Several seed companies reported losses of substantial amounts of vine cutting in the nursery and field stages of production during the last annual meeting. Moreover, during the project’s first exchange visit, The Project Management Team (PMT) noticed several deviances in the operationalization of the HRPTS and production methodologies that could have impacted the healthy growth of plants in the system. Therefore, in a bid to correct and strengthen capacities, YIIFSWA-II specialists and technicians will be working hand in hand with the seed companies at their hubs to enhance their capabilities and boost their productivity in 2021.

To kickoff backstopping activities at the seed companies’ levels, YIIFSWA-II PMT held a 2-day virtual backstopping session for the private seed companies and National Agricultural Research Institutes (NARIs) on 6^th and 7^th April 2021.

Highlighting the purpose for the seminars, Dr. Norbert Maroya, YIIFSWA-II’s Project Leader, said, “a major constraint for the seed producers is how to produce healthy plants that generate good vines for seedling production, which is critical to the production of seed tubers. The vigor (seedling height, health, and growth rate) of a yam vine-cutting seedling is conditional on several factors related to genetics (which the project has taken care of) and environmental influence, which can be manipulated through management. Slight deviations from IITA prescribed protocols will lead to poor productivity. For example, increasing the nitrogen amount in the nutrient composition will boost canopy production but limit tuberization. We’ve researched nutrient composition, and the best composition is what we have prescribed. The nutrient composition is well-balanced and caters to all the needs of the plant.”

Principal Scientists presented the operationalization of each of the High Ratio Propagation technologies (HPRTs) used at the seed companies’ levels for foundation seed yam production. Under the YIIFSWA-II initiative, the seed companies can utilize either the Aeroponics system (AS) or the Drip System Hydroponics (DSH), which was introduced in 2018 as an alternative system for seed production due to the challenges of heat in the AS screen house.  The project addressed the challenge by developing technologies like the nutrient chiller and automated climate control system in the screen house. However, most seed companies are using both the AS and DSH to intensify production.

The Specialists also presented new knowledge generated from production research last year to the seed companies and the NARIs. At IITA Ibadan, Dr. Morufat Balogun Researched the effect of different fertigation regimes for optimal growth in the Hydroponics system.  Based on results, a Regular Fertigation Regime (RFR) of 10 days was more productive than Sequential Fertigation Regime (SFR). After eight weeks of planting, plants under RFR produced 74 more vines than plants under SFR. At IITA Abuja, Dr. Beatrice Aighewi researched the best substrate for foliage and seed tuber production. A total of 4 substrates, namely, carbonized rice husk, composted rice husk, cocopeat, and river sand, were compared to topsoil. Production in composted rice husks using single node cuttings gave better foliage and tuber yields than the other substrates.

Under the AS, several production trials were conducted and replicated for validation on optimal production methodologies. According to Dr. Norbert Maroya, at the onset of the project’s second phase, IITA experienced a devasting setback due to heat, resulting in the loss of lush foliage in the AS within three months. IITA thus developed several complementary technologies to mitigate the challenge of heat in the AS. These technologies are as follows:

• A nutrient automated cooling system keeps the nutrient solution temperature at between 22℃and 26℃. Temperatures below or above the stipulated range either affect the uptake of nutrients or damage the rooting system.
• The project also installed an automated temperature control system composed of misters and showers in the screen house to keep temperatures between the range of 25℃ and 32℃. Once the temperature reaches 32℃, the system turns on and turns off when the temperature reaches 28℃.
• The first screen house in which the AS was established was not conducive for yam growth. The screen house required more height and width for improved aeration to maintain temperatures for healthy plant growth and development. A new structure with enhanced dimensions was constructed.

The project also looked at maximizing field production with limited resources. In 2017, the project started field planting of AS single node vine seedlings with a density of 40,000 per hectare. However, at harvest, 60% of the tubers weighed between 500 g and 1000 g. While the AS vines cutting seedlings showed promise in generating ware size tubers, the project and seed companies need seed size tubers of about 10 g to 150 g (need confirmation on this). After two consecutive trials of planting at a density of 100,000 per hectare under rainfed conditions, the number of big tubers significantly reduced.

At IITA Abuja station, Dr. Beatrice Aighewi conducted in-depth production research on vine cutting production and management for optimal growth and maximizing the screen house space to produce mini tubers. The following are protocols to observe when cutting vines for seedling production:

Cutting and planting

• Cut vines when the plant is turgid (during a dry spell, water plants the day before)
• Cut the vine from the mother plant leaving at least two nodes to produce new shoots.
• Place the cut vine into a water container to prevent the loss of water from the vines through the cut surfaces.
• Make a clean cut through the vine at an angle, with each cutting containing one tiny bud, one leaf, and about a 2 cm stem piece on either side of the node.
• Drop cuttings into the fungicide solution.
• Cuttings should be planted as soon as possible.

Maintenance of cuttings in a nursery

• Water the substrate and plant cuttings early in the morning and/or evening when the temperature is lowest to reduce losses from evaporation.
• Periodically mist over the cuttings to reduce the temperature of the leaves and evaporation. This is critical during the first two weeks of planting.
• Keep the planting medium moist (not wet) and maintain high relative humidity around the plants to encourage rooting.
• Do not apply too much water to avoid a loss of nutrients through leaching (reducing oxygen within the substrate).
• Where automatic sprinklers are used, adjust the timers to suit ambient conditions.
• Use mulch and an overhead shade to reduce evaporation.
• The addition of organic matter to the planting medium increases the water retention capacity
• The leaves of cuttings should stay turgid, especially during the first two weeks of planting (not flaccid or rolled up at the sides, which indicates dehydration)
• Apply fertilizer when needed depending on the type of substrate used.

Dr. Lava Kumar talked about the regulatory requirements for Early Generation Seed (EGS) production under seed certification. Given the novelty of the production system, new certification methods needed to be developed. In the formal seed yam system, two certification methods will be employed to ensure quality. For breeder seed in the lab and screen house, seed companies will have to get accreditation for their labs and screen houses. Conventional certification will be employed for field production of foundation and certified seed production. According to Dr. Lava Kumar, the formal seed yam system uses a stage-gate approach to ensure the quality of the planting materials. He explained that each technology represents a production stage, and each technology has a biosecurity level commensurate to the seed class. Therefore, decisions on quality and management can be easily determined.