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International Potato Centre

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Putri Erna Abidin
added 4 research items
In north-eastern Uganda, the sweet potato crop of small subsistence farmers is severely affected by many pests, including (rough) sweet potato weevils, nematodes and millipedes. Field experiments with sweet potato (Ipomoea batatas (L.) Lam.) were conducted at Arapai Station in Soroti District, north-eastern Uganda in three consecutive seasons to study the differences between the indigenous practice of harvesting piecemeal in combination with storage `in-ground on plants¿ and one-time harvesting after crop senescence, with special reference to damage caused by sweet potato weevils (Cylas spp.), rough sweet potato weevils (Blosyrus spp.), millipedes (Diplopoda) and nematodes. The area has two rainy seasons per calendar year, the first one with long, reliable rains and the second one with short, unreliable rains. Severe sweet potato weevil damage in the vines was responsible for the mortality of 46% of the plants in Experiment 1, which was carried out during the first rainy season. Starting 3 months after planting (MAP), sizable storage roots could be harvested, although their number and weight declined after 4 MAP with piecemeal harvesting. The highest storage-root yield (17.8 Mg ha¿1) was found in Experiment 2 (second rainy season) at the final harvest. The yield of storage roots stored `in-ground on plants¿ during the prolonged dry season (Experiment 3) was very low compared with the yields of Experiment 1 (first rainy season) and Experiment 2 (second rainy season). Sweet potato weevil damage of the storage roots was significantly less with piecemeal harvesting than with one-time harvesting, and piecemeal harvesting also increased the quality of the storage roots for human consumption and commercial purposes. However, with piecemeal harvesting the rough sweet potato weevil (Blosyrus spp.) caused more storage root damage than with one-time harvesting. No statistically significant differences between the two types of harvesting were found for damage caused by nematodes or millipedes. It was concluded that piecemeal harvesting of sweet potato storage roots contributes to the control of sweet potato weevil in both vines and storage roots and hence improves the quality of the harvested roots. As rainfall distribution affects the population dynamics of this weevil this method can only be used during a limited period of the year.
Millipedes can cause considerable damage in the production of sweet potato and some other crops in East Africa. Quantitative information on intake of crop diets by and body weight gain of millipedes was collected in short-term no-choice feeding activity laboratory experiments conducted in north-eastern Uganda using female millipedes of the species Omopyge sudanica. Diets consisted of sweet potato and cassava storage root material, groundnut seeds, or maize grains. Differences in intake and body weight gain between diets were not statistically different. The consumption index, i.e., the ratio between intake and body weight gain, was significantly higher for sweet potato than for most other diets. The efficiency of conversion of ingested food, i.e., 100 × the ratio between body weight gain and intake, was significantly lower for the root crops — especially sweet potato — than for the grain crops. The research showed how difficult it is to obtain reliable, quantitative data on the feeding habits of millipedes, but also illustrated that O. sudanica can cause harm to crops in north-eastern Uganda and elsewhere in East Africa.
This book is based on papers presented at the Ninth Triennial African Potato Association Conference, Naivasha, Kenya, 30 June-4 July 2013.The book focuses on the policies for germplasm exchange, food security and trade in Africa, seed systems, breeding and disease management and postharvest management, processing technologies and marketing systems of potato and sweet potato. The nutritional value and changing behaviours of potato and sweet potato crops are also discussed.
Putri Erna Abidin
added 8 research items
Keywords: Agro-biodiversity, farmer varieties, indigenous knowledge, farmer-participatory research, genetic diversity, genotype-by-environment interaction, germplasm collection, Ipomoea batatas , specific adaptation, yield stability, sweetpotato, variance component estimates. 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 analyzed 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
Sixteen sweet potato varieties were evaluated for fresh storage root yield in 20 trials during 2000¿2001 for three seasons in four locations in Uganda. Of the 16 varieties, 11 were developed by farmers and five by a central breeding programme. The behaviour of the varieties was quantified in terms of wide adaptation (genotypic mean across trials), specific adaptation (genotypic predictions for specific locations) and stability (Shukla stability variance). With respect to all three aspects of yield behaviour, farmer varieties performed on average better than the official varieties. The results illustrate the potential that farmer varieties can have in the improvement of sweet potato in Uganda and other regions where high diversity of sweet potato landraces exists
Agricultural researchers, NGOs and farmers in Malawi have pooled their knowledge and resources to develop and distribute new vitamin-enriched and drought-resistant sweet potato varieties, and to devise and promote new commercial activities that will help its spread.
F. Chipungu
added 2 research items
This book is based on papers presented at the Ninth Triennial African Potato Association Conference, Naivasha, Kenya, 30 June-4 July 2013.The book focuses on the policies for germplasm exchange, food security and trade in Africa, seed systems, breeding and disease management and postharvest management, processing technologies and marketing systems of potato and sweet potato. The nutritional value and changing behaviours of potato and sweet potato crops are also discussed.
The project “Rooting out Hunger in Malawi with Nutritious Orange-Fleshed Sweetpotato (OFSP)” was launched in October 2009 for the benefit of women and children in the country. This 4.5year effort targets 115,000 households to improve vitamin A and energy intake using improved sweetpotato varieties. It also seeks to boost yields by 50% and improve incomes by 20%. The project aligns with the Agriculture Sector Wide Approach to food and nutrition security and crop diversification. With Irish Aid support, CIP initially worked in partnership with government agencies and three NGOs as implementing partners (IPs) and targeted 4 districts. The project established a “1-2-3” seed multiplication system, with clean planting material produced at a primary multiplication site, and decentralized vine multiplication sites (DVMs) doing multiplication at the community level. DVMs run by individuals or groups of farmers with access to irrigation were established by the IPs and supervised by district Extension staff. Multiplication at the DVMs was termed secondary (vine production using rapid multiplication) or tertiary (production of both roots and vines, particularly during the hungry season). A subsidized voucher system was used by partners to allow at risk households to purchase sweetpotato planting material from DVMs. Promotion and awareness campaigns were conducted in each district to stimulate demand for OFSP. By February 2012, the project had reached 36,403 households in 5 districts with subsidized vouchers, and an additional 19,331 beneficiaries through non-voucher sales. Seven IPs in 14 districts partnered in the effort. Lessons learned and sustainability of the system will be discussed.