Sustainable Agriculture May 2009
Fighting plant viruses
Dr Lava Kumar: Senior virologist, IITA, Ibadan, Nigeria
Summary:
When maize plants become infected with maize streak virus, the consequences for the farmer are serious. Yields can be cut by as much as 70%, and there is no way of curing the plants. Preventing plants from being infected is therefore the best strategy. At IITA in Nigeria, the virology department is developing plant varieties that can resist viruses, or not show symptoms even if they become infected.
Suggested introduction:
Every year, millions of dollars are spent by medical science, developing vaccines to combat viruses. And for livestock, diseases such as avian flu have increased the pressure on virus experts to protect animals and slow down the spread of disease. But what about plants? What is being done to protect them from viral attack- and therefore protect food production?
Dr Lava Kumar is head of virology at the headquarters of the International Institute of Tropical Agriculture in Nigeria. He invited Martha Chindong to visit one of his laboratories and see what goes on. She was curious to find out whether viruses that affect plants are similar to the viruses which attack humans and animals.
Tape in:
That is an interesting question...
Tape out:
...for the development of agriculture.
Closing Announcement:
Dr Lava Kumar, one of the world's leading experts on plant viruses, speaking to Martha Chindong.
Making the most of it:
Viruses are often in the headlines. Can you find a virologist to further explain why viruses are so successful at causing problems?
What do farmers do that helps viruses (that affect plants, livestock or people) to spread?
What on-farm techniques are there to stop viruses spreading from plant to plant or animal to animal?
Further information:
Lava Kumar,
Senior virologist,
IITA, Ibadan, Nigeria.
Email: L.kumar@cgiar.org
Transcript
Kumar
That is an interesting question. These viruses, the way they attack either a plant, animal or humans, are fundamentally similar. They are simply adapted to different species.
Chindong
Can we see an example of what you are talking about?
Kumar
As you can see here, this is a maize plant infected with maize streak virus. You can see that it's no longer green colour here, it's all white, it's pale.
Chindong
Ok, green colour is here in patches.
Kumar
Yes, green colour is only in patches, and this green colour here is reduced by at least 70 per cent. That means this plant is inefficient by 70 per cent in producing its food. Therefore obviously it cannot perform as well as the healthy one. That is what virus does to the plant growth.
Chindong
Why are they such a big problem to farmers?
Kumar
For instance, if you have one hectare of maize, it if is infected with this virus called maize streak virus, it reduces the plant productivity by 70 per cent. That means instead of getting 100kg yield you will end up having 30kg. That will straight away impact the food availability.
Chindong
It means even if you apply fertiliser and other chemicals you won't change the yield?
Kumar
Yes, the reason why plant viruses are so difficult to manage is, if a plant is infected with virus there is no cure. Even if you supplement fertiliser the plant will show some recovery but it will never get cured.
Chindong
Do you see this as a threat to African agriculture?
Kumar
Viruses have been always a threat. That is a reason the research programmes at IITA focus on developing crops that resist virus infection. So we have varieties of maize that cannot get infected, or even if they get infected they don't show symptoms. That means they produce yield normally as if nothing happened to the plant. So that is our main focus in this institute.
Chindong
So at the level of the small-scale farmer, is there anything he or she can do once his crops are affected by viruses?
Kumar
I mean this is a very tricky question. For any virus disease, whether it's a plant, or animal or human, the only means to reduce its damage is by preventing infection.
Chindong
Preventing infection by doing what? What are you as a researcher doing to help them out of it?
Kumar
Yes, there are many ways. In this case for instance, it's insects. Leafhoppers bring the virus, like mosquito carries malaria. In the same way this maize streak virus is carried by any leafhopper. So they bring the virus and when they feed on a maize plant which is healthy, when they feed they put virus into the plant. We can control insect vectors, so by spraying. This is one way of control.
Chindong
At the level of the lab where we are, what are you doing to help farmers cope with these viral attacks?
Kumar
We have a number of strategies. The major one is to use resistant varieties that we develop; varieties which resist virus infection. So the good thing with this is we supply farmers seed of resistant crop. You don't have to do anything, just sow the resistant variety and that will take care of everything. In case, if there is no scope for such control, then we use integrated approach where we tackle vectors. We tell farmers how to manage the crop so that he can minimise disease damage.
Chindong
So you as a researcher and working on this topic, how do you feel? Can you describe to us how you feel helping farmers to cope with viruses?
Kumar
I feel it is a great opportunity for me to serve small-scale farmers in Africa. Farmers have always difficulty coping with virus disease problems. By working on such important issues that affect the food production, it is a privilege for me to work through the institute for the development of agriculture. End of track.
