Abstract

Africa is poised at the brink of developing a new wave of crops using biotechnology. This review describes advances in the development of new genetically modified (GM) crops designed to meet the needs of African farmers. Current GM crops being grown in Africa include Bt cotton by farmers in South Africa and Burkina Faso, and Bt maize in South Africa and Egypt. The farmers growing these crops have obtained increased yields, reduced production costs and losses, and higher income. While these traits were bred into African cultivars and adapted to African growing conditions, the technologies largely originated outside of the continent. Now, there are a number of advances in research and development of GM crops specifically of importance to the African people that are underway in African universities and research institutions. These include, stem borer resistant maize, drought tolerant maize, maize resistant to maize streak virus, bananas with resistance to bacterial wilt, nematodes and weevils, biofortified bananas, biofortified sorghum, virus resistant cassava, biofortified cassava, pod borer resistant cowpea, weevil resistant sweet potato, and nitrogen use efficient, water use efficient and salt tolerant rice. As these new technologies come to fruition, they hold promise for increasing productivity, income and health of African farmers.

Key words: biotechnology, genetically modified crops, insect resistance, drought tolerance, biofortification, nitrogen use efficiency  

Introduction

Agriculture is the major economic sector in Africa employing about 65% of the total labor force and contributing about 32% of the continent’s gross domestic product (Asenso-Okyere and Jemaneh, 2012). However, the productivity is low due to reliance on rainfall as opposed to irrigation, limited use of fertilizer on depleted soils, poor agronomic practices, crop losses from pests and diseases and low use of improved seed (Asenso-Okyere and Jemaneh, 2012). Agricultural biotechnology such as genetic engineering in combination with conventional breeding methods is seen as one of the opportunities that can boost agricultural growth (Ojuederie et al., 2011). So far, four African countries are growing genetically engineered crops: South Africa, Burkina Faso, Egypt and Sudan. According to the International Service for the Acquisition of Agric-biotech Applications (ISAAA) reports of 2008 and 2012 on the global status of commercialized biotech crops, the acreage for biotech crops has increased in South Africa and Burkina Faso from 1.8 and <0.1 million hectares respectively to 2.9 and 0.3 million hectares from 2008 to 2012 (James, 2008; ISAAA, 2012). On the other hand, adoption of genetically engineered crops in other African countries has been slow in part due to potential concerns with respect to environmental biosafety, human health and economics (Ojuederie et al., 2011). This has led in some cases to restrictive biosafety policies that impose strong regulatory barriers (Juma, 2011).

Regardless, farmers in Egypt and South Africa are growing Bt maize, farmers in South Africa and Burkina Faso have been cultivating Bt cotton since adoption in 1998 and 2008 respectively and in 2012, farmers in Sudan also started growing Bt cotton (ISAAA, 2011; ISAAA, 2012). Farmers in South Africa and Burkina Faso have benefited from increased income through higher yields (ISAAA, 2011). The average yield increased by 20% resulting in a net gain of $66 per hectare compared to conventional cotton in Burkina Faso. South Africa grows nearly 100% Bt and herbicide tolerant cotton (ISAAA, 2012). South Africa is also planting herbicide tolerant maize and soybean, which reduces weeding (Juma, 2011) and thus less time is spent in fields, increasing available time for children to study. Therefore, some African countries are seeing the benefits derived from GM crops and are focusing on specific areas of research to improve the livelihood of Africans (Ojuederie et al., 2011). Countries like Kenya, Nigeria and Uganda have conducted field trials (ISAAA, 2011); Ghana and Malawi have become open to biotech research (Fukunda-Parr and Orr, 2012) and are now conducting confined field trials. The situation in many African countries is subject to change as each works out relevant legislation and policies for biotechnology. Also, given the changing political climate in many African countries, ultimate use and acceptance of modern biotech will depend on government policies.

The research activities are mainly carried out by the public institutions such as National Agricultural Research Systems and International Agricultural Research Centers in partnership with private companies. These institutions mainly focus on food security and staple crops such as banana, cassava, maize, sorghum, sweet potato and cowpea with primary funding from private foundations such as Bill and Gates Foundation, Rockefeller Foundation along with support from national governments and International developed partners like USAID and UKDFID (FARA, http://www.fara-africa.org/biotech-management-africa/). There are also regional initiatives by International organizations to carry out research that can help boost crop productivity (Fukunda-Parr and Orr, 2012). This review describes the on-going efforts in African institutions and universities to develop GM major staple and food security crops of importance to African farmers. Examples of currently grown GM major staple and food security crops and those under research and development are summarized below and outlined in Table1.

GM crops currently grown in Africa

South Africa

South Africa has been growing GM crops since 1998. South Africa is the leading and the first African country to commercialize GM crops (Environmental Biosafety Cooperation Project, www.sanbi.org). The GM crops approved for commercial release include; Bacillus thuringiensis (Bt) cotton, Bt maize, herbicide tolerant maize, herbicide tolerant cotton and herbicide tolerant soybean.

Cotton is one of the most important sources of income in the cotton growing regions of South Africa. Pests are one of the major limiting factors to cotton production, with bollworms such as H. armigera, Diparopsis castenea, and Earias biplaga and E. insulana being the most damaging (Ismail et al., 2002). In 1997, Bt cotton expressing cry1Ac and cry2Ab for resistance to the cotton bollworm was approved for commercial release. In 1998, cotton farmers started growing Bt cotton (NUCOTN 37-B with BollgardTM) (Gouse et al., 2005). In 1998/1999, 12% of the cotton farmers in Makhathini region had adopted Bt cotton, 40% in 1999/2000 and 60% in 2000/01(Ismail et al., 2002). Increased adoption was attributed to increased yield thus improved income, and reduced pesticide use, which resulted in the potential reduction of pesticide poisoning and environmental pollution (Morse and Bennett, 2008). By 2010, nearly100% of the cotton (8, 300 hectares) grown in South Africa was GM cotton, of which 10% was Bt cotton, 10% herbicide tolerant cotton and 75% stacked (Bt and herbicide tolerant) (The Environmental Biosafety Cooperation Project, www.sanbi.org). In 2011, the total area planted to biotech cotton was 15,000 hectares, of which 95% was stacked (Bt and herbicide tolerant) and 5% herbicide tolerant (ISAAA, 2012).

Maize is a very important staple crop in South Africa. White maize is the staple food while yellow maize is grown mainly for animal consumption (Keetch et al., 2005). Stalk borers such as Busseola fusca and Chilo partellus are a major problem for maize production. In 1998, Bt yellow maize expressing cry1Ab developed by Monsanto Company and found to control Ostrinia nubilalis and South African stalk borers was approved for commercial release (Gouse et al., 2005). The gene was then backcrossed into white maize and commercialized in 2001. According to South African biosafety rules, an approved gene can be introduced into other varieties of the same crop without further regulatory approval (Gouse et al., 2005). In 2003, Syngenta’s Bt maize and herbicide tolerant maize, and Monsanto’s herbicide tolerant maize that enable farmers use herbicides to kill weeds without killing the maize crop were approved for commercial release. In 2007, Monsanto’s stacked (Bt and herbicide tolerant) maize was approved (Vander Walt, 2008). In 2010, South Africa grew 70% Bt maize, 14% herbicide tolerant maize and 16% stacked (Bt and herbicide tolerant) maize of the 1.87 million hectares, the total commercial maize hectares (The Environmental Biosafety Cooperation Project, www.sanbi.org). In 2011, South Africa grew 1.873 million hectares of biotech maize of which 45.2% was Bt maize, 14.4% herbicide tolerant maize and 40.4% stacked (Bt and herbicide tolerant) maize of the 2.6 million hectares, the total commercial maize hectares (ISAAA, 2012).

South Africa also grew 85% or 383,000 hectares herbicide tolerant soybean in 2010 and 2011 (ISAAA, 2012; The Environmental Biosafety Cooperation Project, www.sanbi.org). In 2011, South Africa planted 2.3 million hectares total biotech crop area (ISAAA, 2011). Biotech crops have increased yield and reduced production costs such as pesticides, thus providing better income for the farmers. Herbicide tolerant biotech crops also provide the farmers with flexibility in weed management (Qaim, 2010).

Burkina Faso

In 2008, Burkina Faso became the second country in Sub-Saharan Africa after South Africa to commercialize GM crops by producing Bt cotton (James, 2008). Cotton is the major source of income in Burkina Faso (Karembu et al., 2009). Helicoverpa armigera is the major insect pest to cotton production, causing heavy reliance on pesticides which are expensive and unfriendly to human health and the environment (Vitale et al., 2011). In 2001, Burkina Faso’s National cotton company, Société Burkinabé des Fibres Textiles (SOFITEX) initiated a partnership with Monsanto for commercial introduction of Bt cotton (Vitale et al., 2011).

In 2003, the National Agricultural Research Institute and Monsanto initiated Bt cotton (Gossypium hirsutum) trials with financial support from the United States Agency for International Development (USAID) (International Center for Trade and Sustainable Development, 2006). The field trials of transgenic cotton expressing cry1Ac and cry2Ab genes conducted from 2003 to 2005, showed enhanced resistance to H. armigera with a yield advantage of 15% over the conventional cotton and reduced pesticide use by two thirds (Vitale et al., 2008). The Bt gene was then incorporated into selected cotton varieties that are well adapted to the local environment. After years of field testing, monitoring and regulatory approval, in 2008 Burkina Faso commercialized Bt cotton. 8,500 hectares of Bt cotton were grown for initial commercialization (Karembu et al., 2009). In 2009, the acreage of Bt cotton increased to 115,000 hectares (Adenle, 2011) and 0.3 million hectares in 2010 and 2011 (ISAAA, 2010; ISAAA, 2011).

Egypt

In 2008, Egypt became the first country in the Arab world and Northern Africa to commercialize GM crops, Bt maize (Karembu et al., 2009). Maize is the second most important cereal in Egypt after wheat. Stem borers are the major pests affecting maize production. Chemical use is limited by the high cost and also timing is difficult (Massoud, 2010). In 2002, Egypt started testing Bt maize (Ajeeb-YG), a cross between MON810 and Ajeeb (a local Egyptian maize variety) developed by Monsanto Company (Ezezika and Daar, 2012).

Ajeeb-YG was tested and monitored in field trials from 2002 to 2007 and exhibited improved resistance to the three economically important maize borers, pink corn borer (Sesamia cretica), European corn borer (Ostrinia nubilalis) and purple-lined corn borer (Chilo agamemnon) (Karembu et al., 2009; Massoud, 2010). Ajeeb-YG also exhibited 30% higher yield than the conventional yellow hybrid maize. Other benefits from the Bt maize included reduced pesticide use, improved grain quality and reduced levels of mycotoxins due reduced damage from maize borers that increase susceptibility of maize to fungal attack, and greater flexibility in planting time (Ezezika and Daar, 2012). In 2008, Egypt planted 700 hectares of Bt maize (Hillocks, 2009) and 2,000 hectares in 2010 (Ezezika and Daar, 2012). Egypt planted nearly 100,000 hectares of Bt maize in 2011 (ISAAA, 2011).

Sudan

In 2012, Sudan became the fourth African country to commercially grow Bt cotton (ISAAA, 2012). Cotton is one of Sudan’s major cash crops as well as the principal export crop (Encyclopedia of Nations, 2008). The African bollworm (Helicoverpa armigera) is one of the major pests of cotton in Sudan, causing yield losses of up to 60% (Ahmed et al., 2002). Its management relies heavily on use of synthetic pesticides, which are costly and pose risk to human health and the environment (Wondafrash et al., 2012). Use of Bt technology is an alternative that is selective and easily degradable. Bt cotton has successfully controlled cotton bollworms in some African countries such as South Africa and Burkina Faso (ISAAA, 2011). In 2012, about 10,000 farmers from the rain fed and irrigated areas in Sudan planted 20,000 ha of Bt cotton (ISAAA, 2012).

GM major staple and food security crops under research and development

Maize (Zea mays L.)

Maize is one of the most important sources of energy for the poor in Africa (Smale et al., 2011). It comprises the diets of many small holder farmers who grow it primarily in mixed cropping systems. Small to medium scale farmers, who cultivate less than 10 hectares, grow 95% of the maize produced in Africa (Thomson, 2008). Maize production is limited by various environmental factors such as insect pests, diseases and abiotic stresses (FARA, 2009), some of which are current targets for improvement via biotechnology. Examples of ongoing crop improvement projects are summarized below.

Insect resistant maize

Stem borers are one of the most important pests that cause significant yield losses in African agro-ecological zones where the crop is grown (Obonyo et al., 2008). Losses range from 15 to 40%, and total crop failure can occur under conditions that favor insect infestation (Thomson, 2008). Pesticides are very expensive and hazardous to the environment and human health (Obonyo et al., 2008).

The International Maize and Wheat Improvement Center (CIMMYT) initiated development of maize resistant to stem borers using molecular and transgenic techniques (Mugo et al., 2002). This initiative known as Insect Resistant Maize for Africa (IRMA) is a joint venture between CIMMYT and Kenya Agricultural Research Institute (KARI) with financial support from Syngenta Foundation for Sustainable Development. The resistance is derived from genes that encode delta-endotoxins from Bacillus thuringiensis (Bt cry proteins) (Mugo et al., 2002). The CIMMYT maize hybrid, CML216 X CML72 was transformed with Bt cry genes (cry1Ab, cry1Ac, cry1B, cry1E, cry1Ca and cry 2Aa) under the control of ubiquitin and rice actin promoters (Mugo et al., 2005). Initially constructs carried the selectable (Basta herbicide resistance) marker. Subsequently, transgenic maize without markers was developed due to biosafety concerns (KARI and CIMMYT, 2007). Backcrossing was done to the target CML216 to develop several inbred lines carrying different Bt events. The transgenic lines were tested in CIMMYT’s biosafety greenhouses in Mexico and showed high levels of resistance to pyralid stem borers such as Chilos partellus (Mugo et al., 2005).

Transgenic Bt leaves and seeds together with a non-transgenic near isogenic line from Mexico were then taken to Kenya in 2002 and 2004 respectively for testing with the Kenyan stem borers (KARI and CIMMYT, 2007). Laboratory, greenhouse and field studies carried out showed that the Bt maize controlled only four (Chilo partellus, Chilo orichalcociliellus, Eldana saccharina and Sesamia calamistis) of the five major stem borers in Kenya and non of the Bt genes was effective against all the stem borers (Mugo et al., 2005). Confined field trial evaluation of Bt maize events carrying cry1Ab and cry1Ba genes also showed control of Chilo partellus, Eldana saccharina and Sesamia calamistis and no substantial control of Busseola fusca (Mugo et al., 2011). Therefore, there is need for additional Bt genes or stacking of the genes to enhance resistance against the stem borers especially the economically important species (Busseola fusca) (De Groote et al., 2011; Mugo et al., 2011). Successful transformation events will be backcrossed into African maize inbred lines or open pollinated varieties (OPVs) (CIMMYT, http://apps.cimmyt.org/english/wpp/gen_res/irma.htm).The project is implemented in Kenya from where the results will be made available to other interested African countries (CIMMYT, www.cimmyt.org/en/projects /insect-resistant-maize-for-africa).

Drought tolerant maize

Drought is a serious problem to agricultural systems like those in Africa that rely mainly on rainfall (Boubacar, 2012). Maize is seriously affected by drought leading to crop failure, hence food insecurity, a situation likely to worsen with climate change (Boko et al., 2007). As a result, the Kenya-based African Agricultural Technology Foundation (AATF) in partnership with the National Agricultural Research Systems (NARS) of Kenya, Uganda, Tanzania, Mozambique and South Africa, CIMMYT and Monsanto with funding from the Bill and Melinda Gates Foundation and Howard G. Buffett Foundation are developing water-efficient maize for Africa (WEMA) (AATF, www.aatf-africa.org/projects/aatf_projects//wema). The Bacillus cold-stress protein gene (cspB) was donated royalty-free by Monsanto and is being transferred into African maize varieties (Thomson et al., 2010).

Studies carried out by Castiglioni et al. (2008) showed that cspB conferred improved tolerance to cold, heat and water deficits in transgenic plants. Transgenic Arabidopsis exhibited improved cold tolerance, while transgenic rice showed improved tolerance to cold, heat and water deficit. When the cspB gene was introduced into maize, the gene conferred improved yield under controlled drought and water deficit in the western dryland conditions in U.S (Castiglioni et al., 2008). These studies provide a possibility of how genetic engineering can be adapted to develop maize varieties that can withstand the drought conditions in Africa, thus improving the livelihood of the poor communities that depend on maize. Monsanto’s MON 87460 is being subjected to confined field trials in South Africa, Kenya and Uganda through their National Agricultural Research Systems (NARS). Similar confined field trials are planned for other member countries like Tanzania and Mozambique through their NARS (Thomson et al., 2010).

In addition, scientists at the University of Cape Town are also developing maize tolerant to drought. The genes (XvSap1, XvAld1, XvPrx2 and XvG6) used were isolated from the desert plant, Xerophyta viscosa (Thomson et al., 2010). These genes contribute to the dehydration process in this plant, enabling it to withstand up to 95% water loss for long periods (Grange, 2009). The plant can rehydrate completely upon watering within a period of 2 to 3 days depending on the species (Thomson et al., 2010). According to Thomson et al. (2010), studies carried out showed that constitutive expression of anti-stress genes in transgenic plants inhibited their growth in absence of the stress. Consequently, maize has been transformed with constructs with genes cloned downstream the stress-inducible promoter XvPsap1 involved in early responses to drought (Thomson et al., 2010). Preliminary results from the greenhouse studies showed that the transgenic plants will tolerate moderate stress such as late rains that often reduce agricultural output (Grange, 2009).

Maize resistant to maize streak virus

Maize streak virus (MSV), which belongs to genus Mastrevirus in the Geminiviridae family, is endemic to Africa and the major viral pathogenic constraint to maize production, making resistance a key target for crop improvement (Shepherd et al., 2010). The virus is transmitted by leafhoppers and the farmers cannot afford pesticides to destroy the vector (Shepherd et al., 2010). Conventional means to develop resistant varieties have been unsuccessful due to the limited genetic variability for virus resistance in maize, and thus the need for transgenic means (Shepherd, 2007).

Scientists at the University of Cape Town and Pannar Seed have developed maize resistant to MSV. Maize was transformed with the mutated MSV replication-associated protein gene (rep1-219Rb-) cloned downstream of the constitutive maize ubiquitin promoter (Shepherd et al., 2007; Thomson et al., 2010). Hi-II (non-commercial variety) was used in transformation because it was easily transformed. Hi-II transgenic maize plants were crossed with an elite inbred line (MW3-highly susceptible commercial white maize genotype) at Pannar and the resultant plants showed resistance to MSV when challenged (Shepherd et al., 2007). Subsequently, transgenic maize plants without selectable markers and antibiotic resistance genes were generated in a minimal transgene cassette background (Thomson et al., 2010). T1 and T2 generation transgenic plants showed delayed symptom development when challenged with the virus, compared with the susceptible Golden Bantam and a conventionally bred MSV tolerant hybrid (Pan77). The developed transgenic maize plants await confined field trial planned for the 2012/2013 season (Thomson et al., 2010).

Bananas (Musa spp.)

Bananas are a very important staple and source of income for a number of African countries (Viljoen, 2010). East Africa produces most of the bananas in Africa, with Uganda being the second largest producer in the world after India (Tripathi, 2011). Productivity is severely constrained by a range of pests such as nematodes and banana weevils, and diseases like the banana bacterial wilt, Fusarium spp and black Sigatoka (Shotkoski et al., 2010; Viljoen, 2010).

Bananas with resistance to bacterial wilt

Banana bacterial wilt caused by Xanthomonas campestris pv. musacearum is the most devastating disease to banana production in East and central Africa (Ssekiwoko et al., 2010). The disease is spread through planting infected suckers, use of contaminated agricultural implements and insects that feed on male buds. The disease can lead to total loss of the banana plantation, hence food shortages (Tushemereirwe et al., 2003). Cultural practices such as cutting and burning or burying infected plants, using clean farm implements and removal of male buds using forked sticks have been used but are highly labour intensive, hence the need for resistant varieties. All varieties are susceptible and there are no sources of resistance among the banana germplasm, thus the need for genetic engineering (Tripathi et al., 2004).

The International Institute for Tropical Agriculture (IITA) in partnership with National Agricultural Research Organization (NARO)-Uganda and Kenya Agricultural Research Institute (KARI) with financial support from the Gatsby Charitable Foundation and United States Agency for International Development (USAID) have developed transgenic bananas using Pflp and Hrap genes from sweet pepper (FARA, http://www.fara-africa.org/biotech-management-africa/). The genes were provided royalty free by Taiwan’s Academia Sinica through AATF. The Pflp and Hrap genes have been shown to confer resistance against bacterial pathogens through enhanced harpinpss-mediated hypersensitive response (Ajay-Kumar et al., 2005; Badri Venkata et al., 2003). Oncidium orchids and tobacco plants expressing Pflp gene exhibited enhanced resistance to Erwinia carotovora, and E. carotovora subsp. Carotovora and Pseudomonas syringae pv. tabaci respectively (Liau et al., 2003; Hsiang-En et al., 2004). Arabidopsis plants transformed with Hrap gene showed enhanced resistance to E. carotovora subsp. Carotovora, a soft rot pathogen.

These studies showed that Pflp and Hrap genes could potentially provide resistance against other bacterial pathogens like Xanthomonas campestris pv. musacearum, a pathogen that causes wilt in bananas (Tripathi, 2011). The transgenic banana plants exhibited resistance in screen house experiments. They were planted in a confined field trial in Uganda in October, 2010 (Tripathi, 2011). The transgenic banana plants showed improved resistance under field conditions and plans are underway for the second confined field trial (Tripathi et al., 2013). The Pflp and Hrap genes were stacked to enhance durability of resistance against banana bacterial wilt. The transgenic lines developed were evaluated under screen house conditions (Tripathi, 2011) and await field testing (Tripathi et al., 2013).

Bananas with resistance to nematodes and weevils

Nematodes and weevils are serious pests in banana production. Nematodes damage roots while weevils damage the corm, both impairing water and nutrient uptake and thus reduced bunch weight (Gold et al., 2001; Speijer and Kajumba, 2000). Serious nematode and weevil damage leads to plant toppling and snapping respectively, hence crop loss. Cultural practices such as pairing and hot water treatment have been used by farmers but are highly labour intensive (Shotkoski et al., 2010; Viljoen, 2010). Farmers on the other hand cannot afford expensive chemicals, thus the need for resistant varieties. Conventional breeding has challenges as most of the cultivated bananas are sterile, highly polyploid and also have a long generation time, and thus the need for genetic engineering (Tipathi, 2003).

Scientists at NARO-National Agricultural Research Laboratories (NARO-NARL, Uganda) have transformed bananas with Bt cry genes (cry5B and cry6A) from the University of California (San Diego) and cystatin genes from the University of Pretoria and University of Leeds to provide bananas with resistance to nematodes and weevils. This project is funded by the government of Uganda, Bioversity International, Rockefeller and USAID (FARA, http://www.fara-africa.org/biotech-management-africa/).

Studies carried out showed that Bt crystal proteins (cry5B, cry6A, cry14A and cry21A) were nematicidal (Wei et al., 2003). These crystal proteins are active against multiple nematode species and their potential to damage the nematode intestine is similar to the mechanism of controlling Lepidopteran insect pests (Wei et al., 2003). Transgenic tomatoes expressing cry6A and cry5B showed improved resistance to an endo-parasitic root-knot nematode, Meloidogyne incognita through reduced egg production, and reduced gall formation, egg numbers and egg masses produced respectively (Li et al., 2007; Li et al., 2008). These studies show that crystal proteins from B. thuringiensis have the potential to control plant parasitic nematodes and thus could provide a solution to controlling parasitic nematodes in transgenic bananas.

On the other hand, cystatins prevent the action of cysteine proteinases that are predominant in parasitic nematodes preventing digestion. This suppresses nematode growth, ability to lay eggs and build up of populations that damage crops (Atkinson, 1996). Cysteine proteinases are not involved in mammalian digestion (Atkinson et al., 1995) and cystatins are part of the human diet, for example cereal seeds and eggs, they therefore do not affect human health and the environment (McPherson et al., 1997). Studies carried out show that the engineered version of oryzacystatin (Oc-I, Δ86) conferred resistance in transgenic Arabidopsis thaliana to both cyst and root nematodes (Urwin et al., 1997) and 70% resistance levels to transgenic Cavendish banana (Atkinson et al., 2004). Other studies carried out by Kiggundu et al. (2010) showed that papaya cystatin infiltrated into the stem disk reduced development of the banana weevil larvae by 68%. These studies showed that cystatins could facilitate protecting bananas against pests including nematodes and weevils.

The transgenic banana plants developed at NARO-NARL (Uganda), with nematode resistance were challenged with parasitic nematodes in the screen-house and promising plants were planted in a confined field trial in 2012 (SourceWatch, 2012). There is another partnership between NARO-NARL (Uganda) and Rahan Meristem (Israel) with funding from Rockefeller foundation, in which RNAi technology has been used to develop transgenic bananas resistant to nematodes, targeting the nematode collagen synthase (FARA, http://www.fara-africa.org/biotech-management-africa/).

Bananas biofortified with vitamin A and iron

Micronutrient deficiency is a major problem especially in the developing world including Africa. It is associated with malnutrition and ill health. Vitamin A and iron deficiencies are especially a concern among children and women (Mason et al., 2001). Use of Vitamin A and iron supplements is of great value but expensive for African governments to sustain and if left to the poor people, are not affordable. Fortification of foods especially the staple crops is of utmost importance as most people can easily access these foods (Mason et al., 2001).

The scientists at NARO-NARL (Uganda) in partnership with Queensland University of Technology (Australia) with funding from the Bill and Melinda Gates foundation have developed biofortified bananas. The gene constructs for Ferric chelate reductase II (FROS2) for iron content and Phytoene synthase II (APsy2) for production of vitamin A precursor, beta carotene were designed at Queensland University of Technology (Australia) (FARA, http://www.fara-africa.org/biotech-management-africa/). The confined field trial under evaluation was planted in 2010 (Wamboga-Mugirya, 2011). The biofortified transgenic bananas have showed improved iron and pro-vitamin A content (Arinaitwe, 2013).

Sorghum (Sorghum bicolor)

Sorghum which is indigenous to Ethiopia and Sudan, is a drought and heat tolerant staple in the semi-arid areas of Africa (Ashok Kumar et al., 2010). Sorghum is one of the major sources of energy in the sorghum growing regions in Africa (Mastandrea, 2009). However, it has a low iron and zinc content, low pro-vitamin A and poor protein digestibility. This leads to micronutrient deficiency especially among children and women from poor communities that rely on sorghum (Ng’uni et al., 2011). Vitamin A and mineral supplements are of great importance but poor people cannot afford them. Breeding crop varieties with improved nutrient content is very important because most people can access staple foods (Ng’uni et al., 2011).

Therefore to give sorghum additional nutritional value, biofortified sorghum with high-lysine storage protein, increased levels of pro-vitamin A, iron, and zinc has been developed using RNAi technology under the African Biofortified Sorghum (ABS) Project (ABS, www.biosorghum.org). Lysine and net protein digestibility have been improved by suppression of kafirin species (Taylor and Taylor, 2011), which are hydrophobic protein bodies resistant to digestion (Jhoe de Mesa-Stonestreet et al., 2010). Suppression of a gene involved in phytate biosynthesis also increased availability of iron and zinc (Kruger et al., 2012). Studies carried out by Waters and Pedersen (2009) showed that availability of several minerals in sorghum is highly correlated, thus improving one could increase others. The initial phase (2005-2010) of the project was funded by the Bill and Melinda Gates Foundation and coordinated by Africa Harvest, and the second phase (2011-2015) is funded by the Howard Buffet Foundation and coordinated by Pioneer Hi-Bred, DuPont Company (Wambugu et al., 2012; Komen and Wafula, 2013).

The ABS project is run by an international consortium under the leadership of Africa Harvest. Pioneer Hi-Bred Inc. donated the technology, Council for Scientific and Industrial Research (CSIR) from South Africa tailored technology use in Africa and over the years, several institutions have participated. University of California (Berkeley) studied digestibility and processing methods and left the consortium in 2008 (Mastandrea, 2009). University of Pretoria (South Africa) assisted in food preparation and milling qualities of ABS. Biofortified sorghum has been field tested in U.S. Pioneer has successfully backcrossed the traits into four major African sorghum varieties, Macia, malisor84-7, Tegemeo and Sima (Mastandrea, 2009).

The International Crops Research Institute for Semi-Arid Tropics (ICRISAT), Africa Harvest, and National Agricultural Research Systems (NARS), Kenya Agricultural Research Institute, Environmental and Agricultural Research Institute (Burkina Faso), Agricultural Research Council (South Africa) and Institute of Agricultural Research (Nigeria) are involved in product development. On the other hand, regional organizations such as AATF, West and Central African Council for Agricultural Research and Development (CORAF/ WECARD) in West Africa and Africa Harvest assist in policy guidance (ABS, www.biosorghum.org). Confined field trials have been conducted in Nigeria and Kenya and more confined field trials are planned for South Africa, Burkina Faso and Egypt (Wambugu et al., 2012).

Cassava (Manihot esculenta)

Cassava is a very important drought and heat tolerant food staple in Sub-Saharan Africa. Africa produces half of the world’s total production, with Nigeria being the leading producer (Hillocks, 2002). Cassava production is constrained by different abiotic and biotic stresses, which include pests such as cassava green mite and cassava mealy bug, and diseases like cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) (Bull et al., 2011). CMD is caused by a begomovirus, family Geminiviridae (Bull et al., 2011) while CBSD is caused by Ipomovirus virus, family Potyviridae (Patil et al., 2011). Both viruses are transmitted by the white fly and spread through planting infected materials (Bull et al., 2011; Ntawuruhanga and Legg, 2007). CMD causes leaf distortion reducing photosynthesis, hence stunted growth and reduced crop yield (Bull et al., 2011). CBSD causes brown streaks that eventually destroy the tuberous roots rendering them useless (Ntawuruhanga and Legg, 2007). Breeding for resistance using conventional means is limited by the crop’s high heterozygosity and long life cycle, hence the need for genetic means (Vanderschuren, 2012).

Virus resistant Cassava

Virus resistant cassava is being developed under the Virus Resistant Cassava for Africa (VIRCA) project, a collaboration involving Donald Danforth Plant Science Center (U.S), the Kenya Agricultural Research Institute (KARI) and National Crops Resources Research Institute (NaCRRI-Uganda) with funding from Monsanto Fund, USAID, Bill and Melinda Gates Foundation and Howard G. Buffett Foundation. The objective of the partnership is to improve farmer preferred cassava for resistance to CMD and CBSD using pathogen-derived RNAi technology, obtain regulatory approval to carry out field trials in Kenya and Uganda, and make the resistant varieties available to small holder farmers (Taylor et al., 2012). In the first phase (2005-2010) and second phase of the project, cassava was transformed with small interfering RNA (siRNA) sequences specific to the cassava viruses causing CMD and CBSD. This was done at the Danforth Center and transgenic lines that showed improved resistance under greenhouse conditions were shipped to Uganda and Kenya and field tested in 2009 and 2011 respectively (Patil et al., 2011; Taylor et al., 2012). The transgenic lines field tested exhibited moderate CMD severity (Odipio et al., 2012).

There is ongoing work to incorporate this resistance into the farmer-preferred varieties with natural resistance to CMD in the Lake Victoria region (The Donald Danforth Plant Science Center, www.danforthcenter.org/science/programs/international_ programs/virca/).

Biofortified cassava

Cassava tubers are very rich in carbohydrates but low in proteins, vitamins and other micronutrients, increasing the incidence of malnutrition among communities in Africa that depend on cassava (Levyva-Guerrero et al., 2012). Some cassava varieties contain high levels of cyanogenic glucosides that are harmful to humans (Biosciences for Farming, 2012). The Danforth Center in partnership with scientists from other international institutions are developing cassava with improved protein, zinc, iron and vitamin A levels, reduced levels of cyanogenic glucosides and improved storage qualities with funding from the Bill and Melinda Gates Foundation under the BioCassava Plus Project (The Donald Danforth Plant Science Center, www.danforthcenter.org/ science/programs/international_ programs/bcp/). The genes used include, Erwinia crtβ phytoene synthase and the Arabidopsis 1-deoxyxylulose-5-phosphate synthase (DXS) for β-carotene, the precursor for provitamin A, FEA1gene from Chlamydomonas reinhardtii for iron content, Arabidopsis ZAT and ZIP transporters for zinc content, hydroxynitrile lyase (HNL) for reduced cyanogenic glucosides and improved protein, alternative oxidase (AOX) for improved storage qualities, and zeolin, a storage fusion protein for improved protein content (Sayre et al., 2011). All the transgenes were driven by a class II patatin promoter in storage roots. The project focuses primarily on Kenya and Nigeria where cassava is the major staple food. The Kenya Agricultural Research Institute and National Root Crop Research Institute (Nigeria) ensure that farmer-preferred varieties are improved (The Donald Danforth Plant Science Center, www.danforthcenter.org/science/programs/international_ programs/bcp/).

Greenhouse and field experiments conducted in Puerto Rico (U.S.A) showed that increased zinc in storage roots resulted in reduced zinc levels in leaves, making the transgenic plants appear zinc deficient and stunted, thus the need to refine the approach (Sayre et al., 2011). Expression of HNL increased total protein, reduced linamarin (a cyanogenic glucoside that produces toxic hydrogen cyanide) in roots without affecting leaf levels that provide protection against generalized herbivores (Narayanan et al., 2011). Zeolin expressing cassava plants also had increased protein content and reduced linamarin content (Abhary et al., 2011). Co-expression of phytoene synthase and DXS showed more elevated levels of carotenoids as compared to expression of phytoene synthase alone. The transgenic lines with increased β-carotene also had extended shelf life (4 weeks). β-Carotene is an antioxidant that quenches reactive oxygen species. Expression of AOX also reduced reactive oxygen species, increasing shelf life. Vitamin E was unaffected by enhanced carotenoid accumulation, even though the pathways have a common intermediate (Sayre et al., 2011). Expression of FEA1 increased iron levels in the roots without affecting the iron levels in the leaves, and zinc levels in the roots and leaves (Ihemere et al., 2012)

In addition, this international consortium is developing cassava varieties with improved resistance to CMD and CBSD based on siRNA technology. IITA in partnership with Catholic Relief Services, NARS in East and Central Africa, Natural Resources Institute, and Food and Environmental Research Agency (UK) developed CMD resistant varieties using conventional breeding. The partnership was under the Great Lakes Cassava Initiative (GLCI) with funding from the Bill and Melinda Gates Foundation. However, all varieties are susceptible to CBSD and thus the need for transgenic approaches (Biosciences for Farming, 2012). Scientists at ETH Zurich (Switzerland) have developed transgenic cassava expressing hairpin RNAs targeting CMD viral sequences (Vanderschuren et al., 2009). ETH Zurich also developed transgenic cassava, expressing small RNAs targeting the two viral strains that cause CBSD. This technology has been introduced into the famer-preferred cassava varieties with natural resistance to CMD, using a modified transformation method (Zainuddin et al., 2012). The transgenic farmer-preferred varieties showed improved resistance to both the viral strains that cause CBSD and also to East African cassava mosaic virus (Vanderschuren et al., 2012). Another team at Danforth center has also developed transgenic cassava constitutively expressing hairpin siRNAs targeting near full-length coat protein (FL-CP) sequence targeting cassava brown streak virus (CBSV) (Yadav et al., 2011). The transgenic cassava plants showed improved resistance to CBSD.

The confined field trials for biofortified cassava with improved nutrition conducted in Puerto Rico (U.S) were promising and provided the basis for approval in Kenya and Nigeria. Confined field trials for pro-vitamin A and iron enriched cassava were approved in Nigeria in 2009 and the Kenya protein and iron biofortified cassava confined field trial was approved in 2010. The Nigerian enriched cultivar is CMD resistant while that of Kenya is susceptible, and therefore can be improved by crossing the two cultivars (The Donald Danforth Plant Science Center, www.danforthcenter.org/science/programs/international_ programs/bcp/).

The transformation technologies have been passed on to African laboratories, Biosciences Eastern and Central Africa (BecA, Nairobi-Kenya), University of Witwatersrand (South Africa), IITA (Ibadan-Nigeria) and Mikocheni Agricultural Research Institute (MARI, Tanzania) (Vanderschuren, 2012). The partnership between the University of Witwatersrand and ETH Zurich has developed a transgenic industry-preferred cassava variety (Chetty et al., 2012). MARI and Danforth center are developing cassava expressing siRNA sequences specific to cassava mosaic virus and cassava brown streak virus isolates in Tanzania (Biosciences for Farming, 2012). IITA is also characterizing natural enemies to whiteflies for biological control, so as to reduce virus spread and physical damage that increases susceptibility to other pests and diseases. Transgenic cassava lines developed at ETH Zurich, with improved resistance to CBSD have been selected in partnership with IITA for field testing upon regulatory approval in Tanzania (The Cassava Research Team, ETH Zurich, 2011).

Furthermore, the Southern Africa Biotechnology Program (SABP) is also developing virus resistant cassava varieties and industry-preferred cassava varieties with high quality starch using an optimized protocol from ETH Zurich (Chetty et al., 2012) for Southern Africa. It is a partnership with Michigan State University’s Institute of International Agriculture (U.S), University of Witwatersrand, Agricultural Research Council and the Industrial Development Corporation (South Africa), Wageningen University (Netherlands), CIAT-Agrobiodivesity and Biotechnology Project, the Latin America Consortium to Support Cassava Research and Development (CLAYUCA), the Danforth Center-International Institute for Tropical Agricultural Biotechnology, IITA- Southern Africa Root Crops Research Network (SARRNET), Chancellor College (Malawi) and the National Institute of Agricultural Research (Mozambique) (The Southern Africa Biotechnology Program, 2011). The program is working with the Danforth Center to survey and characterize CMD distribution in Malawi, Mozambique and South Africa, and thereafter field test CMD resistant transgenic varieties developed at the Danforth Center upon regulatory approval. The program is also working closely with the USAID funded Program for Biosafety Systems to assist in biosafety policy guidance in the region (The Southern Africa Biotechnology Program, 2011).

Cowpea (Vigna unguiculata)

Cowpea is a very important drought tolerant food legume and source of income in Sub-Saharan Africa (Langyintuo et al., 2004). It is a good source of proteins, vitamins and mineral nutrients. Cowpea is also a good ground cover that prevents erosion and improves soil fertility through nitrogen fixation in mixed cropping systems (Timko and Singh, 2008). However, cowpea production is constrained mainly by insect pests such as aphids, thrips, bruchids, pod-sucking bugs and the pod borer (Maruca vitrata) (Dugje et al., 2009). The pod borer is the most devastating insect pest, causing yield losses of 0.5 to 2.5 tons per hectare. The larvae feed on tender plant parts, stem, peduncles, flower buds and pods (Dugje et al., 2009). Conventional breeding is limited by the incompatibility of cowpea with its wild relatives that contain natural resistance, and thus the need for genetic engineering (Adesoye et al., 2008).

The African Agriculture Technology Foundation (AATF) in partnership with the Network for the Genetic Improvement of Cowpea for Africa (NGICA, U.S), Commonwealth Scientific and Industrial Organization (CSIRO, Australia), IITA, Monsanto Company, Kirkhouse Trust, the NARS of Nigeria, Ghana and Burkina Faso and PBS (U.S) are developing farmer-preferred cowpea varieties with resistance to the pod borer using conventional and genetic modification. The project is funded by USAID and the Rockefeller Foundation (AATF, www.aatf-africa.org/ projects/aatf_projects/cowpea_improvement). The cowpea varieties that have been modified by CSIRO were identified by the NARS and the cry1Ab used, was provided royalty free to AATF by Monsanto Company.

The transgenic cowpea lines developed showed improved resistance to the pod borer in the confined field trials conducted in Puerto Rico (U.S) in 2008 and 2009. Confined field trials conducted in Nigeria and Burkina Faso also showed promising results, and confined field trials are planned for Ghana upon regulatory approval (CSIRO Plant Industry, 2010). The fourth and second confined field trials are underway in Nigeria and Burkina Faso respectively (AATF, 2012).

Sweet potato (Ipomoea batatas)

Sweet potato is a very important food crop, which is highly adaptable and produces large amounts of food per unit area in Sub-Saharan Africa (Mwanga et al., 2011). It is a very good source of carbohydrates, vitamins A, B and C, iron, potassium, zinc, protein and fiber (Low et al., 2009). Sweet potato production is constrained mainly by diseases such as sweet potato virus disease and Alternaria blight, and pests like the weevils (Cylas spp.) (Mwanga et al., 2011). Cylas puncticollis and C. brunnues are the major species in Africa (Smit and VanHuis, 1999). Weevils damage tubers causing 60 to 100% yield loss. Damage is largely caused by larvae that feed inside the tubers. Conventional breeding is limited by high heterozygosity, polyploidy, low seed set and incompatibilities (Mwanga et al., 2011), hence the need for other options such as genetic engineering.

There is ongoing work to develop transgenic sweet potatoes expressing Bt cry proteins for the control of the most important weevil species in East Africa. The project initiated by the International Potato Center (CIP) under the Sweet-potato Action for Security and Health in Africa (SASHA) programme, with funding from the Bill and Melinda Gates Foundation, Rockefeller Foundation and USAID is targeting sweet potato production in Uganda and Kenya (SASHA, 2012). The partners in this project include; NaCRRI-Uganda, NARO-NARL (Uganda), BecA, Kenyatta University (Kenya), University of Puerto Rico-Mayaguez, Auburn University, Donald Danforth Plant Science Center (U.S.A) and University of Ghent (Belgium).

Seven Bt toxins (cry ET70, cryET33/cryET34, cry3Aa3, cry3Ba2, cry3Bb3, cry3Ca1 and cry7Aa1) were tested for their efficacy against C. puncticollis and C. brunnues using an artificial weevil diet (Ekobu et al., 2010). All of them were toxic, with cry7Aa1, cryET33/cryET34 and cry3Ca1 having highest toxicity. Four of them were selected based on toxicity and low sequence identity for the potential cross-resistance. Sweet potato cv. Jewel was transformed at the International Potato Center (CIP), Peru with the cry genes (Trovar et al., 2009) using a transformation method developed by Luo et al. (2006). Gene constructs were developed using sporamin and β-amylase promoters to express high Bt protein levels in the tubers, where highest weevil damage occurs (Trovar et al., 2009). The transgenic sweet potatoes were field tested in Puerto Rico and produced promising results, which provided the basis for transfer to the target countries. The transgenic sweet potato lines shipped to Uganda in 2011 (Kasozi, 2012) and Kenya from Peru have undergone greenhouse evaluation and await confined field trial evaluation (SASHA, 2012). The transformation system has been optimized for African farmer preferred sweet potato varieties. The transgenic events have been developed in Uganda and Kenya, and are ready to be tested (SASHA, 2012).

Rice (Oryza sativa)

Rice is an important crop and the most rapidly growing food source in Sub-Saharan Africa, especially in urban areas where consumer preferences have shifted in favor of rice (Africa Rice Center (WARDA)/ FAO/SAA, 2008). However, consumption exceeds production leading to continuous importation of rice, taking away financial resources that would have been used to develop other sectors (FARA, 2009). Low yield and low quality are some of the challenges to rice production, attributed to biotic, abiotic stresses and lack of good agronomic practices (WARDA/ FAO/SAA, 2008). Drought, salinity and limited fertilizer use are some of the factors that lead to low rice yields and quality. Salinity is increasingly becoming a problem in rice growing coastal lowland and mangrove swamps of Africa (AATF, www.aatf-africa.org). Fertilizer use is also too inadequate to replace the nutrients removed in harvested crops (Gregory and Bumb, 2006). Nitrogen is often the most limiting factor in crop production and its inadequacy affects protein and nutritional quality, and also the integrity and strength of the kernel (Blumenthal et al., 2008).

The African Agriculture Technology Foundation (AATF) in partnership with Japan Tobacco (JT), Arcadia Biosciences, University of California, International Center for Tropical Agriculture (CIAT), NARS in Burkina Faso, Nigeria, Ghana and Uganda, Public Intellectual Property Resource for Agriculture (PIPRA) with funding from USAID and United Kingdom’s Department for International Development (DFID) initiated the Nitrogen Use Efficient Water Use Efficient and Salt Tolerant Rice (NEWEST) rice project (AATF, 2012). The project is developing farmer preferred rice varieties with enhanced nitrogen use efficiency, water use efficiency and salt tolerance, targeting Burkina Faso, Nigeria, Ghana and Uganda (AATF, 2012). JT provided the transformation technology (PureIntro®) royalty free to AATF, while Arcadia Biosciences donated the trait technologies (Alanine aminotransferase (AlaAT) for nitrogen use efficiency from barley and AtNHX1 for salt tolerance from Arabidopsis and is developing the transgenic rice plants (Arcadia Biosciences, www.arcadiabio.com).

Studies showed the rice cv. Nipponbare transformed with the AlaAT gene driven by a rice tissue specific promoter OsAnt1 exhibited increased biomass and grain yield compared to the non transformed rice plants grown under fixed nitrogen concentrations (Shrawat et al., 2008). Transgenic cotton plants expressing the Arabidopsis gene AtNHX1 that encodes a vacuolar sodium / proton antiporter showed high salt tolerance, with more biomass and fiber production compared to non-transgenic cotton plants under saline conditions (He et al., 2005). These studies showed the potential for improved nitrogen use efficiency and salt tolerance in the drought tolerant New Rice for Africa (NERICA) farmer preferred varieties (Arcadia Biosciences, www.arcadiabio.com). Arcadia Biosciences has introduced the traits into the upland and lowland NERICA farmer preferred varieties.

The confined fields for the NUWEST rice had been approved and prepared in two partner countries; Ghana and Uganda as of December 2012, and planted in 2013 (Mignouna, 2012; Boadi, 2013).

Cotton (Gossypium hirsutum)

Cotton is the major source of cash income and foreign exchange in Sub-Saharan Africa (Hillocks, 2009). Insect pests are the major constraint to cotton production in Africa (Javaid, 1995), with cotton bollworms as the most important insect pests. The cotton bollworms in Africa include; the African bollworm (Helicoverpa armigera), the spiny bollworm (Earia spp.), red bollworm (Diparopsis spp.) and the pink bollworm (Pectinophora gossypiella) (Hillocks, 1995). Management of cotton pests relies heavily on pesticides, which negatively affect the environment and human health. Pesticides are also expensive making the net gains from cotton low (Hillocks, 2009). Bt cotton is an important crop protection technology that can be incorporated into the integrated pest management strategy to reduce the risks from pesticide use (Dahi, 2012; Hillocks, 2009).

The Egyptian Ministry of Agriculture, Agricultural Research Center (ARC), Agricultural Genetic Engineering Research Institute (AGERI), Cotton Research Institute (CRI) and the Plant Protection Research Institute (PPRI) in partnership with Monsanto Company are field testing Bt cotton in Egypt, targeting H. armigera, E. insulana, P. gossypiella and the cotton leaf worm (Spodoptera littoralis) (Dahi, 2012). The American cotton variety (Gossypium hirsutum) was transformed with cry1Ac and cry2Ab, which was then crossed with the Egyptian varieties (Gossypium barbadense) (Giza80, Giza90 and Giza89). Results from the confined field trial indicated that the transgenic Egyptian varieties Bollgard II (MON 15985) showed improved resistance against the bollworms (Dahi, 2012).

In Kenya, transgenic cotton (Gossypium hirsutum) Bollgard I and II containing cry1Ac and cry2Ab was also introduced for confined field trial evaluation targeting the African bollworm and cotton semi-looper (Cosmophila flava) (Waturu et al., 2008). The partners include; Monsanto International Sarl, Deltapine (South Africa), International Service for the Acquisition of Agric-biotech Applications (ISAAA), African Biotechnology Stakeholders Forum (ABSF), Kenya’s National Biosafety Committee, KARI-Institutional Biosafety Committee and Kenya Plant Health Inspectorate Service (KEPHIS). Their results showed that Bt cotton significantly reduced the target pest populations (Waturu et al., 2008).

Uganda’s confined field trials of Bt cotton (cry1Ac and cry2Ab) and herbicide tolerant cotton started in 2009 (Biotech Uganda, 2010), targeting bollworms and weeds respectively.      The partnership involves the National Agricultural Research Organization (NARO), Cotton Development Organization (Uganda), Monsanto Company, Cornell University, Agricultural Biotechnology Support Project II (ABSPII) and Program for Biosafety Systems (PBS) with funding from USAID (Miti, 2009; ABSPII, http://www.absp2.cornell.edu/projects). The transgenic cotton showed improved resistance to cotton bollworms and improved herbicide tolerance respectively (Miti, 2009). These results show that Bt cotton is an important component in the pest management strategies and herbicide tolerance will help in the management of weeds that outcompete cotton in its early growing stages (Hillocks, 1995).

In addition, as of July 2013 Malawi had successfully managed the first confined field trial of Bt cotton planted in January 2013 (NEPAD-ABNE, 2013).

Potato (Solanum tuberosum)

Potato is one of the most important food crops in the world (Grafius and Douches, 2008). Potato is highly adaptable and produces large quantities of nutritious food per unit area. It is rapidly becoming a valuable source of income in Sub-Saharan Africa due to the increasing demand for fast food and snacks in the urban areas (Cromme et al., 2010). Insect pests are a serious problem to potato production, reducing yield and quality of tubers. These pests include the Colorado potato beetle (Leptinotarsa decemlineata), potato tuber moth (Phthorimaea operculella, Zeller) and aphids. The potato tuber moth is the important insect pest of potato in the tropic and sub-tropical regions (Cooper et al., 2009). The larvae cause damage in the field and storage by boring into leaves, stems and tubers. Larval damage exposes the tubers to fungi causing rotting and thus rendering them useless for human consumption (Estrada et al., 2007). Pest management relies mainly on pesticides which are expensive and unsafe for human health and the environment (Douches et al., 2002). Crop loss in storage ranges from 40% to 90% in Africa (Cooper et al., 2009). Numerous Solanum spp have natural resistance to insect pests but these properties are difficult to transfer into commercially desirable cultivars using conventional breeding due to the polyploidy in potato (Grafius and Douches, 2008). Genetic engineering is an alternative that could increase resistance to the potato tuber moth.

Michigan State University funded by USAID through the Agricultural Biotechnology Support Project (ABSP) initiated the development of transgenic potatoes (Spunta) resistant to the potato tuber moth in 1992 using the Bt gene (cry1Ia1) obtained from Syngenta Seed company. Other partners include; the International Potato center (CIP), the Agricultural Research Council (ARC) in South Africa and the Agricultural Genetic Engineering Research Institute (AGERI) in Egypt (Douches et al., 2009). Spunta is a long, white, table-stock cultivar grown widely in the subtropical regions. The transgenic potato lines over expressing the gene under the control of CaMV35S promoter showed enhanced resistance against the tuber moth (Douches et al., 2002). Confined field trials were conducted in Egypt and South Africa based on results from the experiments in the U.S (Douches et al., 2009). Laboratory and field experiments in U.S showed that transgenic Spunta-G2, -G3 and -6a3 were resistant to the potato tuber moth (Douches et al., 2009; Douches et al., 2011). The field trials also demonstrated that the agronomic performance of Spunta-G2 and -G3 was similar to that of the non-transgenic Spunta (Douches et al., 2002; Douches et al., 2004).

Confined field trials were conducted yearly from 1997 to 2001 in Egypt and 2001 to 2007 in South Africa. Field and storage evaluations in Egypt and South Africa showed that the transgenic potato lines were resistant to the tuber moth and also not agronomically different from the non-transgenic Spunta (Douches et al., 2002; Douches et al., 2004; Douches et al., 2010). Spunta-G2 was then crossed with the two popular South African potato varieties and the progeny were also resistant to the tuber moth (Douches et al., 2009). Molecular and protein safety evaluations, and composition analyses showed no difference with the non-transgenic Spunta, showing that Spunta-G2 was safe for human consumption (Quemada et al., 2010; Zarka et al., 2010). South Africa was then selected for product commercialization because the potato tuber moth is an important constraint, product efficacy was well demonstrated in the evaluations, the functioning biosafety regulatory framework, the well developed commercial potato industry and the well established environment for commercialization of GM crops like cotton, maize and soybean (Douches et al., 2009).

The application for general release of Spunta-G2 was submitted by the Agricultural Research Council to the Directorate of Biosafety of the Department of Agriculture, Forestry and Fisheries in 2008 (Thomson et al., 2010). The required information was submitted. However in 2009, the South African regulatory authorities did not approve the release of the GM potato to the general public on grounds that the potato tuber moth was not a major pest for stored potatoes but rodents, segregation of GM potatoes from non-GM potatoes required infrastructure that was not in place, and toxicity and allergicity data was not satisfactory (Thomson et al., 2010).

Other GM research activities in Africa

Some African countries continue to carry out biotech research on other crops. Kenya is developing insect resistant pigeon peas at Kenyatta University (Komen and Wafula, 2013). Egyptian scientists have developed salt tolerant cotton, virus resistant tomato, drought and heat tolerant wheat, virus resistant squash, virus resistant potato, transgenic maize plants for production of hepatitis B virus vaccine (Abdallah, 2010; Mansour, 2009; Momtaz et al., 2007; Wagdy, 2004). Scientists at the University of Cape Town in South Africa genetically engineered tobacco plants to produce vaccines against cervical cancer (Mthembu, 2004). Scientists in South Africa have also developed sugarcane with herbicide tolerance, stalk borer resistance and perturbations to enzymes involved in sucrose metabolism (Meyer and Snyman, 2013); grape vines with fungal and viral resistance, and grape berry quality; and virus resistant ornamental bulb species (Esterhuizen, 2012).

Conclusion

There are a number of promising projects currently underway in African institutions to develop GM crops of importance to African diets, food supply and income. These projects have the potential to deliver improved crops with improved nutritional value; increased pest and disease resistance; and improved salt and drought tolerance.  Ultimately, their deployment will depend on the farmers’ and consumers’ awareness about GM benefits and confidence in their governments, functional biosafety framework and approval by regulatory authorities.

Acknowledgements

This paper is a part of the AU/NEPAD African Biosafety Network of Expertise (ABNE) initiative funded by the Bill and Melinda Gates Foundation. Special thanks go to Professor Rebecca Grumet and Professor Jim Hancock for the helpful review of the manuscript.