Download Virus Disease Resistance in Peppers, A. A. Cook, Florida

FLORIDA STATE HORTICULTURAL SOCIETY, 1959
110
VIRUS DISEASE RESISTANCE IN PEPPERS
A. A. Cook
Florida Agricultural Experiment Station
Gainesville
Bell pepper production in Florida has been
affected considerably by virus diseases in re
cent years (1, 15, 17). Seven different viruses
are known to infect peppers under field con
ditions, but only five have been isolated from
plants grown in central Florida (1). These
are the tobacco etch, potato Y, tobacco mosaic,
cucumber mosaic, and aster ringspot viruses.
In certain localities within the state par
ticular viruses may cause more damage than
others. In central Florida tobacco etch, to
bacco mosaic, and potato Y viruses were most
frequently encountered by Anderson and Corbett (1). Simons (15, 17) found the cu
cumber mosaic and potato Y viruses most
detrimental in south Florida. Occurrence of
the latter disease has been correlated with
potato production (14).
Virus disease (s.) can be controlled partially
by several means. All such measures necessar
ily affect 1) the original source of the in
fection and its subsequent introduction into
the crop field and/or 2) the spread of the infec
tion within the field. The success of any at
tempt at disease control is directly propor
tional to its effectiveness against either or
both of these factors.
Crop plants may introduce the disease into
the field if transplants are used. Seedlings may
be infected while still in the plant bed, but
show no symptoms until after transplanting.
Perennial weeds in fence rows or along ditch
banks frequently are infected with one or more
of the viruses that affect peppers. Insects,
particularly aphids, that have fed on such
plants immediately before entering the crop
field are one of the most important means
by which virus disease(s) are introduced
Florida
No. 912.
Agricultural
Experiment
Station
Journal
Series,
into pepper fields. Some virus infections may
be traced to field laborers who handle the
plants, especially those who use tobacco.
All of the viruses that affect pepper in
Florida can be spread to healthy plants by
laborers who have previously handled infected
plants. Dissemination by this method may be
considerable, particularly in the case of to
bacco mosaic. Aphids, however, probably are
the single most important means of withinfield spread. These vectors are capable of
efficient transmission of the other four viruses
despite the fact that they do not remain in
fectious for a long time after feeding on a
diseased plant. Their capabilities as vectors
result from an ability to populate rapidly and
because adults can fly considerable distances
while infectious.
Introduction of virus infections into the
field through transplants can be avoided by
direct seeding. None of the viruses affecting
pepper in Florida infect the seed. Diseased
plants should be rogued. In addition labor
ers should wash their hands with soap
and water before field work to reduce withinfield spread by laborers. Virus sources can be
eliminated by the use of herbicides on ditch
banks and fence rows. Particular attention
should be given to eradication of such plants
as nightshade, wandering jew, and Physalis sp.
No practical method, however, has been de
vised to eliminate the damage effected by in
sects as vectors of virus diseases. Simons (16)
found that neither insecticides nor border
plantings of crops, that were physical barriers
to aphid movement and immune to pepper
viruses, were completely effective control
measures.
While there has not yet been devised a
practical means of pepper virus disease con
trol through use of cultural practices, some
success has been attained from the use of re
sistant varieties. Resistance to tobacco mosaic
virus first was reported and studied by Holmes
(8, 9), who noted two distinct types of re-
COOK: PEPPER VIRUS RESISTANCE
sistance. The most desirable type of resistance
was characterized by a hypersensitive (ex
tremely susceptible) reaction. Plants with this
type of resistance, typified by the variety Ta
basco, exhibited local necrotic lesions on in
oculated leaves which dropped soon after in
oculation. There was no further (systemic)
development of the disease. Plants with the
other type of resistance, termed "imperfect
localization," showed large yellowish lesions.
While there was systemic development of the
disease in plants with this type of resistance,
they did not become mottled and produced
salable fruit. This information made possible
the eventual development of varieties resist
ant ("imperfect localization" type) to this
disease, one of which was Yolo Wonder (11).
Greenleaf (6, 7) noted resistance to tobacco
etch virus in two species of pepper and de
termined the nature of inheritance. This re
sistance was found to result from a slow rate
of virus multiplication within the resistant
plants. Mild symptoms eventually appeared on
many plants, but there remained a distinct
difference in reaction of susceptible and re
sistant plants.
Workers in Puerto Rico (10, 13) found
resistance to potato Y virus in a hot pepper
(Cuaresmeno). This resistance was incorpor
ated into a variety named Puerto Rico Won
der (5, 12). That particular strain of potato
Y virus found in Puerto Rico is distinct from
the strains of this virus found in Florida, how
ever.
In view of the facts considered in the pre
ceding discussion, a program was initiated to
find, study genetically, and incorporate into
an acceptable horticultural variety of bell pep
per, resistance to the major virus diseases of
pepper in Florida. All available pepper stocks1
were screened for resistance to 1) tobacco
mosaic, 2) tobacco etch, and 3) potato Y
viruses by mechanically inoculating test plants
using the carborundum-gauze pad technique.
A selection designated Pll, originally collected
in Florida, was found to have resistance to all
three viruses (2). One of the two peppers
studied by Greenleaf (herein referred to as
P342) was found also to be resistant to these
diseases.
1 Kindly supplied by Associated Seed Growers, Inc., W.
A. Burpee Co., Ferry-Morse, Kilgore, and F. H. Woodruff and
Sons seed companies, Southern Regional Plant Introduction
Station, Experiment, Georgia and colleagues of the author.
- Designated S. C. 46252 by Greenleaf.
111
The resistance to the three viruses was
not, however, of equal degree nor inherited
in the same manner. Furthermore, some var
iation in reaction to different strains of the
same virus was noted. Plants of these two
pepper lines, when inoculated with three strains
of tobacco mosaic virus, reacted in a hyper
sensitive manner. The inoculated leaves ex
hibited local necrotic lesions within five days
after inoculation. Within ten days these leaves
dropped and there was no further develop
ment of the disease. This reaction is typical
for plants with the single dominant factor
L. Some strains of tobacco etch virus caused
symptoms in Pll and P34 plants only when
a graft inoculation technique was used. A
single recessive gene, designated eta by Green
leaf, was postulated for this reaction. Pll and
P34 plants were immune to five strains of
potato Y virus. No symptoms were induced
irrespective of method of inoculation. A single
recessive gene, t/a, was proposed for this
reaction (3).
The discovery of the multiple virus disease
resistance of these two peppers was signifi
cant for several reasons. It was the first re
ported instance of combined resistance to
three virus diseases in pepper, a factor that
should enable plant breeders to develop var
ieties with resistance to more than one virus
disease in considerably less time. The L type
of tobacco mosaic resistance, unquestionably
more desirable than the V resistance of var
ieties now in production, had not been found
previously in the bell pepper species (Capsi
cum annuum L.) (18). Immunity to potato
Y virus in pepper had not been noted previousFrom further studies it was determined that
the genetic factors, L, eta, and t/a derived
from Pll were the same as the corresponding
factors from P34 (4). Furthermore, it has been
established that the factors eta and ya in both
peppers are closely associated on the same
chromosome with the resistances resulting
therefrom usually being inherited as a single
factor.
The preceding information has been ob
tained by inoculation of progenies resulting
from crosses between Pll and P34 and four
commercial varieties of bell pepper. In the
course of these studies to obtain basic in
formation about virus disease resistance, in
dividual plant selections have been made in
112
FLORIDA STATE HORTICULTURAL SOCIETY, 1959
an attempt to develop commercially accept
able lines of bell pepper with resistance to all
three viruses. This controlled breeding pro
gram has now progressed through five genera
tions in a period of three years with final
selections anticipated within another two years.
In the intervening time, studies similar to
those described above for tobacco mosaic, to
bacco etch, and potato Y viruses are planned
for cucumber mosaic virus. Other investiga
tions will include a critical evaluation, now in
progress of a single line found to have resist
ance to tobacco mosaic and potato Y virus. A
limited quantity of seed of this latter pepper
may be available for field testing in the fall
of 1959. This pepper may alleviate in part
the virus disease problems of the pepper in
dustry in Florida until such time as other var
ieties are available.
LITERATURE
CITED
1. Anderson, C. W. and M. K. Corbett. 1957. Virus
diseases of peppers in Central Florida; survey results 1955.
Plant Dis. Reptr. 41:
2.
143-147.
Cook, A. A. and C. W. Anderson. 1959. Multiple virus
disease resistance in a strain of Capsicum annuum. Phytopath
ology 49: 198-201.
3. Cook, A. A. and C. W. Anderson. 1959. Inheritance
of resistance to potato virus Y derived from two strains of
Capsicum annuum. Phytopathology 49: (In press).
4. Cook, A. A. 1959. Genetics of resistance to two virus
diseases in Capsicum annuum. (Abstract). PhytopatKota^v 49*.
(In
press).
5. Dale, W. T. 1956. Virus diseases of solanaceous crops
in Trinidad. Tropical Agr. (Trinidad) 33: 35-50.
6. Greenleaf, W. H. 1953. Effects of tobacco etch virus
on peppers (Capsicum sp.) Phytopathology 43: 564-570.
7. Greenleaf, W. H. 1956. Inheritance of resistance to
tobacco etch virus in Capiscum frutescens and in Capsicum
annuum. Phytopathology 46: 371-375.
8. Holmes, F. O. 1934. Inheritance of ability to localize
tobacco mosaic virus. Phytopathology 24: 984-1002.
9. Holmes, F. O. 1937. Inheritance of resistance to tobacco
mosaic disease in the pepper. Phytopathology 27: 637-642.
10. Perez, J. E. and J. Adsuar. 1955. Antigenic relation
ship between Puerto Rican pepper-mosaic virus and a strain
of potato virus Y. Jour. Agr. Univ. Puerto Rico 39: 165-167.
11. Porter, D. R. and S. G. Younkin. 1952. Introducing
the new mosaic-resistant Yolo Wonder Pepper. Seed World
12. Riollana, A., J. Adsuar, and A. Rodriquez. 1948.
Breeding peppers resistant to a Puerto Rican type of mosaic.
Proc. Amer. Soc. Hort. Sci. 51: 415-416.
13. Roque, A. and J. Adsuar. 1941. Studies on the mosaic
of peppers (Capsicum frutescens) in Puerto Rico. Jour. Agr.
Univ. Puerto Rico 25: 40-50.
14. Simons, J. N., R. A. Conover and J. M. Walter. 1956.
Correlation of occurrence of potato virus Y with areas of
potato production in Florida. Plant Dis. Reptr. 40: 531-533.
15. Simons, J. N. 1956. The pepper veinbanding mosaic
virus in the Everglades area of south Florida. Phytopathology
46: 53-57.
16.
Simons,
physical
barriers
J.
N.
on
1957.
field
Effects
spread
of
of
insecticides
pepper
and
veinbanding
mosaic virus. Phytopathology 47: 139-145.
17. Simons, J. N. 1957. Three strains of cucumber mosaic
virus affecting bell pepper in the Everglades area of south
Florida. Phytopathology 47: 145-150.
18. Smith, P. G. and C. B. Heiser, Jr. 1951. Taxonomic
and genetic studies on the cultivated peppers, Capsicum
annuum L. and C. frutescens L. Amer. Jour. Bot. 38: 362-368.
VAPAM AND VPM SOIL FUMIGANT MUST BE APPLIED
PROPERLY TO BE EFFECTIVE
Donald S. Burgis and A. J. Overman
Asst. Horticulturist and Asst. Microbiologist
Gulf Coast Experiment Station
Bradenton
A new carbamate soil fumigant (sodium
methyl dithiocarbamate, available commercial
ly as Vapam and VPM) has given such good
results in experimental plots that it is now
recommended for field use.
Increases in yield
and quality of vegetables grown in soils treat
ed with the fumigant are superior to those cur
rently obtained from soils treated with the
nematocides used for the past decade. This
new fumigant differs in that it acts as an herb
icide and soil fungicide as well as nematocide.
The new fumigant injected 5 to 6 inches be
low the surface o£ a row to be field-seeded to
tomatoes 10 to 14 days following treatment
allows the seedlings to emerge in a weed-free
band 8 to 10 inches wide. The volatile gas
released by the fumigant kills weed seeds and
perennial grasses as it filters upward and
escapes from the soil. Depth of the injection
is very important. If it is too deep the fumi
gant may not return to the surface so that all
control in the top layer of soil is lost. If in
jection is too shallow escape of the fumigant
vapor may be too rapid, resulting in an erratic
control of weeds and generally poor treatment.
A depth of 5 to 6 inches below the surface
of the finished bed has been found to be
most satisfactory.
When the decision has been made to fum
igate a field, the first step is to begin the prep
aration of the land early enough to insure
the rotting of all previous crop roots and other
plant debris. Maximum benefit of fumigation
is dependent on the diffusion through the
soil of the gases produced by the chemical
and the vapors' contact with the disease or
ganisms. Therefore, all plant parts in the soil
must be well rotted so that the toxic vapors
can reach the disease organisms which are
generally harbored in the plant tissues. It is