Untapped Potential of Livingstone Potato, an Indigenous and Underutilised Root Crop in Zimbabwe: a Review

African Crop Science Journal by African Crop Science Society is licensed under a Creative Commons Attribution 3.0 Uganda License. Based on a work at www.ajol.info/ and www.bioline.org.br/cs DOI: https://dx.doi.org/10.4314/acsj.v27i2.14

UNTAPPED POTENTIAL OF LIVINGSTONE POTATO, AN INDIGENOUS AND UNDERUTILISED ROOT CROP IN ZIMBABWE: A REVIEW

G.T. KUJEKE, U. MAZARURA, E. NGADZE, E. GASURA, J.T. RUGARE, A. MATIKITI and R.T. MASEKESA

Department of Crop Science, Faculty of Agriculture, University of Zimbabwe, P. O. Box MP 167, Mount Pleasant, Harare, Zimbabwe Corresponding author: [email protected]

(Received 19 December 2018; accepted 20 May 2019)

ABSTRACT

The Livingstone potato (Plectranthus esculentus), a tuberous root vegetable indigenous to Africa, remains a neglected and underutilised crop species (NUCS). Of late, there has been a shift in how the NUCS are viewed as consumers become increasingly aware of their nutritional and medicinal value. The objective of the review was to highlight research developments of the Livingstone potato and to identify existing research gaps in a quest to unlock the potential of this crop. Traditionally, the vegetable has been utilised for food, economic and medicinal benefits. However, recent research developments in Africa have demonstrated that the Livingstone potato is highly nutritious and can provide raw materials for the agro and pharmaceutical sectors. While these are notable developments, more needs to be done, especially in Zimbabwe where there is very little researched information on its production and utilisation. The economic impact could potentially be at household, farmer and national level through establishing strong value chains. This is important in order to increase awareness and promote the crop, whose production is on the decline. The diversity and nutritional value of the Livingstone potato needs to be evaluated in Zimbabwe, as a step towards crop improvement, which is key to improved productivity. Continuous production at a large scale will help preserve the germplasm and prevent the genetic erosion currently taking place. This review echoes previous calls for the government of Zimbabwe to take bold steps to support the NUCS, such as the Livingstone potato, at policy level and to fund programmes that deal with such crops.

Key Words: Medicinal, nutritious, Plectranthus esculentus

RÉSUMÉ

La pomme de terre Livingstone (Plectranthus esculentus), un légume-racine tubéreux indigène d’Afrique, reste une espèce qui est négligée et qu‘ on la n‘ utilize pas. Ces derniers temps, I y a eu le changement pour la façon de conciderer la pomme de terre Livingstone parceque les consommateurs deviennent de plus en plus conscients de leur valeur nutritionnelle et médicinale. L’objectif de la revue était de mettre en évidence les développements de la recherche sur la pomme de terre Livingstone et 308 G.T. KUJEKE et al. d’identifier les lacunes de la recherche existante dans le but de decouvrir le potentiel de cette culture. Traditionnellement, le légume a été utilisé pour de ressources alimentaires, économiques et médicinales. Toutefois, des travaux de recherche récents en Afrique ont montré que la pomme de terre Livingstone était très nutritive et pouvait fournir des matières premières aux secteurs agricoles et pharmaceutiques. Bien qu’il s’agisse d’évolutions notables, il reste encore beaucoup à faire, en particulier au Zimbabwe, où très peu d’informations ont été recueillies sur sa production et son utilisation. L’impact économique pourrait potentiellement être au niveau des ménages, des agriculteurs et de pays. Ceci est important pour sensibiliser et promouvoir la culture, dont la production est en déclin. La diversité et la valeur nutritionnelle de la pomme de terre Livingstone doivent être évaluées au Zimbabwe, dans la perspective d’une amélioration des cultures et essentiellement l’amélioration de la productivité. Une continuite de la production à grande échelle aidera de préserver le germoplasme et de prévenir l’érosion génétique en cours. Cette revue fait écho aux appels precedents et au gouvernement du Zimbabwe pour prendre des mesures audacieuses et soutenir la pomme de terre Livingstone en financant des programmes qui font les recherches sul la pomme de terre Livingstone.

Mots Clés: Médicinal, nutritif, Plectranthus esculentus

INTRODUCTION have not been previously classified as major crops, have previously been under-researched, The Livingstone potato (Plectranthus currently occupy low levels of utilisation; and esculentus) is dicotyledonous and belongs to are mainly confined to smallholder farming the Lamiaceace (Labiatae) family, which is also areas (Azam-Ali, 2010: Chivenge et al., 2015). known as the mint family. With 236 genera Globally, the Livingstone potato is and more than 7000 species, the Lamiaceae is considered a minor crop in terms of total the largest family among medicinal plants production and commercial value; and its (Schippers, 2000; Paton, 2013). The species market is reportedly limited and has declined is widespread throughout the African over the years, in favour of more ‘modern’ continent, in the wild and under cultivation root crops such as yam (Dioscorea spp.), (Fox and Young, 1982; Codd, 1985; Dhliwayo, cassava (Manihot esculenta) and sweet potato 2002; Allemann and Hammes, 2003). It is a (Ipomoea batatas) (Schippers, 2000). The perennial or woody herb that is aromatic, and production of such indigenous minor vegetable differs from most members of the Lamiaceae crops by the rural smallholder farmers has also family because it produces edible tuberous led to the stigma associated with poor rural organs at the base of the stem (Kemas et al., lifestyles, which regard them as low status 2013). Also known as the kaffir, wild, native foods; and as such, they have been neglected or finger potato, the Livingstone potato is not for a long time (Fusire, 2008). Despite this a member of the Solanaceace family to which status, these indigenous vegetables are still the common Irish potato (Solanum tuberosum) valued in rural areas mainly because of the food belongs (Greenway, 1944; Busch, 2015). security benefits, and in certain instances, The Livingstone potato is one of the earliest economic benefits when surplus produce is African crops to be domesticated, and has now sold (Dhliwayo, 2002). become a rarity after a long history of Of late, there has been a shift in the cultivation throughout the African continent perception of the NUCS and an increase in (Schippers, 2000). It is regarded as a lost crop awareness of their nutritional and medicinal and as such, has been classified among the value (Ngugi et al., 2007). The importance of neglected and underutilised crop species the NUCS is currently viewed in terms of (NUCS) (Williams, 2002; Eke-Okoro et al., potential for alleviating hunger directly, through 2008). The NUCS are defined as crops that increasing food production in challenging Untapped potential of the Livingstone potato 309 environments where major crops are severely Zimbabwe are located in Manicaland (Nyanga, limited; and through nutritional enhancement Makoni and Mutasa) and Mashonaland East to diets focused on staples (Mayes et al., provinces, where individual farmers in a few 2011). The Livingstone potato is one such villages in Seke, Hwedza and Chihota grow crop that has been identified as a priority crop this crop (Dhliwayo, 2002). for research by the Southern and Eastern Generally, there is paucity of literature on African Network for Underutilised Species the improved agronomic practices for (SEANUC) (Williams and Haq, 2002). There Livingstone potato (Allemann, 2002). Any is a dearth of researched information on reported production requirements for the production and potential uses of the Livingstone potato are generally those of a Livingstone potato in Zimbabwe. This review closely related crop, Hausa or coleus potato documents research efforts on the Livingstone (Solenostemom rotundifolius), which is in the potato, whose full potential has not been same Lamiaceae family (Tindall, 1983; realised especially in Zimbabwe, and aims to Schippers, 2000). No research has been identify the knowledge gap between recent conducted in Zimbabwe in order to optimise technological advancements worldwide and the the agronomy for improved productivity. This level of adoption so as to address any is the case for many underutilised crops such outstanding research questions with regards as the African yambean (Sphenostylis to its production. stenocarpa) and cocoyam (Colocasia spp.) (Williams and Haq, 2002; Mayes et al., 2011). Production status of Livingstone potato. Padulosi et al. (2013) also stated that the The Livingstone potato is believed to have underutilised and neglected crops tend to be originally been selected from wild plants in produced using traditional methods, mostly by either the Central African Republic or the Upper women as is the case with the Livingstone Niger Valley of the Hausaland region of Nigeria; potato in Zimbabwe (Dhliwayo, 2002: Kujeke and spread with the migration of people across et al., 2015). Africa over the last 2000 years (Xaba et al., The Livingstone potato produces seed 2011). In Southern Africa, the Livingstone which develops slowly and is heterogeneous potato can be found in Malawi, Namibia, (Schippers, 2000). However, Mwanja et al. Swaziland, Angola, South Africa and Zimbabwe (2015) reported that, while the Livingstone (Schippers, 2000). Its distribution points to potato plant produced flowers at 158-215 days its ability to thrive in almost all climates, as it after planting, the flowers dried up without is able to grow successfully in heavy humid fruiting or seed-setting in all cultivars tested, as well as in hot dry climatic conditions probably because of the interplay of genetic (Allemann, 2002). It also grows in the wild, and environmental factors. It is for this reason in dry woodlands, forest margins, rocky hill- that cultivated forms of Livingstone potato are slopes and bushveld savanna (Xaba et al., normally propagated vegetatively from small 2011). tubers. Further research is essential on the In Zimbabwe, the Livingstone potato is fruiting or seed setting as it impacts on the found in the wild as well as in cultivated lands. sexual propagation that leads to genetic Its habitat in the wild consists of rocky variation, which could be beneficial with woodlands, rocky sandy miombo woodlands, regards to improved varieties. and Brachystegia woodlands. It has been In Zimbabwe, Dhliwayo (2002) and Kujeke sighted in the wild in Acturus, Christon Bank, et al. (2015) highlighted that the crop was also Macheke, Matobo Mutorashanga and in certain propagated through tubers only, on raised beds rocky woody areas of Harare (Hyde et al., in wetlands or vleis; while dryland cultivation 2012). The major production areas in is practiced in parts of the eastern highlands 310 G.T. KUJEKE et al. of the country. Production through rooted Livingstone potato is characterised by lower cuttings or suckers is reportedly possible yields, it will also produce harvestable yields (Tindall, 1983; Allemann, 2002); though not where major food crops may fail (Safwan and practiced in Zimbabwe. Production under Mohammed, 2016). Yields of Livingstone dryland as is practiced in Malawi and areas potato can be as low as two to six tonnes per near the Mozambican border (Dhliwayo, hectare (Tindall, 1983), as opposed to on - 2002). It is likely that most communities that station yields. Schippers (2002) reported a practice wetland production on ridges in yield potential of 13-25 t ha-1 and up to 60 t Zimbabwe, have not been fully exposed to the ha-1 under optimal experimental conditions, alternative method of dryland cultivation. using tissue culture produced plantlets in South Current laws in Zimbabwe prohibit wetland Africa (Haq, 2004). The high yields obtained cultivation (Muzenda et al., 2002). under experimental conditions clearly Production reportedly commences with demonstrate a need for optimising the current field preparation in winter; whereby raised beds traditional production methods in Zimbabwe. are constructed in the wetlands (Dhliwayo, Information gathered from farmers during a 2002). Under dryland cultivation, clearing of survey by Kujeke et al. (2015) on the vegetation is done followed by deep ploughing. production status of the crop, revealed that The ideal soil types for the Livingstone potato production is currently on the decline in under wetland and dryland production are not Zimbabwe due to various factors, mainly poor defined. Research carried out by Allemann and rainfall pattern over the years leading to a Hammes (2006) showed that tuberisation was reduction in the area under wetlands. This, affected by photoperiod. The specific genotype therefore, implores for further research into tested required exposure to four short day enhancing sustainable production under cycles. Since the photoperiod requirement is dryland conditions to prevent the genetic genotype specific, it is imperative to conduct erosion of the crop due to climate change as research on the existing germplasm for wetlands continue to dry up. improved productivity. Allemann and Coertze (1996) reported that Post-harvest handling. The harvested no serious pests and diseases attacked the Livingstone potato tubers are highly perishable Livingstone potato. However, wild pigs, and as such, its production is faced with the rodents, nematodes and caterpillars were later challenge of high post-harvest losses. The found to be a problem and a few diseases harvested tubers are generally kept in cool areas which include soft rots and blights have been and underground pits. A grass or leaf mulch is noted (Schippers, 2000: Kujeke et al., 2015). normally used for the open storage; ashes and The occurrence of pests and diseases can be grass are used for the underground storage. influenced by the prevailing environmental In either system of storage, tubers will conditions, the susceptibility of germplasm, normally keep for at least two months in and the cultural practices during production. Zimbabwe (Dhliwayo, 2002). Ezeocha and It is imperative that research be conducted to Ironkwe (2017) investigated the effect of determine the effective methods to manage the different storage methods on the physiological specific pests and diseases that may impact and nutritional quality of the harvested tubers on the production of the Livingstone potato. in Nigeria. Their work revealed that the best The crop is reportedly ready for harvesting storage methods for the tubers are storing the six to nine months after planting (Schippers, tubers in pits with alternate layers of river sand, 2000). While bulk harvesting can be done, the wood ash and wood shavings. These storage crop can also be harvested piece meal as and methods are appropriate for the smallholder when needed (Dhliwayo, 2002). Although the farmers who produce the Livingstone potato. Untapped potential of the Livingstone potato 311 The Livingstone potato as a source of food. which is held in high esteem amongst the Livingstone potatoes are grown for their communities (Dhliwayo, 2002). thickened roots or stems, which generally While the tuberous roots of the Livingstone develop underground (Bradshaw, 2010). potato form the primary product that is These plant organs have been found to be rich consumed especially in Zimbabwe (Dhliwayo, sources of carbohydrates and are commonly 2002: Kujeke et al., 2015), other parts of the used as a dietary staple (Dansi, 2011). As a plant have been proven to be edible. The choice food source, the Livingstone potato can be of the plant part used for food is probably used as a substitute for potato or sweet potato related to the genetic differences that exist (Allemann, 2002), with its taste being within lines or varieties grown throughout the described as slightly bitter than turnips (typical continent. In Kenya, in the Embu district, the of immature tubers), to having a unique Livingstone potato herbaceous stems are pleasant taste likened to turnips or parsnips, crushed using hand mills, soaked in water for thus making it a delicious vegetable (Bryant, about an hour, and the sieved liquid is used as 1907; Fox and Young, 1982; Tredgold, 1986; a food additive to sweeten gruel (Allemann, Schippers, 2000). The tubers can also be 2002; Lukhoba et al., 2006). Demissie (1991) boiled with beans or rice as a main meal, while makes reference to the leaves being cooked the leaves of some varieties can be cooked as and used as vegetables in Ethiopia; while in a vegetable (Demissie, 1991). The basic the Eastern Cape in South Africa, women preparation of the tubers involves washing, communal farmers have been reported to grow scraping, boiling, frying or roasting. The tubers selected lines of the Livingstone potato whose can be eaten on their own or added to stews, leaves can be cooked and eaten (Haq, 2004). soups or other dishes (Tredgold, 1986; Burkill, The National Botanical Institute (1999) 1995; Xaba et al., 2011). The taste and dry reported studies of herbarium samples to have matter content probably determine which revealed that the people of the Njoke district variety is cooked or eaten raw, or as a snack, of Tanzania pickle the flowers of the as is the practice in Zimbabwe (Dhliwayo, Livingstone potato. In Zimbabwe, the tubers 2002). are the only edible part (Dhliwayo, 2002: In West Africa, the Livingstone potato is a Kujeke et al., 2015). It is, therefore, worth highly regarded vegetable root crop. For investigating whether the leaves can be instance, in Cameroon, the boiled and very consumed as genetic differences existing soft root vegetable has been used in the past between lines may be the cause of the as the first solid food given to young children differences in the part plant eaten. during the transition from breastfeeding to Food selection is governed by a number of more solid and starchy foods like yam or millet sensory characteristics’ such as taste’ smell (Panicum miliaceum) (Schippers, 2000). In texture, colour (and other visual Nigeria, the crop is used for making special characteristics)’ even sound (e.g. dishes during traditional ceremonies in crunchiness), and physiologically perceived commemoration of the ancestors (Schippers, characteristics, like “fillingness” or 2000). In addition, the fresh tubers can also “burningness” (Pelto et al., 1989). be dried for later use and prepared together Underutilised vegetables can be used to prepare with arrowroot or cocoyam for special various value - added products, which can lead occasions like funerals. The drying of the fresh to improved consumption of such crops tubers demonstrates the potential of the (Thillakawardane, 2009). Ukpabi et al. (2011) vegetable to be processed. A dish of mashed investigated the culinary and sensory tuberous roots known in Zimbabwe as characteristics of the Livingstone potato, and Chikone, is considered a traditional delicacy found the mealy boiled tubers and crispy salted 312 G.T. KUJEKE et al. French fries from the experimental tubers to composite flour blends. Their work showed be generally acceptable. There are limited that the Livingstone potato flour could be used culinary uses of this crop in Zimbabwe, and to substitute up to 15% of wheat flour in bread this might also seriously limit its production making, without adversely affecting the and demand (Dhliwayo, 2002). Good sensory sensory and microbial stability of the bread. and culinary characteristics are vital as they No research of this nature has been conducted can enable researchers to fully exploit the using the Zimbabwe Livingstone potato Livingstone potato by exploring its value landraces. addition. Characterisation of the nutrient composition of the Livingstone potato landraces indigenous Nutritional benefits of Livingstone potato. to Zimbabwe has not been done. Knowledge Although uncommon in industrialised of the nutritional composition would be of countries, malnutrition in children and other benefit to the communities that consume it. vulnerable groups remains a scourge in many The addition of crops like the Livingstone developing countries, especially in sub - potato to the diet adds diversity and diverse Saharan Africa (Kramer and Allen, 2015). diets deliver nutrition and greater health with Consideration of indigenous vegetables which additional benefits for human productivity and are usually rich in nutrients such as vitamin A livelihoods (Chivenge et al., 2015). and iron, that are often lacking in the diets of children and pregnant women, is imperative Genetic improvement. Underutilised root (Smith and Eyzaguirre, 2007). Of all the tuber crops such as the Livingstone potato represent vegetables, the Livingstone potato is regarded a pool of indigenous germplasm whose as highly nutritious, with high percentages of potential has not been fully unlocked by starch, essential amino acids and significant researchers. While they may never rise to the levels of calcium, iron and vitamin A; in addition current status of exotic vegetables like to the useful trace elements and minerals (Xaba potatoes and tomatoes globally, they are still et al., 2011). The protein value is reportedly worth investigating (National Research better than Irish potato; while the fat and total Council, 2006). The strongest argument for ash levels are higher compared to published promoting these crop species is simply that, values for other roots and tubers (Temple et since people continue to use them, this al., 1991). constitutes a recognition of their value, Allemann and Hammes (2003) compared sufficient to suggest that research priorities the chemical composition of the Livingstone should be visited (Blench, 1997). This is the potato tubers from South Africa with case in Zimbabwe, where communal farmers corresponding values for taro, cassava, raw in the Mashonaland East and the Eastern potato and two cultivars of raw sweet potato, Highlands provinces continue to produce the Brondal (white flesh) and Mafutha (orange Livingstone potato for food and income. flesh); as well as Nigerian varieties of P. From a breeding perspective, the genetic esculentus (Allemann and Hammes, 2003). potential of a crop is determined by the They concluded that the Livingstone potato combination of the genes it contains and their tubers can be a potential source of elements mutual interactions with the environment to and compounds which are often deficient in produce the phenotype that could either be the diet of rural South Africans, thus helping high yielding, resistant to pests, diseases or to alleviate malnutrition. Further, Ezeocha and drought (Mayes et al., 2011). A prerequisite Ironkwe (2017) carried out sensory evaluation for any genetic improvement program is the and microbial stability checks of bread samples knowledge of the extent of the genetic variation produced from wheat/Livingstone potato present between genotypes and the genetic Untapped potential of the Livingstone potato 313 distance between all closely related species with require an assessment of diversity at some which hybrids could be produced (Beeching level, to select resistant and highly productive et al., 1993). Such information is currently varieties (Mondini et al., 2009). This is yet to unavailable for the Livingstone potato in be done for the Livingstone potato germplasm Zimbabwe. in Zimbabwe. The assessment of the genetic diversity within and between plant populations is Medicinal attributes of the Livingstone routinely performed using various techniques, potato. The Lamiaceae or mint family to which such as morphological, biochemical the Livingstone potato belongs, is a very characterisation and the use of molecular important medicinal family, mainly comprising markers (Govindaraj et al., 2015). The genetic of herbs or shrubs often with an aromatic smell markers represent genetic differences between (Raja, 2012). Other common members include individual organisms or species. While they most culinary herbs such as basil, mint, generally do not represent the target genes rosemary, sage, marjoram, thyme, lavandula, themselves, they act as ‘signs’ or ‘flags’ orthosiphon, ocimum, leucas, anisomeles, (Collard et al., 2005) which can be used to colebrookea, coleus, hyptis, oreganum, show the diversity between crop species. brunella, scutellaria, lamium, teucrium and Without characterisation and evaluation the perilla (Venkateshappa and Sreenath, 2013). useful variation of these species remains poorly Members of this family also possess oils, understood (Padulosi and Hoeschle-Zeledon, which are mostly present in leaves. However, 2004). Kyesmu and Mantell (2002) provide the oils can also be found in all above ground only documented molecular research for the parts of the plants and are valuable in cosmetic, Livingstone potato. Their work focused on flavouring, fragrance, perfumery, pesticide, DNA extraction methods for use in DNA finger and pharmaceutical industries (Özkan, 2008). printing of the Livingstone potato clones from A review by Caroviæ-StanKo et al. (2016) Nigeria. No molecular studies have been clearly demonstrated that the species of this conducted for the Livingstone potato landraces family possess antioxidant, antimicrobial, and in Zimbabwe and as such, this review anti-inflammatory properties. highlights this research gap. With regards to the Livingstone potato, The dearth of research information on the there are different schools of thought production of the Livingstone potato in concerning its medicinal attributes. There is Zimbabwe is exacerbated by the fact that little a general appreciation among the communal is known regarding the diversity of the communities that the tuberous roots have germplasm, both in current production and in medicinal properties, albeit being viewed as part the wild. It is, therefore, important to collect of folk medicine. A survey done in 2001 in and evaluate the germplasm, in order to provide Zimbabwe by Dhliwayo (2002), reported that researchers with resource material for crop the Livingstone potato has been used to cure improvement (Dhliwayo (2002). There is a stomach aches, nausea, backache and possibility of improving yields to levels problems associated with the female obtained in other countries like South Africa reproductive system. Allemann (2002) also (60 t ha-1) if farmers use improved propagating reported similar medicinal uses. On the other material and improved agronomic practices hand, the National Research Council (2006) (Burkill, 1995). The improvement of the focuses on the Livingstone potato as being a Livingstone potato genetic resources is one-product plant, which is a food and chooses dependent on the continuous introduction of to ignore the purported medicinal properties wild relatives, traditional varieties and the use associated with the root vegetable. of breeding techniques. These processes all 314 G.T. KUJEKE et al. Perhaps the key issue is that the knowledge antioxidants, and thus could be used in the about the medicinal attributes of the NUCS treatment of ailments implicating free radicals. such as the Livingstone potato remain hidden Eleazu et al. (2014a) demonstrated the in indigenous knowledge systems, thus potential of Livingstone potato in the justifying the continued utilisation and management of diabetes and hyperlipidemia. preservation of certain crops (Chivenge et al., Their research showed the an•tidiabetic actions 2015). However, there is strong evidence that of Livingstone potato and its ability to supports the medicinal attributes associated ameliorate glomerular complications and liver with the Livingstone potato (Lukhoba et al., hypertrophy in diabetics. Eleazu et al. (2014b) 2006). The medicinal properties can play an also investigated the effect of Livingstone important role in the lives of rural people who potato incorporated feeds on diabetes and its produce and consume them, particularly those complications in streptozotocin-induced in the remote parts of the developing countries, diabetes in rats. The results of the study which have limited access to adequate health indicated the antidiabetic actions of Livingstone facilities (Safwan and Mohammed, 2016). potato and its ability to amelio•rate glomerular Kyesmu (1994) recommended that a critical complication and liver hypertrophy in chemotaxonomic survey of the Livingstone diabetics. potato plant should be undertaken, as the The bioactive principles/natural products biochemical constituents could be of medicinal in Livingstone potato that justify its biological significance or have other uses. The onus for properties as used in folklore medicine were researchers is to extensively explore the presented by Eleazu and Eleazu (2015). Their medicinal attributes of the different landraces work showed that by isolating and identifying of the Livingstone potato, as a step in some compounds with biological activities in improving awareness and use since it is the Livingstone potato, new drugs could be virtually untapped. developed from this plant in the future to treat Burkill (1995) reported that a decoction can various diseases. The research findings put to be taken for treating taenia (human tapeworm) rest the speculations (Dhliwayo, 2002) that in the Ubangi area of Democratic Republic of have existed with regards to the Livingstone Congo (DRC); while a bolus of crushed leaf potato’s medicinal properties. These can be used as a suppository for oxyuris developments are very important and should (human thread worm). Lukhoba et al. (2006) be investigated further using the Livingstone extensively reviewed the ethnobotanical uses potato landraces found in Zimbabwe. Positive of the Plectranthus genus to which the results would have a huge impact as diabetes Livingstone potato belongs. Their review appears to be a growing problem in the African highlighted the following medicinal attributes: region where studies have shown that its the treatment of a wide variety of digestive prevalence in Zimbabwe has increased disorders, headache as well as cytotic and anti- significantly over the past three decades tumor promoting activities (Morris and (Mutowo et al., 2015). Msonthi, 1996; Mooi et al., 1999; Pakia et al., 2003). The growing interest in the substitution Socio-economic impact. While orphan or of synthetic food antioxidants with natural minor crops like the Livingstone potato are ones, in the maintenance of human health, has typically not traded internationally, they can fostered increased research on the screening play an important role in regional food security of plants for the identification of antioxidants. (Mabhaudhi et al., 2017). In addition to the For example, Eleazu et al. (2010) stated that food security benefits, the Livingstone potato flour made from three varieties of the offers an economic advantage due to its Livingstone potato was a natural source of Untapped potential of the Livingstone potato 315 uniqueness and suitability to environments in industries, especially in the manufacture of which it is grown using low inputs. solid dosage forms. Ochekpe et al. (2013) Historically, stems of the Livingstone potato evaluated the binding and disintegrating plant are reported to have been used to make property of starch from tubers of the baskets by the Ngomi people in the district of Livingstone potato in chloroquine phosphate KwaZulu-Natal in South Africa (National tablets at a use level of five percent, and Botanical Institute, 2000). Further exploration compared this with similar tablets formulated of this practise could prove to be beneficial to with maize or cassava starches as binder and communities that grow the vegetable, with disintegrant. Although maize starch gave the regards to employment creation and income best results, the Livingstone potato starch fared generation through the marketing of the better compared to the cassava starch, thus products. In Nigeria, research by Okereke proving its potential which warrants further (2012) has shown that Livingstone potato meal research, especially in Zimbabwe where there can be used to reduce the cost of broiler feed, has been no research conducted. by including up to 30% of the Livingstone potato meal as a replacement for maize meal. Gender issues. In certain cases, underutilised This is significant in the sense that the savings crops like the Livingstone potato are associated from the reduced cost of broiler feed can be with specific gender roles, with women being channelled to cater for other expenses required seen as particularly significant in the for improved livelihoods of those who produce production of these crops (Mabhaudhi et al., broilers for consumption or for sale. 2016). Haq (2004) reported that in African rural communities, the women are empowered Industrial application. Emmambux and through producing these crops which they can Taylor (2013) recommended that African process or sell directly to provide income for starches should be investigated for non-food essentials such as school fees and health care uses for applications such as adhesives, thus, sustaining their livelihoods. In addition, pharmaceutical excipients, sizing treatment, they possess the valuable indigenous printing for paper manufacture, and warp knowledge on the production and utilisation sizing and fabric printing for textile industries. of these crops. This is clearly demonstrated The starch quality of Livingstone potato has in Zimbabwe with regards to the Livingstone been shown to be similar to that of the starches potato, where the root vegetable is mainly found in cassava and sweet potato (Delpeuch produced by women in the communal areas et al., 1978). This clearly opens an avenue in and is primarily sold in nearby towns with the Zimbabwe for further exploration into its remainder being retained for household processing for commercial starches. consumption (Dhliwayo, 2002: Kujeke et al., Singh et al. (2003) reported that starch 2015). Schippers (2000) also places emphasis was one of the most widely used excipients in on the role of women in the production, the food and pharmaceutical industries, where processing and marketing (mainly retailing) of the starches were used as fillers, glidants, the Livingstone potato. In South Africa in the thickeners, binders, disintegrates as well as Eastern Cape, the farmers reportedly sell the gelling, bulking, and water retention agents. fresh Livingstone potato tubers and cooked Muazu et al. (2011) demonstrated that leaves in the local markets as well as to Livingstone potato starch compared well to travellers (Haq, 2004). maize starch BP (British Pharmacopoeia) in physicochemical properties; and could Promoting the Livingstone potato in therefore, serve as an alternative to maize Zimbabwe. There is a need to develop strong starch BP as an excipient in the pharmaceutical value chains for the Livingstone potato in 316 G.T. KUJEKE et al. support of rural agricultural development and ACKNOWLEDGEMENT food security. This can be achieved through the research value chain, production, agro- The authors acknowledge the International processing, and marketing (Mabhaudhi et al., Foundation for Science (IFS grant No: C/ 2017). Strategic interventions that help to make 5431-1) and the Deutscher Akademischer the Livingstone potato more commercially Austausch Dienst (DAAD: A/1395622) In competitive by developing improved ‘modern’ country scholarship for funding the research varieties need to be taken (Padulosi et al., on the Livingstone potato in Zimbabwe. 2013). For example, biotechnology techniques have been employed to provide virus free REFERENCES planting material which consequently has helped to improve yields in sweet potato and Allemann, J. and Coertze, A. 1996. Wild cassava. Micro-propagation becomes an ideal Potato (ARC-Roode plant Vegetable and choice to rapidly upscale the production and Ornamental Plant Institute, Information delivery of large quantities of superior cultivars Sheet A2 Indigenous Root Crops). Pretoria, and as such, offers a good distribution channel South Africa: ARC-Roodeplaat Vegetable for improved yet underutilised crops (Dawson and Ornamental Plant Institute, Private Bag et al., 2009). Tissue culture is regarded as X, 293. one of the most basic biotechnological tools Allemann, J. 2002. Evaluation of Plectranthus available in sub-Saharan Africa and its vast and esculentus NE Br as a potential vegetable varied applications have significantly crop. PhD, University of Pretoria, South contributed to the safeguarding, improvement Africa. and distribution of vegetatively propagated Allemann, J. and Hammes, P. 2003. Chemical orphan crops (Dubois, 2009). The same composition of South African Plectranthus biotechnology techniques can also be esculentus tubers: Research in action. South investigated and applied for the Livingstone African Journal of Science 99:127-129. potato in South Africa where lack of improved Allemann, J. and Hammes, P. 2006. Effect of planting material has also contributed to its photoperiod on tuberization in the decline in production (Dhliwayo, 2002: Kujeke Livingstone potato (Plectranthus esculentus et al., 2015). NE Br. Lamiaceae). Field Crops Research Government policies should also focus on 98:76-81. programmes that include increased awareness Azam-Ali, S. 2010. Fitting underutilised crops of the Livingstone potato. The University of within research-poor environments: Zimbabwe has also taken the initiative to Lessons and approaches. South African research the NUCS (Brazier, 2016; Mapfumo, Journal of Plant and Soil 27(4):293-298. 2018) and research is currently ongoing on Beeching, J.R., Marmey, P., Gavalda, M.-C., other NUCS which include cocoyam, Noirot, M., Haysom, H.R., Hughes, M. A. amaranth, spider plant, sweet potato as well and Charrier, A. 1993. An assessment of as the Livingstone potato. However, more genetic diversity within a collection of needs to be done by involving stake holders in cassava (Manihot esculenta Crantz) the industry so that innovations are rapidly germplasm using molecular markers. disseminated and popularised. The government Annals of Botany 72: 515-520. is urged to support such initiatives through Blench, R.M. 1997. Neglected species, funding this research area so that the full livelihoods and biodiversity in difficult areas: potential of the NUCS such as the Livingstone how should the public sector respond. potato can be realised. Natural Resource Perspectives Paper, 23. Untapped potential of the Livingstone potato 317 Bradshaw, J. 2010. Root and tuber crops. tubers). Guarino, L., Ramanatha Rao, V. Handbook of Plant Breeding, 295. Springer, and Goldberg, E. (Eds.). Benin. pp.1-8. London. https://cropgenebank.sgrp.cgiar.org/ Brazier, A. 2016. Underutilized crops images/file/procedures/collecting2011/ championed at local university [Online]. Chapter21-2011.pdf Accessed 2 February Harare, Zimbabwe: Bio Innovation 2017. Zimbabwe. http://naturallyzimbabwean. Dawson, I.K., Hedley, P.E., Guarino, L. and com/2016/01/15/underutilized-crops- Jaenicke, H. 2009. Does biotechnology championed-at-local-university/ Accessed have a role in the promotion of underutilised 20 February 2016. crops? Food Policy 34:319-328. Bryant, A.T. 1907. A description of native Delpeuch, F., Favier, J.C. and Charbonniere, foodstuffs and their preparation, Print for R. 1978. Characteristics of starches of Natal Government. The Times Print. and tropical food plants. Annals of Agricultural Publishing Company, RSA. Technology 27(4):809-826. Burkill, H. 1995. The useful plants of West Demissie, A. 1991. Potentially valuable crop Tropical Africa: Volume 3. Families JL. plants in a Vavilovian center of diversity: Kew: Royal Botanic Gardens, Kew xi, Ethiopia. International Conference on Crop 857p.-. ISBN. Genetic Resources of Africa. Nairobi, Busch, B. 2015. Plectranthus esculentus Kenya. 26-30 September 1988. [Online]. Pretoria, South Africa: SA National Dhliwayo, P.D. 2002. Underexploited tuber Biodiversity Institute. Available: http:// crops in Zimbabwe: A study on the pza.sanbi.org/plectranthus-esculentus production of Livingstone potato [Accessed 2016]. (Plectranthus esculentus). Plant Genetic Caroviæ-Stanko, K., Petek, M., Martina, G., Resources Newsletter pp. 77-80. Pintar, J., Bedekoviæ, D., Æustiæ, M. H. Dubois, T. 2009. Importance of tissue culture and Šatoviæ, Z. 2016. Medicinal plants of for orphan crops. Inside this Issue 6:50. the family lamiaceaeas functional foods: A Eke-Okoro, O., Olojede, A. and Nwadili, C. review. Czech Journal of Food Sciences 2008. Studies on the optimum minisett 34: 377-390. sizes for rapid multiplication of rizga Chivenge, P., Mabhaudhi, T., Modi, A.T. and (Plectranthus esculentus), hausa potato Mafongoya, P. 2015. The potential role of (Solenosterum rotundifolium), and neglected and underutilised crop species as turmeric (Curcuma longa) in Nigeria. future crops under water scarce conditions International Symposium on underutilized in Sub-Saharan Africa. The International plants for food security. Nutrition, Income Journal of Environmental Research and and Sustainable Development 806:169- Public Health 12:5685-5711. 172. Codd, L. 1985. Lamiaceae flora of Southern Eleazu, C., Amadi, C. and Oti, E. 2010. Total Africa 28 (4). Botanical Research Institute, antioxidant capacity, polyphenolic Pretoria 79-102. composition and cytotoxicity of three Collard, B., Jahufer, M., Brouwer, J. and varieties of Livingstone potato (Rizga). Pang, E. 2005. An introduction to markers, Nigeria Agricultural Journal 41:39-45. quantitative trait loci (QTL) mapping and Eleazu, C. and Eleazu, K. 2015. Nutrient marker-assisted selection for crop composition, antioxidant capacity and improvement: the basic concepts. natural products in Livingstone potato Euphytica, 142:169-196. (Plectranthus esculentus). Journal of Food Dansi, A. 2011. Collecting vegetatively Processing and Preservation 39:3050- propagated crops (especially roots and 3058. 318 G.T. KUJEKE et al. Eleazu, C., Eleazu, K., Chukwuma, S., Kemas, U., Nep, E. and Ochekpe, N. 2013. Okoronkwo, J. and Emelike, C. 2014a. Comparative evaluation of the binding/ Effect of Livingstone potato (Plectranthus disintegrating properties of Plectranthus esculenthus NE Br) on hyperglycemia, esculentus starch. World Journal of antioxidant activity and lipid metabolism of Pharmacy and Pharmaceutical Sciences 2: streptozotocin induced diabetic rats. 906-920. Toxicology Reports 1:674-681. Kramer, C.V. and Allen, S. 2015. Malnutrition Eleazu, C.O., Eleazu, K.C., Ironkwe, A. and in developing countries. Paediatrics and Iroaganachi, M.A. 2014b. Effect of Child Health 25:422-427. Livingstone potato (Plectranthus Kujeke, G.T., Masekesa, R.T., Icishahayo, , esculenthus NE Br) on diabetes and its D., Ngadze, E. and Mazarura, U. 2015. A complications in streptozotocin induced survey of the production practices of diabetes in rats. Diabetes & Metabolism Livingstone potato (Plectranthus Journal 38:366-374. esculentus), an indigenous and underutilized Emmambux, M.N. and Taylor, J. 2013. vegetable in Zimbabwe. Journal of Morphology, physical, chemical, and Agriculture and Ecology Research functional properties of starches from International 4(4):175-187. cereals, legumes, and tubers cultivated in Kyesmu, P.M. 1994. Plectranthus esculentus Africa: A review. Starch Stärke 65:715-729. N.E. BR. A minor tuber crop in dire need Ezeocha, C.V. and Ironkwe, A. G. 2017. Effect of rescue from extinction. Lamiales 3-5. of storage methods and period on the Lukhoba, C.W., Simmonds, M.S. and Paton, physiological and nutrient components of A.J. 2006. Plectranthus: A review of Livingstone potato (Plectranthus ethnobotanical uses. Journal of esculentus) in Abia State, Nigeria. Open Ethnopharmacology 103:1-24. Agriculture 2:213-219. Mabhaudhi, T., Chimonyo, V. and Modi, A. Fox, F.W. and Norwood Young, M.E. 1982. 2017. Status of underutilised crops in South Food from the veld; edible wild plants of Africa: opportunities for developing Southern Africa. Delta Books, Craighall, research capacity. Sustainability 9:1569. Johannesburg, South Africa. 245pp. Mabhaudhi, T., O’reilly, P., Walker, S. and Fusire, M. 2008. Seed production manual for Mwale, S. 2016. Opportunities for Indigenous Vegetables: A guide for small underutilised crops in Southern Africa’s scale farmers. Harare: Community Post–2015 Development Agenda. Technology Development Trust (CTDT). Sustainability 8:302. Govindaraj, M., Vetriventhan, M. and Mapfumo, T. 2018. The Livingstone potato. Srinivasan, M. 2015. Importance of genetic Ndeipi. Harare, Zimbabwe: Mike Garden. diversity assessment in crop plants and its Mayes, S., Massawe, F., Alderson, P., Roberts, recent advances: an overview of its J., Azam-Ali, S. and Hermann, M. 2011. analytical perspectives. Genetics Research The potential for underutilized crops to International . improve security of food production. Greenway, P.J. 1944. Origins of some east Journal of Experimental Botany 63:1075- African food plants: Part I. The East 1079. African Agricultural Journal 10:34-39. Mondini, L., Noorani, A. and Pagnotta, M.A. Haq, N. 2004. Women reintroducing neglected 2009. Assessing plant genetic diversity by crops. LEISA-LEUSDEN 20:28-29. molecular tools. Diversity 1:19-35. Hyde, M.A., Wursten, B., Ballings, P. and Mooi, L.Y., Ali, A., Norhanom, A., Salleh, Palgrave, C. 2012. Flora of Zimbabwe. K.M., Murakami, A. and Koshimizu, K. 1999. Anti-tumor promoting activity of Untapped potential of the Livingstone potato 319 some Malaysian traditional vegetables Okereke, C. 2012. Growth performance of (ulam). Natural Product Sciences 5: 33-38. finisher broilers on Livingstone-potato Morris, B. and Msonthi, J.D. 1996. Chewa (Plectranthus esculentus) Tubers Meal. medical botany: A study of herbalism in Pakistan Journal of Nutrition 11: 411-413. southern Malawi, LIT Verlag Münster. Özkan, M. 2008. Glandular and eglandular Muazu, J., Musa, H., Isah, A.B., Bhatia, P.G. hairs of Salvia recognita Fisch. & Mey. and Tom, G.M. 2011. Extraction and (Lamiaceae) in Turkey. Bangladesh characterization of kaffir potato starch: A Journal of Botany 37:93-95. potential source of pharmaceutical raw Padulosi, S. and Hoeschle-Zeledon, I. 2004. material. Journal of Natural Product and Underutilized plant species: what are they? Plant Resources 1(2):41-49. LEISA-LEUSDEN 20:5-6. Mutowo, M., Gowda, U., Mangwiro, J. C., Padulosi, S., Thompson, J. and Rudebjer, P. Lorgelly, P., Owen, A. and Renzaho, A. 2013. Fighting poverty, hunger and 2015. Prevalence of diabetes in Zimbabwe: malnutrition with neglected and A systematic review with meta-analysis. underutilized species: Needs, challenges and International Journal of Public Health 60: the way forward. Bioversity International. 1-11. Pakia, M., Cooke, J. and Van Staden, J. 2003. Muzenda, S., Machingaidze, A.B., Riches, C., The ethnobotany of the Midzichenda tribes Ellis-Jones, J. and Chivinge, O.A. of the coastal forest areas in Kenya: 2. 2002. Weed management options for Medicinal plant uses. South African Journal seasonal wetlands (VLEIS) in semi-arid of Botany 69:382-395. areas of masvingo province, Zimbabwe. Paton, A. 2013. Lamiaceae Flora Zambesiaca Proceedings of the Seventh Eastern and 8 (8). Includes a Picture 275-278. Southern Africa Regional Maize Pelto, G., Pelto, P. and Messer, E. 1989. Conference, Nairobi, Kenya. pp. 113-119. Research methods in nutritional Mwanja, Y., Goler, E. and Gugu, F. 2015. anthropology. Food and Nutrition Bulletin. Flowering and seed-setting studies in Supplement (UNU). Livingstone potato (Plectranthus esculentus Raja, R.R. 2012. Medicinally potential plants NE BR.) in Jos-Plateau, Nigeria. of Labiatae (Lamiaceae) family: An International Journal of Plant Breeding overview. Research Journal of Medicinal and Genetics 9:275-279. Plant 6:203-213. National Research Council, 2006. Lost crops Safwan, I. and Mohammed, U. 2016. Review of Africa: Volume II: Vegetables (Vol. 2). on the nutritional value, cultivation and National Academies Press. Washington utilization potential of some minor and D.C., USA. pp. 269-285. under-utilized indigenous root and tuber Ngugi, I. K., Gitau, R. and Nyoro, J. 2007. crops in Nigeria. International Journal of Access to high value markets by Advanced Research 4:1298-1303. smallholder farmers of African indigenous Schippers, R.R. 2000. African indigenous vegetables in Kenya. Regoverning Markets vegetables: An overview of the cultivated Innovative Practice Series, IIED, London. species. University of Greenwich, Natural Ochekpe, N. A., Kemas, U. C. and Nep, E. I. Resources Institute: London, UK. pp. 81- 2013. Chemical modifications and their 83. effects on binding/disintegrating properties Singh, N., Singh, J., Kaur, L., Sodhi, N. S. of Plectranthus esculentus starch in and Gill, B. S. 2003. Morphological, thermal chloroquine phosphate tablets. American and rheological properties of starches from Journal of PharmTech Research 3(3): 867- different botanical sources. Food Chemistry 877. 81:219-231. 320 G.T. KUJEKE et al. Smith, I.F. and Eyzaguirre, P. 2007. African Venkateshappa, S. and Sreenath, K. 2013. leafy vegetables: Their role in the World Potential medicinal plants of Lamiaceae. Health Organization’s global fruit and American International Journal of vegetables. African Journal of Food, Research in Formal, Applied and Natural Agriculture, Nutrition and Development Sciences 1:82-87. 7(3):1-17. Williams, J.T. and Haq, N. 2002. Global Thillakawardane, T. 2009. Market research on underutilized crops: An opportunities for value-added products of assessment of current activities and underutilized fruits and vegetables. Acta proposals for enhanced cooperation. Horticulturae 806(2):465-472. International Plant Genetic Resources Tindall, H.D. 1983. Vegetables in the tropics. Institute. International Centre for Macmillan Press Ltd London. pp. 241-242. Underutilised Crops. Southampton, UK. Tredgold, M.H. 1986. Food plants of 19pp. Zimbabwe: With old and new ways of Williams, J.T. 2002. Global research on preparation, Mambo Press. Gweru. 103pp. underutilized crops: An assessment of Ukpabi, U.J., Oti, E. and Ogbogu, N.J. 2011. current activities and proposals for Culinary and sensory characteristics of enhanced cooperation, Bioversity Hausa potato (Solenostemon rotundifolius) International. and Livingstone potato (Plectranthus Xaba, P. and Croeser, P. 2011. Wild esculentus) tubers in Nigeria. Journal of Potato. Veld & Flora 97(4):180-181. Stored Products and Postharvest Research 2:301-304.