Cassava (Manihotes culenta Crantz) is among major food and income security crops in sub-Saharan Africa. However, high seed dormancy and delayed germination limit seed propagation. Using traditional stem cutting causes loss of superior genotypes and decreases productivity as a result of low multiplication ratio (1:10) and viral and bacterial diseases.Thus, the aim of this study was to optimize and screen efficient in vitro protocols for rapid multiplication and production of disease-free cassava planting materials through nodal culture technique. The experiment was laid out in a 5 x 5 factorial arrangement in Completely Randomized Design with five cassava genotypes (Warima, Munafa, SLICASS 6, Coco cassada and SLICASS 7) and five BAP supplemented MS medium (0, 0.02, 0.1, 1.0 and 2.0 mg/L), replicated three times. Results revealed that, BAP supplement significantly (p<0.001) influenced numbers of leaves and shoots compared to plantlet height growth traits of nodal cassava explants in culture. Virus indexing of infected plants from screen house using species specific primer pairs, OjaRep/EACVMRep and OjaRep/ACMVRep, confirmed the presence of East Africa Cassava Mosaic Virus (EACMV) and the African Cassava Mosaic Virus (ACMV) at an amplicon of approximately 650bp and 400bp, respectively. The study demonstrated the effectiveness of cytokinin supplemented MS medium in enhancing growth of cassava; and the adequacy and effectiveness of the PCR technique in identifying ACMV and EACMV using nodal cuttings. Future studies will involve molecular characterization of the EACMV strain(s) existing in the country.

A study on rapid propagation of cassava through tissue culture was conducted with three elite cassava genotypes: Slicass 6, Slicass 11 and Cocoa from Sierra-Leone. They showed slow growth in Murashige & Skoog (MS) basal medium which was proven to be optimal for a vast number of cassava accessions. Prior to mutation induction, a large population needs to be produced for mutagen susceptibility test and for mutant population development. The ultimate objective of this study was to investigate the effects of plant growth regulators on the shoot development of three cassava genotypes. In vivo shoot tips were sterilized and sub-cultured on MS media supplemented with six combinations of plant growth regulators (PGRs) at different concentrations. The results showed that from all media used, the MS medium with 1.0 mg/L α-naphthalene acetic acid (NAA) showed the best response for rooting (5.50), fresh weight (0.29 g), root number (10.00) and plantlet height (3.81 cm), while 0.1 mg/L 6-benzylaminopurine (BAP) was found to be more favourable to shoot development of leaves (6.38). The highest plant height and fresh weight were 3.81 cm and 0.29 g, respectively for Cocoa at 1.0 mg/L α-naphthalene acetic acid (NAA), 10.00 roots for Slicass 6 at 1.0 mg/L, 6.37 leaf numbers for Slicass 11 at 0.1 mg/L 6-benzylaminopurine (BAP) and 5.6 at 1.0 and 1.5 mg/L α-naphthalene acetic acid (NAA). These observations indicate that a supplement of 0.1 mg/L 6-benzylaminopurine (BAP) in MS medium can be useful in propagation of recalcitrant cassava and low concentration of α-naphthalene acetic acid (NAA) will be beneficial in root induction prior to acclimatization with promotion in recovery of the ex vitro plants before field assessment.

<p>A study on economic evaluation of some weed management strategies and herbicide residues analysis on roots of cassava (<em>Manihot esculenta</em> Crantz) was conducted during 2014 and 2015 cropping season in Kumasi, Ghana. Cost and benefits were computed from the use of two manual weedings (hoeing and cutlassing), two pre-emergence herbicides (Butachlor 60% EC and Terbulor 500 EC) with two-supplemenatary hoe weeding, weed-free and weedy check. These were evaluated using two varieties of cassava, Ampong (Early branching) and Dokuduade (Late branching). The treatment was a factorial laid out in a randomized complete block design (RCBD) with four replicates. Partial farm budgeting were used for economic analysis of data and herbicide residues analysis in roots of cassava were determined using Gas Chromatography-Electron Capture Detector (GC-ECD). Results showed that Terbulor 500 EC with two supplementary hoe weeding was more economical, profitable and beneficial than those other treatments applied in the production of cassava. In addition, the average concentration of Terbulor 500 EC (0.003 mg/kg) and Butachlor 60% EC (0.001 mg/kg) residues in roots of cassava varieties were below the maximum residue limit (MRL) of 0.01 mg/kg set by Ghana Standards Authority for cassava. In conclusion, Terbulor 500 EC with two supplementary hoe weeding was more effective and financially rewarding and both herbicides had lower residual effects on cassava.</p>

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A two-year (2017 and 2018) field trials was conducted in the School of Agriculture, Njala University, Sierra Leone, to evaluate weed management practices on weed dynamics and productivity of maize. The experimental trials were laid out in a randomized complete block design (RCBD) with three replications. The treatment combinations comprised of weedy check (Control), two hoe weeding at 4 and 8 weeks after planting (WAP), Double force ® at 4 L ha -1 plus one hoe weeding at 8 WAP, Gliricidia sepium leaves mulch at 40 kg m -2 plus one hoe weeding at 8 WAP, weed-free check and Atrazine 500 SC at 3 L ha -1 plus one hoe weeding at 8 WAP. The results showed that growth and yield physiognomies differ significantly (P<0.05) among weed control practices across both years. The weed-free check treatment recorded the highest growth and yield physiognomies with respect to reduced weed density and increased weed control efficiency followed by herbicidal treatments, while weedy check had the lowest growth and yield attributes across both years. Nonetheless weed-free check required lot of labour force which was not economical to the farmer's point of judgment. Thus, Double force ® at 4 L ha -1 plus one hoe weeding at 8 WAP proved to be better in controlling weeds, increasing crop yield and economical compared with other weed management practices. Hence Double force ® at 4 L ha -1 plus one hoe weeding at 8 WAP was recommended as a pre-emergence herbicide in maize production for effective and environmentally friendly weed control method.

Au cours de la dernière décennie, les accessions du manioc de la République Centrafricaine ont fait l’objet de nombreux travaux entre autres les cultures in vitro et la micropagation. Cependant les plants issus de la culture in vitro nécessitent une période d'acclimatation avant leur transfert en champ, d’où l’intérêt de cette étude dont l’objectif était d’évaluer l’effet de la qualité du sol et des facteurs de croissance sur l’acclimatation. Des explants de jeunes pousses obtenus à partir de la culture des segments nodaux sous serre étaient transplantés dans des tubes à essai contenant le milieu MS et placés dans la salle de croissance. Les microboutures issues de la culture in vitro ont été traitées avec des phytohormones de croissances et repiquées dans des bacs de culture contenant le fumier et le sol et replacées sous serre. En outre, les plantules issues de la culture in vitro ont été transférées ex vitro en entier dans des pots de culture contenant le fumier et le sol pour suivie sous serre. La micropropagation ex vitro a montré le meilleur taux de survie dans le fumier que dans le mélange respectivement de 90% et 45%. Une meilleure croissance en hauteur a été révélée dans le fumier que dans le sol avec respectivement 2,68 cm et 1,05 cm. Ces observations étaient également confirmées par le plan d’expérience de transfert ex vitro des plantules entières dans les pots. Les données auxiniques sur le fumier ont révélé que l’Acide Indole-3-Acétique (ANA) semble être plus indiquée pour l’acclimatation que Acide Indole-3-Butyrique (AIB) et Acide α-Naphtalène acétique (ANA). Cette technique développée sur une accession de manioc pourrait être étendue à d'autres accessions et d’autres espèces végétales d’intérêt agronomique. Over the last decade, cassava accessions in the Central African Republic have been the subject of numerous studies, including in vitro culture and micropagation. However, the acclimatization of in vitro-grown plantlets to an ex vitro environment by gradually weaning them towards ambient relative humidity for the better survival of young and physiologically sensitive plantlets. This study therefore aimed to evaluate the effect of soil quality and growth factors on acclimatization. Sprouted shoots obtained from greenhouse nodal segment culture were transplanted into test tube containing MS medium were incubated in a controlled growth room. Microcuttings from in vitro culture were treated with growth phytohormones and transplanted in culture trays containing manure and soil and placed in the greenhouse. In addition, the seedlings from in vitro culture were transferred ex vitro whole into culture pots containing manure and soil for follow-up in the greenhouse. The ex vitro micropropagation showed the best survival rate in manure than in the mixture of 90% and 45% respectively. Better height growth was revealed in manure than in soil with 2.68 cm and 1.05 cm respectively. These observations were also confirmed by the experimental design of ex vitro transfer of whole seedlings in pots. The auxin data on manure revealed that Indole-3-Acetic Acid (IAA) seems to be more suitable for acclimatization than Indole-3-Butyric Acid (IBA) and α-Naphthalene Acetic Acid (NAA). This technique developed on a cassava accession could be extended to other accessions and other plant species of agronomic interest.

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