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     

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     

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     

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     

The possible involvement of a spore agglutinating factor(s) in various plants in establishing host specificity by various strains of black rot fungus, Ceratocystis fimbriata

Extracts, possibly containing a factor(s) which agglutinatesspores of Ceratocystis fimbriata, were obtained from the sweetpotato, potato, taro, cucumber and kidney bean. The factor(s)seemed to be involved in the expression of host specificityby various strains of C. fimbriata. The agglutinating factor(s)from sweet potato root had a high molecular weight and was inactivatedby pronase or macerozyme treatment. (Received March 6, 1974; )     

Seed Storage and Germination and Seedling Proliferation in Taro, Colocasia esculenta (L) Schott

Taro seeds maintained under c. 40 per cent r.h. and 22 ±2°C retained higher viability than those stored under otherexperimental conditions. Germination was more than 60 per centon a number of defined and undefined media. Rates above 80 percent were obtained on a greenhouse potting mix or its extractor distilled water with filter paper as a support. When maintainedin the dark, seedlings cultured in vitro on one of several definedmedia etiolated and produced atypical, elongated internodeswhich resemble those of vining aroids. Plantlets which developedat their nodes were removed and raised to maturity. Colocasia esculenta (L.) Schott, taro, seed storage, seed germination, seedling proliferation     

Studies on factor(s) in sweet potato which specifically inhibits germ tube growth of incompatible isolates of Ceratocystis fimbriata

Sweet potato root contained a factor or factors which differentiallyinhibited the growth of various isolates of Ceratocystis fimbriata.The factor scarcely inhibited germ tube growth of sweet potatoisolate, compatible to sweet potato. On the other hand, thegrowth of prune, oak, taro and almond isolates, all incompatibleto sweet potato, was strongly inhibited. The germ tube growthof coffee and cacao isolates, incompatible to sweet potato,were less inhibited. Inhibitory factor was distributed throughvarious fractions when centrifuged on a sucrose density gradient.The germ tube growth of pre-germinated oak isolate became lesssensitive to the inhibitory factor after being treated withpronase, suggesting the interaction of the factor with someprotein-containing surface structure of the fungal cell. Treatmentof the factor by phospholipase c, lipase and pronase causedno changes in its inhibitory activity, whereas periodate treatmentpartially inactivated the factor. These results suggest thatthis inhibitory factor constitutes one of the factors determiningthe specificity in sweet potato-C. fimbriata interactions. (Received July 18, 1977; )     

Reversible Structural Changes Associated With Callus Formation and Plantlet Development from Aseptically Cultured Shoots of Taro (Colocasia esculenta var antiquorum)

Taro callus maintained on Knop's medium with 2, 0·2 or0·02 mg l^–1 2,4,5-trichiorophenoxyacetic acid (2,4,5-T)or Linsmaier-Skoog (LS) containing 1 mgl^–1 of the cytokininadenine-N-benzyl-9-tetrahydro-2H- pyran-2-yl (SD8339) or 6 dimethylaininopurineand 0·1 mgl^–1 -naphthaleneacetic acid underwenta transition to a stable organized growth form which is referredto as a calloid. On transfer to LS medium th 0·2 mgl^–12,4,5-T in the absence of cytokinin the calloid reverts backto callus. Colocasia esculenta(L.)Schott, taro, callus, calloid, in vitro selection, histology, micropropagation, tissue culture, cytokinin     

Accumulation and Partitioning of Dry Matter in Taro [Colocasia esculenta (L.) Schott]

A field study was conducted as part of an ongoing effort tocollect data on patterns of leaf area development and dry matteraccumulation and partitioning among various plant parts duringgrowth and development of two taro cultivars. Plants were harvestedfor biomass about every 6 weeks during the growing season. Ateach harvest, plants were separated into various plant parts,and their dry matter content was determined. The first 80 dafter planting were characterized by low rates of dry matteraccumulation, with only leaves, petioles, and roots showingsubstantial growth. Afterwards, increases in total dry matterwere mainly the result of corm and sucker growth. Corm bulkingoccurred after the attainment of maximal leaf area indices.The absence of an optimal leaf area index for a longer periodof time may have prevented the realization of higher dry matteryields. The partitioning of dry matter to the corms of bothcultivars remained almost constant especially after 150 d afterplanting. This process was in contrast to the partitioning ofdry matter to the suckers, which increased significantly untilthe end of the growing cycle.Copyright 1995, 1999 Academic Press Taro, Colocasia sp., growth, dry matter partitioning     

Efficacy of Fungicides for Control of Phytophthora Leaf Blight of Taro

Six fungicides were evaluated under greenhouse, laboratory,and dryland field conditions for control of Phytophthora leafblight of taro incited by P. colocasiae. Five separate criteriawere utilized to evaluate these fungicides: fungicidal activityin vitro; and fungicidal activity in vivo under conditions ofsimulated dew, simulated rainfall, greenhouse, and dryland fieldenvironments. In in vitro tests zoospores were killed at thefollowing concentrations: Dithane M-45, 5 ppm; Difolatan, 9ppm; Polyram, 65 ppm; Tribasic Copper Sulphate, 145 ppm; Benlate,210 ppm; and Dyrene, 260 ppm. Excellent control was obtainedwith Difolatan; good control with Dithane M-45 and Polyram;and poor control with Benlate, Tribasic Copper Sulphate, andDyrene. Results of in vivo tests correlated with those of thein vitro tests. Difolatan, Benlate, and Dyrene were the mostphytotoxic while Tribasic Copper Sulphate, Polyram, and DithaneM-45 were the least phytotoxic.     

Production of resistant starch from taro (Colocasia esculenta L. Schott) corm and determination of its effects on health by in vitro methods

The aim of the study was the production of resistant starch from taro (Colocasia esculenta L. Schott) corm and determination of its effects on health by in vitro methods. Starch was isolated from taro corms with 98% purity, and 10.4±0.5% amylose content. By application of heating, autoclaving, enzymatic debranching, retrogradation, and drying processes to taro starch for two times, resistant starch (RS) content was increased 16 fold (35.1±1.9%, dry basis). The expected glycemic index (eGI) of taro starch and taro resistant starch was determined as 60.6±0.5 and 51.9±0.9, respectively and the decrease in the glycemic index of taro resistant starch was found as statistically significant (P<0.05). The in vitro binding of bile acids by taro starch and taro resistant starch relative to cholesterol decreasing drug cholestyramine were 5.2±0.2% and 7.6±1.7%, respectively.     

PCR-based approach for mining of resistant gene analogues in taro (Colocasia esculenta)

Primers based on the conserved motifs were used to isolate nucleotide-binding sites (NBS) type sequences in taro (Colocasia esculenta). Cloning and sequencing identified three taro NBS-type sequences called resistance gene analogues (RGAs) that depicted similarity to other cloned RGA sequences. The deduced amino acid sequences of the RGAs detected the presence of conserved domains, viz. P-loop, categorising them with the NBS–leucine-rich repeat class gene family. Phylogenetic characterisation of the taro RGAs along with RGAs of other plant species grouped them with the non-toll interleukin receptor subclasses of the NBS sequences. The isolation and characterisation of taro RGAs have been reported for the first time in this study. This will provide a starting point towards characterisation of candidate resistance genes in taro and can act as a reference guide for future studies.     

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。     

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).     

The genetic structure of taro: a comparison of RAPD and isozyme markers

Germplasm characterization and evolutionary process in viable populations are important links between the conservation and utilization of plant genetic resources. Here, an investigation is made, based on molecular and biochemical techniques for assessing and exploiting the genetic variability in germplasm characterization of taro, which would be useful in plant breeding and ex situ conservation of taro plant genetic resources. Geographical differentiation and phylogenetic relationships of Indian taro, Colocasia esculenta (L.) Schott, were analyzed by random amplified polymorphic DNA (RAPD) and isozyme of seven enzyme systems with specific reference to the Muktakeshi accession, which has been to be proved resistant to taro leaf blight caused by P. colocasiae. The significant differentiations in Indian taro cultivars were clearly demonstrated by RAPD and isozyme analysis. RAPD markers showed higher values for genetic differentiation among taro cultivars and lower coefficient of variation than those obtained from isozymes. Genetic differentiation was evident in the taro accessions collected from different regions of India. It appears that when taro cultivation was introduced to a new area, only a small fraction of genetic variability in heterogeneous taro populations was transferred, possibly causing random differentiation among locally adapted taro populations. The selected primers will be useful for future genetic analysis and provide taro breeders with a genetic basis for selection of parents for crop improvement. Polymorphic markers identified in the DNA fingerprinting study will be useful for screening a segregating population, which is being generated in our laboratory aimed at developing a taro genetic linkage map.     

Antibiosis and antixenosis to Aphis gossypii (Homoptera: Aphididac) in Colocasia esculenta

Fifty cultivars of taro, Colocasia esculenta (L.) Schott (Araceae), collected from islands in Micronesia and Polynesia, eight cultivars from the University of Hawaii's taro germplasm collection, and a closely related aroid, Xanthosorna sagittifolium (L.) (Araceae), were screened for antibiosis and antixenosis to Aphis gossypii Clover. Life history data for A. gossypii were collected by assessing survivorship and fecundity of aphids caged on taro leaves in the field. Significant differences in aphid reproductive rate and longevity were observed among the taro cultivars, and cultivars were ranked from most resistant to most susceptible. Antixenosis was assayed in the laboratory in a multiround choice test where A. gossypii were offered four leaf discs excised from different taro cultivars. Additionally, field observations of aphid abundance on taro cultivars were made to corroborate clip cage studies and laboratory experiments. 'Iliuaua','Rumung Mary','Maria', 'Ketan 36', and'Agaga' were the most resistant in terms of reducing aphid fecundity and survivorship, whereas the Iliuana,'Purple', 'TC-83001', and 'Putih 24' were least preferred in aphid choice tests. X. sagittifolium consistently exhibited strong aphid resistance. Resistant cultivars identified in this study may form the basis of breeding programs seeking to combine aphid resistance with other desirable agronomic traits in taro.     

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.     

Predicting Prehistoric Taro (<Emphasis Type="Italic">Colocasia esculenta var. antiquorum</Emphasis>) Lo’i Distribution in Hawaii

Predicting Prehistoric Taro ( Colocasia esculenta var. antiquorum ) Lo’i Distribution in Hawaii. The artificial wetlands created through taro (Colocasia esculenta var. antiquorum) cultivation have played an important but controversial role in discourse on Hawaiian culture, history, and natural resource management. The extent of taro cultivation has risen and fallen dramatically with changes in population, trends, and culture since Hawaii was first settled by humans. However, since peak taro cultivation occurred before most historical records, it is unknown how much artificial wetland was created in prehistoric times. Past estimates of the extent of taro cultivation have been based on prehistoric population estimates, which are in themselves highly contested. Here we present a simple model based on geographic and climate limitations to predict the maximum amount and distribution of land that could have been dedicated to taro production on the main Hawaiian Islands. Using geographic information systems technology, and historical records of taro distribution, we created a map of potential prehistorical taro sites and total land cover. Our model predicts that prehistoric taro could have covered up to 12 times more land than suggested by past estimates. Limitations to this model include the use of current geographic characteristics to predict historical land use patterns and difficulties in creating parameters general enough to capture all sites without overestimating taro cultivation. Despite these limitations, this model does well encompassing known prehistoric and historical taro localities and should serve as a basis for revising estimated taro coverage.     

烟草和香芋上斜纹夜蛾的自然种群生命表

应用作用因子生命表方法,组建烟草和香芋上第2、3代斜纹夜蛾Spodoptera litura（Fabricius）自然种群生命表,分析作用因子对斜纹夜蛾种群数量的控制作用。结果表明,2005和2006年烟草和香芋上第2、3代斜纹夜蛾种群的增长倍数均以香芋高于烟草。无论烟草还是香芋上第2、3代斜纹夜蛾,均以“捕食及其它”的排除作用控制指数最大。如排除所有天敌等作用因子的作用,2005年烟草上第2、3代斜纹夜蛾自然种群趋势指数将分别增长31．2029和50．0371倍,香芋上第2、3代斜纹夜蛾自然种群趋势指数将分别增长29．3492和41．2873倍;2006年烟草上第2、3代斜纹夜蛾自然种群趋势指数将分别增长33．1421和75．4167倍,香芋上第2、3代斜纹夜蛾自然种群趋势指数将分别增长31．5357和70．5355倍。说明天敌等自然作用因子对斜纹夜蛾种群数量有较为明显的控制作用,而烟草上的自然作用因子的作用要强于香芋上的自然作用因子。     

芋侧球茎发生发育的形态学机理

观察了魁芋和多子芋腋芽、侧球茎发生发育的形态学变化规律,分析了主球茎顶芽和不同发育期腋芽中蛋白质的组成。结果表明,魁芋每一叶轮上腋芽数目为１;多子芋为３或３个以上,其中一个体积较大。魁芋侧球茎发育初期伸长的速度大于增粗,首先形成圆柱型,然后顶端膨大形成体积很小的侧球茎。多子芽腋芽伸的同时茎部明显变粗,首先形成圆锥型,然后发育成品种特有的形状。根据发育进程将腋芽发育分成ＡＢ１－ＡＢ９个时期,将主球茎