Generally, a “five percent rule” applies with seed lots. A seed lot with five percent or more total defects is too high to use. To determine the physiological age of seed potatoes, gather a sample, place them indoors and allow them to sprout. Observe the sprouts that
come from the sample to determine the physiological age of the seed. There are distinct stages through which potato seed passes.

 Dormant Seed:
If the potatoes do not sprout at all, they may still be in a period of dormancy. Most potatoes undergo a dormant or resting period. The length of dormancy varies with the variety. There are chemical and non-chemical means to break or greatly reduce the dormancy period.

 Young Seed:
Young seed is characterized by apical dominance. Young seed will have one or just a few sprouts. These sprouts emerge from eyes on the apical or bud end of the tuber. There is a strong, internal inhibitor that keeps eyes on the center and stem end of the tuber from sprouting. Eyes distant from the apical end may never sprout. Young seed will produce a plant with few stems. A low stem number leads to a low tuber set. Larger, but fewer, tubers would be expected from young seed.

 Middle-aged Seed:
Middle-aged seed will have multiple sprouts. All the eyes on the potato could sprout. There is no clear apical dominance; eyes from the bud end, the middle and the stem end will sprout. Middle-aged seed produces plants with multiple stems that lead to high tuber sets.

 Old Seed:
Old seed will have branched sprouts that can appear hairy. These sprouts are weak, and they will not produce a vigorous plant. Typically, plants from old seed will produce high tuber sets, but the plants lack the vigor to bulk the tubers to a desirable size.

 Potato No Top:
Seed can be so old that small tubers form on the sprouts once they emerge from the eyes. “Potato No Top” is the name given to this disorder of extremely old seed. Seed with “Potato No Top” disorder should not be used. Any stress during the growing season produces potatoes that are physiologically older than those grown without stresses.

 Seed Treatments
Chemical seed treatment is often used as insurance against disease. Chemical seed treatment is recommended if seed is to be planted in very wet, very dry or very cold soils.

 Planting Quantity per Hectare
The quantity of seed required per hectare depends on the average seed size and the seed spacing. Larger seed has been shown to produce bigger yields in some varieties. Bear in mind, however, that many other factors besides seed size and physiological age of the seed determine the final yield. These include soil temperature at planting, accuracy of the planter, soil moisture, fertility and diseases.

Seed Selection, Seed Rate and Spacing for Potato Planting Seed
Selection:
1. Potato propagated by means of tubers.
2. Tuber should be true-to-type or genetically pure.
3. It should be free from infestation of pests and diseases like tuber moth, bacterial wilt (ring disease) and viruses.
4. Seed potatoes should be free from bacterial wilt and viral diseases.
5. It should be healthy, well matured and uniform in size.
6. Each tuber should have two to three sprouted buds.
7. It requires a rest period of about 2.5 to 3 months before they can be used for seed.
8. Medium to big sized tuber should be used for planting.
9. Medium sized tubers are plated whole while big sized tubers are cut into pieces, each about 30 gm in weight and having 2 to 3 sprouted buds.

Seed Rate:
Size-depended 1. Whole tubers- 33k to 66k/ha.
Spacing: In-row: 15- 35 cm (Size depended)
Inter-row: 75- 90cm. (Depends on how mechanized one is)

Factors Causing Poor Potato Emergence
There are many factors affecting potato emergence and stand
establishment. Having a checklist of factors causing poor potato emergence
is a useful tool for growers
The checklist is an excellent source of information when emergence is not
as good as expected. Let’s see if additional problems causing poor
emergence and stands develop this season. If so, they will be added to the
checklist.

Factors Causing Poor Potato Emergence Checklist
1. Anaerobic conditions due to field flooding.
2. Seed damaged by low temperatures in the field, in storage or in transit.
3. Late blight seed infection.
4. Fusarium dry rot seed infection.
5. Pythium leak, pink rot seed infection.
6. Soft rot, blackleg seed infection.
7. Rhizoctonia infecting emerging sprouts.
8 Black Dot eye infection.
9. High Mosaic Virus infection. Weak plants emerge and die in a short period of time
10. MH spoiled seed due to field drift.
11. CIPC contaminated seed in storage.
12. Herbicide residues in seed due to drift.
13. Herbicide carryover in soil.
14. Herbicide damage in sandy soils with low organic matter. There isn’t enough organic matter to tie up the chemical. It leaches down and burns the sprouts.
15. Planting cut seed of varieties with eyes concentrated at the bud end resulting in many blind seed pieces.
16. Little potato disorder of physiologically old seed.

Features of Quality Seed Tuber
 Free from seed-borne disease and pests.
 Seed tuber must not be mixed with other variety.
 High sprouting vigor.
 A seed tuber weight should be 30-50 gm.
 In visual, the seed tuber should be healthy, free of excessive wrinkles and no disease symptoms.

Importance of Good Quality Seed Tuber
High quality tuber seed is considered an important tool for increasing productivity. There are several advantages of use of quality seeds and they are given below:

 Quality seed tuber gives more production.
 Quality seed tuber production
can contribute to food security
via increasing productivity.