)Veg. Crops MR 67-4
SECURING GOOD SEED POTATOES FOR FLORIDA
Florida Agriculture Extension Service JUL 11 1972
There is no substitute for good quality seed potatoes to h~ jg gOja
high quality potatoes. Most Florida growers buy certified seed, shipped into the
state from northern U. S. and Canada. Growers have from time to time experienced
difficulty in securing certified potatoes in good condition.
Potato seed certification dates back to 1914 when certain standards and require-
ments were recommended for the production of quality potato seed. Since then many
states and Canada have developed potato seed certification programs, designed to
put on the market good seed.
The enforcement of certification standards is the responsibility of the Colleges
of Agriculture, the State Department of Agriculture, or grower's organizations
authorized by the state. These organizations must see that the minimum standards
as agreed upon, are met before the potatoes can be marketed as certified seed.
The production of certified seed depends upon the quality of foundation seed
stock and the manner in which it is grown. Foundation seed is obtained by select-
ing tubers of a variety and growing from one eye, under controlled conditions, a
single plant. If the plant proves to be free of seed-borne diseases the remaining
eyes of the tuber are planted for increase. These disease-free tubers are planted
in units in an isolated area and rogued during the growing season to remove all
diseased, weak, off-type plants or varietal-mixtures. These potatoes are used for
the production of certified seed.
Certified potato seed is grown in the northern states and Canada or at high
altitudes in other states where conditions are favorable for potato production and
less favorable for the development of insects responsible for the spread of many
virus diseases. They are grown under a system of inspection performed by the
certifying agency. The plants are inspected at least twice during the growing
season and the harvested tubers are stored in approved storage and inspected in the
bin. For each inspection a minimum percentage of affected plants or tubers for each
disease is allowed. The tolerance varies for different diseases and by certifying
states but is usually between 0 to 5 percent.
The maximum tolerances allowed for various diseases and varietal mixtures by
the a~taastB Crop Improvement Association at first and second field inspection
International Crop Improvement Association
Minimum Field Standards*
Factors First Inspection 2nd Inspection
Leaf roll 2 percent 1 percent
Mosaic 3 percent 2 percent
Spindle tuber 1- percent 1 percent
Other Viruses 3 percent 2 percent
Total Virus 4 percent 2 percent
Bacterial Ring Rot 0 0
Varietal Mixture 1 percent .5 percent
*Black leg, late and early blight, Fusarium wilt, any other disease
or abnormal condition at discretion of the certifying agency.
Certified seed potatoes meeting the above requirements must be inspected in
the bin just prior to or at time of shipment. This is to determine the presence
and amount of tuber defects and diseases on potato tubers. Example Blackwart,
Ringrot, nematodes, powdery scab, late blight, early blight, Fusarium wilt, corky
ringspot, tuber moth, cuts and bruises. The standards for these defects may vary
between states as they are established by the certifying agency.
Potatoes may be bruised or damaged during harvest and movement into storage.
Under favorable climatic conditions, temperature and humidity, injured potatoes
will heal in 24 to 48 hours by producing a protective layer of corky cells eliminat-
ing future damage. However, below 500 F and above 900 F this healing process takes
place very slowly allowing disease producing organisms to enter, which may complete-
ly spoil the tuber. Thus proper curing conditions following harvest may greatly
affect the quality of the seed. Storage temperature of 400 F and a relative humidity
of 85 percent is recommended to prevent the spread of diseases. The conditions are
not always maintained in storage and especially during shipment from the seed pro-
ducer to the Florida growers. Thus tuber defects and diseases may increase during
this period. Florida growers should purchase certified seed potatoes that meet
U.S. grade standards when received.
It is recommended that certified seed potatoes purchased for planting in
Florida should (1) meet the minimum standards established by the International Crop
Improvement Association. (2) All seed potatoes should conform to U.S. No. 1 grade
standard except for size (tuber size should be printed on tag.). (3) Be free from
serious damage. Tubers should not show more than 1/3 of the area affected by
sunburn and not more than 3 percent of rot from any specific disease, otherwise the
usual tolerances for U.S. No. 1 grade would apply.
The meeting of the standards given during the growing, harvesting, storing and
shipping of certified seed potatoes will insure the arrival in Florida of seed
potatoes of good quality. The maintenance of this quality from time of arrival
until planted will be effected by the storage conditions of the potatoes from time
of arrival until planted.
Should growers be dissatisfied with seed quality from a given area there are
many states meeting the standards of certified seed that are anxious and fully
capable of furnishing quality seed. At least one year of prior notification may be
necessary to assure a supply of certified seed of any specific variety. This is
particularly true if large quantities of seed are desired.