Development of micropropagation system for yam (Dioscorea spp.) using somatic embryogenesis

Inadequate availability of disease-free planting materials remains a major constraint to yam production. The tissue culture technique has been used to regenerate disease-free plantlets from pre-formed, heattreated meristems followed by micropropagation. This procedure, however, has a low multiplication ratio with an average of 1: 4 every eight weeks. Embryo production from somatic cells (somatic embryogenesis, SE) is a system in which each somatic cell can regenerate a complete plantlet. However, previous reports show low SE induction frequencies and significant variations in success rates among different genotypes while hardly any report exist for improved varieties that farmers desire, especially in Nigeria. Studies were carried out to evaluate the effects of different plant growth regulators (PGRs) on induction of somatic embryogenesis of the following genotypes: one improved Dioscorea alata (TDa 291) and three improved (TDr 95/19177, TDr 89/2665, TDr 95/18544) and one landrace (Obioturugo) of Dioscorea rotundata. Leaf, stem, and axillary bud explants were cultured in MS basal medium containing fifteen treatment combinations of 2,4-Dichlorophenoxyacetic acid (2,4-D), Naphthaleneacetic acid (NAA), Benzylaminopurine (BAP), Picloram, and Uniconazole-P (UP). The genotype TDr 95/19177 was tested for SE in Temorary Immersion Bioreactor System (TIBS). The incidence of induction of callus formation and plantlet regeneration from the three explants were recorded. Embryogenic callus induction was highest (87%) from axillary buds cultured on modified MS + 2 mg/l of 2,4-D + 1 mg/l of NAA while 1 mg/l of BAP + 9. 9 mg/l of UP had the highest percentage plantlet regeneration of 50% in TDr 95/18544 and an average of 37% across genotypes at a mean of 5 plantlets per explant. The genotype TDr 95/19177 was successfully regenerated via indirect somatic embryogenesis in the SETIS Type Temporary Immersion Bioreactor System

Key for a profitable and sustainable seed yam business enterprise: business plan and market development with record keeping for seed yam farmers

Bill & Melinda Gates FoundationPeer Revie

Seed yam production from whole tubers versus minisetts

Open Access Article; Published online: 22 June 2020Yam (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. Depending on the size, seed tubers are often cut into setts, minisetts, or planted whole. An experiment was conducted to investigate the effects of using whole tubers versus minisetts to produce seed yams. Six treatments constituted combinations of whole tubers and minisetts, and three tuber-size classes, viz., 30–59 g, 60–89 g, and 90–120 g (averaged and referred to as 45 g, 75 g, and 105 g, respectively). The experiment was conducted as a randomized complete block design with three replications. Results showed that plants from whole tubers emerged from the soil faster and yielded 48% more than those from minisetts. The mean yield of 105 g minisetts (18.3 t/ha) was statistically similar to that of 45 g whole seed (17.9 t/ha). Using 45 g whole seed would save about 2 t/ha of the harvested crop for use as food instead of seed. So, planting small whole tubers is more profitable than minisetts and is recommended to yam growers

Genetic purity of yam (Dioscorea spp.) multiplied through different seed multiplication techniques based on DArT SNP markers

Open Access ArticleObtaining high-quality planting material for cultivation is a persisting challenge for yam (Dioscorea spp.) production in Africa. Efforts to provide a solution to this challenge have led to varying seed multiplication techniques but whose efficiency in maintaining the genetic purity of yam genotypes during the rapid multiplication process is yet unknown. Three improved varieties Swaswa, Kpamyo and Asiedu were multiplied through tissue culture, aeroponics system, field condition and vine cutting techniques. Leaf samples were collected at every stage of multiplication in the different techniques as well as the original mother plant for DNA fingerprinting. From a total of 16,922 SNP markers, an average heterozygosity of 0.091 was obtained with minor allele frequency of 0.119, and polymorphic information content of 0.166. The transition to transversion ratio was 62:38%. Hierarchical clustering of the genotypes and technologies discriminated the multiplied materials into three clusters with the first cluster consisting of only the variety Asiedu multiplied through aeroponics, vine and tubers collected from vine cutting and grown from the field. The second cluster consisted predominantly of the variety Kpamyo, with a little admixture from Asiedu. The third cluster consisted of only Swaswa. The different seed multiplication methods showed great potentials in conserving the genetic purity of genotypes used. Therefore, the use of these seed multiplication techniques could offer a lasting solution to the low multiplication ratio of yam without compromising the genetic integrity and offers a great opportunity for establishing a formal yam seed system

Yam propagation using Aeroponics technology

Aims: To study yam propagation and seed yam tuber production in aeroponics system.Study Design: The experiment was conducted in a randomized complete block designand treatments were replicated three times.Place of Study: This experiment was carried out at the International Institute of TropicalAgriculture Headquarters at Ibadan in Nigeria.Methodology: The experiment tested fresh vine cuttings of five yam genotypes of twospecies in an aeroponics system. Three genotypes of Dioscorea rotundata (TDr 89/02475,TDr 89/02665 and TDr 95/18544) and two yam genotypes of D. alata (TDa 98/01176 andTDa 291) were evaluated.Results: Vines of both D. rotundata and D. alata rooted within 2 weeks in aeroponicssystem. The rooting of vine cuttings varied significantly among genotypes with a maximumof 98% for TDa 98/01176 and a minimum of 68% for TDr 89/02665. Mini-tubers harvestedafter 4 months of growth in aeroponics weighed between 0.2 and 2.7g. A second harvest 6months later gave mini-tubers of up to 110g. The analysis of variance showed significantdifference (P<0.05) among genotypes for rooting at 2 weeks after vine planting, number ofplant surviving at 90 days after planting and percentage of plants with bulbils. The best genotypes were TDr 95/18544 and TDr 89/02665 for survival at 90 days after vine plantingand percentage of plant producing bulbils in the aeroponics system respectively.Conclusion: This study revealed that yam genotypes performed differently in aeroponicssystem for vine rooting and production of mini-tubers and bulbils

A Latent Class Modelling Approach to Evaluating Farmer’s Preferences for Pona Seed Yam Certification System and Their Willingness to Pay in Ghana

The study employed choice experiment and latent class model to assess farmers’ preferences for seed yam certification system and their willingness to pay for certified seed yam in selected yam producing Districts in Ghana. A total of 9120 choice experiments were conducted to elicit data from 380 yam farmers. The study identified three classes/ market segments of farmers regarding preferences for Pona seed yam. The results show that farmers have more utility towards fully certified seed yam and are willing to pay GH¢719.60 (US$189.4) for a bunch (100 tubers weighing about 45kg) of fully certified seed yam. However, farmers were found to have high utility towards medium-sized Pona seed yam and are willing to pay a premium of GHC¢12.5 (US$3.3) for this attribute. The study has demonstrated high potential for the commercialization of seed yam production in Ghana through a formal seed yam certification system