Callus Growth and Plantlet Regeneration in Taro, Colocasia esculenta var. esculenta (L) Schott (Araceae)

Explants of taro cultivars belonging to Colocasia esculentavar. esculenta have been nearly impossible to culture untilrecently. Here, we describe a method which induces callus formationfrom bud explants of Colocasia esculenta var. esculenta cv.Akalomamale, brings about shoot and root production, and leadsto plantlet regeneration. The medium used is half-strength Murashige-Skoog(HMS) solution containing 25 ml taro tuber extract (TE), 2 mg2, 4, 5-trichlorophenoxyacetic acid and 200 mg glutamine 1^–1.TE is an important requirement for bud explants and callus tissues.Root induction on callus-derived shoots (i.e. plantlet formation)occurs on HMS containing only 25 ml TE and 100 ml coconut water1^–1. Taro, Colocasia esculenta var. esculenta (L) Schott (Araceae), coconut water, micropropagation, plantlet regeneration, root formation, taro extract, tissue culture     

Plant regeneration in vitro of South Pacific taro (Colocasia esculenta var. esculenta cv. Akalomamale,Aracea)

Summary Axillary bud expiants from South Pacific (Solomon Islands) taro, Colocasia esculenta var. esculenta cv. Akalomamale (Araceae) cultured on a modified Murashige-Skoog medium containing 1 mg NAA 1^–1 and TE formed callus and produced multiple plantlets. Explants died if NAA was present at levels lower than 0.1 mg 1^–1. BA was not required and may have been inhibitory. Plantlets developed faster and became larger following transfer to a hormone-free medium two weeks after the start of culture. Fully grown plants were established in a potting mix and are growing well in a greenhouse.Abbreviations BA benzyladenine - BM basal medium - Ca Colocasia esculenta var. antiquorum - Ce Colocasia esculenta var. esculenta - Ck cytokinin(s) - CW coconut water - HSMSM half strength Murashige Skoog macroelements - HSMS half strength Murashige and Skoog medium - IM initial medium(ia) - MS Murashige and Skoog medium - NAA naphthaleneacetic acid - SM second medium - TE taro corm extract - UCI University of California, Irvine     

Amino acid sequences of ferredoxin isoproteins from Japanese taro (Colocasia esculenta Schott)

The amino acid sequences of ferredoxins (Fd A and Fd B) from Japanese taro (Colocasia esculenta Schott) were determined. They consisted of single polypeptide chains of 98 residues, and both Fds had molecular masses of 10700 and 10500, respectively. There was a 92% homology between the sequences of the isoproteins (Fd A and Fd B). These sequences were compared with those of the closely related plant Fds and their phylogenetic tree was constructed. Two ferredoxin isoproteins from Hawaiian taro (Colocasia esculenta Schott) were also isolated and their N-terminal sequences were determined to be identical to those of Japanese taro.     

Induction of callus from axillary buds of taro (Colocasia esculenta var. esculenta,Araceae) and subsequent plantlet regeneration

Summary Axillary buds of taro (Colocasia esculenta var. esculenta, Araceae) cultured on half strength Murashige-Skoog medium (HMS) containing taro extract (HMSTE) and 2, 4, 5-trichlorophenoxyacetic acid produce a compact, hard, slow growing callus which is not very active morphogenetically and produces only a few plantlets. When cultured on HMSTE plus 5 mg 1^–1 each of naphthaleneacetic acid and benzyl adenine (HMSNB) the buds produce a fast growing, friable and morphogenetically active callus. Meristematic regions form on the friable callus after 30 days on HMSNB. If transferred to HMSTE at this point the callus gives rise to plantlets. Addition of taro extract to the media is required for the culture of buds, induction of callus and plantlet regeneration.Abbreviations BA benzyl adenine - BNA b-naphthoxyacetic acid - CW coconut water (liquid endosperm) - DW dry weight - FW fresh weight - HMS half strength Murashige-Skoog medium - HMSCW HMSTE plus 100 ml CW 1^–1 - HMSNB HMSTE plus 5 mg 1^–1 each NAA and BA - HMSTE HMS plus 25 ml taro extract 1^–1 - HMSTR HMSTE plus 2 mg 2,4,5-T 1^–1 - MNA methyl-1-naphthaleneacetate - NAA naphthaleneacetic acid - OCPAA ortho-chlorophenoxyacetic acid - TE taro extract - 2,4,5-T 2,4,5-trichlorophenoxyacetic acid     

Seminal Root Growth in Sorghum (Sorghum bicolor) Under Allelopathic Influences from Residues of Taro (Colocasia esculenta)

The length of the seminal root (SR) axis and the number andlength of lateral roots (LRs) of sorghum (Sorghum bicolor Moench)were markedly inhibited by taro [Colocasia esculenta (L.) Schott]residues incorporated into a sand growing medium. The sand profilewas divided equally into zones with and without residues. Productionand elongation of the first-order LRs of the SR axis facingthe zone containing taro residues were severely suppressed.On the side facing the zone that was free of residues, productionand elongation of LRs was not inhibited. SR and LR growth wasdrastically impaired and many plants were killed when taro residueswere incorporated in large amounts into the uppermost 2 cm ofthe growing medium. The activity of the allelopathic substancesin the root zone appeared to be location-specific. Sorghum bicolor, seminal root, lateral root, Colocasia esculenta, taro, taro residues, allelopathic substances, root growth     

Structure and In Vitro Growth of Zygotic Embryos of Taro (Colocasia esculenta var. antiquorum)

Zygotic embryos of taro, Colocasia esculenta var. antiquorumwere examined using both light and scanning electron microscopyand cultured on Linsmaier-Skoog (LS) medium without the additionof growth regulators. Embryos present within mature seed consistof a hypocotyl-root axis and an undeveloped cotyledon and aresurrounded by two major types of endosperm cells, aleurone andstarchy endosperm. Embryos cultured on LS medium developed intomature plants only in the presence of endosperm tissue. Excisedembryos turned green after 2–4 d in culture and reacheda rapid growth period between days 4 and 6. Culture of taroembryos leading to viable plantlet development depends upon(1) removal of the outer and inner integument, and (2) the presenceof endosperm tissue (including an intact aleurone layer). Colocasia esculenta var. antiquorum, Araceae, taro, embryo culture, integument, endosperm     

In-Vitro Selection for Salt Tolerance of Taro (Colocasia esculenta var antiquorum)

Cultures of taro, Colocasia esculenta var antiquorum (L.) Schott,established from shoot tip explants were used to select forsalt tolerance. Presently, cultures are being maintained andproduce plantlets in 10–70 per cent artificial seawater.The results indicate that in vitro selection techniques forsalinity tolerance may prove useful in the development of salttolerant taro cultivars. In vitro selection, callus culture, micropropagation, salt tolerance, Colocasia esculenta, taro     

Antimetabolic effects of plant lectins towards nymphal stages of the planthoppers Tarophagous proserpina and Nilaparvata lugens

Taro Colocasia esculenta (L. Schott) and rice (Oryza sativa L.) form a major part of the staple diet of pacific islanders. Pest constraints hamper the sustainability of taro and rice production in the Pacific region. Insect feeding trials were conducted in vitro to determine the effects of plant lectins against planthopper pests of taro and rice. Lectins were incorporated into artificial diet at 0.1% (w/v) level. The lectins Galanthus nivalis agglutinin (GNA) and concanavalin A (Con A) showed significant antimetabolic effects towards third instar nymphs of taro planthopper (Tarophagous proserpina Kirkaldy) whilst Pisum sativum agglutinin (PSA) showed no significant effects toward the insect. Psophocarpus tetragonolobus agglutinin (PTA) showed significant antimetabolic effects towards third instar nymphs of rice brown planthopper (Nilaparvata lugens Stål). PTA also reduced honeydew excretion levels of rice brown planthopper, over a 24-hour period, demonstrating antifeedant properties of the protein.     

Trypsin inhibitors from Colocasia esculenta,Alocasia macrorrhiza and Cyrtosperma chamissonis

Trypsin inhibitors from three edible aroids of the family Araceae, viz. taro (Colocasia esculenta) var. esculenta) giant taro (Alocasia macrorrhiza) and giant swamp taro (Cyrtosperma chamissonis) obtained from the Pacific region, were isolated by affinity chromatography and purified by gel filtration. The M_r of these inhibitors, as determined by gel filtration were 35 000–38 000, but were ca 20 000 by SDS gradient PAGE. A time course of heating in SDS showed a ready dissociation of the native protein into subunits of equal size. Further experiments showed that there were no disulfide bonds between these subunits. A single N-terminal sequence was found for each inhibitor showing that the two subunits had similar primary structure. Each of the N-terminal sequences showed homology with that of soybean trypsin inhibitor. To our knowledge, this finding follows only one other example of a Kunitz family inhibitor being located in a monocotyledonous, rather than dicotyledonous, plant species, and indicates that the ancestral gene from which Kunitz family inhibitors originate predates the evolutionary divergence of flowering plants into monocotyledons and dicotyledons.     

Oxalate Exudation by Taro in Response to Al

Roots of taro (Colocasia esculenta [L.] Schott cvs Bun-long and Lehua maoli) exuded increasing concentrations of oxalate with increasing Al stress. This exudation was a specific response to excess Al and not to P deficiency. Addition of oxalate to Al-containing solutions ameliorated the toxic effect of Al.     

Taro (<Emphasis Type="Italic">Colocasia esculenta</Emphasis> [L.] Schott) Cultivation in Vertical Wet-Dry Environments: Farmers’ Techniques and Cultivar Diversity in Southwestern Ethiopia

Taro (Colocasia esculenta [L.] Schott) Cultivation in Vertical Wet-Dry Environments: Farmers’ Techniques and Cultivar Diversity in Southwestern Ethiopia. Taro (Colocasia esculenta [L.] Schott) is a food crop that was domesticated in Asia and the Pacific region and is now grown in the humid tropics. Following its arrival in Africa in ancient times, it may have adapted to the drier environments. In this ethnographic study, I present a particular case of taro cultivation and uses by a group of farmers in the mountains of southwestern Ethiopia. There are 36 named cultivars of taro for which diversity is maintained through different cultivation techniques and culinary practices in wet and dry environments that vary in elevation. Because taro in dry lowland environments has recently been replaced by the introduction of new crops, it is possible that the drought-tolerant eddoe-type cultivars, which are traditionally dominant in Africa, are now in danger of disappearing.     

江西铅山红芽芋脱毒苗球茎愈伤组织诱导及其再生体系的建立

以江西铅山红芽芋脱毒苗为试材,研究不同因素对红芽芋脱毒苗球茎愈伤组织诱导及其再生体系的影响,以期对红芽芋脱毒苗的再生体系进行优化。结果表明,红芽芋脱毒苗球茎愈伤组织诱导的最佳培养基是MS+TDZ 2 mg·L^-1+2,4-D 1 mg·L^-1。红芽芋脱毒苗球茎愈伤组织分化的最佳培养基是MS+TDZ 2 mg·L^-1+NAA 1 mg·L^-1。红芽芋脱毒苗不定芽生根的最佳培养基是1/2MS+NAA 0.5 mg·L^-1+PP₃₃₃ 0.5 mg·L^-1。红芽芋再生苗最好的移栽基质为发酵后的腐锯木屑。红芽芋脱毒苗球茎愈伤组织再生苗移栽时最佳的PP₃₃₃浓度为20～50 mg·L^-1。本试验成功建立了红芽芋脱毒苗球茎愈伤组织的再生体系,为红芽芋脱毒苗转基因的研究和种质创新奠定了基础。     

Cryopreservation of invitro-grown shoot tips of taro (Colocasia esculenta (L.) Schott) by vitrification. 1. Investigation of basic conditions of the vitrification procedure

Invitro-grown shoot tips of taro (Colocasia esculenta (L.) Schott.) were successfully cryopreserved by vitrification. Excised shoot tips precultured on solidified MS supplemented with 0.3M sucrose and maintained under a 16 h phtoperiod at 25°C for 16 h were loaded with a mixture of 2M glycerol plus 0.4M sucrose for 20 min at 25°C. The shoot tips were then sufficiently dehydrated with a highly concentrated vitrification solution (PVS2) for 20 min at 25°C prior to immersion into liquid nitrogen. Successfully vitrified and warmed shoot tips resumed growth within 7 days and developed shoots directly without intermediate callus formation. The average rate of shoot recovery amounted to around 80%, and the vitrification protocol appeared to be very promising for the cryopreservation of taro germplasm.Abbreviations DMSO Dimethylsulfoxide - EG ethylene glycol - LN liquid nitrogen - MS Murashige & Skoog medium (1962) - TDZ thidiazuron     

Genetic Variability in Taro, Colocasia esculenta (L.) Schott (Araceae)

An examination of two seedling populations indicates that geneticvariability can be obtained in taro by means of sexual propagation. Colocasia esculenta, dasheen, taro, alkaloids, anthocyanins, calcium oxalate, chlorophyll, genetic variability, nitrogen content, protein levels, in taro seedlings     

Evolutionary origins of taro (Colocasia esculenta) in Southeast Asia

As an ancient clonal root and leaf crop, taro (Colocasia esculenta, Araceae) is highly polymorphic with uncertain genetic and geographic origins. We explored chloroplast DNA diversity in cultivated and wild taros, and closely related wild taxa, and found cultivated taro to be polyphyletic, with tropical and temperate clades that appear to originate in Southeast Asia sensu lato. A third clade was found exclusively in wild populations from Southeast Asia to Australia and Papua New Guinea. Our findings do not support the hypothesis of taro domestication in Papua New Guinea, despite archaeological evidence for early use or cultivation there, and the presence of apparently natural wild populations in the region (Australia and Papua New Guinea).     

Quantitation of oxalates in corms and shoots of <Emphasis Type="Italic">Colocasia esculenta</Emphasis> (L.) Schott under drought conditions

Oxalate (calcium oxalate) accumulation in taro plants (Colocasia esculenta (L.) Schott) impacts their nutritional quality, producing acridity, causing lips, mouth and throat tissues swelling if consumed fresh. The oxalate content is related to photosynthesis, through the glycolate–glyoxylate oxidation pathway. The plant’s photosynthetic rate usually increases in non-stressed conditions. Differences in photosynthetic rate are indirectly related to the chlorophyll content index. Protein accumulation and starch variation are also important traits to understand the taro oxalate synthesis caused by drought and how they affect corm quality. The purpose of this study was to quantitate oxalates in taro corms and shoots submitted to drought conditions and to evaluate how stress response can affect the nutritional quality of taro whole-plant. Seven taro genotypes from Madeira, Canaries and Pacific Community (SPC) collections were grown in greenhouse conditions and submitted to different watering regimes for drought tolerance screening. Corms and shoots were harvested and evaluated for oxalates (soluble, insoluble and total), chlorophyll content index (CCI), crude protein, starch, starch solubility in water and starch swelling power. All accessions had very high calcium oxalate content. Drought-tolerant genotypes showed good osmotic response by oxalate precipitation and mobilization through shoot to corm tissues, photosynthesis adaptation by increase of CCI, protein accumulation, and very low starch hydrolysis. Sensitive-drought genotypes showed less mobilization of calcium oxalate, decreased photosynthetic rate and protein synthesis, and slight increase of starch hydrolysis. Variation in taro oxalate content is consistent and significantly correlated with the photosynthetic rate, carbohydrate metabolism and protein synthesis.     

Antioxidative enzymes and isozymes analysis of taro genotypes and their implications in <Emphasis Type="Italic">Phytophthora</Emphasis> blight disease resistance

Assessment of the differential expression of antioxidative enzymes and their isozymes, was done in 30 day-old ex vitro raised plants of three highly resistant (DP-25, Jhankri and Duradim) and one highly susceptible (N-118) genotypes of taro [Colocasia esculenta (L.) Schott]. Antioxidative enzymes were assayed in the ex vitro plants, 7 days after inoculation with the spores (15,000 spores ml⁻¹ water) of Phytophthora colocasiae Raciborski to induce taro leaf blight disease. Uninoculated ex vitro plants in each genotype were used as control. The activity of superoxide dismutase (SOD) and guaiacol peroxidase (GPX) increased under induced blight condition when compared with control. Increase in antioxidative enzymes was more (67–92%) in the resistant genotypes than that (21–29%) of the susceptible genotype. The zymograms of SOD and GPX in the resistant genotypes, with pathogenic infection, showed increased activity for anodal isoform of SOD and increased expression and/or induction of either POX 1 or POX 2 isoforms of GPX. In susceptible genotype, expression of the above isoforms was faint for SOD and nearly absent for GPX under both blight free and induced blight conditions. Induction and/or increased activity of particular isoform of SOD and GPX against infection of Phytophthora colocasiae in the resistant genotypes studied led to the apparent conclusion of linkage of isozyme expression with blight resistance in taro. This might be an important criterion in breeding of taro for Phytophthora leaf blight resistance.     

Field efficacy and predicted host range of the pickerelweed borer, Bellura densa, a potential biological control agent of water hyacinth

The North American noctuidmoth Bellura densa offers promise as abiological control agent for use in Africa andother countries invaded by water hyacinth. Anaugmentative release at a pond in Florida, USA,eliminated water hyacinth within a few months. Laboratory studies, though, indicated thatoviposition was indiscriminate and thatdevelopment was completed on taro (Colocasia esculenta [Araceae]) as well as onseveral Pontederiaceae. Acceptability of taroas a larval food plant was confirmed in thefield when larvae were found in isolated standsof taro in Florida. Evidence of use of Peltandra virginica (Linnaeus) (Araceae) wasnoted at another site. The distribution oflarval damage was compared at a site containinga mixture of 97% taro and 3% pickerelweed(Pontederia cordata). Larvae damaged87% of the pickerelweed compared to only about5% of the taro, suggesting spillover ontotaro. In another study, 416 larvae wereliberated into a concrete tank containing waterhyacinth (818 plants) surrounded by taro (96plants). Three months later, taro accountedfor only 4% of the damaged plants, less thanthe 11% expected if host selection had beenrandom. In a similar study, larvae wereliberated onto water hyacinth in a large tankdivided into thirds, with pickerelweed or taroat either end and water hyacinth in the middle. The distributions of F₁ egg masses andincidence of damage 3 months later indicatedthat pickerelweed was preferred over taro, but26% of the taro plants were damaged. Weconclude that while B. densa prefersplants in the Pontederiaceae, it is notrestricted to this plant family. Plants in theAraceae would be at risk if this insect werereleased outside of North America, particularlyin cropping situations near water hyacinthinfestations. Bellura densa could beuseful for water hyacinth management in theU.S. if effective augmentation strategies weredeveloped.