Improving yields through local crop breeding
In Kenya’s Central Rift Valley, sweet potato farmers have struggled to produce healthy, high yielding crops, with much of their harvest lost to plant viruses or damaged by weevils. In response, sweet potato breeders from the Kenya Agricultural Research Institute have worked with farmers in the area to select and develop better varieties of sweet potato, which are tolerant of viruses, high yielding and contain high levels of nutrients and vitamin A. Breeder Laura Karanja explains the process, and how through planting the new varieties and attention to farming practices such as weed control, farmers can expect to double their yields. She also points out the importance of breeding crops specific to local areas, in order to match local conditions such as rainfall patterns, soil moisture and altitude.
Karanja We realise that Central Rift Valley farmers were very much interested in growing and producing sweet potatoes but the local varieties which they had were low yielding, they had diseases and pests especially viruses and weevils. They were also low in nutritive values and we decided it is important to start the programme of breeding sweet potatoes specifically for Central Rift Valley and our high altitude areas.
Onditi Which are some of these varieties that you want to promote for the farmers in the Central Rift Valley of Kenya?
Karanja We want high yielding varieties with high dry matter, high vitamin A and also acceptable by the farmers. Currently we have released about five varieties and these varieties, two of them specifically are orange fleshed with high vitamin A. One is yellow and one is white and one is light orange.
Onditi How different are they from the normal varieties that we've known for ages?
Karanja These varieties have got high vitamin A, they have got zinc and calcium which are quite good for health issues and also for children under five years old, pregnant ladies and ailing people and they are important in that they boost immunity. That vitamin A boots immunity in these people. And they are also resistant or tolerant to viruses. They are also suitable for this high altitude in that they have got high dry matter. In the past, especially in these areas, the varieties which have been produced there have been of low, poor quality. They are watery and also they have got bland taste and they are very susceptible to diseases and weevils.
Onditi You are now having new varieties or you are breeding new varieties. How are you involving farmers because farmers will be the consumers of these new varieties?
Karanja In these new varieties we have involved the farmers right from the onset of the programme. Farmers are brought in at all stages of evaluation, where they use their own criteria of selection, which included yields, according to farmers, size of the tubers, dryness, colour of the skin and flesh, taste and value addition of the sweet potato varieties. In all these activities farmers were very much involved. We call it farmer participatory evaluation or breeding.
Onditi How can a farmer manage the growing of this sweet potato? Is it different from the traditional ways that we have known for many years?
Karanja In sweet potato one of the critical things is to plant the material at least when there is some moisture and also control the weeds. If they can control the weeds, which sometimes host these pests, that will be very important. The other way is to pull out any diseased material to avoid spreading.
Onditi With good management, how do you compare the harvests or the quantities of these new varieties with the traditional ones?
Karanja For these materials which we have produced the average yield is about 20 tons per hectare and the varieties which were there before were between 9 and 12 tons per hectare. So the yields double with appropriate varieties and also good management.
Onditi We are focusing on breeding locally and you are breeding these varieties in the Central Rift Valley of this country. Why is it important that breeding focuses on a particular area?
Karanja Each area you find that it has got different rainfall patterns, also moisture and also elevation. Because you can find the potatoes which do well in low areas might not perform as well in high altitudes. So the elevation is very important, soils and moisture is important, and if you can plant maybe a crop which does very well at sea level and you take it to high altitudes of maybe Elgon area, Mount Elgon area, it might not perform the same way. But if you are breeding it and you say this particular variety is good for coastal area and this is good for high altitude area you will be able to supply the growers with appropriate varieties.
Onditi Where do you see the future in terms of improving food security in this country in Kenya and other parts of Africa with these new varieties that you are developing?
Karanja Currently there are about ten million people who are producing sweet potato and if they can double their yields, that means there will be not much of food insecurity. And the other thing is, especially in value addition, there can be cottage industries which will attract even the youth at village level to participate in production of sweet potato products, which will improve their income, improve their health and improve their finances. End of track
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