Farmers’ perceptions of practices and constraints in cassava (Manihot esculenta Crantz) chips production in rural Cameroon

A survey aimed at collecting information on practices and constraints in the production of cassava (Manihot esculenta Crantz) chips, a transformed cassava product obtained through fermentation anddrying of its fresh roots was carried out in 45 villages located in three geographical regions (Yaoundé, Mbalmayo, and Ebolowa) of the humid forest zone of Cameroon. A structured questionnaire to interviewfarmers was employed. Out of 225 farmers sampled, 212 (94%) relying on chips as food and source of income were women. Overall, 51% of all farmers marketed chips locally. Three distinct forms of chipssuch as broken pulp (62%), balls (25%), and pellets (13%) were cited as being locally produced by farmers. These were obtained either through air fermentation (cassava pellets), or submergedfermentation (broken pulps and balls), using starters or fermenting agents (31% of responses) or without using them (69%). Chips were mainly home-stored in jute and or/plastic bags (43% ofresponses), open or closed containers (36%), or on devices hanging over the fireplace (21% of responses) for as long as 180 days. Dark spots or discolouration occurring as a result of chips damagewere reported by the majority of respondents (82%) as frequent on cassava chips. These were related to insufficient drying (42%), the use of infected cassava roots by plant pathogenic microbes from thefields (12%), or too long drying of chips under sun light (11% of responses). To avoid dark spots and/or discolouration, 112 farmers out of a total of 185 who were aware about chips damage, practiced sundrying, and 21% of this total dried their chips over the fireplace to control chips damage. Pests and diseases problems (47% of responses), mainly related to the incidence of Stictococcus vayssiereiRichard (Homoptera: Stictococcidae) and lack of market (26%) were cited by farmers as the most important constraints in cassava chips production. From the results obtained, this study outlined thatthe potential utilization of cassava and its derived products for industrial purposes is not yet exploited in the locations investigated. Additionally, the study also raised concerns about the safety and hygiene associated with traditionally processed and stored cassava chips in the investigated areas

Isolation of Monoclonal Antibodies with Predetermined Conformational Epitope Specificity

Existing technologies allow isolating antigen-specific monoclonal antibodies (mAbs) from B cells. We devised a direct approach to isolate mAbs with predetermined conformational epitope specificity, using epitope mimetics (mimotopes) that reflect the three-dimensional structure of given antigen subdomains. We performed differential biopanning using bacteriophages encoding random peptide libraries and polyclonal antibodies (Abs) that had been affinity-purified with either native or denatured antigen. This strategy yielded conformational mimotopes. We then generated mimotope-fluorescent protein fusions, which were used as baits to isolate single memory B cells from rhesus monkeys (RMs). To amplify RM immunoglobulin variable regions, we developed RM-specific PCR primers and generated chimeric simian-human mAbs with predicted epitope specificity. We established proof-of-concept of our strategy by isolating mAbs targeting the conformational V3 loop crown of HIV Env; the new mAbs cross-neutralized viruses of different clades. The novel technology allows isolating mAbs from RMs or other hosts given experimental immunogens or infectious agents

Cassava production and processing characteristics in southern Cameroon: an analysis of factors causing variations in practices between farmers using Principal Component Analysis (PCA)

A questionnaire-based survey study was carried out during a 3 month period, from January to April 1998, in 45 villages belonging to three locations (Yaoundé, Mbalmayo, and Ebolowa) of southern Cameroon. The survey was aimed at collecting constraints and processing practices related information from farmers growing cassava and transforming it into chips. Information in the questionnaire contained some characteristics associated with cassava chips production (processing methods, forms of chips produced, their end uses, drying and storage facilities used, the major problems associated with their production) and cassava cultivation (cassava varieties, harvesting periods of these varieties, and their preferred attributes). A total of 225 farmers were interviewed and the results obtained showed that farmers in Yaoundé and Mbalmayo processed and stored chips in similar ways. Similarly, harvesting periods after planting also differed between Ebolowa and both Yaoundé and Mbalmayo. Storage methods and storage facilities were mainly related to the different forms of chips produced. Chips’ discoloration frequently reported by the majority of farmers (87%) was as a result of their insufficient drying. Principal component analysis was implemented to determine those factors accounting for differences observed in farmers’ practices. Eleven principal components were derived from the variables used in analysis. Five principal components accounting for 72.75% of the total variations were associated with the data set collected in Yaoundé and Mbalmayo. An equal number expressing 78.2% of the overall variance was likewise obtained at Ebolowa. For a number of reasons such as traditional patterns of nutrition, market purposes, the relative proximity with the nearest city, these components suggested that storage methods, end uses, and production constraints were differently perceived by the respondents. They also showed that the different forms of chips produced were more market oriented, and that a number of constraints experienced by farmers were closely related to the way they managed their fields, or market outlets

Aspergillus species of cassava chips in storage in rural areas of southern Cameroon: their relationship with storage duration, moisture content, and processing methods.

A survey was carried out to monitor during a two-month period the incidence of Aspergillus in samples of stored cassava chips traditionally produced in southern Cameroon. Seventy-two samples associated with two forms of chips (cassava balls and cassava pellets) were collected in two locations (Yaoundé and Ebolowa) and 13 Aspergillus species were isolated. In both locations, Aspergillus versicolor was seldom isolated, whereas A. flavus and A. clavatus were most frequently isolated. The level of recovery of isolates obtained was not affected by location and form of chips, but by the duration of storage (P < 0.01) and the moisture content (P < 0.05). Five core species were identified, which formed more than 70% of the total isolates associated with the samples analyzed. These were A. clavatus, A. flavus, A. fumigatus, A. niger and A. ochraceous. Correlation coefficients computed between pairs of these species based on total isolation figures for the two locations showed that some were significantly associated. A. clavatus, A. niger and A. ochraceous were positively related to one another in a significant way. Similarly, significant correlations, positive or negative, were observed between the moisture content and all core Aspergillus species. The larger number of these toxigenic fungi isolated raises concerns on the potential of stored cassava products as a natural substrate liable to mycotoxin formation

Aflatoxin-producing Aspergillus spp. and aflatoxin levels in stored cassava chips as affected by processing practices

Cassava chips (cassava balls, and cassava pellets) are derived cassava products traditionally produced byfarmers in sub-Saharan Africa following fermentation, and drying of fresh roots of cassava, and are widelyconsumed in Cameroon. Once produced, this food commodity can be stored for more than two monthsand contaminated by a wide array of harmful microbes. In order to assess persistence of toxigenic fungiin cassava chips, aflatoxin-producing fungi (Aspergillus flavus, Aspergillus nomius,andAspergillus parasit-icus) and aflatoxins were contrasted at regular intervals in home-stored cassava chips collected in twolocations of southern Cameroon throughout a two-month monitoring period. Three hundred and forty-six isolates of aflatoxin-producing fungi were found to be associated with all samples.A. flavuscontam-inated more samples in both types of chips (267 isolates in 53 samples), followed byA. nomius(58 iso-lates in 15 samples), whereasA. parasiticuswas rarest. A direct competitive Enzyme-linkedimmunosorbent assay (ELISA)-based method was implemented to quantify the content in aflatoxins.Eighteen of the samples contained some aflatoxins at detectable levels whereas 54 did not. The levelsof aflatoxin ranged between 5.2 and 14.5 ppb. The distribution of aflatoxin in positive samples dependedon 8 parameters including pH, moisture content, storage duration, types of chips, level of contaminationby aflatoxin-producing fungi, processing practices and storage facilities. From analysis of variance results,only pH (p< 0.01), duration of storage (p< 0.01), population of aflatoxin-producing species (0.0001) andthe chip type (p< 0.05) were significantly related to aflatoxin in positive samples. A stepwise regressionanalysis (forward selection procedure) indicated that aflatoxin levels were significantly (p< 0.01) corre-lated with processing practices, storage facilities, and storage duration of the chips

Farmers perceptions of practices and constraints in cassava (Manihot esculenta Crantz) chips production in rural Cameroon

A survey aimed at collecting information on practices and constraints in the production of cassava (Manihot esculenta Crantz) chips, a transformed cassava product obtained through fermentation and drying of its fresh roots was carried out in 45 villages located in three geographical regions (Yaoundé, Mbalmayo, and Ebolowa) of the humid forest zone of Cameroon. A structured questionnaire to interview farmers was employed. Out of 225 farmers sampled, 212 (94%) relying on chips as food and source of income were women. Overall, 51% of all farmers marketed chips locally. Three distinct forms of chips such as broken pulp (62%), balls (25%), and pellets (13%) were cited as being locally produced by farmers. These were obtained either through air fermentation (cassava pellets), or submerged fermentation (broken pulps and balls), using starters or fermenting agents (31% of responses) or without using them (69%). Chips were mainly home-stored in jute and orplastic bags (43% of responses), open or closed containers (36%), or on devices hanging over the fireplace (21% of responses) for as long as 180 days. Dark spots or discolouration occurring as a result of chips damage were reported by the majority of respondents (82%) as frequent on cassava chips. These were related to insufficient drying (42%), the use of infected cassava roots by plant pathogenic microbes from the fields (12%), or too long drying of chips under sun light (11% of responses). To avoid dark spots andor discolouration, 112 farmers out of a total of 185 who were aware about chips damage, practiced sundrying, and 21% of this total dried their chips over the fireplace to control chips damage. Pests and diseases problems (47% of responses), mainly related to the incidence of Stictococcus vayssierei Richard (Homoptera: Stictococcidae) and lack of market (26%) were cited by farmers as the most important constraints in cassava chips production. From the results obtained, this study outlined that the potential utilization of cassava and its derived products for industrial purposes is not yet exploited in the locations investigated. Additionally, the study also raised concerns about the safety and hygiene associated with traditionally processed and stored cassava chips in the investigated areas

Control of leaf spot disease caused by Cercospora sp on groundnut (Arachis hypogaea) using methanolic extracts of yellow oleander (Thevetia peruviana) seeds

Abstract A study was carried out in Yaounde (Cameroon) on two cultivars of groundnuts treated with methanolic extracts of Thevetia peruviana seeds (METPS), to evaluate the epidemiology of Cercospora leaf spots (CLS) and the antifungal potentials of these extracts under natural conditions. METPS were obtained by maceration of seed powder (0,33 kg/l) in methanol. Two concentrations of METPS (1.8 and 3.7 kg/ha), a benomyl and a control treatments were used in four replicates of a randomised block design. Disease severity, incidence, lesion size and yield were assessed. Two foliar applications of antifungal substances were effected at 15 days interval. The epidemic on both groundnut varieties was low in plots sprayed with METPS and benomyl when compared with the control. Disease incidence, lesion size and CLS severity were reduced to 37.25, 33.10 and 32.61 % respectively in plots sprayed with METPS compared to the control. The Bafia var. was more tolerant to CLS than the 55-437 var. Groundnut yield increased by 32.89 and 41.37 % for the Bafia var following applications of METPS and benomyl respectively. These results suggest that integrating host resistance and METPS efficiently protects groundnut against CLS