In the Lake Zone, Tanzania, between 2009-2012, 88 decentralized vine multipliers (DVMs) were established by the Marando Bora project. Five years later, the follow up study traced 81 of the DVMs. 40% of the DVMs had sold planting material of Marando Bora varieties in the last year; a further 16% had maintained the improved varieties for own use. The percentages of DVMs retaining different improved varieties were: Polista: 48%; Kabode: 34% Ukerewe: 23%; Ejumula: 12%; and Jewel: 11%. Depending on variety, between 9-21% of DVMs had obtained replacement materials.
2019 SASHA Brief 13. Early generation seed production for roots, tubers and bananas is financially viable for private sector seed companies in East Africa.
CIP conducted a financial feasibility study for a private seed company engaged in early generation seed (EGS) production for root, tuber and banana crops. The study showed that the business is financially viable in the long-run based on the existing business for production and sale of banana, cassava, sweetpotato and potato planting materials. The business required an initial total investment of US$1 million and running costs of US$0.15 million during an eight-month establishment period. The payback period for this level of investment would be between three to seven years, with an average annual return of between 34-70%. Inclusion of sweetpotato in the business increased its financial viability over time
2019 SASHA Brief 12. A new method for estimating sweetpotato early generation seed requirements to supply commercial and institutional markets.
A user-friendly tool to estimate the requirements for Early Generation Sweetpotato Seed (EGS) is now available for use by public sector seed producers. The method was first used in Uganda to estimate the seed requirement by root producers for quality seed of improved varieties; then estimates of the number of basic seed multipliers this will require; and finally, the amount of pre-basic cuttings and tissue culture plantlets to be produced. Results indicate a need to treble the existing pre-basic seed production capacity; decentralize pre-basic screenhouse capacity to get broader national coverage; improve screenhouse design and utilization to increase efficiency and reduce the cost of pre-basic seed production. Scaling EGS production and linkages through the chain will only be successful if there is an expansion in the root markets driving demand for quality seed.
2019 SASHA Brief 11. Bridging the gap between pre-basic seed producers and decentralized multipliers for a sustainable sweetpotato seed system in Tanzania.
A study was conducted to understand the economic sustainability of basic seed enterprises to bridge the gap between pre-basic seed producers and decentralized vine multipliers. Four commercial seed multipliers were supported on a 2:3 (multiplier: CIP) cost-share basis. They were trained in entrepreneurial skills, marketing, business planning, and quality seed production. Business plans are now under implementation, and basic and pre-basic seed producers are now well-linked. The basic seed business required an initial investment of US$ 6,241, for a multiplication period of 12 months. US$ 1,314 is for the screenhouse to conserve quality seed. The payback period is one to two years, with an average annual return of 23-52%.
2019 SASHA Brief 10. Is sweetpotato root production cost-effective when using planting material conserved in protected structures in high virus pressure areas?
Two methods of protected vine conservation beds (insect protected net tunnel (Fig. 1) and miniscreenhouse (Fig. 2)) were compared with an open field control to assess cost effectiveness for quality seed production and subsequent root production. Mean percent Sweet Potato Virus Disease (SPVD) infection was not significantly different across methods of protected and open field conservation; however, there was increasing virus infection from generation 0 to generation 2 for each method. Although net tunnels produced more cuttings per unit area. Sweetpotato planting material sourced from the mini-screenhouse produced higher root yields (14.2 t/ha) than the net tunnel (11.5 t/ha) or open field (9.3 t/ha). Sweetpotato root production (per kilogram) is cost-effective and root producers can reduce their production costs by 21% if they buy planting material from commercial multipliers who use miniscreenhouses for conservation of planting material. In high sweetpotato virus disease pressure areas, support for the use of protected structures by medium to large scale multipliers is justified to increase availability of quality basic seed for farmers.
2019 SASHA Brief 09. Efficiency of insect-proof net tunnels in reducing virus-related seed degeneration in sweetpotato.
Affordable insect-proof net tunnels proved effective in reducing virus-related degeneration in sweetpotato in Tanzania. Re-infection in high virus pressure area was prevented for up to 20 months and 18 months for Polista and Kabode varieties, respectively. Seed degeneration modeling showed that virus buildup could lead to significant yield loss after 4 generations in the open field but would not be reached within 10 generations if seed was sourced from the protected structure and multiplied once before use (Fig. 1).
A nutrient media for multiplying pre-basic sweetpotato vines under a sandponics system was optimized. The vine multiplication rate for pre-basic seed multiplication increased by 22% using sandponics. The cost of producing a 3-node cutting has been reduced by $0.027. Root yields were 7.1 t/ha higher using sandponics sourced planting material compared to material sourced from the conventional screen house production system.
The Sweetpotato Digital Catalogue (Fig. 1) presents a collection of the best performing sweetpotato varieties or “best bets” in Africa. Standardized information of 80 varieties in use in15 Sub-Saharan Africa (SSA) countries can be found at www.sweetpotatoknowledge.org on the web Information on a particular variety can be downloaded for printing, as can the entire catalogue Contact details are provided so that users can obtain disease-free, pre-basic cuttings or tissue culture plantlets of these varieties.
Research conducted on diverse sweetpotato germplasm showed that some genotypes form their roots at the same time, that are of the same maturity (discontinuous storage root formation and bulking) and other continue to form roots over time (continuous root forming), which aligns with the traditional practice of piecemeal harvesting. The genetic control of these two types is different and their cross combination permitted transgressive segregant progenies, which may form the basis for developing superior varieties. Molecular markers, as well as putative genes for the two types of growth have been discovered and will serve as foundation knowledge for accelerating breeding for the traits through marker-assisted selection.
A trained sensory panel was developed to assist with breeding for sweetpotato quality preferences of consumers in West Africa. Lexicons of terms to precisely describe boiled and fried sweetpotato sensory quality have been developed using trained sensory panel. Trained panel results showed that there is no direct relationship between sugar content and sweetness in boiled sweetpotato. Results showed that consumers liked the new high yielding varieties ranging from sweet to low sweet. Different clusters of consumer preference were detected and will help targeting of breeding efforts
2019 SASHA Brief 04. Major achievements in breeding for drought tolerance and high iron orange-fleshed sweetpotato in Mozambique: Lessons learned and achievements in phase 2 (2014-2019)
Successful second round of accelerated breeding completed, with the release of 4 orange-fleshed (OFSP) and 3 purple-fleshed (PFSP) drought tolerant sweetpotato varieties in 2016. Third round will be completed in 2019. Early season and terminal drought have negative effects on storage root yield (Fig. 1). Thick vines offer a morphological adaption to drought which may offer an advantage for remobilization of assimilates from leaves and stems to storage roots. Many widely adopted varieties are early bulking and satisfy piece meal harvesting, a desired trait given the predicted shortened seasons in Southern Africa under climate change. Among the 15 drought-tolerant OFSP released in 2011, Delvia and Irene have emerged as the most widely-adapted across different agro-ecologies. First enhanced iron (Fe) OFSP clone (MUSG150522) selected from Umbeluzi populations. Fe bioavailability study from comparing enhanced Fe OFSP clone to low Fe clone conducted among Malawian women of reproductive age by ETH-Zurich in 2019.
2019 SASHA Brief 02. A breakthrough: Hybrid population breeding validated in Peru, Uganda, and Mozambique
Determine the response to selection for yield and quality in three applied breeding populations for a complete reciprocal recurrent selection cycle for (i) OFSP wide adaptation and earliness, (ii) OFSP for high iron, and (iii) OFSP for low sweetness after cooking. Apply the concept of elite crossings in sweetpotato for the first time. These are recombinations of a small number of “super” parents, based on results of largescale trials, to fully exploit the within family variance of these crosses. Estimate the superiority of hybrid population means in hybrid population H0 (hybrid population established from two parental gene pools) in one applied breeding population with emphasize on yield and SPVD resistance, as well demonstrate the genetic gains to be achieved in yield and SPVD resistance by established elite crossings. Demonstrate for the first time in sweetpotato that hybrid breeding results in breeding populations which show pronounced heterotic increments under regular water supply and drought stress conditions. If so, the case can be made that a hybrid breeding approach leads to higher yield stability in sweetpotato bred for drought prone areas.