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Cassava - Science topic

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I am doing my research based on Indigenous knowledge, skills, tool, and techniques using cassava as the main crop to address climate change and food security in Papua New Guinean rural communities.
if you know of any websites to search or any articles to read or even better, if you've done some research on this topic and would to give me some tips, please let me know.
Thank you.
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Past project discussions
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can you represent other result similat to your result and compare between them
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"Empirical Analysis of the impact of New Technology adoption on the productivity of Cassava Flake in Nigeria: Case study, Cross River State Agricultural Zones"
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Dear @Ernest Samuel Impact factor (Clarivate analytics) is the widely accepted indicator to assess the importance of journals. You can choose journals based on the quality and quantity of data generated across years and locations, suitability of your article to specific journals, publication options ( open access/subscription based), and the like.
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If no, what other source of root crops can we accumulate such glycogen like polymer
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Dear @Ancel Rei Salazar Acuña You can access the below mentioned link, and the attached pdf; hope, these would be useful to you.
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i confused why MOCAF has higher starch digestibility than native cassava flour. i think it should lower because fermentation will break the amylopectin chain. But why?? could anyone help me?
I'm using DNS reagent to determine the digestibility
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We usually find that the Chips that is made from Cassava is more harder to chew as compared to the potato chips that we have in the market. So, please suggest a pretreatment for thbis Problem.
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You can check the paper below for more information:
Regards,
K
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Due to the presence of Polyphenol Oxidase that could cause browning in some cassava varieties of best quality traits, there is need for browning inhibitors.
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Dear @Emmanuel Oladeji Alamu Please also verify the attached PDF; hope, it may be useful.
In India, one institute "ICAR-CTCRI" has been working on root and tuber crops; you can contact the relevant scientist.
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Hi everyone?
I'm doing my thesis about Promoter regions in some jasmonate genes on cassava (M. esculenta). I have any questions about the DNA cloninig...
Is possible lose some pair bases (bp) of the promoter's sequence?. I mean, If I have my amplified product (promoter) of 1000 pb by PCR (normal), will I get the same sequence of 1000 pb (promoter) on the DNA cloning?
Under what circumstances get lose pair bases of a sequence?
Does get lose some DNA pb being inserted on a plasmid?
On the other hand, occurs the same in the DNA sequencing?
Excuse my english (is my first post) :)
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I agree with Sylvester Ochwo.
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Hi everyone!
Would be my first time that I make DNA Cloning (for my thesis), but I don't understand some things...
I dont know, ¿What plasmid (vector) use to cloning my promoter sequence of 1000pb (aprox)?, based on tree genes . Is used E. coli like a "host" ?
Futhermore, What is the rules to choose a correct/appropriate plasmid? Also, I'm looking for a plasmid inexpensive.
Thank yo (excuse my english)
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Hi Michael!
Thank you for your answer!
After the DNA clonning , I will make the DNA sequencing... With that I can Identify the Cis- regulatory elements (CRE´s)
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The affected plant (with others) has been under drought for sometimes and planted on re-used soil. Could these have any connections to the disease?
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The 2 likely diseases of cassava are necrosis and anthracnose (the canker, like you called it). And from the close-up view, I would go with your diagnosis (the latter).
Regarding the possible mode of transmission, the anthracnose disease is a fungal one, and is air-borne. The existence of infected stems or leaves is enough to spread the fungal spores, irrespective of whether the infected vegetative part is dead or not. Infected soil could as well be threatening. In your case, wind could have spread the disease during the drought season, if your soil is innocent.
I recommend you completely eradicate (destroy by burning) old/infected stems, and practice shifting cultivation; bearing in mind that the same fungal spp. can attack other crops like paw-paw and pepper.
Kind regards
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We intend to find out the effect of cassava effluent on a particular river that serves various purposes downstream.
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@ Williams F. Hansen, thanks for the insight.
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I want to understand the pros and cons of each starch hydrolysis method in the production of ethanol.
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In the ethanol prduction process from cassava starch, two main steps are involved: Hydrolysis and Fermentation. Hydrolysis converts cassava starch to glucose using acids or enzymes. Fermentation produces ethanol from glucose by ethanologenic organisms. Both acid and enzymatic methods have their own merits and demerits.
First of all, I would like to focus on merits and demerits of acid hydrolysis. In terms of merits, acid hydrolysis produces higher yield of glucose if the process is pefoemed at optimized conditions of acid concentration, solid to liquid ratio, reaction temperature, reaction time and agitation speed. Cost of acid is cheaper than enzymes. Process conditions may not be harsh. In terms of demerits, degradation products of glucose form during hydrolysis. It happens sometime, which is beyond experimenter's control. In such case, glucose yield decreased. Also, to everyone's knowledge, stoichiometrically, at 100% recovery, only 1.11 gram of glucose can be produced per gram of starch.
Next, let's discuss about enzyme hydrolysis. In terms of advantages, enzymes are specific, versatile and produce enhanced yield at optimum conditions of pH, temperature, time, mixing, concentrations of substrate, enzyme and inhibitor. In terms of disadvantages, cost of enzymes are expensive than acids. A single enzyme is not sufficient to produce glucose from starch. A mixture of amylases and amyloglucosiodases (or glucoamylases) are required for hydrolysis. In enzymatic hydrolysis itself, three steps are involved: Gelatinization, liquefaction and hydrolysis. Again, experimenter should keep stoichiometry in mind.
Thank you for this question which openend up my mind to provide elaborate answer,
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I want develop an HPLC or LC-MS for cyanogenic glycosides determination in cassava. Please share any protocols or references.
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We have more than 1000 cassava genotypes. We want to make the core set of germplasm. Is there any statistical analysis or programme to identify the core germplasm?
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You can use clustering and/or PCA
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The endophytes are in vitro....if u have pictures it will be of great help, thank you.
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Thank you very much
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Cassava is C3, C4 or C3-C4?
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Please look at the following below links which may help you in your analysis:
Thanks
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I need to know the best formulation for starter cultures to reduce softening time
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Kindly see the following RG link.
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Hello fellow scientists, I'm working on tissue culture for a number of food crop and terrestrial plants. Does anyone have an an optimized protocol for nappier grass, cassava and sweet potatoes? If anyone has any materials,kindly share them with me. My personal email - odongo.george@students.ku.ac.ke .
Thank you
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hello
i dont know
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Hello everyone,
I am working on a project where I am dealing with four different conditions. thats I am putting samples containing milk and cassava in plastic and container for storage under refrigerated and ambient conditions to determine the viability and effects of the conditions (plastic and glass, cassava and milk, and refrigerated and ambient) on the samples. I took measurements on every 24hours and 48hours every seven days for a period of one month. now I have available data but don't know how to go about with the analysis. I am familiar with sass.
can some please me.
best regards.
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Hi
Which model to use is according to your research question.
Need to clarify the statement:" every 24 hours and 48 hours for every week for a period of one month . " this will affect how the measurements are organized.
Hope that it is of benefit.
Yours,
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I observed that SPAD readings in cassava plants supplemented with irrigation were higher as compared to the plants grown under water deficit stress condition. I found the reverse trend in other research paper. Is it possible? Is there any possible explanation for this?? I shall be grateful if any research paper is provided reporting the same findings.
Thank you in advance
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Thank you for the insight (@Pratapsingh Khapte)
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The effluent is starchy, what sterilization method could be applied? In addition, how can we ensure substrate quality for quality control? Can we enrich the effluent with essential nutrients?
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The technology of producing ethanol from starch is internationally well developed. Waste stream of cassava - ethanol can be used for biogas production. For detail information consult https://www.probos.nl and https://www.jstor.org and https://www.academicjournals.org
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I am currently working on exploring the microbiome of cassava roots. So, I need to extract DNA from soil and root samples and the current political situation ordering the kit that I wanted (DNeasy PowerSoil Pro Kit (50)-Qiagen) due to usage in previous microbiome paper ( ) may not be possible within my timeframe.
The local supplier has these two kits available:
Does anyone have experience with these or know of papers where they have been used?
I'll be most grateful for advice!
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Hey Astrid,
I agree with Abhijeet. Try out the kit that is favoured in your country, if you have enough DNA to work with, that's all you want. Just put it out in the methods when you publish. Cheers!
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Hello,
I am currently working on exploring the diversity of endophytic bacteria and fungi in cassava roots. I first tried macerating the root samples with mortar and pestle, but this was very difficult due to the roots strong fibers. It looked like I was loosing most of the moisture into the mortar. As I need 1 gram to do my dilutions I wonder what tips can you give on how to get the most out of my samples while still ensuring getting the correct dilution?
A colleague suggested trying to mascerate using a Genogrinder. Do you think this is possible or is it too destructive of the sample? Could I add my 9 ml of MQ water and then my 1 gram sample with the beads?
I have also been considering cutting root slaps and making imprints directly onto the agar, does anyone have good experience with this?
Kind regards,
Astrid
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In order to assess the development of Fusarium oxysporum in roots and stems of cucumber plants, I cut the tissues in circa 1-2 mm slices with a scalpel or cutter before suspending in sterile water, blending for10 sec, check that all slices remain in the suspension, followed by 60 sec blending at high speed. One ml samples of the macerate and serial dilutions (1ml +9ml water in sterile test tubes) are poured in sterile Petri dishes and suspended in autoclaved 1.5% agar medium at 45°C.
The size of the blender will depend on the size of your sample and degree of colonisation. If you are planning dilutions you could already blend with a larger amount than 1ml.
The duration of blending probably requires adjustment. You can compare number of colonies developing for sub samples blended for various durations and so determine the duration which gives you the maximum number of fungal and/or bacterial colonies. For the bacteria you may spread 0.1 ml. of the suspension on the surface of the medium rather than incorporating it in the medium.
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We want to estimate the HCN content in cassava roots and tubers. Ezeigbo et al (2015) mentioned the method to estimate HCN content. But, They did not mention the preparation of alkaline picrate solution. Please help us.
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It is prepared by taking 9.16 gm of picric acid and volume is made upto 1000ml with 1N sodium hydroxide
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I am researching on development of activated carbon from cassava peelings in Uganda. However, there are many cassava varieties and are grown in different agricultural zones. My interest is in knowing whether there is any significant difference of the peel bio-composition depending on the zone where a variety is grown.
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Thanks Vitor.
So, does this mean that in my study I should concentrate on analysing the cassava varieties rather than basing on the ecological zones?
The most recent study shows that there are 217 cassava varieties grown in the 6 agro-ecological zones of Uganda (Nakabonge et al., 2017). How can I be able to zero onto particular varieties like 6 to base my study? 217 is alot and I am sure each variety has a different composition and hence the peel compositions too are different.
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I was trying to express the protein of sri lankan cassava mosaic virus coat protein gene which was cloned into pET28A+ expression vector and transformed into BL21(DE3) cells. Insead of getting the desired band size I am getting large band size after IPTG induction (instead of getting 35 kDa, i am getting around 120 kDa protein band size induced in SDS PAGE ). Can anyone help me to solve this issue?
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Hello,
Did you get the correct band size after PCR amplification?
Which restriction sites did you opt for?
Did you go for sequencing of the clone you used before the expression of protein?
It will help in understanding the situation better. Also, can you show me the gel picture?
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The best pH of a good silage should be around 5.5. We are trying to develop a methodology that can measure the pH of cassava over time to ensure that the quality is maintained. 
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it is a good method for measurement of PH
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I'm tring to establish a spiralling whitefly colony in the laboratory. I collected cassava leaves with eggs last month and now they have started emerging and needs to transfer them to a new host. Can anyone suggest me how to collect and release them. Thanks.
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Thanks for the references but they don't say how to collect and establish spiralling whiteflies in the lab for research.
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I want to compare leaf water potential of cassava leaves grown under normal condition and mid-season water deficit stress. I am looking for suggestions or precautions to be taken at the time of recording leaf water potential in field, which may be the selection of leaf (lower/higher canopy), sampling size etc.
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The inherent variation among plants needs also to be considered and this depends to a large extent on the variation in soil water content. Proper randomisation is of huge importance, especially if measuring outdoors as water potential will track changes in wind and irradiation. If you use paired measurements in time (one from each treatment) then you will minimise bias. Leaves are not replicates, just samples. Be aware of what are the true replicates in your experimental design (pots, plots, etc) and take mean or median of all leaves/plant measured within a single experimental unit. With a careful sampling strategy and well controlled conditions you will need fewer that 300-400 leaves per treatment. With a sampling strategy that does not control for bias, you will not get reliable estimates with any number of leaves.
Other important points: timing of measurements, traditionally, either pre-dawn or midday. In either case, the measuring period should not extend for more than one or two hours unless you include time in your data analysis. If outdoors, try to measure under clear sky conditions, and avoid days with changing cloud cover in the case of midday measurements. Handling of leaves: be very fast, the shortest the time between leaf excision and enclosing it into the chamber, the better. Try to keep this time to less than one minute, be even faster at midday if stomata are open.
Youngest fully expanded leaves are frequently used. If measuring at midday, make sure to avoid shaded leaves. Use a stereo microscope or magnifier and make sure you can easily see when the cut surface gets wet. Increase the pressure slowly enough so that you can record the exact balancing pressure value. Discard any leaf that is broken, especially in the petiole or veins as this will allow N2 to enter the xylem directly.
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how can i isolated protein from leguminous sources and incorporate into cassava flour to enrich it.
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You can enrich / fortify cassava with protein-rich food material as described in the attached article. In this work optimum (daily nutritional requirement for a balanced diet) protein content in carbohydrate-rich cassava was sought.
Soybean was preferred over several others, such as groundnut due to its exceptionally rich protein content with less lipid; to enable manipulation of nutritional composition without offset. Feel free to contact me if you need anything extra.
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Is it feasible to adopt OBR to produce bio-oil from cassava waste or other agricultural waste material. If it is feasible, what are the influence variables that can influence bio-oil yield?
An article related to research in the study is welcome!
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Liquid biofuel (bio-oil) can be produced by pyrolizing cassava peel. It is cost effective method.
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weed growth after 24weeks after planting and its effect on cassava yield?
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Many researchers and producers (farmers) say that cassava is good as animal feed, especially as an energetic suplement in pigs or small ruminants. Do you have any experience in the use of cassava as animal feed in pigs or small ruminants? How do you use cassava and by-products in animal feed?, Could you recommended some formulations for pigs and small ruminants using cassava and by-products? Cassava has a big potencial as animal feed!!
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thanks, it is true, we can use cassava for both, human and animals (because animal will give food too for us!!). In times of climate challenges cassava is and will be an important crop that we need to take in account
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Quality cassava genetic improvement depends on the availability of superior cassava landraces and this is being threatened in Uganda due to changing social economic status and challenges as a result of  climate change effects and disease occurrence with in and among cassava landraces.
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you can go through
Climate change and on farm conservation of crop landraces in centres of diversity
How social organization shapes crop diversity: an ecological anthropology approach among Tharaka farmers of Mount Kenya
Evolutionary response of landraces to climate change in centers of crop diversity
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Need to relate the staple cereals data with cheap substitute such as cassava flour. 
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If you want to work on FAOSTAT data in a GIS, you can use the QGIS. This program has a FAOSTAT plugin and you can spatialize the data.
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Plant pathology
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Dear Salvador,
many thanks for your reply and clarification, your suggestions will be more helpful for me in the continuation
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cassava specific gene  for identification by PCR or rea;time PCR
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you can use mitochondrial DNA sequence (cytochrome ) to generate cassava specific primers.
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i wish to know how cassava foliage  can improve milk yield in dairy cattles
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Hi Okunlola,
I do not know if cassava chip would be interesting for you. Check papers on cassava chip effects on milk production due to its content in malate (papers published in 2006and 2007 by Wanapat if I am not wrong).
In this sense, also the attached article could help you.
Regards.
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It is known that cyanogenic glycosides in cassava decreases Iodine uptake by thyroid and suppresses circulating T4; which is critical problem where iodine intake is marginal. There are scientific measures to reduce such harm full chemicals from food, can blanching be considered as one of these  methods?
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Thank you all.
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The particle size of dry materials can be determined by standard ASAE S424.1, but I have to measure the particle size of the cassava pulp to evaluate the efficiency of cassava milling process. I can not dry the material because the particles stick and lead to erroneous results.
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The most reliable techniques are photo-optical methods:
- Several publications show, that photooptical analysis (either SOPAT - www.sopat.eu, PVM or any other in-situ microscope or endoscope probes) gives reliable data opposed to laser or ultrasonic based in-situ devices [Boxall et al. 2010, Hu et al. 2006, Maaß et al. 2011, Pacek et al. 1994 ]
- Especially the transformation from chord lenght distributions into real particle size distribution is difficuilt
- Photooptical devices are the only ones able to differentiate between for example the ice crystals and a fat droplet in the same sample, FBRM or the like will always try to average across the different components
- I know only one photooptical device which offers an image analysis software capable to investigate highly concentrated samples fully automated
Literature
Hu, B., et al., Evaluation of drop size distribution from chord length measurements. AIChE Journal, 2006. 52(3): p. 931-939.
Boxall, J.A., et al., Measurement and calibration of droplet size distributions in water-in-oil emulsions by particle video microscope and a focused beam reflectance method. Industrial & Engineering Chemistry Research, 2010. 49(3): p. 1412-1418.
Maaß, S., et al., Experimental comparison of measurement techniques for drop size distributions in liquid/liquid dispersions. Experiments in Fluids, 2011. 50(2): p. 259-269.
Pacek, A.W., et al., Video technique for measuring dynamics of liquid-liquid dispersion during phase inversion. AIChE Journal, 1994. 40(12): p. 1940-1949.
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I am working on behavioral chemical ecology of whiteflies in cassava landscapes, therefore I am looking for methods to approach the study.
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you can contact
Research Assistant-African Cassava Whitefly Project
Organisation: Root Crops Research Program, National Crops Resources Research Institute (NaCRRI), National Agricultural Research Organization (NARO), 
Contact Information: ocittipatrick@gmail.com T|
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The main objective is to evaluate these propriendades and relate to the energy needed to disintegration of this material.
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Hi,
you can use the single fiber tensile test to determine the mechanical properties of fibers using the single filament tensile tests procedure described in ASTM D-3322-01 standard test method.
Regards,
BELOUADAH Zouheyr
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I want to make fermented cassava flour and I need to do the quantitative analysis of glucose from the flour in order to determine the DE. I saw some methods that simple but give good results, those are Somogyi-Nelson and Luff Schoorl. What is the difference from both method? And can I use one of them for my analysis? Thank you very much for your attention.
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Leonardus,
If you want to quantify the amount of fermentable sugars, such as glucose and maltose, please refer to the following publication (HPAEC-PAD). 
If you do not avail of chromatography, you can calculate the free glucose using a simple colorimetric assay. Please, refer to the second article (GOPOD assay kit from Megazyme). 
If you want to determine the DE, i.e. reducing sugars in the dry solids, Somogyi-Nelson will suit you very well.
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I have synthesized a cDNA library in pGADT7 vector in yeast strain y187 with Clontech's Mate and plate cDNA library synthesis kit and now when I am doing a Y2H screening with my bait in pGBKT7 in Y2H gold strain I am not seeing any interaction/growth. I grew them on SDO/AbA/XaGal. All control experiments were good.
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Firstly, I would like to suggest you to double check the bait vector, and ensure the bait protein could be translated properly. Since all control experiments were good, there's not any technical problem here. So screen again confidently and carefully, and make sure everything in good condition, including yourself. Good luck.
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I'm carrying out an M.Sc research on the effect of cassava effluent on water quality and planktons. I got these specimens fom my sampling but need to identify them.
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A5 is a nauplius larvae of a cyclopid copepod.
A4 and A6 are not organisms. They are pieces of detritus.
A2 is a filamentous algae.
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i am trying to search for previous work on cassava stump (trimmings on either side of cassava)
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Parts of cassava plant especially roots, leaves and peels have been tested for non-ruminant feeding especially in pigs and poultry (see Livestock Research for Rural Development Journal). However, little has been done on  stems/stump. It could be argued that stems are of low/little nutritional value (roughage/cellulose etc.) for non-ruminants (have no capacity like ruminants to digest roughage EXCEPT rabbits, which have specialized caecum combined with copraphogia/caecotrophy). However, you could try the efficacy of using stems but first determine the nutritional composition and ascertain whether it is worth conducting research on this kind of alternative feedstuff for non-ruminants.
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I am planning to regenerate cassava from nodes and my plantlets are turning white after subculturing in basic culture media that i have incorporated with silicon.
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The loss of pigment is the defective state for chlorophyll and can result from a genetic mutation due to propagation conditions. Make sure you have good light with 12 hr photoperiod and if possible have day and night temperatures which are constant. When mutations occur they can be stimulated by hormones in use they may mean that you need to lower them. Also when plants become habituated to sugar in media they may not continue to depend on photosynthesis providing a mutation favorable environment. Lowering sugar might be helpful.  When people have issues like these many revert to coconut water rather than synthetic cytokinin.
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My invitro cassava plantlets are being assesed for disease development and resistance. I have to inoculate them with bacterial solutions but extreme caution has to be observed so that the inocula doesn't drop in the growth media. What appropriate methods work best in inoculating bacteria in tissue cultured plants.
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Dear Keisha Njenga
Bacterial pathogens generally need a wound in order to infect their host. If your are microprogating cassava plantlets and testing for tolerance or resistance you will want to keep the progeny clearly identified and separated. For your bacterial inoculation you will need a standard population which can be measured according to optical density of your suspension. Once you have your hardened plantlets you can take your standard inoculum and dip a cluster of pins into it and wound a leaflet. If your plantlets are in pots I would place a bag over the pot to maintain high humidity and after that I would transplant into the field and see the adult plant reaction. You will want to take data on bacterial incidence and the severity of the disease. Good Luck. 
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We are developing cassava population by intermating more than 30 clones planted in high land of West Lampung, Sumatra, Indonesia.  Can anyone provide us efficient protocol of artificial hybridization of cassava?  We appreciate
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We hybridizing crops like cassava you may have pigmented and nonpigmented strains.
Generally the nonpigmented plants are due to recessive genes. The highly colored condition such as purple plants are due to a dominant gene for anthocyanin production.
Use you nonpigmented strain as females and the colored strains as males in your crosses. The idea is the any seed from noncolored female having a seedling which is colored is a successful cross. The non pigmented female strain is demasculated before stigmas are receptive. Pollen ready purple plants are used as an anther pollen source and the tweezer used to collect pollen which is brushed on the stigma of the female when it is a receptive maturity. 
Breeders use a pod to row technique to evaluate and follow in a progeny breeding scheme with evaluation and culling of unwanted reactions and types.
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I implementing a discrete choice experiment to model cassava planting material alternative choice. In my questionnaire, I presented each respondents with 16 choice experiments or choice sets with each choice set having 2 alternatives or choices with an opt-out option. The explanatory variables are the attributes (11 in total) of cassava planting material with varying attribute levels that have randomly fitted between 2 alternative. With this, I am fitting a conditional logit model. In my data set, some explanatory variables are represent by dummy variables while others were categorical variables with up-to 3 categories.
Since each choice experiment has 2 alternative options and an opt-out option, each choice set has 11 rows and each respondent was presented with 16 choice sets.
(The sample of the original attribute and sample data is show below) Attributes of the cassava planting material
Cassava stem attributes Alternative A Alternative B Alternative C
Yield Low (<20 Tons/Ha) Moderate (20-30 Tons/Ha) High (>30 Tons/Ha)
Disease tolerance Susceptible Tolerant
Raw taste Bitter Sweet
Cooked taste Bitter Sweet
Mealiness Hard Mealy Watery
Maturity Late (>18 months) Intermediate (13-18 months) Early (6-12 months)
Seed availability Scarce Available Plenty
In soil longevity Short term (Up to 1 year) Long term (Above 1 year)
Shelf-life of stakes Low shelf-life High shelf-life
Suitability in crop systems Suitable Not suitable
Price 10,000 27,000 40,000
Which one would you choose?
Yes 0. No
1. Yes 0. No 1. Yes 0. No
Choice set
Attribute Alternative 1 Alternative 2 Alternative 3
Yield Low (<20 tons/ha) Low (<20 tons/ha) Opt out
Disease tolerance Susceptible Susceptible
Raw taste Bitter Bitter
Cooked taste Sweet Sweet
Mealiness Mealy Mealy
Maturity Late (>18 months) Intermediate (13-18 months)
Seed availability Available Plenty
In soil longevity Short term (Up to 1 year) Short term (Up to 1 year)
Self-life of stakes Short term Short term
Suitability in crop system Suitable Suitable
Price 10000 27000
Question: Which alternative do you prefer? 1. Yes 0. No 1. Yes 0. No
Sample data
Respondent Choice_set Choice Yield_new Disease_tol Rawtaste Cookedtaste Mealiness Maturity_1
1 1 1 3 1 1 1 2 3
1 1 0 3 1 1 1 1 2
1 2 0 1 0 0 1 3 3
1 2 1 1 1 0 1 3 3
1 3 1 3 1 1 1 2 3
1 3 0 3 1 1 1 1 2
1 4 0 2 0 1 0 1 2
1 4 1 3 0 1 1 1 2
1 5 0 3 0 1 1 1 3
1 5 1 3 0 1 1 3 3
1 6 1 2 1 0 1 3 3
For clogit to work, I tried select choice set as the grouping variable but stata shows "variable Choiceset has replicate levels for one or more cases".
clogit y Yield Disease_tol Rtaste Ctaste Mealines Maturity Seed_avail InSoil_long Shelflife Suit_crop_sys nprice , group(Choice_set )
I want to establish the attributes preferred by the respondents including the level and later determine the willingness-to-pay and potential demand,
Can someone clarify for me this?
But i get this comment "note: multiple positive outcomes within groups encountered.note: 2021
groups (4042 obs) dropped because of all positive or all negative outcomes"in the output window.
This seems to be an error i have been struggling with, how can i eliminate this? Does this have bearing on my results.
The choice sets contained an opt-out option "respondent will not buy if there are only the 2 alternatives available" .
The opt-out option has no attribute levels, i want to include in the data. Below is sample data with 2 alternatives (Alt 1 & 2) and opt-out option (Alt 3).
Is it correct include zeros for the attribute levels of opt-out option.
input float Choicesetid byte(Respondent Choiceset Alt Choice Yield Distol Rtas Ctas Mealns Maturity Seedava Soillong Shelflife Suitcropsys nprice)
1 1 1 1 1 3 1 1 1 2 3 2 1 1 1 -2
1 1 1 2 0 3 1 1 1 1 2 3 1 1 0 -2
1 1 1 3 0 0 0 0 0 0 0 0 0 0 0 0
2 1 2 1 0 1 0 0 1 3 3 2 0 0 0 -1
2 1 2 2 1 1 1 0 1 3 3 2 0 1 0 -2
2 1 2 3 0 0 0 0 0 0 0 0 0 0 0 0
3 1 3 1 1 3 1 1 1 2 3 1 1 0 0 -2
3 1 3 2 0 3 1 1 1 1 2 2 1 0 1 -2
3 1 3 3 0 0 0 0 0 0 0 0 0 0 0 0
4 1 4 1 0 2 0 1 0 1 2 1 1 0 1 -2
4 1 4 2 1 3 0 1 1 1 2 3 1 0 1 -2
4 1 4 3 0 0 0 0 0 0 0 0 0 0 0 0
Thanks
Stephen
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Could you contact me by e-mail .. my feeling is that you are doing several things wrong (jos@ing.puc.cl); please send me the question text in word and I will answer it
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step-wise methodology
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You may try Dr.Dipjyoti answer.
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There is an indigenous food from Indonesia, called growol. It's made of fermented cassava. The production process, especially during soaking, the bacteria (predominantly by lactic acid bacteria) will degrade starch into other oligosaccharides, disaccharides or monosaccharides. A research about that food conclude that consume growol regularly can reduce dhiarrea prevalency in children under five years old. The research claimed that it was caused by prebiotic effect. I still disagree because during heating process, by steam, the bacteria (LAB) will die.  
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my opinion, some strain of LAB has a ability to produce alpha galactosidase,that produce some sugars i.e GOS (galacto oligosaccharide) as we all know that GOS has a prebiotic effect and can utilize by several strains bifido and lactobacilli since growol fermented by lactobacillus plantarum
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A preliminary survey of spiraling whitefly was conducted in 2001 and 2002 in the western area of Sierra Leone. I think a more comprehensive survey of the pest in the 14 geographical districts in Sierra Leone is necessary.  Collaboration and funding is required for this study. We need to look at the impact of both Bemisia tabaci and Aleurodiscus dispersus, as both good candidates for mosaic virus. Several crops, including cassava, papaya, etc are at risk. This situation needs to be checked and answers provided. I am looking forward to any help. Thanks and God bless you. SMKanteh 
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What is the best management approach for Chromolaena odorata?
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I have a plan to conduct a study about the different cultivar of cassava found in Romblon. And, to determine the phylogenetic tree of cultivar, what kind of morphometric analysis should I use?
Thank you.  :)
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I am planning to use a Traditional Morphometric Analysis to determine the quantitative measurement of morphological parts. If I already get a morphometric data, is it applicable to undergo a phylogenetic analysis to determine the evolutionary relationship of a different cultivars of Cassava?
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Recent observation from a survey currently undertaken in Sierra Leone indicates that cassava is being serious damage by grasshopper, irrespective of variety (improve and local). This was observed in areas with high Chromolaena odorata infestation. My advice to the farmers affected was to brush and remove all saim weed plants around the cassava farms. Grasshoppers use Saim weed as a host, but does not feed on it, why? What phytochemicals are present in Saim weed that inhibits feeding by grasshopper.
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Hi Grace,
I think your suggestion is good.
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Moringa is widely known for its medicinal and food value. Can it be utilized for plant disease control? What are some of the phytochemicals in moringa leaves?
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Hi Hammad,
Thanks for the information. It was for information search, to avoid plagiarism. A paper on this topic we be sent for publication soon by me and other co-authors.
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I would like to compute light interception and use efficiency for cassava growth. I got data from a field experiment conducted in a location where solar radiation nor sunshine hours data were not available. Only daily minimum and maximum temperatures and rainfall data were available. What is the best way to estimate daily solar radiation in this case? Computer programs and scientific references are welcome! Thanks for your suggestions
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Guillaume, you might want to look at NASA power to see if they have data for your location (see power.larc.nasa.gov, under the section Access Data, select Agroclimatology); and also the improved Bristow-Campbell approach to estimating solar radiation based on temperature and rainfall. I'll send you some references. Best
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My cassava are not growing normally. The leaves are plaques and the top buds are dying. When the top buds completely lose activity, a hibernation bud at below will be activated, and the whole dying will happen all over again.
I was told to give each one of them 50mL 1/4 MS medium every week. Some of them do recover, but at least half of them are still dying.
Does anyone know what is going on?
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Simple and practical suggestion.  Discard the experiment.  Grow the Casava in new pot with fresh soil outside the green house and then take them in to see if it is the green house problem.  If the experiment can be done outside the green house in normal soil using leaves or buds, that may be easier as Casava grows in almost any type of environment.  All the best.
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We are studying the influence of parboiling (rice) and blanching (cassava) on the physical properties of their respective flours.
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It depends on many factors.  Starch is paracrystaline.  So, lack of birefringence is an indicator of gelatination.  You could make a slurry and observe under polarized light.  Compare this to standard flour.  If only 20% or less granules exhibit the polarization cross, it is considered gelatinized.
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I am doing some work on IDD. Though the salt iodization program has proven successful. However, there is a local development that can unhinge the program. The local staple (cassava) is now processed from the tuber to the finished product in one day instead of the traditional four days. This is bound to be reflected in the thiocyanate content of the finished product with possible yet unquantified effect.   
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Dear Tennsion, Please see the attached paper which describes simple procedure for the determination of cyanides in cassava. The only disadvantage of this protocol is that it involves picric acid but on the other hand it is commonly used among farmers in the country.
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and I want to know if it is true to all resistant varieties. 
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Dear Dr. Hajar,  
I believe that this review of Dr Navas Castillo and colleagues will be very useful and will bring some new information about this virus complex and other emerging viruses in the world.
Navas-Castillo et al. Emerging virus diseases transmitted by whiteflies. Ann. Rev. Phytopathol, 2011. 49:219-248.
Fernando Sanhueza Salas
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I want to know which parameters should I measure periodically to know the effect of the effluents on the plants while the experiment lasts.
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The physico-chemical parameters (pH, DO, BOD, COD, K, P, N, oil and grease, metal contents etc.) of POME & CME need to be determined b4 ur study their effects on E. crassipes & P. stratiotes. The physico-chemical characteristics of the soil/sediment where they grow is also important if u have the required funds. lastly, the effects on plant growth parameters shd be determined
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How can I extract and quantify the cyanide that has been extracted from cassava tubers into the fermentation medium?
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When I used to work with cassava I applied a test kit as described in the attached paper. I subjected cassava bagasse to fermentation and I quantified the content of cyanides following method. It gives reliable results and it is good for frequent measurements. You may also consider gas chromatography but it is more expensive solution and it requires handling of potassium cyanide which is very toxic.
Best regards.
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Molecular characterization, Isolation of the pathogen from Cassava leaf itself
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1) Collect samples of diseased plants from different farms/regions.  Record location coordinates, weather conditions at the site of collection, make photo of  the leaves, keep plant material dry for herbarium.
2) Isolate yellow-pigmented bacteria using semi-selective medium (better to use 2 or 3 different ones) - at least 100 isolates
3) Subculture the bacteria on YDC and prove that you have pure culture
4) Store the bacteria at -80 or in sterile water at room temperature
5) Test the bacteria identity as Xanthomonas and as Xanthomonas axonopodis pv. manihotis using IFA or specific PCR primers published elsewhere.
6) Test the proved Xanthomonas strains for virulence by HR on tobacco, Pelargonium or Plectrantus, and on young Cassava plants in controlled conditions (glasshouse, climatic chamber).
7) Use only virulent strains of Xanthomonas to isolate DNA in 2-3 replications - at least 100 ng/mkl. for  at least 30 strains in your study + type strains for the pathogen Xanthomonas axonopodis pv. manihotis and related species, obtained from international collections and used in other studies (reference strains for species, genetic groups , etc.)
8) Use BOXA PCR or single-adapter AFLP to group the strains and remove from your collection obviously different strains of other species.
9) Use AFLP, AP-PCR for fingerprinting and grouping strains based on their genetic similarity. 
10) Use  MLST for type strains of your groups to show relation of your collection to previously studied bacteria from Cassava. 
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I am doing starch from cassava, but when I hydrolyse my sample I have more than 100% hydrolysis.
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 Rastilav is Ok.
The introduction of 1 molecula of water per every  bond hydrolized, increase  the mass of the hydrylisis system. The factor is aprox. 1.1
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I was wondering if it was necessary to remove the cyanide present in cassava peels before applying dilute acid hydrolysis as a pretreatment step. In addition, if it is neccesary, can I please get suggestions on how to remove the cyanide before hydrolysis. Thanks.
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Nigeria produces an estimated 38.2 million tonnes of cassava annually (data from 2007). This represents about 37 % of world output. So you see it is very important tuber crop in Nigeria. There hasn't been any reported case of serious pest or diseases affecting cassava production in Nigeria. Apparently the farmers have mastered the art of growing the crop.
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I have observed that the cassava once stored for 3 to four days result in a bluish black colour and also a kind of foul taste. Can anyone say why? 
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It can be indicating the presence of hydrogen cyanide (HCN) in high level, which is toxic. Cassava naturally contain cyanogenic glycosides, named Linamarin and Lotaustralin, that can be removed by washing intensively. 
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We constructed a transgenic cassava line with RNAi structure to knock out a gene, but now the subcultured cassava is growing slowly, especially their roots. That gene might be important for the root development.
I need them to develop tuberous roots in no more than one year so we have to find a way to promote their growth...Now they are in MS medium.
Anyone has some idea how to promote the roots to grow faster? Thanks a lot.
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Dear Randall
Except for the salt, are there any other reasons? Our wild type cassava and other GM ones grow well in the MS medium, and only the new one grows slowly. Thanks.
 
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I would like to study the interaction between cassava viruses and a sort of cassava genotypes. I would like to do this by measuring virus concentration. Is it right to call this virus titer/concentration? I am working with RNA viruses.
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Hi,
Titer is expressed as
-infectious unit/mL.
-viral protein pg/mL (p24 core protein for HIV-1),
-RNA copies/mL
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I heard of Picrate tests. Have you?.
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Madhu Lin thats great. I am greatly encouraged by the answer and the paper sent. Thanks. Hope to be with u in India as my Institute is having some understanding with yours to do more research collaborations. Madu thanks again
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What are your views?
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Thanks for this important and food-security-relevant question. While IITA Ibadan and others have done a lot for breeding against virus-diseases and palatabilty, more and more areas get under cassava again after being lost for decades. The theoretical and partly practically high yield-potential of cassava is one of THE challenges for the years to come, also considering the strong move of agronomy towards improving the availability of industrial raw-materials as well as energy-crops.....in addition to the highest priority FOOD and food-security. In crop-husbandry matters I see enormous further potentials in a) planting cassava in contour-line-oriented landscaping for better rain-harvesting; b) planting cassava in alley-systems, mixed cropping, esp. with leguminous soil-cover and Nitrogen-suppliers; c) Using all sorts of organic mulching-materials for weed-suppression, water-retention and nutrient-supply. Note: mulching can reduce water-loss by evaporation in the range of up to 50% !; d) Integrating cassava into perma-culture systems which were the predominant land-use manner before "man-made negativ impacts"; e) Allowing commercial large-scale mechanized cassava-plantations only with a wise eco-system, socio-system and minimum crop-rotation or alley-cropping-systems. e) Establishing a permanent system of variety-testing in farmers' fields and not only behind 3-m-high research-station-fences.
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What is the most suitable method? Is there any prospect for using diatomite as an absorbent? What is the biggest challenge for color removal technology by diatomite?
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Hello, Nguyen,
Actually I don't know what caused the colorization of cassava ethanol wastewater. But I think the pollution should come from the starting material - that is, the organic molecules with chromopores in cassava. These molecules normally are much bigger than ethanol and I think any adsorbent with developed mesopores can remove the color effectively. In addition, catalytic degradation should also be a promosing approach to decolorization. You can consult our publications for further information. Hope my answer will help you.
Chen, X.G., Lv, S.S., Liu, S.T., Zhang, P.P., Zhang, A.B., Sun J., and Ye, Y.* (2012): Adsorption of methylene blue by rice hull ash. Separation Science and Technology. 47, 147-156. doi: 10.1080/01496395.2011.606865
Zhang, A.B., Pan, L., Zhang, H.Y., Liu, S.T., Ye, Y., Xia, M.S., Chen, X.G.*(2012): Effects of acid treatment on the physico-chemical and pore characteristics of halloysite. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 396, 182-188. doi:10.1016/j.colsurfa.2011.12.067
Lv, S.S.1, Chen, X.G.1, Ye, Y.*, Yin, S.H., Cheng, J.P., and Xia, M.S. (2009): Rice hull/MnFe2O4 composite: Preparation, characterization and its rapid microwave-assisted COD removal for organic wastewater. Journal of Hazardous Materials 171, 634-639. doi: 10.1016/j.jhazmat.2009.06.039