Tag: brown streak

Breeding cassava for the next generation

Posted on by janet.crompton

Last week I helped to harvest and score cassava tubers a breeding trial at the National Crops Resources Research Institute (NaCRRI). The trial is part of the NEXTGEN Cassava project which applies genetic techniques to conventional breeding and aims to produce new varieties with Cassava brown streak disease (CBSD) and Cassava mosaic disease (CMD) resistance.

Why cassava and what’s the CBSD problem?

Approximately 300 million people rely on cassava as a staple food crop in Africa. It is resilient to seasonal drought, can be grown on poor soils and harvested when needed. However cassava production is seriously threatened by CBSD, which can reduce the quality of tubers by 100% and is currently threatening the food security of millions of people.

Cassava brown streak symptoms on tubers

Crossing cassava from around the world

Cassava varieties show a huge variation in traits including disease resistance. The NEXTGEN Cassava project has crossed 100 parent plants from Latin America with high quality African plants to produce new improved varieties, with higher levels of CBSD and CMD resistance. Crossing involves rubbing the pollen from one parent variety on to the female flower part (pistil) of the second parent variety to produce seeds.

Cassava flowers used to cross different varieties

 

Cutting back on time

The process is not easy. The complex heritability of traits in cassava means that many plants have to be screened to identify plants with the best traits. To cut down on this time, researchers from Cornell University sequenced the DNA from 2,100 seedlings and selected plants containing sequences linked to desirable traits.

Screening for resistance

These plants were transferred to field site in Namulonge, where there is a high level of CBSD, making it easier to spot resistant plants. After 12 months the tubers were dug up and cut into sections. Each root was scored for the severity of CBSD. Plants which  show no disease symptoms have now been selected for the next stage of breeding. Eventually varieties will be tested for their performance at sites across Uganda and given to farmers for their feedback.

We harvested and scored tubers for Cassava brown streak symptoms. I then tagged disease free plants for selection!

 

Time to harvest!

 

Alfred Ozimati is managing the breeding  programme

I helped to score and tag plants, it was hard work! I was impressed by the stamina of the workers who harvested from 8 am until 3 pm without a rest. I was struck by the mammoth task of breeding cassava for so many traits and by the programme manager Alfred Ozimati’s determination to get the work done as quickly as possible. Alfred is currently a  PhD student at Cornell University; he kindly offered to answer these questions:

What are the challenges of conventional breeding and how does sequencing help to address these?

Typical conventional breeding cycle of cassava is 8-10 years before parents are selected for crossing. The sequencing information allows a breeder to select parents early at the seedling stage, allowing more crossing cycles over time than conventional cassava breeding. With sequencing, the process of releasing varieties with improved CBSD and CMD resistance should take about 5 years.

What are your long term hopes for the project and the future of cassava breeding?

We hope to use genomic selection routinely, to address any other challenges cassava as a crop of second importance to Uganda will face. And also to take the technology to other East African, cassava breeding programs to faster address their major breeding constraints.

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This blog has been written by University of Bristol Cabot Institute member Katie Tomlinson from the School of Biological Sciences.  Katie’s area of research is to generate and exploit an improved understanding of cassava brown streak disease (CBSD) to ensure sustainable cassava production in Africa.  This blog has been reposted with kind permission from Katie’s blog Cassava Virus.

 

Katie Tomlinson

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Talking sweet potatoes at the Source of the Nile

Posted on by janet.crompton

Last month I was invited to the Source of the Nile agricultural trade show in Jinja, Uganda. The show brings together all aspects of agriculture: from crops to chickens, cows and tractors. The event attracts over 120,000 visitors each year and runs for seven days.

I was needed on a National Crops Resources Research Institute (NaCRRI) stand where Agnes Alajo (a PhD student and breeder) was selling improved sweet potato varieties, which are resistant to pests and diseases with higher levels of pro-vitamin A.

It is estimated that around 35% of children and 55% of child-bearing mothers in rural Uganda suffer from vitamin A deficiency, which is associated with preventable child blindness and mortality. The orange-fleshed NAROSPOT varieties developed by NaCRRI are enriched with pro-vitamin A and it’s hoped their adoption will help improve the deficiency problem.

The stand also had an impressive array of biscuits, cakes and even juice made from processing sweet potato. Agriculture is very important in Uganda; it accounts for around 24% of GDP and 43% of the working population are subsistence farmers (2013). Processing sweet potatoes to produce flour can be economically viable and provides farmers with an opportunity to add value to their crop, boost income and reduce poverty.

The range of products made through processing sweet potato

I had to hurriedly absorb information about sweet potato, as very soon hoards of excited school children arrived. The main challenge was that not everyone can speak English and my UK accent was quite difficult for them to understand. I had to speak clearly and slowly to get my message across. Often teachers had to repeat what I had said in their local language. There are over 40 local languages in Uganda, so even Ugandans can find it difficult to communicate!

Agnes explains the importance of pro-vitamin A rich sweet potatoes to school students

Agnes explains the importance of pro-vitamin A rich sweet potatoes to school students
There was a lot of interest from young people who want to pursue agricultural careers and are attracted to opportunities for commercialization. Most people were very intrigued about the cakes, and couldn’t believe that they were made using sweet potato flour. Unfortunately, we couldn’t give out samples to taste until the end of the week, which caused a lot of pleading and disappointment!

Walking around the show I discovered giant cassava tubers, a “speaking head” and impressive looking cabbages. I later  saw the source of the Nile itself!

I had a great time walking around. There was plenty of entertainment and I also got to see where the Nile flows from Lake Victoria!

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This blog has been written by University of Bristol Cabot Institute member Katie Tomlinson from the School of Biological Sciences.  Katie’s area of research is to generate and exploit an improved understanding of cassava brown streak disease (CBSD) to ensure sustainable cassava production in Africa.  This blog has been reposted with kind permission from Katie’s blog Cassava Virus.

 

Katie Tomlinson

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Using GM to fight cassava brown streak disease

Posted on by janet.crompton

Last week I helped plant a new confined field trial for genetically modified (GM) cassava in western Uganda. The aim is to find how well the plants resist Cassava brown streak disease (CBSD).

Before planting, the National Crops Resources Research Institute (NaCRRI) held discussions with people from the local government and farmers’ groups. It’s vital to engage the local community so that people are correctly informed and on-board with the project. There were certainly some very strange myths to debunk!

Henry Wagaba (Head of Biosciences at NaCRRI) explained the huge losses caused by CBSD, which spoils tubers and can wipe out entire fields. CBSD is now the most devastating crop disease in Uganda and there are no resistant varieties currently available.

To fight the disease, NaCRRI researchers have developed GM cassava plants, which show high levels of resistance to CBSD at sites in southern and central Uganda. This trial will test how the plants perform in the growing conditions in western Uganda. Work will also be carried out to cross the GM plants wither farmer varieties to improve their growing and taste qualities.

I enjoyed getting stuck in and planting my first GM cassava!

GM crops are a contentious topic in Uganda. The passing of a National Biotechnology and Biosafety law has stalled in Parliament for over three years due to disagreements. Currently GM technology is used for research on banana, cassava, maize, potato, rice and sweet potato. However these are not approved for human consumption.

In nearby countries Kenya and Sudan, GM food products have been approved and many of these food products are imported into Uganda without regulation. It’s hoped the law will be passed soon to enable Ugandan farmers to reap the benefits of GM crops and protect against any potential risks.

Before the trial, I went on a safari in the Queen Elizabeth National Park, where I saw elephants, hippos and even lions!
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This blog has been written by University of Bristol Cabot Institute member Katie Tomlinson from the School of Biological Sciences.  Katie’s area of research is to generate and exploit an improved understanding of cassava brown streak disease (CBSD) to ensure sustainable cassava production in Africa.  This blog has been reposted with kind permission from Katie’s blog Cassava Virus.

 

Katie Tomlinson

More from this blog series:  

Taking a trip to the cassava field!

Posted on by janet.crompton

At the end of last week I was lucky enough to be invited on a trip to the field. I didn’t really know what to expect but was very excited to find out!

The purpose of the trip was to collect data for the 5CP project to find out how different varieties of cassava respond to Cassava brown streak disease (CBSD) and Cassava mosaic disease (CMD) in different areas.

We set off at 5.30am in the morning; the first stop was Lake Victoria to catch a ferry to the Sesse Islands. The team consisted of me, the driver (Bosco), research assistant (Gerald Adiga) and research technician (Joseph). Along the road, we saw several accidents, sadly a far too common occurrence in Uganda…

Due to delays, the ferry was rammed, and by the time we arrived it was almost the evening. We raced to the agricultural school with the field trial. Here the team have planted blocks of 25 clean cassava varieties from five African countries and our job was to score them for disease symptoms. CBSD and CMD are not very common on the Sesse Islands, and so most of the plants were healthy.

An agricultural student digs up a healthy cassava plant.

After a night of drinking Guinness in a corner shop we headed out, again at 5.30am! This time we headed to the city of Mbarara in the western region. The drive was really beautiful, passing Lake Mburo National Park and mountains covered with matoke.

Whilst scoring the cassava plants here we noticed a super abundance of whiteflies, which carry CBSD viruses. The weather had been particularly dry, allowing the whiteflies to breed like crazy. Fortunately, CBSD is also uncommon in this area and very few plants were diseased.

Super abundance of whiteflies on cassava which carry CBSD viruses.

The data from the 5CP project will help farmers to decide which cassava varieties offer the most protection against CBSD and CMD in their local areas; helping to protect them from the devastating yield losses caused by these diseases.

Fun stuff

On the way back we passed the equator line, and I got the chance to take some touristy photos. This week I also saw the Ndere dance troupe, who showcase the different dance and music styles from all over Uganda and other neighbouring countries. It was a lot of fun, some dances bared a weird resemblance to morris dancing and marching brass bands!

Crossing the equator!
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This blog has been written by University of Bristol Cabot Institute member Katie Tomlinson from the School of Biological Sciences.  Katie’s area of research is to generate and exploit an improved understanding of cassava brown streak disease (CBSD) to ensure sustainable cassava production in Africa.  This blog has been reposted with kind permission from Katie’s blog Cassava Virus.

 

Katie Tomlinson

More from this blog series:  

Clean cassava to solve brown streak problem?

Posted on by janet.crompton

Since arriving in Uganda, I’ve been learning a lot about the affects of Cassava brown streak disease (CBSD), which is devastating cassava production and threatening food security. The disease is spread by the whitefly insect, which picks up the virus from an infected plant and carries it to neighbouring healthy plants.

Cassava plants are grown by planting stem cuttings in the ground, which go on to become new plants. If farmers use cuttings from infected plants, the new plants will also become infected. This is a big problem, as infected cuttings can be transported to new areas, spreading CBSD across large distances.

What can be done?

Tolerance

Huge efforts are being put into a number of different solutions. These include breeding new cassava varieties, which are tolerant to CBSD. This is a very long and challenging process, as cassava plants also need to be resistant to Cassava mosaic disease (CMD) and have yield/taste properties which farmers and consumers prefer.

The National Crops Resources Research Institute (NaCRRI) has recently developed a new variety: NAROCASS1, which is tolerant to CBSD and resistant to CMD. This is now being used in areas where CBSD is particularly common and severe. Unfortunately, even tolerant cassava varieties can contain CBSD viruses and so it’s vital that farmers have access to clean cuttings.

Cassava variety NAROCASS1 with CBSD tolerance and CMD resistance.

Clean seed system (CSS)

The cassava CSS project in Uganda is run by NaCRRI and involves picking the very youngest tip of the cassava plant to produce embryonic tissue, which develops into a new plant. These plants are then checked to see whether the CBSD virus is present before being taken to nurseries where they are carefully multiplied and eventually used for clean planting material for farmers. As you can imagine, this process takes a long time and is much more expensive than taking cuttings from a mature cassava plant. However it means that farmers can benefit from quality assurance that the cuttings they buy are virus free and stand the best chance of remaining healthy.

A clean cassava plantlet produced through tissue culture.

The cassava CSS project has been running as a pilot for three years. It will be very interesting to hear how this project goes, as it’s likely to be a major solution to the CBSD problem.

Reviewing progress

Last week I had helped take minutes for the annual CSS review at NaCRRI, which involved lots of manic typing and concentration! As part of the review I got to visit a field where an entrepreneur is growing clean cassava plants. The plants certainly looked healthy, with no CBSD and CMD symptoms at all. With so much to think about, we still found time to have a cocktail party to let of some steam!

Clean cassava seed entrepreneur David Mpanga explains how he uses record keeping to track of outgoings and income.
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This blog has been written by University of Bristol Cabot Institute member Katie Tomlinson from the School of Biological Sciences.  Katie’s area of research is to generate and exploit an improved understanding of cassava brown streak disease (CBSD) to ensure sustainable cassava production in Africa.  This blog has been reposted with kind permission from Katie’s blog Cassava Virus.

 

Katie Tomlinson

More from this blog series:  

Cassava virus: Journey from the lab to the field – Settling in to Ugandan life

Posted on by janet.crompton

Katherine Tomlinson from the School of Biological Sciences at the University of Bristol Cabot Institute, is spending three months in Uganda looking at the cassava brown streak virus. This virus dramatically reduces available food for local people and Katherine will be finding out how research on this plant is translating between the lab and the field.  Follow this blog series for regular updates.

I arrived late on Thursday night and spent the weekend getting acquainted with the hustle and bustle of Kampala life. I visited the impressive Gadafi mosque, cathedral, and food markets, which are full of just about every fruit and vegetable you could imagine.

On Friday, I met with my internship supervisor, Dr. Titus Alicai who is the leader of the Root Crops Research Programme at the National Crops Resources Research Institute (NaCRRI); he filled me on some of the exciting activities I’ll be taking part in, including visits to cassava field sites.

I was picked up and taken to NaCRRI in Namulonge on Sunday, stopping off at markets along the way to pick up my food supplies. I am lucky to have Everline looking after me; she’s helping me to settle into Ugandan life. NaCRRI is absolutely beautiful, it’s full of crops including cassava, sweet potato, mango, pineapple, banana, and there are even vervet monkeys running around.

National Crops Resources Research Institute, Uganda… where I’ll be spending the next three months!

At the start of the week , I was given a tour of the institute including the labs where they analyse cassava tubers for nutritional and chemical content; a vital part of the process in developing crops which not only offer maximum disease resistance, and yield but also taste good.

I then visited the molecular biology labs, where they analyse crop samples for the presence of Cassava brown streak disease viruses. This was very familiar with similar equipment to our lab at the University of Bristol. The lab manager discussed the challenges of obtaining all the expensive reagents required and how this affects their work. Other challenges include intermittent power supply, which means they need a stack of battery packs to back up the -80 freezers and PCR machines. I am looking forward to spending some time here, to learn more about the similarities and differences between molecular work in the UK and Uganda.

On Wednesday, I went to the field with some University internship students, who were scoring cassava plants for Cassava brown streak disease and Cassava mosaic disease symptoms. After their training these students will be able to advise farmers about the diseases in their local areas. It was also my chance to see symptoms in the field, where infected leaves showed a distinctive yellowing pattern.

Inspecting cassava plants for disease symptoms with University internship students

I spoke to one student who has a small farm and has experienced Cassava brown streak disease first hand. He mentioned that the disease is very common in his area, and here even tolerant cassava varieties become infected and their tubers ruined.

Characteristic Cassava brown streak disease symptoms on cassava leaves

Today I am meeting with the communications team, to find out about the projects I will be involved with, including an outreach programme with farmers surrounding the NaCRRI site to encourage them to use crop breeds developed by the institute, which offer higher disease resistance.

That’s it for now I’ll be writing another update next week so watch this space! In the meantime if you have any questions please get in touch via Twitter: @KatieTomlinson4.

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This blog has been written by University of Bristol Cabot Institute member Katie Tomlinson from the School of Biological Sciences.  Katie’s area of research is to generate and exploit an improved understanding of cassava brown streak disease (CBSD) to ensure sustainable cassava production in Africa.  This blog has been reposted with kind permission from Katie’s blog Cassava Virus.
Katie Tomlinson

More from this blog series:  

Getting ready to go… cassava virus hunting!

Posted on by janet.crompton

Katherine Tomlinson from the School of Biological Sciences at the University of Bristol Cabot Institute, is spending three months in Uganda looking at the cassava brown streak virus. This virus dramatically reduces available food for local people and Katherine will be finding out how research on this plant is translating between the lab and the field.  Follow this blog series for regular updates.

It’s just three days until I set off on my trip to Uganda, where I’ll complete an internship with the National Crops Resources Research Institute in Namulonge. I’ll be working for three months with their Communications team to learn how research is translated between the lab and the field.  I am currently a BBSRC South West DTP PhD student at the University of Bristol, researching how cassava brown streak disease viruses spoil cassava tubers and dramatically reduce available food for local people.

Image above shows Katherine inspecting cassava plants for cassava brown streak disease symptoms in the School of Biological Sciences GroDome.

Cassava plants produce carbohydrate rich root tubers and are a staple food crop for approximately 200 million people in sub-Saharan Africa. After rice and maize, cassava is the third most important source of carbohydrates in the tropics. Unfortunately, cassava is prone to viral infections, including cassava brown streak disease (CBSD), which can render entire tubers inedible. CBSD outbreaks are currently impacting on the food security of millions of cassava farmers in east Africa; it appears to be spreading westward, threatening food security in many countries.
Spoiled cassava tubers due to cassava brown streak disease (photo credit: Dr. E. Kanju, IITA).
Working the lab, I regularly infect plants with CBSD viruses to study how they replicate, move and prevent plant defence responses. However, in the field there is a much more complex interplay of different viral strains, cassava varieties, white fly population dynamics and environmental conditions which all contribute towards the disease. It’s vitally important that information about all of these contributory factors is shared between scientists and farmers to help control the disease and inform future research.I’m looking forward to assisting with field trials where different cassava varieties are being tested for resistance and meeting the farmers who face the challenges of controlling the disease. I hope to learn how information is shared and distributed and get some research ideas for when I return. I’ll be blogging my experiences on my personal blog and for the Cabot Institute blog.

NaCRRI is in Namulonge, in the Wakiso district of Uganda (photo credit: Slomox, Wikimedia).

Preparation, preparation, preparation…

At the moment, there are a lot of ‘to do’s; making sure I’ve had all the necessary vaccinations, packed factor 50 sun cream, mosquito net, DET and a massive first aid kit! It seems a little over the top at the moment but should stand me in good stead for the adventure ahead…
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This blog has been written by University of Bristol Cabot Institute member Katie Tomlinson from the School of Biological Sciences.  Katie’s area of research is to generate and exploit an improved understanding of cassava brown streak disease (CBSD) to ensure sustainable cassava production in Africa.  This blog has been reposted with kind permission from Katie’s blog Cassava Virus.

 

Katie Tomlinson

More from this blog series:  

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