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Copyright 2005, Board of Trustees, University
Homestead AREC Research Report SB75-1 February 6, 1975
SSeed Propagation of Xanthosoma caracu (Cocoyam)
as a Potential Means of Pathogen Elimination
"--- and Genetic Improvement-/
r uVME LIBRARY 2
R. B. Vo in and F. W. Zettler-
Xanthosoma carac'- o mn called malanga, yautia or cocoyam, is an important
tropical v getable grown in south lorida. During the 1973-74 season an estimated
2200 acre we grown in Dade cou ty, Florida for commercial market (12). Edible
corms andl 6tea s'-nigF y crop were marketed along with other subtropical
vegetables incTTT 4ak.k.~ian boniatos, calabaza, name and yuca. Slightly over
10,000 acres was planted to these crops in 1973-74.
Last year Dade County shipped over 2 million pounds of cocoyam to U.S. markets (12).
Small amounts of taro (Colocasia sp.) are also produced (marketed primarily in
North Florida) however cocoyam is much preferred and appears to be much better
adapted to Florida's soil and climate.
It has been reported that Dasheen Mosaic Virus (DMV), a flexuous-rod shaped virus
of the Potato Virus Y (PVY) group was present in a large group of plants in the
Araceae family growing in Florida (9, 15). Plants showing DMV symptoms were also
reported in 24 commercial plots of cocoyam and taro produced in Puerto Rico (2).
Viral infection was verified by host range studies. Recently DMV was identified in
taro and cocoyam in Venezuela (3). That DMV is very prevalent in south Florida can
be easily verified by widespread symptoms in cocoyam fields under commercial pro-
duction. The disease incidence is not decreased from season to season since the
crop is propagated vegetatively and growers repeatedly use the same stock from year
to year to establish new fields.
A concentrated effort was undertaken to develop methods to eliminate this virus
from stocks of caladium and dieffenbachia, very important and popular plants in
Florida's nursery and ornamental trade. Symptoms of DMV infection are foliar
distortion, mosaic patterns which spoil normal variegated leaf patterns and much
reduced growth rates. Shoot-tip culture or mericlone isolation was found to be an
effective method of DMV elimination in caladium as well as in yautia and taro (6,7).
Seed propagation was discovered to be an additional method effective in excluding
virus from caladium and dieffenbachia (8).
The discovery of viral elimination by seed production in ornamental aroids prompted
us to search for methods of producing seed in Xanthosoma cultivars. While there is
an early report of seed production in Colocasia (11), we have found no reported
record of viable seed ever having been produced in edible Xanthosoma.
1/ This report was presented at the 14th Annual Meeting of the Caribbean Division
American Phytopathological Society, Trinidad and Tobago, 1974. This investi-
gation was supported in part by the United States Department of Agriculture
Contract No. 12-14-7001-284.
2/ Assistant Plant Pathologist, University of Florida Agricultural Research and
Education Center, Homestead 33030 and Associate Plant Pathologist, University of
Florida, Gainesville, 32611
A field in which cocoyam was being grown commercially in south Florida was used for
* this study. The cultivar, Santo Domingo, was reportedly from stock obtained from
Cuba. We believe the species to be caracu. This cultivar in contrast to others
of the same species commonly grown in Florida produced flowers quite readily.
Pollen was collected from distal staminate portions of spadices and applied by brush
within 1 hour to ovulate portions of neighboring spadices as described for caladium
and dieffenbachia (8). Fertilized ovaries gradually enlarged after pollination and
matured 5-7 weeks later. Ripened fruits contained 1-10 brown striated seeds about
1.4 x 1.0 mm. The seeds germinated in 12-18 days after being placed on moist peat
moss or a Hoagland's nutrient agar media. The largest of 350 plants obtained from 2
spadices produced a leaf 9.5 x 20 cm. 8 wks after a transfer to soil. The seedlings
all exhibit similar morphology but they varied in their growth rates and thriftiness.
While viral symptoms of DIV were evident in the field planting no symptoms have yet
become apparent in seedlings growing in isolation. These plants are continuing to
be grown in isolation for further study. The process of shoot-tip culturing which
has proven successful in other aroids is also being studied.
Seed production in cocoyam has yet another aspect not yet mentioned. There have
been reports of cultivar improvement through selection of superior stocks in Hawaii,
Puerto Rico, and recently in Trinidad (1, 5, 14). While progress has been made
through clonal selection we believe greater progress perhaps could be done evalu-
ating progeny derived from genetic reassortment. The probability of variation
certainly would be greater. The problem still remains that only a few of the more
desirable and edible cultivars have been known to produce flowers under field con-
ditions. It may be that flowering can be induced using growth regulating chemicals
or by using an altered growing environment.
S There appear to be at least 3 species of cocoyam grown in Florida based on
Haudricort's thorough review (10) and on Engler's classification (4). Xanthosoma
caracu produces white tubers and is most in demand. There are at least two cultivar;
one with oblong cormules and another which produces shorter, pear shaped cormules.
The former produces greater yields but seldom flowers. X. atrovirens is grown and
preferred by only a few for its yellow tubers. X. violaceum is least preferred and
is generally sorted out and discarded where ever it occurs. We concur with Dr.
Morton (13) that X. sagittifolium does not occur in Florida.
Published reports of morphological differences, as well as our own observations
indicate that variability exists and could provide a fairly wide genetic base from
which to work. We remain optimistic that selection through breeding offers a
potential means of cultivar improvement in cocoyam as well as a way of eliminating
inherent viruses namely DMV. The cocoyam, popular as it is in several areas of the
world, could very well play an increasing role in providing a nutritional food
staple for tropical and subtropical areas.
The authors gratefully acknowledge Leandro Ramos, Laboratory Technologist I and
Jorge Parrado, Laboratory Assistant II U. of Fla., AREC, Homestead 33030 for their
excellent technical assistance.
@ 1. Acosta Matienzo, A. and J. Velez Santiago. 1970. Yield trials with
Xanthosoma varieties. J. Agr. Univ. of Puerto Rico 54(3). 562-569.
2. Alconero, R. and F. W. Zettler. 1971. Virus infections of Colocasia and
Xanthosoma in Puerto Rico. Plant Dis. Reptr. 55:506-508.
3. Dehrot, E. A. and A. Ordosgoitti. 1974. Dasheen mosaic virus infection in
Colocasia and Xanthosoma in Venezuela. Plant Dis. Reptr. 58:1032-34.
4. Engler, A. 1915. Das Pflanzenreich, Regni vegetabilis conspectus. pg. 41-62.
5. Gooding, H. J. and Campbell, J. S. 1961. Preliminary trials of West Indian
Xanthosoma cultivars. Trop. Agriculture Trin. 38:145-52.
6. Hartman, R. D. 1974. Dasheen mosaic virus and other phytopathogens eliminated
from caladium, taro and cocoyam by culture of shoot tips. Phytopathology
7. Hartman, R. D. and F. W. Zettler. 1972. Mericloning as a potential means of
obtaining virus free plants from aroids commercially produced in Florida.
Proc. Fourth Org. Soil Vegetable Crops Workshop. 60-62.
8. Hartman, R. D., F. W. Zettler, J. F. Knauss and Eleanor M. Hawkins. 1972.
Seed propagation of caladium and dieffenbachia. Florida State Hort. Soc.
9. Hartman, R. D. and F. W. Zettler. 1972. Dasheen mosaic virus infections in
commercial plantings of aroids in Florida. Phytopathology 62:804. (Abstr.).
10. Haudricort, A. 1941. Los Colocasiees Alimentaires taross et Yautias). Rev,
Internal. de Bot. Appliquee et d'Agric. Trop. Vol. 21:40-54.
11. Kikuta, K., Leo D. Whitney and G. K. Parris. 1938. Seeds and seedlings of
the Taro, Colocasia esculenta. Amer. J. Bot. 25:186-188.
12. Marketing Florida Sub-Tropical Fruits and Vegetables. Summary 1973-74.
Federal-State Market News Service; Orlando, Florida.
13. Morton, Julia F. 1972. Cocoyams (Xanthosoma caracu, X. atrovirens and X.
nigrum), ancient root and leaf vegetables, gaining in economic importance.
Florida State Hort. Soc. Proc. 85:85-94.
14. Plucknett, Donald L. 1970. Colocasia, Xanthosoma, Alocasia, Cyrtosperma,
and Amorphophallus. In: Tropical root and tuber crops tomorrow Vol. 1.
Proc. of the 2nd Intern. Symp. on Trop. Root and Tuber Crops. University of
15. Zettler, F. W., M. J. Foxe, R. D. Hartman, J. R. Edwardson, and R. G. Christie.
1970. Filamentous viruses infecting dasheen and other araceous plants.