Related Stories By Peter Mietzner Published: 20120410
Unlocking value of indigenous veggies


As noted in earlier instalments of this column, vegetable amaranth is in a sense invisible to the authorities.

This is despite the fact that indigenous vegetables offer unique opportunities to diversify farming systems, ensure food security and alleviate poverty, while increasing income and improving human health. Indigenous vegetables are reported to be tolerant to harsh environmental conditions and adapted to local conditions.

These crops are also part of the region’s cultural heritage, hence their current consumption by many rural villagers is widespread.

African leafy vegetables form part of the daily staple diet and are rich in nutrients, eg vitamin A and iron.

Most of these crops are currently wild harvested, while few are cultivated.

Indigenous vegetables sub-programmes aim to develop improved cultivation methods, and promote, market and commercialise African leafy vegetables.

Traditional crops worldwide are in urgent need of protection from global warming, according to the UN Food and Agriculture Organisation (FAO).

“In Africa, we would not be just talking about the major staple crops and commercial crops we are familiar with on the international market, but we would also be talking about minor crops, which are neglected crops such as minor millets, yam, cassava, groundnuts,” says the secretary of the treaty, Shakeel Bhatti, who emphasises the important role those crops play in local food security in Africa - especially in subsistence farming.

He says traditional crops have often been neglected when it comes to agricultural and development aid, but the treaty has been working to fund support for these “under-utilised crops.”



Horticultural Development



Selection and crossbreeding is one area that could bring rapid advances.

Amaranthus species demonstrate high levels of variability in leaf size, leaf shape, branching, bolting pattern, growth and regrowth ability, and colour.

Indeed, the vast wide geographical spread of the genus has produced many landraces, and in their present undeveloped state, amaranths offer more genetic diversity than do many much better understood crops.

The huge gene pool in widely separated areas can be tapped for the future development of the crop.

This is an excellent genus as well as an excellent time in history for plant explorers and local plant lovers to get engaged.

One of the least known and least developed species is Amaranthus thunberghii, a semi-wild species native to Southern Africa.

This seems to have exciting potential and clearly deserves increased attention.

It grows very fast and is resistant to water stress.

It is also tolerant to many insect pests such as aphids, fall armyworm etc.

A thunberghii has a more prostrate growth habit than its relatives, which may or may not be a benefit.

It has been classified as an aphid-trap plant, which opens up intriguing possibilities for research endeavours.

Although vegetable amaranths have been neglected, this dereliction is, as we’ve said, not universal.

Asian growers have been making selections by decades.

Named varieties suitable for widespread culture are available from seed companies in Hong Kong, Taiwan, the United States, and elsewhere; many can be located on the Internet.

These “elite” forms are probably the most technologically-advanced and most thoroughly developed forms.

Regarding vegetable amaranths, much crop improvement has been done, but more could be accomplished by studies of: pest and disease resistance; nutrient uptake and nutrient content at different stages of growth; yields from clipping versus successive planting; regrowth after harvest (“ratooning”) and the best height at which to clip the plant and the best intervals between clippings; seed production and farmer-selection techniques; leaf-to-stem ratio; delayed flowering; planting and cultural practices for efficient use of land, water, and fertiliser; and crop rotation to avoid soil-borne diseases.

Also in need of studying is the forage use of leafy amaranth.

The recent Chinese experience is especially illustrative of the potentials and the possible means for feeding pigs with “pigweed.”

Africa has a relatively rich indigenous knowledge and indigenous vegetables have been used by the African people for thousands of years to solve food, developmental and environmental problems.

“Traditional knowledge and crops have proved vital in adapting to the changes since farmers in all study sites choose traditional crop varieties over modern ones because they are better and adapt to climate changes,” says Dr Krystyna Swiderska, a senior researcher at the IIED.



Food Technology



Deserving of research and testing are:

food quality, including tenderness and storage methods to prolong the life of the harvested produce; leaf colour and anti-nutritional factors. It seems likely that the bright red and purple-leafed types are the least desirable as foods; accumulation of anti-nutrition factors in response to type and quantity of fertilisers and soil; the variation in flavour among varieties; effect on nutrient retention by processing, such as boiling, steaming, or drying (for later availability during the dry season);

provitamin A and iron bio-availability; product development; toxicological studies; and nutritional studies, such as supplementation effects.

Actually, some research in these areas has already been conducted and efforts are needed to make the results more widely known and better used.



Vitamin A



On the face of it, amaranth leaves could be an important remedy for vitamin A-deficiency, one of the world’s horrors that is subject to increasingly intense outside interventions.

Many or most of the programmes could incorporate vegetable amaranth.

Benefits could accrue not only to Africa but to Indonesia (a country notable for this blindness-inducing affliction) and other parts of Asia.



Leaf-Protein Isolates



A future promise of vegetable amaranths is the development of leaf-protein concentrates. Compared with most other species, amaranth leaf protein is highly extractable.

In one trial, amaranth had the highest level of extractable leaf protein among 24 plant species studied.

During the extraction of protein, most other nutrients are extracted as well: for example, provitamin A, polyunsaturated lipids (linoleic acid), and iron.

Heating or treating the extract with acid precipitates the nutrients  as a leaf-protein concentrate.

In the process, most harmful compounds are eliminated, as they remain in the soluble phase.

The green cheese-like coagulum is washed with water slightly acidified with dilute acetic acid (vinegar) to reduce further amounts of possible anti-nutritive factors.

The resulting leaf-nutrient concentrate is especially useful for young children and other persons with particularly high protein, vitamin A, and iron needs.

The fibrous pulp left after extracting the amaranth greens is a suitable feed for animals.

The protein quality of the amaranth leaf-nutrient concentrate is excellent.

It is, however, species dependent, probably because of the presence of secondary substances.

In Kenya, under the Songa Mbele Community Development Initiative (Somcodi), farmers are being encouraged to go back to growing indigenous crops such as arrowroot, sweet potatoes, bananas, yams, sorghum, cowpeas, millet and cassava.



Special Interest Projects



It has been reported that amaranth is highly suitable for incorporation into crop rotations. It is usually unaffected by common soil diseases such as nematodes, and fungal and bacterial wilt.

Recent reports claim that amaranth benefits from inter-cropping with species such as celosia and/or jute (Corchorus).

Further confirmation is in order because this could be an exceptionally important finding.

Rotations between these rather similar potherbs could be advantageous to nutrition and dietary variety as well as yield.



Species Information

Botanical Name: Amaranthus spp.

Family: Amaranthaceae



Common Names: hanekam, kalkoenslurp, misbredie, varkbossie (Afrikaans); African/ Indian/Chinese spinach, tampala, bledo, pigweed, bush greens, green leaf; boroboro (Fulani); imbuya, thepe (Tswana); vowa (Venda); umfino, umtyuthu, unomdlomboyi (Xhosa); imbuya, isheke (Zulu); bonongwe (Chewa).



Next Week: We start looking at the “wonder” plant known as moringa. Although few Westerners have ever heard of it, moringa is potentially one of the planet’s most valuable plants, at least in humanitarian terms.

Perhaps the fastest growing useful tree, it commonly tops 3m — or even 5m — within a year of the seed being placed in the ground.

Sources: UN, FAO, NAS, IIED, World Bank, Forum for Food Security in Southern Africa, How Stuff Works, Wikipedia, Rural 21, Agricultural Research Council (SA), American Agricultural Economics Association, New Era, SciDev.net, Agricultural Union, Agronomic Board, Nourishing the Planet, own.