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Publications

Use of the environmental impact quotient to estimate impacts of pesticide usage in three Peruvian potato production areas

In Peru, potato farmers rely on fungicides to control late blight, the most important disease, and insecticides to control a variety of pests. The study aims to estimate the environmental and human health risk associated with pesticide use through the use of the environmental impact quotient (EIQ) to represent the total hazard posed by all pesticides applied over different potato cultivars.

 

About half of the fungicide (total formulation) was applied per hectare in Huamachuco (0.8 kg/ha), compared to the other two locations: 2.0 kg/ha in Chaglla and 2.4 kg/ha in La Encañada. Insecticide use in Chaglla was only 0.38 kg/ha while in Huamachuco it was about 0.59 kg/ha and in La Encañada over 2.28 kg/ha. Environmental impact values per hectare were about three to four times higher in La Encañada than in either of the other two locations primarily due to heavy use of highly hazardous insecticides. Lack of correlation of environmental impact with productivity indicated opportunities for improvement.

The high degree of variability in products used among locations as well as the different toxicological properties of the products used makes a purely amount-based comparison of pesticide use less illuminating. The EIQ was helpful in providing information on the potential environmental effect of current application practices. Modifying pesticide application patterns through adequate training on more efficient pesticide use and on integrated pest management strategies would be an effective way to reduce farmer health and environmental impacts in Peru.

CURING AND THE PHYSIOLOGY OF WOUND HEALING

Damage is inevitable during handling and marketing of sweetpotato and is exacerbated by practices such as over-packing sacks. Most plant tissues have mechanisms for healing wounds. This is exploited to improve storability of root crops after harvest by ‘curing’, where they are placed in an environment to promote healing of wounds incurred during harvesting and handling . Sweetpotato is similar in this respect to other root and tuber crops such as potato, cassava and yam.

Descriptions of wound healing in sweetpotato date from the 1920s when Weimer and Harter (1921) described how moisture and temperature affect wound periderm formation and the efficiency of the wound cork in preventing infection. Artschwager and Starett (1931) distinguished three stages of healing:

  1. desication of surface cell layers
  2. thickening of cell walls (suberization or liginification) in underlying cell layers
  3. formation of a new ‘wound’ periderm underneath the lignified cells. 

Each of these processes is described in more detail in this document.

Investigating carotenoid loss after drying and storage of orange-fleshed sweet potato

Biofortified orange-fleshed sweetpotato (OFSP) is being promoted to tackle vitamin A deficiency, a serious public health problem affecting children and pregnant/lactating women in sub-Saharan Africa. The aim of the study was to quantify and understand the factors influencing carotenoid losses in dried OFSP. Losses were determined in chips after drying and storage. A preliminary study demonstrated that carotenoid levels were not significantly different following either solar or sun drying. Carotenoid loss after drying was generally correlated with high initial moisture content and high carotenoid content in fresh sweetpotato roots. Losses of pro-vitamin A were less than 35% in all cases. Flour made from OFSP could therefore be a significant source of provitamin A. In contrast, storage of chips at room temperature in Uganda and Mozambique for four months resulted in high losses of pro-vitamin A (ca. 70-80% loss from the initial dried product). Low-cost pre-treatments, such as blanching, antioxidants and salting, did not reduce carotenoid losses during storage. Enzymatic catabolism of β-carotene in dried OFSP was considered unlikely because of low peroxidase activities at low water activities and the loss of peroxidase activity during storage. To understand further the factors causing the losses, dried sweet potato chips were stored under controlled conditions of temperature (10; 20; 30; or 40ºC), water activity (0.13; 0.30; 0.51; 0.76) or oxygen (0 [under nitrogen]; 2.5; 10 or 21% [air]). Oxygen was the main cause of degradation followed by temperature. An Arrhenius kinetic model was used to show that carotenoid breakdown followed first order kinetics with an activation energy of 68.3kJ.mol-1 that was in accordance with the literature. Experimental observations fitted well with data predicted by the kinetic model. The formation of the volatile compounds, β-ionone; 5,6-epoxy-β-ionone; dihydroactinidiolide; β-cyclocitral that were clearly related to the degradation of β-carotene, helped further understand breakdown patterns of β-carotene.

Sweetpotato breeding for northeastern Uganda: Farmer varieties, farmer-participatory selection, and stability of performance

Between 1999 and 2001, the author conducted various studies, primarily in northeastern Uganda, aimed at rapidly assessing the potential of farmer varieties of sweetpotato (Ipomoea batatas) from northeastern Uganda in contributing to the varietal improvement programme in Uganda. These studies included: (i) collection of germplasm (farmer varieties) and farmer knowledge about varieties from five districts in northeastern Uganda; (ii) assessment of morphological diversity and duplication in the collected germplasm; (iii) farmer participatory on-station selection of promising varieties from the collected germplasm for on-farm and multi-locational testing; (iv) farmer-managed on-farm testing in Soroti District (northeastern Uganda) of selected farmer varieties, cultivars from the Ugandan breeding programme and local farmer varieties; (v) multi-locational testing and stability analysis of selected farmer varieties and officially released cultivars from the Ugandan breeding programme in multiple test environments (20 tests over three seasons). Additionally, the author presents results from a multi-national, multi-locational test of elite sweetpotato germplasm in eastern Africa used to study selection efficiency. During germplasm collections, a total of 206 accessions were collected, along with farmer knowledge about them, and of these 188 were classified as distinct accessions, exhibiting considerable morphological variation. Many accessions were collected from remote locations where sweetpotato is not a commercial crop, while relatively few accessions were collected from areas where the crop is important commercially. During the on-station assessment of the collected germplasm, 11 accessions were selected for further testing from a total of 160 accessions evaluated at two sites. Nine of the 11 accessions selected by farmers were common to both sites. Farmer selection criteria were verified, with a high weighting given to fresh storage root yield, storage root number and harvest index, in addition to root dry matter content and appearance. During on-farm trials over two years, the 11 farmer varieties were generally preferred over local varieties, and cultivars from the Ugandan breeding programme. During multi-locational trials, the 11 farmer varieties on average performed better with respect to broad adaptation, specific adaptation and yield stability, than the cultivars from the breeding programme. In addition, some of the farmer varieties showed specific adaptation to local environments. Results of the multi-national trial were analysed to generate recommendations for optimum selection efficiency, and indicated a two-step selection procedure with two locations and one replication at Selection Step 1 and five locations and two replications at Selection Step 2 (total test capacity of between 450 and 950 plots). During the farmer participatory phases of this research, farmers were highly competent in sweetpotato varietal selection and were aware of the genotype-by-environment interactions and biodiversity. Results illustrate the potential that farmer varieties can have in the improvement of sweetpotato in Uganda and other regions where high diversity of sweetpotato landraces exists, and allowed us to recommend an approach for the rapid and efficient selection of superior genotypes from local germplasm in East Africa.

Working with farmer groups in Uganda to develop new sweet potato cultivars: decentralisation and building on traditional approaches

Scientists and farmers in Uganda identiÞed preferred sweet potato: (1) varieties through participatory varietal selection (PVS); and (2) new clones from seedling populations through a participatory plant breeding (PPB) approach. During these two processes, farmers identiÞed 51 attributes of their landraces and of released varieties and used 21 criteria to select clones from amongst the seedling populations. Scientists had, in publications, listed attributes (11 main attributes identiÞed), morphological descriptors (11) of released varieties and varietal needs (23) of sweet potato farmers. One released variety (NASPOT 1) was selected by farmers during PVS, mostly for its high and early yield of large, sweet and mealy roots, and several clones were selected through PPB amongst the seedling populations for a wider range of attributes. Some varietal attributes needed by farmers were not included by scientists either because they were very laborious, for example, selecting on-station for clones suitable for sequential piece-meal harvesting, or because occurrence of important abiotic or biotic stresses such as drought or pest damage were difÞcult to predict. Farmers seldom mentioned disease resistance but did mention pest resistance, consistent with easy visibility of both the causes of and the damage due to pests. Unlike scientists, farmers made no mention of a need for cultivars to have perceptually distinct features, despite this being a common attribute of landraces of most crops.

Farmer criteria for selection of sweetpotato varieties

In Tanzania, despite its importance in food systems there has been little expansion in the aggregate acreage of sweetpotato over several years. The poor uptake of some new varieties in the past has underlined the importance of incorporating the preferences of growers and consumers into the breeding process. This chapter describes surveys conducted in Tanzania to determine the farmer criteria for preferred sweetpotato varieties. The opinions of farmers on available varieties indicate that there is considerable room for improvement.

Novel Plant Regeneration for Egyptian Sweetpotato (Ipomoea Batatas (L.) Lam.) Abees Cultivar via Indirect Organogenesis Stimulated by Initiation Medium and Cytokinin Effects

In this study, a simple and efficient plant regeneration system in Egyptian sweetpotato Abees recalcitrant cultivar via indirect organogenesis was established. Two initiation medium and different regeneration medium were tested. Hormone free initiation medium (HFIM) treatment was found to be critical for induction of regenerative callus. Likewise, callus diagnostic structural histology confirmed de novo differentiation of meristematic domes in induced callus tissues and their further development into bud primordia. Shoot regeneration was dramatically improved by subculture of the initiated callus from HFIM onto different enriched cytokinin regeneration medium. Although, an overall analysis of variation also revealed a significant response for media used for shoot regeneration. The highest significant number of regenerated shoots per shooted callus (2.33) and frequency of regenerated shoots (80.90%) were obtained on benzyl adenine containing medium (BARM). Subsequently, regenerated shoots were rooted on hormone free medium (RM). Regenerated plants were acclimatized in controlled environment growth chamber and successfully established in the greenhouse. Hence, we report a reliable regeneration system for local recalcitrant cultivar Abees which could be used to exert selection pressure to abiotic stress or to transfer genes of agronomic interest and produce transgenic plants.

Biotechnology Applications for Improving Sweetpotato Production

Sweetpotato, (Ipomoea batatas L.), is a vegetatively propagated crop. Due to the cycles of propagation, viruses are accumulated, which contributes to the decline of sweetpotato yield and quality. Stem cuttings of Abees cultivar were collected from several locations in Egypt and kept under controlled greenhouse conditions. Samples were tested for the presence of sweetpotato feathery mottle virus (SPFMV) infection using dot-ELISA. Infected plants were subjected to thermotherapy by incubation at 42°C/ day and 39°C/ night for 3 weeks followed by meristem tip culturing, then they were allowed to grow in vitro. RT-PCR was carried out to confirm the success of SPFMV elimination. Tissue culture formed plants were tested routinely for successive 2 years using dot-ELISA. 0% infection was reported in the in vitro propagated plants. 

Introduction of sweetpotato to in vitro culture – OP58

The establishment of tuber crops into in vitro culture requires the isolation of vegetative structures (explants) containing buds. Explants should be inoculated in vessels containing a nutritive substrate (culture medium) where buds will grow to became whole plantlets. For the case of sweetpotato, the preferred explant for in vitro culture is the apical or axilar bud of the stem. Because plant material may carry superficial contaminants, a surface sterilization process to eliminate microorganisms is conducted. Fungi and bacteria that are not adequately eliminated can grow and contaminate the culture media damaging the explants in culture. The procedure detailed in this OP has been found to reduce contamination to less than 5% on plant material samples taken from potted plants.

Sweetpotato Breeding Under the Sweetpotato for Profit and Health Initiative- SPHI

This is a poster with summarized information on Sweetpotato Breeding under the SPHI Project. Sweetpotato is playing an increasingly important role in African agriculture, combating food insecurity and undernourishment, particularly vitamin A deficiency. The Sweetpotato for Profit and Health Initiative (SPHI) aims to reposition sweetpotato in African food economies, and improve the lives of 10 million families by 2020. SPHI works through diverse research and development partnerships and seeks to ensure that women and children benefit from its efforts. The Sweetpotato Action for Security and Health in Africa (SASHA), of the SPHI, supports significant pre-breeding and capacity-building efforts from regional Sweetpotato Support Platforms (SSPs) in Uganda, Mozambique and Ghana. From these locations, CIP breeders work with national and regional partners.

 

Pre-breeding (population improvement) efforts at each location focus on key attributes of regional importance and use recurrent selection and an accelerated sweetpotato breeding (ASPB) approach to advance populations rapidly. ASPB involves early evaluation of clones and families across environments, and is also used by partners for selecting new varieties. High dry matter and provitamin A content are a priority at each of the SSPs, with specific emphasis in southern Africa on drought tolerance, in eastern Africa on resistance to sweetpotato virus disease (SPVD), and in West Africa on non-sweet types. Near infrared spectroscopy is used at each SSP for rapid analysis of quality attributes. The relative efficiencies of controlled versus polycross methods and the use of heterosis are also being systematically assessed. Breeding efforts at SSPs are backstopped by germplasm and expertise from CIP headquarters and elsewhere. It is anticipated that outputs from each SSP may be useful to other SSPs and national programs. Capacity building and breeding efforts in each region are undertaken in close collaboration with national programs and within regional structures, such as ASARECA, and with support from various sources, including AGRA

Are millipedes a pest in low-input crop production in north-eastern Uganda? Farmers' perception and experimentation

Farmers’ perception was collected and experiments were done, through a series of research work between 2000 to 2003 in north-eastern Uganda. This research work included: (i) Field survey on farmers’ knowledge on sweet potato production and perception of millipede infestation; (ii) Field assessment of pests in sweet potato and other major crops conducted in the planting seasons of 2000 – 2002; (iii) Feeding activity of the East African millipede Omopyge sudanica Kraus, based on no-choice laboratory experiments, and (iv) Comparison of the indigenous cultural practices of piecemeal harvesting and storage roots ‘in-ground on plants’ with one-time harvesting after crop senescence in trials conducted in the planting seasons of 2002 – 2003. There was inadequate information about millipedes in general and possible control strategies in East Africa. Therefore a literature study was also done to gain more knowledge about this animal. All research work has been compiled into a PhD Thesis by Wageningen University in The Netherlands. Five chapters have been published in a peer reviewed journal article and documented.