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Yam (Dioscorea rotundata Poir.) is a major staple and cash crop for millions of households in West Africa, where about 93% of the world crop is produced. The tuber serves as food and seed. Dependin...

The study analysed the varieties, sources and quantities of seed yam demanded by farmers for cultivation in order to inform policies aimed at ensuring adequate supply of quality seed yam of desirable varieties at an affordable price to boost yam productivity for improved income and livelihoods. A structured questionnaire was administered to 380 randomly selected yam farmers in three major yam producing districts in Ghana in 2015. The data analysis was done using STATA statistical software. The study identified Pona/Punjo, Lariboko, Asana, Afebetuye, Dente, Olondo and Kparinjo as the yam varieties mainly cultivated by farmers in a reducing order with high market demands by consumers. Own production remains the major source of seed yam for farmers. The estimated monetary value of quantity of seed yam used by farmers for cultivation in 2014 farming season was GH¢ 198, 552,841.0 (USD 51,706,469.0) in the study locations. About GH¢ 5,679,979.0 (USD 1,479,161.2) worth of quantities of seed yam was obtained from the market and other sources. The results demonstrate the existence of market potential for commercial seed yam production and supply in Ghana. Commercial seed yam certification system and yam breeding activities should target the identified yam varieties.

Yam (Dioscorea spp.) is a valuable food security crop in West Africa, where 92% of the world production occurs. The availability of quality seed tubers for increased productivity is a major challenge. In this study, minitubers weighing 1, 3, and 5 g produced from virus-free single-node vine cuttings of two improved yam varieties (Asiedu and Kpamyo) growing in an aeroponics system were assessed for suitability in seed production at a population of 100,000 plants ha−1. A 3 × 2 factorial experiment with randomized complete block design and three replications was set up during the cropping seasons of 2017 to 2019 at the International Institute of Tropical Agriculture Research Station in Kubwa, Abuja, Nigeria. Results showed field establishments of 87%–97.8%. Yields differed with minituber size, variety, and cropping season, the highest was 31.2 t ha−1 in 2019 and the lowest, 10 t ha−1 in 2018 from 5 and 1 g Kpamyo minitubers, respectively. The estimated number of tubers produced per hectare by 1, 3, and 5 g minitubers was 101,296, 112,592, and 130,555, with mean weights per stand of 159.2, 187.3, and 249.4 g, respectively. We recommend using less than 6 g minitubers for seed yam production due to their high multiplication rates.

Lack of good-quality planting materials has been identified as the most severe problem militating against increased agricultural productivity in sub-Saharan Africa (SSA) and beyond. However, investment of research efforts and resources in addressing this menace will only be feasible and worthwhile if attendant economic gains are considerable. As a way of investigating the economic viability of yam investment, this research has been initiated to address problems confronting yam productivity in eight countries of SSA and beyond: Nigeria, Ghana, Benin, Togo, Côte d’Ivoire, Papua New Guinea, Jamaica, and Columbia. Research options developed were to be deployed and disseminated. Key technologies include the adaptive yam minisett technique (AYMT), varieties adapted to low soil fertility and drought, nematode-resistant cultivars (NRC), and crop management and postharvest practices (CMPP). This article aims at estimating the potential economic returns, the expected number of beneficiaries, and poverty reduction consequent to the adoption of technology options. Estimates show that the new land area that will be covered by the technologies in the eight countries will range between 770,000 ha and 1,000,000 ha with the highest quota accounted for by AYMT. The net present value will range between US$584 and US$1392 million and was highest for the NRC. The CMPP had the lowest benefit-cost ratio of 7.74. About 1,049,000 people would be moved out of poverty by these technologies by 2037 in the region. These technologies are less responsive to changes in cost than that in adoption rate. Therefore, the realization of the potential economic gains depends on the rate and extent of adoption of these technologies. Giving the knowledge-intensive nature of some of these interventions, capacity building of potential adopters will be critical to increasing the sustainability of the yam sector, thereby enhancing food security and reducing poverty.

With about 70% of yam tuber been water, yield is critically affected during bulking as a result of onset of temporal drought. As a consequence of climate change, farmers who are into Dioscorea rotundata (white yam) production for local and international market lose their investments mainly due to erratic precipitation, drought spells culminating into low yields of just 12t/ha compared to the potential of about 22-49t/ha depending on the variety. Innovative land uses technologies with higher and sustained productivity for yam production are imperative. This study verifies improved agronomic package for sustainable yam production in yam growing areas in the forest – savannah transition zone of Ghana during the 2015 and 2016 cropping seasons. The improved agronomic package included use of ridging as seedbed, seed treatment before planting, fertilizer application at a rate of 30:30:36 N:P205:K20 kg/ha plus 15 kg/ha Mg and 20 kg/ha S as MgSO4 and the use of minimum stakes (trellis; 30-50% less number of stakes used by farmers staking). This was compared with farmers’ practice which consisted of mounding, no fertilizer application and no seed treatment. The results revealed significant (P ≤ 0.01) yam yields of more than 60% difference between the improved agronomic practice and farmers’ practice from Ejura, Atebubu and Kintampo yam growing communities. Adoption of improved agronomic practices does not only sustain yam production and address deforestation but also provide higher returns on investments promoting climate resilience by small holders.

White Guinea yam (Dioscorea rotundata Poir.) is an important staple to millions of people in West Africa. Obtaining good quality planting material for yam cultivation is a major challenge. Multiplication ratios are low, and seed tubers are prone to contamination with pests and pathogens in the traditional systems of production. Some approaches to producing quality seed of yam are as follows: farmers select small whole tubers from a ware crop harvest; stimulate the production of seed tubers by ‘milking’ ware tubers while the leaves of the plant are still green (double harvest system); cut ware tubers into setts about the same sizes as regular seed tubers; or use the ‘Anambra’ system where smaller setts are cut and used to produce seed tubers. New methods that have been developed to address some of the challenges of quantity and quality of seed tubers are not yet widely applied, so farmers continue to use traditional methods and save seed from a previous harvest to plant the ware crop. This document presents an overview of traditional and modern methods of seed yam production and gives a perspective for the future. Among the modern methods of seed yam production, only the minisett technique, which uses 25–100 g tuber pieces, is currently used at farmer level, although on a limited scale. While tissue and organ culture techniques are the most rapid methods of multiplying disease free propagules, their limitations include high costs, need for skilled personnel and specialized equipment. The aeroponics and temporary immersion bioreactor methods of producing seed yam are relatively new, and still need more research. To build and sustain a viable seed yam production system, a multiplication scheme is required that combines two or more methods including tissue culture for cleaning the seed stock.

Twenty-one yellow-fleshed cassava genotypes were evaluated over two years in five major cassava growing agroecological zones in Nigeria. The trials were established in a randomized complete block design with four replications to assess genotype performance and Genotype × Environment interaction for cassava mosaic disease (CMD), fresh and dry root yield (FYLD; DYLD), root dry matter content (DMC), and total carotene concentration (TCC). Combined analysis of variance showed significant differences (P<0.001) among genotypes (G), environment (E), and Genotype × Environment interaction (GE) for all the traits tested. For reaction to CMD, the best genotypes showing stable resistance were TMS 07/0539 and TMS 07/0628. For root yield, the best genotypes were TMS 01/1368 and TMS 07/0553. Genotype TMS 07/0593 was the best for DMC and TCC across the 10 environments. Variation among genotypes accounted for most of the Total Sum of Squares for CMD (72.1%) and TCC (34.4%). Environmental variation accounted for most of the Total Sum of Squares for FYLD (42.8%), DYLD (39.6%), and DMC (29.2%). This study revealed that TMS 07/0593 has the highest and most stable TCC, DMC with the lowest CMD severity score and appeared to be the best genotype.

Yam production is constrained by scarcity of clean seed, pests, diseases and low soil fertility in the informal seed system, which is still operational, causing up to 90% yield losses. Although meristem culture can be effective for producing healthy seed yam, its use is limited by slow rate of regeneration and propagation in conventional tissue cultures. In most crops tested, temporary immersion bioreactor systems (TIBs) increased propagation rates. To determine the potential of TIBs in improving the yam seed system, 23 databases were consulted and three returned a total of eight publications with only 2 for Dioscorea rotundata-cayenensis . Both plantlets and microtubers can be produced in TIBs, which will facilitate production of quality breeder, foundation and certified seeds and fast-track genetic improvement and the evolution of a formal from informal seed production system. Control of contamination, direct use of field explants, culture of micro-explants like immature embryos and anthers, increasing the size of microtubers produced and standardization for various economically important yam genotypes are knowledge gaps that require immediate research attention. No report has put a cost on yam TIBs, but it will be necessary to use cost-effective TIBs to encourage integration public-private partnerships into emerging formal seed system. Keywords: Tissue culture, healthy seed yam, temporary immersion bioreactors, dioscorea spp. African Journal of Biotechnology , Vol 13(14), 1614-1622

Improved quality seeds out-yield farmers' saved seeds significantly. However, the limited availability of such seeds through the conventional seed supply system is due to socio-economic factors and inadequacy of skilled personnel and infrastructure. A community-based seed multiplication system was, therefore, adopted and small seed stocks of soybean, cowpea and yam were distributed to farmer groups in the rural communities in northern Ghana, northern Nigeria and central Togo, respectively, between 1996 and 1999 for further multiplication. An impact assessment after 4 years showed a significant ease of farmers' access to improved seeds and development of linkages with pesticide dealers, credit sources, and extension services as a result of opting for this system. Quality of farmers' saved seeds had improved and farmers' yield had increased over 90 per cent. Extra incomes earned were used to purchase household items, and part invested in transport businesses and rearing of small ruminants as well as in human capital such as paying children's school fees and family hospital bills and meeting other social responsibilities. This system was, therefore, effective in diffusing improved seeds and associated technologies and services to many more farmers and communities within a very short time to improve their socio-economic status. Les graines de qualite amelioree depassaient considerablement en rendement les graines gardees par les agriculteurs. Cependant, la disponibilite de telles graines par le systeme conventionnel de provision de graine est limitee en raison de facteurs socio-economiques, l'insuffisance de personnel qualifie et l'infrastructure. Un systeme de multiplication de graine base a la communaute etait donc adopte et une petite quantite de stocks de graine de soja, de dolique et d'igname etaient distribues aux groupes d'agriculteurs dans les communautes rurales dans le nord du Ghana, le nord du Nigeria et le centre du Togo respectivement entre les annees 1996 et 1999 pour de multiplication davantage. L'evaluation d'impact entreprise apres quatre annees montrait une aisance considerable avec laquelle les agriculteurs avaient acces aux graines ameliorees et aux liens de developpement avec les marchands de pesticide, les lignes de credit et les services de vulgarisation agricole a la suite d' opter pour ce systeme. La qualite de graines gardees par les agriculteurs avait ameliore et les rendements d'agriculteurs avaient augmente plus de 90%. Les supplements de revenus gagnes etaient depenses pour les articles menagers, et une partie du revenun etait investie en entreprises de transport et en elevage de petits ruminants ainsi qu'en ressources humaines telles que le paiement de frais de scolarite de la jeunesse, les factures hospitalieres et pour regler d'autres responsabilites sociales. Ce systeme etait donc efficace pour la distribution de graines ameliorees et la vulgarisation de services et de technologies liees a l'agriculture a beaucoup plus d'agriculteurs et aux communautes dans tres peu de temps pour ameliorer leur situation socio-economique. Ghana Journal of Agricultural Science Vol. 39 (2) 2006: pp. 181-189