Horticulture researchers at the Crop Science Department, University of Zimbabwe are creating a buzz about traditional tuber crops. After tasting some of the products being promoted by the department at last year’s food festival, Naturally Zimbabwean visited the University to find out what was going on ‘in the laboratory’. We were shown around by Gaudencia Kujeke and Annia Matikiti, experts involved in the study of tsenza and madhumbe, respectively.
Tsenza, also known as Livingstone Potato (Plectranthus esculentus) is Gaudencia’s ‘baby’. Native to tropical southern Africa it has been cultivated since prehistoric times. In Zimbabwe the main production areas used to be Nyanga, Makoni and Mutasa districts with isolated villages producing in Seke, Hwedza and Chihota. However, a recent study has shown that main production has shifted to Rusape in MakoniDistrict), Chihota in Marondera and Nyanga to a lesser extent. The tuber is which is mainly produced by women is usually grown in wetlands although and dryland production is possible. Though not well known, tsenza is important because it is an indigenous vegetable that is well adapted to local soil and climate conditions and can easily be cultivated with minimal inputs. According to preliminary nutritional analysis carried out by scientists at London’s Kew Gardens, tsenza is rich in carbohydrates, vitamin A and minerals. (http://www.kew.org/science-conservation/plants-fungi/plectranthus-esculentus-livingstone-potato).
Gaudencia told us about a study carried out in 2001 by the Horticultural Research Institute (http://www.bioversityinternational.org/fileadmin/PGR/article-issue_130-art_65-lang_en.html) which identified 25 varieties (landraces) of Tsenza being cultivated. However a recent survey by her team (http://www.sciencedomain.org/download/MTA2MTJAQHBm) revealed that only 12 landraces are still being grown namely: Ndurwe, Gombwe, Chibanda, Nziye, Sasamwi, Musande, Chizambezi, Nyabewu/Nyabuti, Nyatiya, Mutsaza, Chibhurandaya and Tutsenza. The decline in tsenza cultivation is thought to be due to poor rainfall and lack of a market.
Gaudencia is currently investigating different propagation and cultivation methods as well as different ways to cook and process the crop. Her aim is to encourage more farmers across Zimbabwe to try growing it. She has also been experimenting with different ways to process and cook tsenza. Unlike Irish potatoes, tzenza tubers can be eaten raw and have a fresh, tangy flavour. They can also be boiled, roasted, fried or dried and made into flour for thickening and baking. Nutritional analyses are underway and we look forward to getting an update.
More with madhumbe
Madhumbe, also known as cocoyam or taro (Colocasia esculenta), is a root crop native to east Asia but is widely grown throughout the tropics from Africa to South America to Australia. The crop has been grown in Zimbabwe for centuries, mainly in the eastern districts. At the University of Zimbabwe the plant is being studied by Annia Matikiti. Locally madhumbe and its sister variety magogoya are cultivated for their edible corms which may be eaten roasted, boiled or fried and may also be dried and made into flour. The leaves of madhumbe are also eaten as relish just like spinach.
In Zimbabwe the cocoyam-producing belt stretches from Rusape to Nyanga, from Nyanga to Mutare and Chipinge to some parts of Masvingo. Due to many factors including intermarriages, migration and relocation, individual smallholder farmers in other parts of the country also grow this crop.
Annia notes that despite all the potentials and advantages of cocoyam production in Zimbabwe, the crop has low status. She says “cocoyam can be described as an orphaned, neglected and underutilized crop which has received no scientific research or funding despite its significance for food security in the country”.
She explained that such neglected crops are grown primarily in their centres of origin or centres of diversity by small-scale subsistence farmers, where they are still considered an important part of the local diet. Annia told us that “While these crops continue to be maintained by socio-cultural preferences and use practices, they remain inadequately characterized and neglected by research and conservation”. She notes that crop production by the farmers is declining in favour of more modern root crops such as sweet and Irish potato. This has happened in the Nyanga region, where cocoyam production has been displaced by the more economically lucrative Irish potato.
Meanwhile in other areas such as Honde Valley and Chipinge, cocoyam is contributing substantially to the food and income security of many households. The crop is sold at Mbare Musika and can even be found in upmarket supermarkets like Fruit and Vegetables at Borrowdale and Greendale, thus demonstrating its economic potential.
Cocoyam corms are more nutritious than Irish potatoes with higher levels of carbohydrate, dietary fibre, calcium, magnesium, phosphorus and potassium and vitamins C and E. The young leaves and shoots are a good source of vitamins A and C and contain more protein than the corms but should be boiled twice before eating to remove their bitterness.
Annia is investigating various different cooking and processing methods for the crop including using the flour to make tacos, fritters, cocoyam stew, muffins and chapatis. The corms make an excellent, nutritious substitute for bread if eaten as a snack of for breakfast.
One problem with cocoyam is that the corms contain high levels of calcium oxalate which can lead to the formation of kidney stones in susceptible individuals. The levels can be reduced through boiling or soaking prior to cooking. It is recommended to consume calcium-rich foods together with madhumbe or magogoya to negate the effect of the calcium oxalate.
Annia has also initiated ongoing trials of different propagation and cultivation methods for madhumbe, which is also usually grown in wetlands. Like tsenza the crop does not require any inputs.
Promoting and propagating
The enthusiasm shown for these crops at the food festival has inspired the researchers to make their findings more widely accessible to the general public in Zimbabwe in the hope that a larger producer base and market can be developed for these underutilized crops which have the potential to improve people’s nutrition as well as bring in much needed income for rural communities. For more information contact the researchers directly at the Crop Sciences Department.