POTATO (Solanum tuberosum L.)
I. Application and Amplification of General Seed Certification Standards
A. The General Seed Certification Standards are basic and together with the following specific standards constitute the standards for certification of seed potato.
B. Classification of seed potato on the basis of area of production; There shall be two types of seed potatoes, namely the Hills and Plains - grown and shall be designed as Hill Seed (HS) and Plains Seed (PS) respectively. Hill Seed (HS) shall be grown in the high hills generally 2500 meters above the mean sea level or in situations declared technically suitable for seed production. Plains Seed (PS) shall be grown in such areas where aphid infestation is low during the crop growing season and which are technically suitable for seed production.
II. Land requirements
A crop of seed potato shall not be eligible for certification if grown on land infested with:
- wart (Synchytrium endobioticum (Schilb.) Perc. and or cyst forming nematodes;
- brown rot (Pseudomonas solanacearum (E.F.Sm.). E.F.Sm.or non -cyst forming nematodes within the previous three years;
- common scab (Streptomyces scabies (Thaxt.) Waks. & Henrici).
III. Field Inspection
A minimum of four inspections shall be made as follows:
1. the first inspection shall be made about 45 days after planting in the hills and about 35 days after planting in
the plains to verify isolation, offtypes and the extent of disease infection with specific reference to mild and
severe mosaics, leaf roll, yellows brown rot and other relevant factors;
2. the second inspection shall be made about 60-65 days after planting for early varieties and about 70-75
days after planting for late varieties or at appropriate growth stage depending on the crop duration of the
variety concerned to check isolation, offtypes and extent of disease infection with specific reference of mild
and severe mosaics, leaf roll, yellows brown rot and other relevant factors;
3. the third inspection shall be made immediately after haulms cutting/destruction in order to verify that haulms
have been cut/ destroyed by the prescribed date and in proper manner;
4. the fourth inspection shall be made about 10 days after haulms cutting /destruction and before harvesting in
order to verify that no re-growth of haulms has taken place.
V. Field Standards
A. General requirements
1. Isolation
The fields of seed potato shall be isolated from the contaminants shown in the column 1 of the Table below by the distances specified in columns 2 and 3 of the said Table:
Contaminants Minimum distance (meters)
Foundation Certified
Stage-I Stage-II
1 2 3 4
Fields of other varieties 5 5 5
Fields of the same variety not conforming to the
varietal purity requirements for certification 5 5 5
B. Specific requirements
Factor Stage Maximum permitted (%)*
Foundation Certified
Stage-I Stage-II
1 2 3 4 5
Off types I & II Inspection 0.050% 0.050% 0.10%
Plants showing symptoms of :
- Mild mosaic I& II Inspection 1.0% 2.0% 3.0%
- Severe mosaic, leaf roll I & II Inspection 0.50% 0.750% 1.0%
and yellows
* Total virus - 1.0% 2.0% 3.0%
** Plants infected by brown rot I& II Inspection None None 3 plants
(Syn. Bacterial wilt ) per hectare
(Pseudomonas solanacearum (E.F.Sm.) E.F.Sm.)
*** Re-growth of plants after IV Inspection 0.50% 0.50% 0.50%
destruction of haulms
* Of the two inspections, the higher virus percentage will be considered for the purpose of the specified limits
of tolerance.
** The presence of brown rot infected plants within the specified limits of tolerance shall be permitted in
the areas known to be infected with this disease. In case of plants suspected to be infected with brown rot
the neighbouring plants, one on either side should also be rogued along with tubers.
*** Standards for re-growth after destruction of haulms shall be met at fourth inspection to be conducted
about 10 days after haulms cutting.
Note: 1. All offtypes and diseased plants should be rogued out along with the tubers and destroyed.
2. Gaps in the seed plot should not be more than 10.0%.
3. Haulms must be destroyed as close to the ground as possible before the date specified by the
Certification Agency. Failure to destroy haulms in time shall render the crop liable for rejection.
V. Seed standards
A. Specifications in respect of size and weight of seed material for Foundation Stage I, Foundation Stage II and Certified class shall be as under:
Size Mean length and two widths Corresponding
at the middle of tuber weight
a) Hill Seed (HS)
Seed size 30mm-60mm 25-150gm
Large size above 60mm above 150gm
b) Plains Seed (PS)
Seed size 30 mm-55 mm 25-125gm
Large size above 55 mm above 125gm
Note: 1. The size of tuber will be decided either on the basis of two widths pf a tuber at the middle and that
of length or on the basis of corresponding weight of tuber.
2. In a seed lot, tubers not conforming to specific size of seed shall not exceed more than 5.0% (by
number).
3. a) The seed material shall be reasonably clean, healthy, firm and shall conform to the
characteristics of the variety. The tubers not conforming to the varietal characteristics shall not
exceed 0.050% and 0.10% (by number) for Foundation and Certified seed classes
respectively.
b) Cut, bruised, unshapy, cracked tubers or those damaged by insects, slugs or worms shall not
exceed more than 1.0% (by weight)
c) Greenish pigmentation on tubers will not be a disqualification for certification.
B) Maximum tolerance limit of tubers showing visible symptoms of infestation caused by scale insects will
be as follows:
Maximum permissible limits
Diseases
Foundation Certified
Stage-I Stage-II
1 2 3 4
Late blight (Phytophthora infestans (Mont.) de Bary),
dry not (Fusarium caeruleum (Lib.) Sacc.) or Charcoal
rot (Macrophomina phaseoli (Tassi) G.Goidanich) 1.0% 1.0% 1.0%
(by number) (by number) (by number)
Wet rot (Sclerotium rolfsii) Sacc.) None None None
* Common scab (Streptomyces scabies
(Thaxt) Waks.&Henrici) 3.0% 3.0% 3.0%
(by number) (by number) (by number)
** Black scurf (Rhizoctonia solani Kuehn.) 5.0% 5.0% 5.0%
(by number) (by number) (by number)
*** Total diseases 5.0% 5.0% 5.0%
(by number) (by number) (by number)
* Even if a single tuber infected with common scab is detected in a seed lot, the entire seed lot shall be treated
with approved fungicide before seed lot is declared fit for certification. Seed lots having infected tubers more
than the prescribed limits will not be certified even after treatment.
** (a) A tuber carrying 10.0% or above scurfed surface will be considered as one infected unit.
(b) Seed lots having black scurf infection more than the prescribed limits could be certified after treatment
with approved chemical / fungicide.
*** For all disease, the higher disease percentage will be considered for the purpose of the specified limits of
tolerance.