Crop Protection & Environmental Biology
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Item Clean breeder seed yam tuber production using temporary immersion bioreactors(International Institute of Tropical Agriculture (IITA), Ibadan, 2017) Balogun, M.; Maroya, N.; Taiwo, J.; Ajayi, A.; Ossai, C.; Lava, K.; Pelemo, O.; Aighewi, B.; Asiedu, R.Item Manual for clean foundation seed yam production using aeroponics system(International Institute of Tropical Agriculture (IITA), Ibadan, 2017) Maroya, N.; Balogun, M.; Aighewi, B.; Lasisi, J.; Asiedu, R.Item Effects of basal medium and plant growth regulator regimes on meristem and nodal cultures in white yam (D. rotundata)(International Institute of Tropical Agriculture, Ibadan, Nigeria, 2017) Ajayi, A.; Balogun, M.; Maroya, N.; Asiedu, R.Item The Response of white yam (dioscorea rotundata poir) tuber portions to positive selection for quality seed yam production(2017) Aihebhoria, D.; Aighewi, B.; Balogun, M.The production of yams is constrained by high cost and unavailability of clean planting materials, pests and diseases. Vegetative propagation has also caused a build of up diseases, reported to cause up to 80% yield reduction due to scarcity of quality declared seeds. Planting of disease-free material has been found to be effective in reducing disease problems in plants. This study was conducted to produce clean seed yam by reducing yam diseases through positive selection method. In this method, apparently healthy yam plants were identified, tagged (positive selection), assessed for yam mosaic virus incidence and severity using the scale 0 or 1 and 1-5 respectively. The harvested clean tubers from tagged plants were planted the following season so as to determine the rate of response of each genotype and tuber portion to positive selection. At the end of two cycles of positive selection, analysis of variance for percentage number of positive yam plants, YMV incidence, YMV severity and tuber yield shows significant difference (p ≤ 0.05) between positive selection and no selection for both field and screen house plants. It was observed that positively selected plants performed significantly (p ≤ 0.05) better than no selection plants. For field experiment, Number of positively selected plants was highest in positive TDr89/02665 with mean value of 75.00% while no selection Ogoja had the least number of positive plants (17.8%). A yield increase of 1.80 t/ha was recorded due to the application of positive selection method in two cycles. For screen house experiment, result followed a similar trend; however, with a reduction in YMV incidence and severity. It is worthy to note that tail portions of yam were lest infected with YMV, hence more healthy plants were selected from the tail portion.Item Relative efficiency of positive selection and tissue culture for generating pathogen-free planting materials of yam (dioscorea spp.)(2017) Balogun, M.; Maroya, N.; Augusto, J.; Ajayi, A.; Kumar, L.; Aighewi, B.; Asiedu, R.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 tis¬sue 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 deter¬mined 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.Item Improved propagation methods to raise the productivity of yam (dioscorea rotundata poir.)(Springer, 2015-07) Aighewi, B.; Asiedu, R.; Maroya, N.; Balogun, M.White Guinea yam (Dioscorea rotundata Poir.) is an important staple to millions of people in West Africa. Obtaining good quality planting material for yam cultivation is a major challenge. Multiplication ratios are low, and seed tubers are prone to contamination with pests and pathogens in the traditional systems of production. Some approaches to producing quality seed of yam are as follows: farmers select small whole tubers from a ware crop harvest; stimulate the production of seed tubers by ‘milking’ ware tubers while the leaves of the plant are still green (double harvest system); cut ware tubers into setts about the same sizes as regular seed tubers; or use the ‘Anambra’ system where smaller setts are cut and used to produce seed tubers. New methods that have been developed to address some of the challenges of quantity and quality of seed tubers are not yet widely applied, so farmers continue to use traditional methods and save seed from a previous harvest to plant the ware crop. This document presents an overview of traditional and modern methods of seed yam production and gives a perspective for the future. Among the modern methods of seed yam production, only the minisett technique, which uses 25–100 g tuber pieces, is currently used at farmer level, although on a limited scale. While tissue and organ culture techniques are the most rapid methods of multiplying disease free propagules, their limitations include high costs, need for skilled personnel and specialized equipment. The aeroponics and temporary immersion bioreactor methods of producing seed yam are relatively new, and still need more research. To build and sustain a viable seed yam production system, a multiplication scheme is required that combines two or more methods including tissue culture for cleaning the seed stock.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 of biotechnology applications to conservation, propagation and genetic improvement of yam(CRC Press, 2013) Balogun, M.; Gueye, B.Yam plays a critical role in providing good quantity and quality yield and source of income to combat the challenge of food insecurity in the tropics. Although significant advances in science and technology have improved efficient management and improvement of their genetic resources, the mission of fully exploiting their potentials is yet to be maximally achieved. Lack of formal seed systems increases germplasm losses and reduces yields. Research is needed in the control of tuber dormancy in yam. Biotechnological approaches, especially in vitro culture of meristem/shoot tip combined with thermo/cryotherapy are promising methods to clean yam seeds of pathogens like viruses. The multiplication of clean yam seeds so obtained can be propagated using improved systems such as temporary immersion bioreactors, aeroponics and photoautotrophic systems but knowledge gaps still exist on their use. Although the relative importance of clean materials, survival on farmers’ fields, production cost and multiplication ratio should be determined and considered in deciding the propagation technique to adopt, conventional and improved tissue culture techniques will be indispensable in the production of clean seed yams. Marker-assisted selection, embryo culture, genetic transformation and genome sequencing have been initiated to support conventional genetic improvement, but investigations into the presence of transposable elements, site targeted mutagenesis, somatic embryogenesis and haploid plant production will be necessary to fast track the genetic improvement. These biotechnological approaches will not only enhance the use of disease-free, quality-declared planting materials but also facilitate germplasm exchange and speed up genetic improvement while providing excellent means for conservation.