Agriculture Reference
In-Depth Information
The advantages of using TPS as planting
material include convenience in transportation
(only
100
g of TPS is required per planted hec-
tare), inexpensive, virus-free plants, the ability
to plant the seed at any time during the year, and
high yield potential. However, because each TPS
is genetically different (heterozygous) from the
other, each seed will produce a plant with traits
that may be completely different from those of
the mother plant. This is a major disadvantage if
the consumer or buyer expects a clone of the ori-
ginal potato of interest. Moreover, production
from TPS requires several extra months of initial
growth in a greenhouse, followed by labor-intensive
transplantation into the field. Other disadvan-
tages for TPS use include tuber emergence dis-
orders, a long maturation period, and extreme
sensitivity to adverse environmental conditions.
Compared to TPS, the advantages of vegetative
propagation via seed tubers include the produc-
tion of potato plants that are identical to the
mother plant, quick and vigorous sprout emer-
gence, and higher potato yields. However, where
virus infection pressure is high and formal seed
potato systems non-existent, TPS can be used as
starting material. For producers using TPS, future
improvements may include better plant and tuber
uniformity through orchestrated TPS combinations
and a shorter plant maturation period, which could
lead to the ability to grow seed potatoes from TPS
the first year of production rather than transplants.
2.
Fungi: late blight, early blight, dry rot caused
by various
Fusarium
spp., pink rot and leak,
black dot, white mold, verticillium wilt, soil-
borne issues like silver scurf, stem canker, and
black scurf caused by
Rhizoctonia solani
, com-
mon scab and powdery scab.
3.
Viruses: potato leaf roll, mosaic caused by
many different viruses including potato viruses
X, S, Y, M, and A, tomato spotted wilt, and soil-
borne problems like tobacco rattle and mop top;
potato spindle tuber viroid; and phytoplasma
problems such as purple top and aster yellows.
Primary seed potato pests include tuber moth,
potato cyst nematodes, root-knot nematodes, and
potato rot nematodes; all are considered very im-
portant. There are numerous other pathogens
and disease issues of importance that may be
carried on or in the seed, and these are often of
phytosanitary concern to each country or region.
8.4 The Certification Process
In order to obtain consistent high-quality seed
potatoes, a system of certification is necessary in
many areas of the world. Certification assures
seed buyers that reasonable varietal purity has
been achieved, and seed-related problems like
seedborne pathogens or chemical carry-over are
within established tolerances. Additionally, buy-
ers must be able to purchase certified seed with
the understanding that tuber diseases and prob-
lems will be minimal and specific grade stand-
ards have been met. Thus, the primary purpose
of seed production systems is to maximize prod-
uctivity of the seed to produce marketable pota-
toes by eliminating or minimizing seedborne
pathogens and pests, and by conducting selec-
tion programs to obtain superior clones within a
given cultivar (Grousset and Smith, 1998). The
systems required for formal seed potato certifica-
tion are established in nearly all of the devel-
oped countries currently engaged in potato pro-
duction. Developing countries are beginning to
learn the importance of these systems, although
informal seed potato production is often more
common.
There are many publications about seed po-
tatoes and seed potato production technologies
around the world. Examples include:
Seed Potato
Technology
(Struik and Wiersema, 1999),
Potato
8.3
Diseases and Pests of Concern
No discussion of seed potatoes is complete with-
out a discussion of diseases and pests, since one
of the primary reasons for certification is to pre-
vent seed stocks from degenerating or “running
out” in terms of their productive capacity (Bohl
and Johnson, 2010).
Diseases and pests are extensive in potato
production because of the use of vegetative
propagation. These include pathogens from the
bacteria, fungi, viruses and viroids, and phyto-
plasma groups. A listing of the primary diseases
of concern can be found at the UNECE site
(2010), but the diseases of global concern are:
1.
Bacteria: bacterial ring rot, soft rots, blackleg
and foliar wilts caused by
Pectobacterium carotovora
subspp. and
Dickeya
spp., and brown rot.
