Bio fortification: A case of sweet potatoes

Hidden hunger is caused by a chronic lack of critical vitamins and minerals that puts children and adults at increased risk of stunting, anaemia, blindness, infectious diseases and even death.
Experts state that one in three people globally suffer from hidden hunger and women and children are especially vulnerable.
Bio fortification is a feasible and cost-effective means of delivering micronutrients to populations that may have limited access to diverse diets and other micronutrient interventions. In publication by Science Direct about improving nutrition through bio fortification, a review of evidence from HarvestPlus, 2003 through 2016 it is stated that since 2003, HarvestPlus and its partners have demonstrated that this agriculture-based method of addressing micronutrient deficiency through plant breeding works.

Farmer’s perspective
As such a team of scientists from Ministry of Agriculture Animal Industry and Fisheries, Ministry of Health, Ministry of Education, National Agriculture Research Organisation, HarvestPlus and others have come up to steer this initiative to ensure that bio fortified crop production is enhanced to boost diverse nutritive food consumption in the country.

Types
Dr Gorret Ssemakula the programme leader for sweet potato breeding at the National Crops Resources Research Institute (NaCRRI) Namulonge explains that scientists at Naro have so far bred pro vitamin A orange fleshed sweet potatoes and beans rich in iron and zinc which farmers are already growing across the country.
Other crops in the offing are pro vitamin A cassava, bananas and iron and zinc enhanced maize and perl millet.

Breeding process
Dr Ssemakula explained that bio fortified plants is all about adding micro nutrients to the plant.
“What scientists do is to go out to the field and select locally grown plants for the case of propagated crops which include sweet potatoes, bananas and cassava for the case of Uganda. It is a matter of selecting plants at random with already some percentage of pro vitamin A,” explains Dr Ssemakula.

Released varieties
Farmers are already growing orange fleshed sweet potatoes and varieties that include NASPOT 130 which matures in four months and the yield rate is 20 metrics per hectare per annum, NAROPOT 9 which matures in five months and average root yield in 17 tonnes per hectare with 30 per cent dry matter content, NAROPOT 8 which matures in five months and the yield rate in 20 tonnes per hectare with dry mater content of 33 per cent, SPK OO4 also known as Kakamega which matures in four months and yields 15 tonnes per hectare with dry matter content of 33 per cent and Ejumula which matures in four months and the yield is 19 tonnes per hectare with dry matter content of 34 per cent. These varieties are all resistant to sweet potato virus disease (SPVD) and sweet potato weevils (SPW). Other varieties released which are ordinary white in colour are NAPOT 4, NASPOT 3, NASPOT 5, NASPOT 11, NASPOT 12 O, NASPOT 10 O and NASPOT 1. The yield rate is from 11 – 29 tonnes per hectare depending on the variety.

Soil requirements
Sweet potatoes can be produced in low and high altitudes as long as the soils are fertile.
Seedbed for sweet potato should be fertile and well prepared without big soil clods. The huge soil clods would interfere with tuber development later during growth and development of the crop.
It can be on flat mounds or ridges where three to four vines are planted with spacing of one centimetre apart. This applies to places such as Kabale and it contains soil erosion.

Propagation
Farmers can propagate sweet potatoes as vegetative using stem segments called vines.
These are taken from the top of the old stems and caution should be taken to avoid chloric, mottled, wrinkled or vines with mosaic patterns.
Plants with mosaic patterns could most likely be having a viral disease. Farmers can practise rapid multiplication practices to multiply vines.
Here you use two node cuttings, make a bed spacing two centimetres apart, apply aerial fertiliser and in two months the planting material will be ready for planting.
Farmers can also use the conventional method by cutting vines and planting them in a nursery. Once they have grown 30cm it is ready for planting.

Planting
Sweet potato is either planted in mounds or on ridges using vine cuttings. Vines are the mature stems and are taken from the shoot. A good vine cutting should be about one foot long or about six nodes and should be disease free. In soils that are prone to drying, small mounds are used; big mounds in such a case are over exposed to sunshine and they dry out very fast.
The numbers of vines used do vary, as small mounds will take few vines and the big mounds accommodate more vines. Planting is mostly done by hands, but you can plant sweet potatoes using forked sticks in some cases. Vines for planting should be picked and allowed to wilt in the shade for a week before planting.
This ensures that the vines do not break during planting as fresh vines are brittle. These vines also root easily and ensure faster establishment of the crop in the soil.

Weeding
Sweet potatoes should be kept weed free in the first months and this is done by weeding around the ridges/mounds.
Weeding is normally done by hand. After about two months, the canopy of the crop is normally big enough, covering the ground and this helps to keep away weeds.
It is important to cover cracks arising from growth of the tubers with soil, otherwise if left open will attract weevils that will infect the tuber.

Pests and diseases
The most common pest is weevils; others are caterpillars and grasshoppers which can be controlled using appropriate pesticides
The diseases include SPVD and altarnaria and fusarium wilt among others
Farmers are advised to use resistant varieties such as the Orange Fleshed varieties and they should avoid spreading susceptible seedlings.