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The second phase of the Yam Improvement for Income and Food Security in West Africa (YIIFSWA II) project was implemented through a strong collaboration between research and private sector. Private seed companies were provided with a wide variety of training and development activities on good agronomic practices (GAPs). However, the effects of the training activities were yet to be evaluated. This paper evaluated the contribution of the training on high-quality seed yam production through paying particular attention to how it was tailored to the needs of various farmers, and how the knowledge gained was transferred to the field. The study employed an applied Kirkpatrick model and descriptive statistics to measure the indicators of training effectiveness. Results from a statistical population of 172 farmers using 179 demonstration fields showed that the farmers’ training on GAPs was effective, based on four criteria of the Kirkpatrick training evaluation process. The satisfactory results at the beginning of the hierarchical model have implications on the satisfactory results at the end. Improving the effectiveness of a training depends on defining factors such as (i) Training based on satisfaction in meeting the needs of your trainees and the seed production business; (ii) Training based on learning objectives in improving the trainees’ skills and knowledge; and (iii) Training based on learner attitude change in applying new skills and knowledge in the fields. Conclusions drawn from this study indicated that the training was a reasonable value-added mechanism of improved agricultural knowledge and practices for enhancing high-quality seed yam production in Nigeria.

Yams are staples in West Africa. They are propagated from tubers in an informal seed system. This encourages a build-up of diseases, and necessitates the rapid development of a formal seed system where certified seeds are functional. Although few reports exist on the use of meristem culture to generate pathogen-free yam, the success rate for the most economically important species in the sub-region, Dioscorea rotundata, for the most prevalent viruses is inadequate. To generate pathogen-free yam planting materials, the relative efficiency of tissue culture and positive selection was compared. Twenty-one asymptomatic yam plants were positively selected from 8187 stands of five landraces. Five of these stands were tested virus-negative by multiplex polymerase chain reaction (PCR) for Yam mosaic virus (YMV), Yam mild mosaic virus (YMMV) and Cucumber mosaic virus (CMV), and by PCR for the genus Badnavirus (BV), giving 0.08% success. Single nodes of the positively selected stands were used to establish in vitro plantlets, which were screened onto bacteriological indexing medium. The same was done for meristem- and node-derived plantlets of the improved variety TDr 95/19158. Incidence of endophytes ranged from 18 to 32% in the nodal plantlets while it was 0% in the meristem-derived plantlets. The effect of meristem culture combined with thermotherapy on the virus infection status was determined using virus-tested, one week old in vitro plantlets of eight improved genotypes. These in vitro plantlets were incubated at 36 ± 0.5°C and 16 h photoperiod for 21 days, after which meristems were excised, regenerated into plantlets and re-tested for viruses. Seventy-three percent of the samples were recovered from YMV but the effect on BV was inconsistent. Positive selection can be used as a palliative in generating quality declared seed but meristem culture combined with thermotherapy is more efficient for generating certified seed tubers of yam.

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.

Obtaining 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. [ABSTRACT FROM AUTHOR]