Quantitative Growth Relationships of Cassava (Manihot esculenta Crantz): Crop Development in a Savanna Wet Season

Growth characteristics of Manihot esculenta Crantz cv. Cubanawere determined for a crop, cultivated in savanna soil withfive different levels of fertilizer. A population of 25000 plantsha^–1 was studied using conventional growth analysis techniques. The storage root does not act as a sink for large amouns ofassimilates and differences in growth response were mainly aresult of the morphology development and function of leavesin the cassava canopy (source activity). Thus, during tuberization,the cultivar Cubana produces a progressively higher proportionof new leaves, maintaining throughout the season a relativelyhigh net assimilation rate and leaf area index. Manihot esculenta Crantz, Cassava, source-sink relationship, net assimilation rate, leaf area index, growth analysis     

Transfer of Mass and Energy in a Cassava (Manihot esculenta Crantz cv. Cubana) Community 1. Microclimate and Water Vapour Exchange in a Savanna Climate

The energy balance approach was used to evaluate the transferprocesses which occur between a cassava community, growing duringa savanna wet season, and its environment. Crop performanceunder these conditions was also analysed. During this season, the soil profile remained near saturation,hence net radiation absorbed by the cassava crop during typicallow radiation days, was mainly dissipated as latent heat (78–86per cent); a process which depends on the growth stage and onthe foliage cover of the canopy. However, the seasonal rootenvironment, with a sufficient water supply, contrasted withthe extremely variable shoot environment, because the dailyflux density of short wave radiation input reached values similarto those reported for typical dry season days. On these days,cassava responded to environmental stress mainly by a reductionin transpiration. At the end of the wet season soil water content markedly decreased,an additional stress factor on the roots, which produced a notablereduction of cassava leaf area index. Therefore, the moderatechanges in energy partitioning determined by morphological andphysiological adaptive responses of cassava, produce a hindrancein the equilibrium between water vapour transfer and the surroundingsavanna environment. Manihot esculenta Crantz, cassava, microclimate, energy balance, heat fluxes     

Constituents and secondary metabolite natural products in fresh and deteriorated cassava roots

A phytochemical analysis of cassava (Manihot esculenta Crantz) fresh roots and roots suffering from post-harvest physiological deterioration (PPD) has been carried out. The first isolation and identification of galactosyl diacylglycerides from fresh cassava roots is reported, as well as β-carotene, linamarin, and β-sitosterol glucopyranoside. The hydroxycoumarin scopoletin and its glucoside scopolin were identified from cassava roots during PPD, as well as trace quantities of esculetin and its glucoside esculin. There is no isoscopoletin in cassava roots during PPD.     

Accumulation of Hydroxycoumarins During Post-harvest Deterioration of Tuberous Roots of Cassava (Manihot esculenta Crantz)

The use of the root crop Cassava (Manihot esculenta Crantz)is constrained by its rapid deterioration after harvest. Chemicaland spectroscopic examination revealed the accumulation of fourhydroxycoumarins (esculin, esculetin, scopolin and scopoletin),compounds derived from the phenylpropanoid pathway, during thetime course of post-harvest deterioration. Fluorescence-microscopyrevealed their localization in the apoplast of the parenchyma.Scopoletin and scopolin showed the most dramatic increases inconcentration, peaking by day 2 after harvesting. A smallersecondary peak of scopoletin tended to be more pronounced incultivars showing lower susceptibility to deterioration. Evidencefor the metabolism of scopoletin to an insoluble coloured productby means of a peroxidase is presented. This product may be thecause of the discolouration of the vascular tissue during storage.Copyright 2000 Annals of Botany Company Cassava, hydroxycoumarins, Manihot esculenta, peroxidases, post-harvest physiological deterioration, wound response     

Effects of the Temperature of the Rooting Zone on the Growth and Development of Roots of Potato (Solanum tuberosum)

In solution culture the effect of optimal (20 °C) and supra-optimal(30 °C) root-zone temperatures on root growth and root morphologyof six potato clones (Solanum tuberosum L spp) was studied Growthwas compared with sweet potato (Ipomoea batatas L) and cassava(Manihot esculenta Crantz) Significant genotypical differencesin the responses of potato roots to supra-optimal temperatureswere observed, indicating the potential for selecting heat tolerantpotato clones In both heat tolerant and heat sensitive clones,the size of the root system was reduced by supra-optimal root-zonetemperature This was principally a result of decreased numberand length of lateral roots The first symptom of heat damagewas a reduction in the rate of cell division, followed by cessationof root elongation Bending of the apical root-zone togetherwith the formation of root hairs on the inner (concave) andlateral roots on the outer (convex) side were other symptoms,these coincided with the loss of starch granules in the root-cap Potato, genotypical differences, root morphology, root growth, temperature, Solanum tuberosum L     

An Assessment of Genetic Diversity Within a Collection of Cassava (Manihot esculenta Crantz) Germplasm Using Molecular Markers

Cassava (Manihot esculenta Crantz) cDNA clones were used todetect restriction fragment length polymorphisms in a collectionof Manihot germplasm maintained as in vitro plants at ORSTOM,Montpellier. The collection consisted of mostly African cultivarsof M. esculenta, together with a few M. glaziovii Mueller vonArgau and M. caerulescens Pohl, and some interspecific hybridsbetween M. esculenta and M. glaziovii. The clones revealed significantlevels of polymorphism both within and between the species;sufficient to construct dendrograms indicating the genetic diversitywithin the collection.Copyright 1993, 1999 Academic Press Cassava, Manihot esculenta (Crantz), restriction fragment length polymorphisms, RFLPs, genetic diversity     

Source-to-sink gradient of potassium in the phloem

The potassium contents of bark strips of cassava (Manihot esculenta Crantz) and of phloem exudate of castor bean (Ricinus communis L.) were analyzed at different regions of the stem. In cassava, a peak in potassium content was observed near the first mature leaf, leveling off both above and below this point. In castor bean, only a downward decreasing gradient was observed. In both plants, the direction of the potassium gradient coincided with the presumed direction of assimilate flow.     

Development and application of transgenic technologies in cassava

The capacity to integrate transgenes into the tropical root crop cassava (Manihot esculenta Crantz) is now established and being utilized to generate plants expressing traits of agronomic interest. The tissue culture and gene transfer systems currently employed to produce these transgenic cassava have improved significantly over the past 5 years and are assessed and compared in this review. Programs are underway to develop cassava with enhanced resistance to viral diseases and insects pests, improved nutritional content, modified and increased starch metabolism and reduced cyanogenic content of processed roots. Each of these is described individually for the underlying biology the molecular strategies being employed and progress achieved towards the desired product. Important advances have occurred, with transgenic plants from several laboratories being prepared for field trails.     

Gene-based microsatellites for cassava (Manihot esculenta Crantz): prevalence, polymorphisms, and cross-taxa utility

Background  

Cassava (Manihot esculenta Crantz), a starchy root crop grown in tropical and subtropical climates, is the sixth most important crop in the world after wheat, rice, maize, potato and barley. The repertoire of simple sequence repeat (SSR) markers for cassava is limited and warrants a need for a larger number of polymorphic SSRs for germplasm characterization and breeding applications.     

Characterization of Rhodanese from Cassava Leaves and Tubers

Rhodanese activity has been established in the leaves, in thepeel, and in the flesh of the tuberous part of Manihot esculentaCrantz. The pattern of distribution of enzyme activity is shownto follow that of the concentration of the cyanogenic glucosideestimated on the basis of HCN released. For the first time,the presence of rhodanese is reported in higher plant tissuesother than the leaves. Identity has been established betweenrhodanese from peel, leaves, and flesh of the cassava plant.The enzyme is inhibited by cyanide in the absence of thiosuiphateor cysteine. Rhodanese is suggested to play a role in the detoxificationof cyanide in cassava.     

Overexpression of MinE gene affects the plastid division in cassava

The MinE protein plays an important role in plastid division. In this study, the MinE gene was isolated from the cassava (Manihot esculenta Crantz) genome. We isolated high quality and quantity protoplasts and succeed in performing the transient expression of the GFP-fused Manihot esculenta MinE (MeMinE) protein in cassava mesophyll protoplasts. The transient expression of MeMinE-GFP in cassava protoplasts showed that the MeMinE protein was located in the chloroplast. Due to the abnormal division of chloroplasts, overexpression of MeMinE proteins in cassava mesophyll protoplasts could result in fewer and smaller chloroplasts. Overexpression of MeMinE proteins also showed abnormal cell division characteristics and minicell occurrence in Escherichia coli caused by aberrant septation events in the cell poles.     

Evaluation of the effects of elevated CO2 concentrations on the growth of cassava storage roots by destructive harvests and ground penetrating radar scanning approaches

Cassava (Manihot esculenta Crantz) production will need to be improved to meet future food demands in Sub-Saharan Africa. The selection of high-yielding cassava cultivars requires a better understanding of storage root development. Additionally, since future production will happen under increasing atmospheric CO₂ concentrations ([CO₂]), cultivar selection should include responsiveness to elevated [CO₂]. Five farmer-preferred African cassava cultivars were grown for three and a half months in a Free Air CO₂ Enrichment experiment in central Illinois. Compared to ambient [CO₂] (~400 ppm), cassava storage roots grown under elevated [CO₂] (~600 ppm) had a higher biomass with some cultivars having lower storage root water content. The elevated [CO₂] stimulation in storage root biomass ranged from 33% to 86% across the five cultivars tested documenting the importance of this trait in developing new cultivars. In addition to the destructive harvests to obtain storage root parameters, we explored ground penetrating radar as a nondestructive method to determine storage root growth across the growing season.     

A Rapid Non-destructive Method for the Estimation of Leaf Areas in Cassava

A rapid and non-destructive method of estimating leaf areaswas required for detailed study of new cassava varieties. Theoutlines of leaves were traced in the field and leaf areas wereobtained with a planimeter. Variety Caricass 2 was chosen fordetailed study and 50 leaves of each lobe number (three to ninelobes per leaf) were measured. The length and width were recordedfor all lobes and correlations were made with leaf areas. Alllobe lengths and length x width were highly correlated withleaf area. It is therefore necessary to measure the length ofonly one lobe to get an estimate of leaf area. Comparisons ofleaves with five and seven lobes from Caricass 1, Caricass 3and a local variety showed that these varieties could be measuredin the same way and that the regression coefficient for Caricass2, Caricass 3 and the local variety were not significantly different.A common regression coefficient could be used to estimate leafarea on all three varieties. Manihot esculenta Crantz, cassava, root crop, leaf area     

Effects of Orientation and Root Position on Apical Dominance in a Tropical Woody Plant

Stem cuttings of cassava (Manihot esculenta Crantz), rootedat one or both ends, were grown at a range of orientations fromthe vertical. Basally rooted cuttings showed strong apical dominanceonly in upright or near-upright positions. Basal shoots generallydominated when the stem was horizontal, while completely invertedstems exhibited weak apical dominance or no dominance at all.Cuttings rooted at the apical end were little affected by changedorientation, apical dominance being present throughout. Effectsof each root system could be detected in cuttings rooted atboth ends. The results are discussed in relation to currentthinking on the mechanism of apical dominance, gravimorphiceffects in woody plants, and the role of the ‘root-factor’in the control of shoot growth.     

木薯UGT41基因对细菌性枯萎病的抗性研究北大核心CSCD

糖基转移酶广泛存在于植物中,其中UDP依赖型糖基转移酶(UDP-glycosyltransferases,UGTs)基因家族是糖基转移酶中的一大类。该研究以华南124木薯品种(Manihot esculenta cv.SC124)为材料,利用RT-PCR技术克隆木薯MeUGT41基因,以病毒诱导干扰木薯MeUGT41基因的表达量,并对基因干扰植株进行细菌性枯萎病抗性评价,为研究MeUGT41基因在木薯抵抗细菌性枯萎病的抗病机理奠定基础。结果表明:(1)地毯草黄单胞菌(Xamthomonas axonopodis pv.Manihotis,Xam)可显著诱导木薯MeUGT41基因表达。(2)成功构建MeUGT41的病毒诱导基因沉默(VIGS)载体,将干扰载体转化至木薯叶片进行MeUGT41基因沉默,荧光定量PCR检测结果显示,木薯叶片中MeUGT41基因的表达量显著下降。(3)Xam侵染实验表明,干扰抑制MeUGT41基因表达可显著降低木薯植株叶片对Xam病菌侵染的抵抗能力。研究认为,木薯叶片中MeUGT41基因具有抵抗Xam病菌侵染的能力。     

The effect of the cassava green mite Mononychellus tanajoa on the growth and yield of cassava Manihot esculenta in a seasonally dry area in Kenya

The effect of the cassava green mite Mononychellus tanajoa on the growth and yield of cassava Manihot esculenta was studied over a 10-month period in two field trials near Lake Victoria in Kenya. One plot was maintained free of mites by means of acaricide, while the other was artificially infested.The highest population density of M. tanajoa occurred during the dry season. A maximum leaf area index (LAI) of about 2 was reached at the onset of the dry season. The total leaf area of mite infested plants was reduced compared with uninfested plants during the dry spell. During the following rainy season infested plants recovered and attained the same leaf area as uninfested plants. A multiple regression model predicting the leaf area showed that 58% of the seasonal variation could be explained by plant age, soil water, and leaf injury.The net growth rate of infested plants was lower than that of uninfested plants. Maximum values of 21 (infested plants) and 49 (uninfested plants) g m^-2 week^-1 were attained at the onset of the second rainy season. No difference was found between uninfested and infested plants with respect to net assimilation rates per unit leaf area during the dry season. The net assimilation rates reached a maximum almost at the same time as the growth rates, but the infested plants peaked slightly earlier and at a lower level than the uninfested plants. M. tanajoa did not affect the relative allocation of dry matter into stems and storage roots, but the absolute allocation of dry matter declined with increasing mite injury. Thus, after 10 months the dry matter of infested plants was reduced by 29% and 21% for storage roots and stems, respectively, compared with the uninfested plants.     

Somatic Embryogenesis in Cassava: The Anatomy and Morphology of the Regeneration Process

Anatomical and morphological studies demonstrated that somaticembryos developed similarly on mature seed and clonal leaf explantsof cassava (Manihot esculenta Crantz) cultured for 20–24d on Murashige and Skoog (MS2) basal medium supplemented with4.0 mg l^–1 2,4-D (Stage 1) before transfer to MS2 basalmedium supplemented with 0–01 mg l^–1 2,4-D and 0–1mg l^–1 6-benzylaminopurine (Stage II medium). Within 7d of inoculation onto Stage I medium, cell divisions occurredin the adaxial tissues of cotyledon-piece and leaf-lobe explants,and associated with this was the development of embryogeneticprotusions and ridges on the adaxial surface. Foliose structuresand somatic embryo initials developed from these tissues oncotyledon, embryonic axis and leaf-lobe explants and, when cultureswere transferred to Stage II medium, further somatic embryodevelopment occurred. Somatic embryos apparently originatedfrom groups of cells and were identified by the presence ofa closed root axis, a shoot axis and cotyledons of similar shapeand venation to those of zygotic embryos. Somatic embryos hadno vascular connection with parental cultures. Manihot esculenta, cassava, somatic embryogenesis, tissue culture, anatomy, morphology, morphogenesis     

Proteome characterization of cassava (<Emphasis Type="Italic">Manihot esculenta</Emphasis> Crantz) somatic embryos,plantlets and tuberous roots

Background  

Proteomics is increasingly becoming an important tool for the study of many different aspects of plant functions, such as investigating the molecular processes underlying in plant physiology, development, differentiation and their interaction with the environments. To investigate the cassava (Manihot esculenta Crantz) proteome, we extracted proteins from somatic embryos, plantlets and tuberous roots of cultivar SC8 and separated them by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).     

Germination of Stored Cassava Seed at Constant and Alternating Temperatures

Cassava seed is only capable of germinating over a restrictedrange of constant temperatures. During storage the optimum constanttemperature for germination decreases from about 35 to 30 °Cor possibly less. The rate at which the optimum temperaturechanges during dry storage increases with increase in storagetemperature over the range 0 to 40 °C. Some alternating-temperatureregimes (16 h at the lower temperature; 8 h at the higher temperature)can provide conditions as favourable for germination as theoptimum constant temperatures. Furthermore, it has been shownthat temperature alternation itself is stimulatory because whenthe range of the alternation does not include the optimum constanttemperature value, percentage germination is often higher thancould be obtained at any constant temperature within the range,though this stimulatory response declines during storage. Forthese reasons it is provisionally recommended that cassava seedshould be germinated at 25/35 °C which is as stimulatorya treatment as any which has so far been investigated and hasthe advantage of encompassing the range over which the optimumconstant temperature changes during storage. Manihot esculenta Crantz, cassava, germination, dormancy, seed viability, storage of seeds, after-ripening