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Copyright 2005, Board of Trustees, University
S Homestead TREC Research Report SB85-1 March 11, 1985
In Vitro Responses of Cocoyam (Xanthosoma caracu) Lamina Discs
M. P. Asokan, S. K. O'Hair and R. E. Litz
University of Florida, IFAS
Tropical Research and Education Center
Homestead, FL 33031
In the aroid family (Araceae) edible species are found in five genera:
Xanthosoma, Colocasia, Cryptosperma and Amorphophallus (Engler, 1889).
Cocoyam, Xanthosoma sp. is often grown in moist tropical and subtropical
lowland areas as a starch staple crop (Onwueme, 1978). Like other aroids, it
is known by several common names, including malanga, tannia, yautia, and
macabu. Very little is know about the genetics of edible aroids, although a
wide range of genetic variability exists in the edible aroid germplasm
(Strauss et al. 1980). Identification and recovery of preferred traits is
possible using conventional breeding methods. Some preliminary efforts were
made in breeding studies of cocoyam (Jos et al. 1979; Volin, 1981). As a
result of cross between X. caracu and an ornamental Xanthosoma sp. ('Florida
ornamental'). Seedlings were produced with segregation in several traits,
such as plant height, cormel color, weight, and number. The inheritance
appeared to be quantitatively controlled. Gametic sterility (Jos et al. 1980)
and seed set failure (Coursey, 1968; Shaw, 1975) are obstacles to aroid
breeding. Successful attempts to improve aroids could benefit from tissue
culture procedures, eg., meristem and shoot tip culture to produce
disease-free material, rapid clonal propagation, and developing systems for
regenerating plants from callus, cells and protoplasts. The elimination of
bacterial and fungal pathogens from Dieffenbachia was developed by Knauss
(1976) and involved 3 steps, of indexing and in vitro culture. During each of
the 3 steps, media were closely examined for signs of pathogens. Plants were
thereby freed of bacteria and fungus for use as stock plants for commercial
multiplications. Excised shoot tips of Caladium, taro and cocoyam, free of
dasheen mosaic virus, were cultured successfully on MS media with 1.0 mg/l
Kinetin and 15.0 mg/l IAA hormonal supplements (Hartman,- Al vitro
clonal multiplication techniques based on ofot tip" ciiutuleha been
developed for Dieffenbachia plants by Litz and -on&,er (1977) and aylor and
Knauss (1978). No exogenous auxin was ess ntial for shoot .prolife action.
Leaf, stems and inflorescence explants hav alsob'eden-scccessfully tilized
for propagation of Spathiphyllum (Fonnesbeh and Fonnesbech, 1979),, Stem
pieces appeared to be the best explant source,. .Enhancedi.ptr'o1if ration was
achieved on auxin-free medium with 2.0 mg/l!PeA ("-benzyl-amino)-9-(2-
tetrahydropyranyl)-9H-purine). In Anthurium adventicious shoots were also
induced from callus derived from leaf pieces (Pierik, 1976). Plant
regeneration from leaf explants may also be possible in edible aroids. This
could be used as a model for plant regeneration from cells or protoplasts of
mesophyll tissue. The first report of successful edible aroid tissue culture
was by Mapes and Cable (1972) who cultured shoot tips of several cultivars of
Colocasia esculenta. In taro, organogenesis from callus was reported by Abo
El-Nil and Zettler (1976). Similar results were reported with Xanthosoma
(Staritsky, 1974; Strauss and Arditti, 1980). Extensive taro tissue culture
procedures were documented by Arditti and Strauss (1979).
Recent advances in plant cell culture offer new approaches to crop
improvement. In potato, somaclonal variants have been regenerated from
protoplasts derived from mesophyll tissue (Shepard et al. 1980). This has
become a model for other crops. In order to develop such a system in edible
aroids a study was undertaken to evaluate in vitro responses of lamina tissue
to different media and plant hormonal formulations. This report describes the
in vitro responses of lamina discs to NAA/BA hormonal conditions.
Materials and Methods
Explants were removed from greenhouse grown plants that had been
fertilized with 10% modified Hoagland solution (Johnson et al. 1982). Newly
emerged leaves were collected, washed in 70% alcohol for 4 minutes and 20%
chlorox for 15 minutes followed by thorough washing in sterile double
distilled water. Lamina discs (1.0 cm diameter) relatively free of veins were
inoculated into culture tubes. The medium consisted of modified Murashige and
Skoog basal formula (1962) with 500 mg/1 NH NO The following hormonal
supplements were added to the medium in all combinations: 0.0-8.0 mg/l BA with
0.0-4.0 mg/1 NAA. The pH of the media was adjusted to 5.8 prior to
autoclaving for 15 minutes at 1.1 kg/cm and 1210C. Cultures were maintained
in darkness within a growth chamber at 240C for 3 months, where upon, they
were grown under a photoperiod of 16 h light (1.5 klux) provided by cool white
fluorescent bulbs at 250C. Two weeks after transfer to light, the amount of
callus formation was rated numerically as follows: 1) no callus: 2) localized
callus induction; 3) localized callus proliferation; 4) proliferation over the
entire explant; 5) massive callus proliferation.
Results and Discussion
Callus formation was observed in 88% of the cultures after 3 months.
Maximum callus proliferation was observed within the hormonal range of 1.0-2.0
mg/1 NAA with 0.4-4.0 mg/1 BA. BA was not essential for callus formation,
since callus formation occurred in all cultures free of BA. However, media
without NAA did not support callus formation. This is indicative of the
primary role of auxin in callus production in this cultivar. Maximum callus
proliferation and root formation were observed within the same hormonal range
of 1.0-2.0 mg/1 NAA with 0.4-4.0 mg/l BA. No shoot initiation was observed.
The use of tissue culture systems for cultivar improvement has great promise
for the edible aroids. Development of somaclonal variants coupled with
techniques for screening and isolating such variants can produce exciting
results (Larkin and Scowcroft, 1981). In Colocasia cell cultures have been
exposed to progressively increasing levels of sea water (Arditti, 1981), and
cell lines have been identified that can tolerate 60% sea water. Higher
protein levels and greater disease resistance may also be possible in the
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differentiation of roots and shoots from stem tip cultures of Colocasia
esculenta. Proc. Ann. Meeting Bot. Soc. of Amer. p. 7 (Abstract).
2. Arditti, J. and M. S. Strauss. 1979. Taro tissue culture manual. South
Pacific Commission. March 1979.
3. Arditti, J. 1982. Tissue culture of Taro. Proc. Inter. Sym. Singapore,
4. Coursey, D. G. 1968. The edible aroids. World Crops 20:25-30.
5. Engler, A. 1889. 'Araceae', Engler u prantl, die naturlichen.
6. Fonnensbech M. and A. Fonnesbech. 1979. In vitro propagation of
Spathiphyllum. Sci. Hortic. 10:21-26.
7. Hartman, R. D. 1974. Dasheen mosaic virus and other phytopathogens
eliminated from caldium, taro and cocoyam by culture of shoot tips.
8. Johnson, L. B., D. L. Stuteville, and D. Z. Skinner. 1981. Regeneration
of alfalfa plants from protoplasts of selected regen S clones. Plant
Sci. Lett. 20:297-304.
9. Jos, J. S., Bai Vijaya, and N. Hrishi. 1980. Female fertility in
Tannia. Ann. Bot. 45:123-125.
10. Knauss, J. F. 1976. A tissue culture method for producing Diffenbachia
picta cv. 'Perfection' free of fungi and bacteria. Proc. Fla. State
Hort. Soc. 89:293-296.
11. Larkin, P. J. and W. R. Scowcroft. 1981. Somaclonal variation a novel
source of varibility from cell cultures for plant improvement. Theor.
Appl. Genet. 60:197-214.
12. Litz, R. E. and R. A. Conover. 1977. Tissue culture propagation of some
foliage plants. Proc. Fla. State Hort. Soc. 90:301-303.
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bioassays with tobacco tissue cultures. Physiol. Plant 15:473-497.
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Onwueme (ed.). The tropical tuber crops, John Wiley & Sons, New York,
16. Pierik, R. L. M. 1976. Anthurium andreanum plantlets produced from
callus tissues cultivated in vitro. Physiol. Plant 37:80-82.
17. Shaw, D. E. 1975. Illustrated notes on flowering, flowers, seeds an
germintaion in taro (Colocasia esculenta). Res. Bull. Papua New Guinea
Dept. Agric. Stk. Fish. 13, p. 39-59.
18. Shepard, J. F., D. Bidney, and E. Shahin. 1980. Potato protoplasts in
crop improvement. Science 208:17-24.
19. Staritsky, G. 1974. Xanthosoma brasiliense Engl. propagated virus-free
in vitro?. Trop. Root and Tuber Crop Newsletter, 7:38-39.
20. Strauss, M. S., G. C. Stephens, G. C. Gonzales, and J. Arditti. 1980.
Genetic variability in Taro, Colocasia esculenta (L.) Schotr (Araceae).
Ann. Bot. 45:429-437.
21. Strauss, M. S. and J. Arditti. 1980. Plantlet regeneration from shoot
tip cultures of Xanthosoma caracu. Ann. Bot. 45:209-212.
22. Taylor, M. E. and J. E. Knauss. 1978. Tissue culture multiplication and
subsequent handling of know pathogen-free Dieffenbachia maculata cv.
'Perfection'. Proc. Fla. State Hort. Soc. 91:233-235.
23. Volin, R. B. and A. J. Beale. 1981. Genetic variation in F cocoyam
(Xanthosoma sp.) hybrids. Proc. Fla. State Hort. Soc. 94:235-238.