Tag: clean

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

More from this blog series:  

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

More from this blog series:  

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!
———————————–
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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