Scientists inching closer to disease-free maize varieties

Scientists are working round the clock to tackle Maize Lethal Necrosis (MLN), the viral disease responsible for an estimated 100 per cent loss in maize yields.

Through ongoing screening of lines and hybrids from seed companies in sub-Saharan Africa, and national research organisations such as the Kenya Agriculture and Livestock Research Organisation (Kalro), scientists are identifying and selecting promising varieties that are tolerant and resistant to MLN.

Some of the identified varieties are already undergoing national performance trials (NPTs) in Kenya, Uganda and Tanzania, meaning that if cleared, farmers will be able to plant them from 2017.

Director for Global Maize Programme at the International Maize and Wheat Improvement Centre (Cimmyt), Dr PRASANNA BODUPALLI says five MLN-tolerant varieties are being scaled up to reach farmers from this year. He spoke exclusively to People Daily:

Q. What specific traits do the varieties have that are attributable to their tolerant strength?

A. These pre-commercial hybrids developed by Cimmyt and nominated by partners for NPTs possess high grain yield potential, coupled with MLN tolerance and other adaptive traits including drought tolerance and resistance to foliar diseases.

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Q. MLN is associated with total yield loss. What hopes do farmers have that these varieties will reverse this situation the moment they are commercialised?

A. The extent of grain loss due to MLN depends on the stage of infection. If severe infection happens at an early vegetative stage, there could be 100 per cent yield loss.

If the infection happens at a very late stage (say during grain filling), the loss will not be 100 per cent. The MLN tolerant varieties will certainly provide significant relief to the farming communities.

Our on-farm trials in eastern Africa under severe MLN disease pressure done in natural conditions revealed that compared to the MLN-susceptible commercial varieties that may yield not more than two tonnes per hectare, the MLN-tolerant varieties showed at least five to six tonnes under the same conditions.

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Q. What would be your best advise to farmers in regard to MLN control and the expected release of these varieties?

A. First, Cimmyt would like the seed companies to actively replace the existing MLN-susceptible maize varieties with the high-yielding tolerant varieties, especially in the MLN endemic areas in Eastern Africa.

The job does not just end with the commercial release of such varieties but also in actively demonstrating the benefits of such varieties through on-farm trials and stimulating demand from the farming communities. Second, we need to tackle the MLN challenge on multiple fronts.

Growing MLN-tolerant varieties is one of the ways for control. Equally important for the farmers is to avoid monoculture of maize—t is important to diversify the cropping systems, especially with legumes. The maize-legume cropping system will not only help improve the soil fertility but will also break the MLN virus cycle.

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