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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).

2019 SASHA Brief 08. Pre-basic sweetpotato vine multiplication using a sandponics system.

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.

2019 SASHA Brief 07. 2019 Sweetpotato digital catalogue now available.

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 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.

2019 SASHA Brief 06. Breeding for continuous storage root formation and bulking in sweetpotato.

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.

2019 SASHA Brief 05. Breeding and prospects for low sweet sweetpotato in West Africa.

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.