Evaluation of growth and yield of seed tubers from some yam (Dioscorea rotundata Poir) varieties using vine cuttings in different substrates in Abuja, Nigeria

Yam (Dioscorea rotundata Poir) is a valuable food security crop in West Africa, accounting for 92% of global production. As a clonal crop, its vegetative propagation involves the use of whole tubers or sett. Improving yam productivity can increase food production and farmers’ income in yam-producing areas, particularly in West Africa. The planting material is very expensive, has a low multiplication ratio, and competes with food, as farmers usually reserve up to 30% of their previous harvest to plant the next crop. This study seeks to use vine cuttings, which have a higher multiplication ratio, as an alternative to the tuber for yam propagation, thereby saving the tuber for use as food. Two trials were conducted in the screen house during the 2020 and 2021 cropping seasons, while another two were conducted in the field during the 2021 and 2022 rainy seasons. These trials were conducted at the International Institute of Tropical Agriculture Research Station in Kubwa, Abuja, Nigeria. In the screen house, the first experiment was set up to test the relative efficiency of composite substrates for seed yam production using vine cuttings of two yam varieties (Asiedu and Kpamyo). Substrates (cocopeat (CP), Composted rice husk (RH), and topsoil (TS)) were mixed in the following ratios: 25%:75%, 50%:50%, and 75%:25%. Vine cuttings were planted in seed trays using these substrates. Experiment two was to compare different hydroponic substrates in producing seed yam from vine cuttings of selected yam varieties. Vine cuttings of Asiedu and Kpamyo were planted in hydroponics substrates of cocopeat, carbonised rice husk, composted rice husk, river sand and topsoil. These trials were laid out as a Randomised Complete Block Design (RCBD) with three replications. The collected data were analysed using analysis of variance. Results obtained showed that the mean per cent vine survival of Kpamyo and Asiedu at 4 weeks after planting (WAP) as influenced by various composite substrates was over 83.0% except for the control x plot, which had the least survival (73%). Fresh tuber yield (g/m2) ranged from 208.3 to 1014.8 g/m2. The best composite substrate was 25% cocopeat mixed with 75% composted rice husk, which showed a 433.54% yield increase over the control plot. For experiment two, the fresh tuber yield (g/m2) of Asiedu and Kpamyo, as influenced by hydroponic substrates, ranges from 988.6 to 1677.7 g/m2. The best hydroponic substrate was composted rice husk, which showed a 826.91% yield increase over the control plot. Composted rice husk was the best substrate for seed yam production; however, the combination of 25% cocopeat plus 75% composted rice husk increased the suitability of the substrate for vine-cutting growth and seed yam production. The high-quality seed yams produced from the screen house experiments were used to establish two field trials to evaluate their growth and yield. The trials were laid out as a Randomised Complete Block Design (RCBD) with three replications. Results showed that tubers produced from composite substrates attained plant stands of 89.4% and 90.4% at 6 WAP for Asiedu and Kpamyo, respectively. The tubers produced from hydroponic substrates had plant stands of 90.5% and 92.2% at 6 WAP for Asiedua and Kpamyo, respectively. For both trials, the highest fresh tuber yield (28.7 t/ha) was obtained from Kpamyo tubers produced from composted rice husk. This shows that minitubers produced in the screen house using vie cuttings in substrates are very viable for field production of seed yam and are recommended for use by farmers and seed companies for large-scale production, thereby reducing the cost of seed yam.