Auburn University's Foundation
Sweetpotato Program
James M. Dangler, Robert A. Burdett, and Marlin H. Hollingsworth'
Commercial swectpotato trans-
plants are prodUced fromn bedded
stol age roots. Growsers fr equently
pi oduIce their Owxn tranlsplants to pre-
vent the introdUCtion ot'disease'. and
pests and to reduIce the Costs Coln-
pared to purchasing transplants.
Having the desired variety available
at planting is also important. Al-
thoug-h transplants appear vigorous
and healthy, they may be off-type,
contain mu1Ltations, or harbor diseases
and insect pests fromn the transplant
bed.
To produce high yields of roots
in the field, growers mnust keep their
rootstock free of pests. Maintaining
the characteiristics of the v ariety is
1Respct1i\ c I y Assis tant Pwifc oi of HO-tiI I I C Protiesor of Ag rononi\ a nd So i I: and
Leaflet 107 November 1994
Alabama Agricultural Experiment Station Auburn University
Lowell T. Frobish, Director Auburn University, Alabama
2 ALABAMA AGRICULTURAL EXPERIMENT STATION
another important function of a
transplant producer. By growing
true-to-type sweetpotatoes, the in-
dustry consistently presents an
appealing product to consumers.
The quality of the roots that are
bedded, therefore, is a very impor-
tant consideration in the sweetpotato
transplant production system.
To help sweetpotato growers
produce a high-quality product, cer-
tification standards have been
developed by the Alabama Crop Im-
provement Association, Inc. The
standards include requirements for
transplants in the bed and the field, the
roots, as well as root storage condi-
tions. The root length (three to nine
inches), diameter (one to three and
one-half inches), and tolerances for
defects, are specified. Transplant
packaging and transportation also
are regulated.
Three classes of sweetpotato roots
are produced in the program (the table).
Foundation (first generation)
sweetpotatoes are the direct progeny
of Breeder's sweetpotatoes. Regis-
tered (second generation) and Certified
(third generation) sweetpotatoes have
greater tolerances for defects and the
presence of pests than Foundation
sweetpotatoes. Sweetpotatoes in any
class may not have storage rot, harbor
sweetpotato weevils, or be mixed with
other varieties of sweetpotatoes.
Avoiding mixes, which occur when
roots or transplants of two or more
varieties are placed together, is very
important.
Transplants for the production
of Foundation sweetpotato roots
must be produced from field vine
cuttings or from sprouts cut, not
pulled, from bedded storage roots.
The requirements for Foundation and
Registered transplants are the same.
In the plant bed, Fusarium blackrot,
scurf, wilt, or stem rot may not be
present. Transplants of varieties can
not be mixed. In the field, plants
must also be free of Fusarium wilt or
stem rot, serious viruses, other objec-
tionable pests, and other varieties of
sweetpotatoes. In the bed, the re-
quirements for transplants to produce
Certified roots are the same as the
other classes in the plant bed. In the
field, however, wilt or stem rot and
virus diseases each may affect up to
0.1% of the crop. When a pest af-
fects the crop and there is no
tolerance established for that pest,
the decision whether to certify the
crop is made by the Association
coordinater on a case-by-case basis.
Off-type (figures 1 and 2) and dis-
eased plants and roots are rogued
from the field or transplant bed.
Certified sweetpotatoes may be "re-
certified" only if a severe shortage
of planting material exists.
Another important difference be-
tween Foundation sweetpotato roots
and the roots in the other classes is
that the internal root quality of Foun-
dation sweetpotatoes is better,
because they are not far removed
from Breeder's Seed. Although the
breeder has the primary responsibil-
AUBURN UNIVERSITY'S FOUNDATION SWEETPOTATO PROGRAM 3
ity to maintain the purity of a variety
that is important to the industry, the
Alabama Crop Improvement Asso-
ciation, Inc., operates the selection
program to carefully maintain the
characteristics of the variety and pro-
vides these sweetpotatoes to
producers. Because commercial
sweetpotatoes usually do not produce
seed and the seed does not breed
true, propagation is vegetative. Un-
fortunately, sweetpotatoes mutate
and variations in root shape, and
external and internal flesh color oc-
cur frequently. This certification
program was initiated in 1982 to
avoid these problems and maintain the
original characteristics of the variety.
Vigilance and strict adherence to good
management practices are required
throughout the program to maintain
the desired characteristics because
these defects are transmitted to the
next generation through transplants
which do not show signs of the
change(s). Certification programs also
are conducted in Louisiana and
North Carolina.
Sweetpotatoes with exterior de-
fects are fairly easy to eliminate from
a lot. Poorly-shaped roots or roots
with growth cracks or veins are not
appealing to the consumer (Figure 3).
Georgia Red and Georgia Jet fre-
quently develop veins at the surface of
the roots. Mutations in skin color
occur less frequently, but this defect
occurs in all varieties (Figure 4). Elimi-
nating internal defects, however, is
more difficult. To reduce the inci-
dence of these defects, each root
of Foundation Seed is cut cross-
wise and examined for changes in
internal flesh texture and color.
Only sweetpotatoes which exhibit
the desired characteristics of the
variety are used to produce trans-
plants.
Sweetpotatoes which have been
stored through the winter may ex-
hibit white-colored flesh. The white
flesh which develops in Jewel is eas-
ily distinguished from the normal
orange flesh (Figure 5). When this
white flesh dries during curing and
storage, cavities may develop
through the length of the root (Fig-
ure 6). Defective Nugget roots turn
purple within seconds after cutting
(Figure 7). The colored area be-
comes dark brown within minutes.
A white section or "wedge" of an
orange-fleshed root may be observed
(Figure 8). Within a few genera-
tions, partial or total degeneration
may occur resulting in sweetpotatoes
with white-colored flesh.
The Alabama Crop Improvement
Association, Inc. produces Founda-
tion sweetpotato roots which are the
progeny of Breeders' sweetpotatoes.
Foundation, Registered, and Certi-
fied roots are available to growers
to improve the quality of their
sweetpotatoes. The roots produced
in the program have a low tolerance
for the presence of insects and dis-
eases. In addition to keeping
sweetpotatoes free of pests, variet-
ies are screened to assure growers
ALABAMA AGRICULTURAL EXPERIMENT 
STATION
Figure 1. Plants ex-
hibiting irregular
S growth, such as
thick stems 
(below),
are rogued in the
field.
N
Figure 2. Plants in
the field or trans-
plants are rogued
if they produce
leaves without
chlorophyll.
Figure 3. (Right) Sweetpotatoes with insect
damage or irregular shapes, veins, or growth
cracks are eliminated from lots of sweetpota-
toes in a foundation program.
Figure 4. Mutations in sweetpotato
skin color occur frequently.
AUBURN UNIVERSITY'S FOUNDATION SWEETPOTATO PROGRAM
Figure 5. White-col-
ored flesh develops
in sweetpotatoes
during extended
storage. Potatoes
on the right and left
are defective.
Figure 6. As water is lost during stor-
age, white-colored flesh of stored
sweetpotatoes develops cavities.
Figure 7. Defective
Nugget sweetpo-
tatoes turn purple
when cut.
)
4'
Figure 8. Wedges
of white tissue or
white roots occur
in many sweet-
potato varieties
within a few gen-
erations if defec-
tive roots are
used to produce
transplants.
,4
6 ALABAMA AGRICULTURAL EXPERIMENT STATION
that the sweetpotatoes are true-to-
type and that varieties are not mixed.
As a result of this program, produc-
ers can obtain planting stock with
the characteristics consumers find
desirable. With good management
and the use of recommended cul-
tural practices, producers can obtain
high yields of quality sweetpotatoes.
MAXIMUM TOLERANCES FOR DISEASE, INSECT DAMAGE, AND INTERNAL QUALITY OF
SWEETPOTATO ROOTS BY CLASS
Maximum tolerance
Defect
2  
Foundation Registered Certified
Blackrot .............................................. None None 0.10%
Internal defects .................................... None No standard' No standard'
Nematode ............................................ None 0.2 % 0.5 %
Other varieties ................................... None None None
Scurf ..................... .. .............. None None 0.10%
Storage rot ............................................ None None None
Sweetpotato weevil.............................. None None None
Wireworm ............................. .............. 1.00 % 2.00 % 5.00 %
'Roots are not examined.
2 When Streptomyces root rot, bacterial 
soft rot, or other diseases or noxious pests 
are
observed, the decision to certify is made according to the severity of the problem.
Information contained herein is available to all persons regardless of race,
color, sex, or national origin.