Department of Biological Sciences
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Item Development of in vitro propagation protocol for some recalcitrant cassava (Manihot esculenta Crantz) genotypes in Sierra Leone(Academic Journals, 2018-05-02) Sesay, Janatu VeronicaA 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. Key words: Cassava, Manihot esculenta, propagation, shoot tip, 6-benzylaminopurine (BAP), α-naphthalene acetic acid (NAA).Item Predicting the adoption of improved cassava varieties in Sierra Leone(Academic Journals, 2021-02-15) Sesay, Janatu VeronicaIn Sierra Leone cassava plays a major role in households’ food and income security. Plant breeders have concentrated on improved varieties with an increasing yields per unit area. This study was designed to identify factors that influence adoption or rejection of improved cassava cultivars by growers. Data were collected using questionnaires, focus group discussions and field walks; locations were selected using multistage stratified random sampling. Logistic regression was used to model uptake of improved varieties. Most farmers usually grow several cultivars and just over half have included an improved variety. Of the six improved varieties released in 2005 by the Sierra Leone Agricultural Research Institute, only SLICASS 4, was widely adopted and three were not recorded in the study. Preferred characteristics are; high yield, sweet taste, early maturity and good cooking quality. Cultivars are more likely to be adopted where; cassava is a major crop, households are experienced in cultivating cassava, they have access to research, contact with extension agents and access to cassava markets. Improved cultivars are less likely to be adopted by small households with few resources. Cassava breeders should recognize what farmers find desirable but success will depend on; communicating research, having active extension agents and good access to markets. Key words: Adoption, improved varieties, cassava, Sierra Leone.Item Genetic Structure and Diversity Study of Cassava (Manihot esculenta) Germplasm for African Cassava Mosaic Disease and Fresh Storage Root Yield(Scientific Research Publishing, 2023) Sesay, Janatu VeronicaA better understanding of population structure and genetic diversity among cassava germplasm for African cassava mosaic disease and fresh root yield traits is useful for cassava improvement programme. Phenotype-based selection for these traits is cumbersome due to phenotypic plasticity and difficulty in screening of phenotypic-induced variations. This study assessed quantitative trait loci (QTL) regions associated with African cassava mosaic disease (ACMD) and fresh storage root yield (FSRY) in 131 cassava (Manihot esculenta) genotypes using a genome-wide association study (GWAS). The single nucleotide polymorphism (SNP) loci and associated candidate genes, when validated, would be a valuable resource for marker-assisted selection in the breeding process for development of new cassava genotypes with improved resistance to ACMD and desirable high root yield. Population structure analysis using 12,500 SNPs differentiated the 131 genotypes into five distinct sub-groups (K = 5). Marker-trait association (MTA) analysis using the generalized linear model identified two QTL regions significant for ACMD and three for FSRY. This study demonstrated that DArTseq markers are useful genomic resources for genome-wide association studies of ACMD and FSRY traits in cassava for the acceleration of varietal development and release.Item Ethnobotanical Knowledge of Local Cassava Varieties and Characteristics Desired by Farmers in Sierra Leone(Scientific Research Publishing, 2023) Sesay, Janatu VeronicaIt has been observed that farmers adopt only a small number of the “improved” cultivars. A nationwide germplasm collection exercise in February 2018 provided the opportunity to collect indigenous technical knowledge (ITK) of the diversity of cassava varieties in terms of: their morphology, growth characteristics, uses (of tubers and leaves) and desirable characteristics. The objective is to see to what extent the objectives of the plant breeders are consistent with what farmers’ value. We performed 405 structured and semi-structured interviews with informants who were selected based on “purposive household sampling”. We found a considerable turn-over in cassava varieties, just over a third (45) have been in cultivation for at least 40 years, however, since the end of the civil war an additional 25 varieties are cultivated, while others varieties seem to have disappeared. One major issue with estimating turnover of varieties is whether the same variety might have several local names, and conversely the same name may be applied to different cultivars. Farmers overwhelmingly use ITK to select and preserve cassava germplasm for future use. Farmers have a clear preference for: sweet taste, high yield, early maturity and easy cooking and preferentially adopt cultivars that have those qualities. Cassava is primarily a human food eaten boiled or fried, some are processed into fufu and gari, and uses as livestock feed and medicine are reported but at low levels. The information produced during this study could help plant breeders choose selection criteria that will ensure their efforts are adopted and sustainable, the importance of preserving the genetic resources of local cultivars is also highlighted.