, three being salt tolerant (Aracy, DTO-28, CFC-69.1) and two salt susceptible (7XY-1, LT-8), according to CIP. The result (dissertation Elhag 1991, p.108) are summarized below as % of untreated:

		rel. shoot length (%)		rel. shoot dry weight (%)		Score
Accession / Clone	CGN no.	120 mM NaCl	160 mM NaCl	120 mM NaCl	160 mM NaCl	(by Elhag)
24687 sparsipilum	18099	61	7	62	18	T
16979 chacoense	17898	60	4	57	23	T
24717 tarijense	18107	54	4	62	17	T / M
15451 vernei	17836	48	11	52	24	M
CIP: Aracy TBR ssp.tuberosum	-	47	21	57	31	M
28043 TBR ssp.andigena	18233	45	5	52	19	M
CIP: DTO-28 TBR ssp.tuberosum	-	26	5	54	16	S
CIP: 7XY-1 TBR ssp.tuberosum	-	26	5	48	23	S
CIP: CFC-69.1 TBR ssp.tuberosum	-	26	6	44	12	S
CIP: LT-8 TBR ssp.tuberosum	-	21	0	34	0	S

Thesis as PDF file , 37mB.

Feedback to: Lana.deBruijn@wur.nl,
Centre for Genetic Resources the Netherlands (CGN), Wageningen, the Netherlands.