FACULTY OF AGRICULTURE
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Item Yam propagation using 'aeroponics' technology(2014) Maroya, N.; Balogun, M.; Asiedu, R.; Aighewi, B.; Kumar, L.; Augusto, J.Aims: To study yam propagation and seed yam tuber production in aeroponics system. Study Design: The experiment was conducted in a randomized complete block design and treatments were replicated three times. Place of Study: This experiment was carried out at the International Institute of Tropical Agriculture Headquarters at Ibadan in Nigeria. Methodology: The experiment tested fresh vine cuttings of five yam genotypes of two species 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 and TDa 291) were evaluated. Results: Vines of both D. rotundata and D. alata rooted within 2 weeks in aeroponics system. The rooting of vine cuttings varied significantly among genotypes with a maximum of 98% for TDa 98/01176 and a minimum of 68% for TDr 89/02665. Mini-tubers harvested after 4 months of growth in aeroponics weighed between 0.2 and 2.7g. A second harvest 6 months later gave mini-tubers of up to 110g. The analysis of variance showed significant difference (P<0.05) among genotypes for rooting at 2 weeks after vine planting, number of plant 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 planting and percentage of plant producing bulbils in the aeroponics system respectively. Conclusion: This study revealed that yam genotypes performed differently in aeroponics system for vine rooting and production of mini-tubers and bulbils.Item Status and prospects for improving yam seed systems using temporary immersion bioreactors(Academic Journals, 2014-04) Balogun, M. O.; Maroya, N.; Asiedu, R.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.Item RESPONSE OF YAM (Dioscorea spp.) ACCESSIONS TO DROUGHT AND ARBUSCULAR MYCORRHIZAL FUNGI(2016) Odoh, N. C.Moisture deficit limits yam production. Availability of drought tolerant yam will improve yield and expand area of production. Soil inoculation with Arbuscular Mycorrhizae Fungi (AMF) improves tolerance of plants to drought. However, there is limited information on the response of yam to drought and AMF inoculum. This study was conducted to identify drought tolerant yam accessions and determine the effects of AMF.Two glasshouse and one field experiments were conducted, each in a randomized complete block design with three blocks. In the first glasshouse experiment, 32 accessions of Dioscorea alata and 49 of D. rotundata obtained from the International Institute of Tropical Agriculture, Ibadan were screened for drought tolerance. Pre-sprouted setts were planted in pots containing 5 kg soil, watered to Field Capacity (FC), wrapped with transparent polyethylene sheets and observed for 90 days. Twelve accessions of each species selected on the basis of their superior performance were further evaluated at three moisture levels: 75% FC at 11 Weeks After Planting (WAP) 25% FC at 15 WAP and 25% FC at 11 WAP,with and without AMF inoculation. Three promising drought tolerant accessions of each species were selected from the second experiment and evaluated in the field. Treatments were two irrigation intervals with 12 mm water (four-day and monthly), three planting dates (monthly: July, August, September) and AMF inoculations (with and without) laid out as split-split-split plot. Data were collected on Fresh and Dry Tuber Weight (FTW and DTW), Harvest Index (HI), mycorrhizal colonisation and number of AMF spores. Data were analysed using descriptive statistics, correlation and ANOVA at α 0.05.The accessions differed significantly in their response to water- and AMF- levels for most growth and yield parameters. The FTW per plant ranged from 24.0±7.7 g (TDa02/00012) to 54.0±10.0 g (TDa297) in D. alata and 13.0±1.8 g (TDr99/02789) to 57.0±9.2 g (TDrAbi) in D. rotundata. Drought stress at 25% FC, 11 WAP resulted in 83% reduction in FTW as compared to a decline of 67.8% at 25% FC, 15 WAP in D. alata. Mycorrhizal inoculation significantly increased the FTW by 58% and DTW by 112% for D. alata while increases of 33% and 38%, respectively were recorded for D. rotundata. The FTW (D. alata and D. rotundata) was significantly correlated with DTW (r= 0.89, 0.91), HI (r= 0.80, 0.78), number of AMF spores (r= 0.53, 0.55) and mycorrhizal colonisation (r= 0.32, 0.30) respectively. In the field, irrigation at four-day intervals improved tuber yield of D. rotundata by 50% relative to monthly irrigation. The highest FTW (10±0.7 t/ha) for D. alata was obtained with the July planting while the September planting had the least (3±0.7 t/ha). Across treatments, accessions TDa02/00012 of D. alata and TDrSaminaka of D. rotundata had the highest FTW of 7.0±1.0 t/ha and 5.0±1.0 t/ha, respectively.Variation for drought tolerance exists among D. alata and D. rotundata accessions studied. Mycorrhizal inoculation improved yam yield under moisture stress. Accessions TDa02/00012, TDa93-36, TDaKesofunfun of D. alata and TDrSaminaka, TDrAloshi, TDrAbi of D. rotundata were most drought tolerant