NORTH DAKOTA STATE UNIVERSITY
Plant Propagation PLSC
368
Dr. Chiwon Lee
POTATO
PROPAGATION
By
Carina De Luca
Abstract
Potatoes are indigenous to the
Andean regions of Peru, Chile and Bolivia, extending northward to the southern Rocky Mountains. Cultivated potato, Solanum tuberosum L., is
a highly heterozygous tetraploid (4x = 48), belongs to the Solanaceae family
together with other crops like tomato and peppers. Potatoes are adapted to an
array of climates and are utilized in many ways. The potato tuber is not only
the principal mean for potato propagation, but also a major human food source.
Potatoes are mainly propagated by vegetative methods (cloning). Potato tubers have nodes or “eyes” from which
the new growth begins. The new stems growing from each “eye” are called sprouts
which giver rise to the new plant. Vegetative seed can be either a whole tuber
or a cut tuber. Physiological age of seed is influenced by growing conditions,
handling, storage and cutting procedures, and it has an impact on how the new
crop grows. Sexual propagation occurs by means of botanical or sexual seed. Most
potato cultivars produce fruit; each
seed will develop into a plant with unique characteristics. This is a process very useful in crop improvements in
breeding programs, but its genotypic variation is of little value to growers.
Tissue culture is another method which permits a very rapid propagation. This
method is used to maintain disease free seed stock, which can be then stored
“in vitro” and be used when is needed.
Introduction
Potatoes are
indigenous to the Andean regions of Peru, Chile and Bolivia, extending northward to the southern Rocky Mountains.
Potatoes purportedly came to North America via Bermuda in 1691. Cultivated
potato, Solanum tuberosum L., is a highly heterozygous tetraploid (4x = 48),
belongs to the Solanaceae family together with other crops like tomato and
peppers. Potato is an annual dicot when grown for botanical seed, but is
treated as a perennial because the vegetative propagation from tuber for
commercial purposes.
http://oregonstate.edu/potatoes/CSS322WebNotes.html
Potatoes are
adapted to an array of climates and are utilized in many ways. There are cultivars developed for different
environments and end uses. Because of
the wide adaptation and many species, a vast genetic resource can be called
upon for introgression of resistance to disease and insect pests, stresses, as
well as improvement of quality traits.
Propagation
The tuber is not
only the principal mean for potato propagation, but also a major human food
source. Potatoes are mainly propagated by vegetative methods (cloning). This is
the primary commercial propagation method. Vegetative reproduction ensures a
uniform crop, contraire to what would happen with sexual propagation. Sexual
propagation of potato is accomplished by planting its “true seed”, but a high
variability exist between this seed and that is why is not commonly used.
However, sexual seed is becoming more and more popular; especially in places
were disease pressure is very high and maintaining disease free seed is
becoming a problem.
I. Asexual, vegetative or clonal propagation:
When
potato growers talk about “seed” they are talking about the tuber and not the
botanical or sexual seed. Potato tubers are actually a modified stem with
approximately 70-75% content of water and a remaining 25-30% of dry mater. They
have nodes or “eyes” from which the new growth begins. The new stems growing
from each “eye” are called sprouts. Sprouts
grow from the tuber after a period of dormancy after they are harvested, this
varies largely between cultivars. After this dormancy is broken, sprouts grow
and when planted, they give rise to the plant stems and from there all the
vegetative part of the plant. Underground, lateral shoots called “stolons” are
formed, from which the new tubers will be formed.
Vegetative seed can be either a whole
tuber or a cut tuber. The standard seed piece used by growers is 2” by 2” or 2
oz.
Potato
tuber cut to form seed pieces
Research has
shown that a seed piece this size has the adequate amount of carbohydrates
levels for shoot initiation and growth. If the tubers are cut, the usual
procedure is to let the cut pieces to suberize or cure, for about 10 days.
Suberization in tubers allows them to develop a corky layer around the seed
piece that prevents the seed piece decay by the entrance of several kinds of
pathogens.
Physiological age of seed
Is not the chronological
age of the seed piece; instead, is the influence of the growing environment of
the seed. Physiological age of seed is influenced by growing conditions,
handling, storage and cutting procedures. Physiological age of the seed will
have an impact on how the new crop grows.
It is very important to manage the
physiological age of the seed because it has a big impact on how the new crop
is going to look like and it will probably, along with many other factors,
determine weather the crop will be of a high quantitative and qualitative
value.
Other than seed age, there are some pros and cons when talking
about vegetative reproduction, some of them include the fact that cloning
assures genetic purity and product uniformity, it also favors high yields. Some
of the disadvantages are that cloning favors disease spread (e.g. viruses,
bacteria, fungi), and also a significant amount of storage space,
transportation and heavy planting equipment is required.
II. Propagation by botanical or sexual seed:
Most potato
cultivars produce fruit but some are pollen sterile or fail to ser fruit for
other reasons. If fruit is established, they usually are small, up to 1.25 “in
diameter and are green colored, resembling a small tomato.
http://www.new-agri.co.uk/02-6/focuson/focuson2.html
The fruit
contains the true seeds of potato plants, containing approximately 300 seeds
per fruit. When the potato plant
reproduces, usually through self-pollination, the chromosomes (along with the
genes they carry) are randomly distributed to the seeds. Each seed will develop
into a plant with unique characteristics. This is a
process very useful in crop improvements in breeding programs, but its
genotypic variation is of little value to growers because a new plant could be
totally different to the mother plant and no uniformity would be seen in the
field. Some of the advantages that true potato seed have are that they don’t
carry any diseases and that seed can be stored in small places contraire to
what happens with tubers.
III. Tissue Culture:
Tissue culture
permits a very rapid propagation. Under traditional propagation, one tuber
yields approximately 8 daughter tubers in one growing season, while with tissue
culture, 100,000 identical plantlets can be produced in eight months, that when
transferred to the field, could produce 50 MT of potatoes.
http://oregonstate.edu/potatoes/CSS322WebNotes.html
Each plant has a
root system, leaves and terminal points or growth points. There is an apical
meristem found at the apex of a potato stem and it also has lateral growth
points. Each of these buds has a meristem which allows it to become a different
plant.
The process of this technique is very simple. Disease free
plantlets are grown in test tubes on a nutrient media. Each plantlet is cut
into 3 to 10 nodal sections after 18-60 days. Each new cutting is planted in a
new test tube. This can be repeated until the desired number of plantlets is
obtained. Plantlets are then removed from the tubes and grown in sterile soil
and let them complete their entire growth cycle. Tubers produced are collected
and stored to later be sold to growers. This is also the process followed to obtain
certified seeds. This first seed lot would be called “nuclear seed” and then
after harvesting the product of this seed you get “Generation 1” (G1) and so
forth.
Meristems have no vascular system, therefore are less prone to
viral, fungal and bacterial infections. For this reason this method is used to
maintain disease free seed stock, which can be then stored “in vitro” and be
used when is needed.
References:
A. Mosley, I. Vales, J. McMorran, S. Yilma. 2000. CSS 322, Principles of Potato Production.
Available at http://oregonstate.edu/potatoes/CSS322WebNotes.html
Hoopes R.W.,
Plaisted R. L. 1987. Potato (Chapter 11) subtracted from the book: Principles of Cultivar Development Volume 2
by Fehr W. 1987. Iowa State University.
Mills H. A. 2001. Vegetable crops: Potato, Solanum tuberosum L. University of
Georgia. College of Agricultural and
Environmental Sciences. Department of Horticulture. Available at: http://www.uga.edu/vegetable/potato.html
Stark, J.C. and
S.L. Love, editors. 2003. Potato
Production Systems. University of Idaho Agricultural Communications,
Moscow, Idaho.