RTB Conference Proceedings

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Libro de Memorias. VIII Congreso Ecuatoriano de la Papa. Soberanía Alimentaria y Nutrición.
(Conference Proceedings, 2019-06) Rivadeneira J.; Racines M.; Cuesta, X.
Este documento sistematiza los trabajos presentados en el VIII Congreso Ecuatoriano de la Papa, el cual se realiza cada dos años. Este congreso constituye un espacio que reune a los actores de la cadena de valor de la papa y presenta los avances en diferentes temas de la investigación, desarrollo e innovación en la region.
Sweetpotato industry round table proceedings
(Conference Proceedings, 2015-12) Department of Science and Technology, Philippines; Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development; International Potato Center
Phenotypic evaluation of a multi-location cassava breeding trial to improve a genomic selection training population
(Conference Proceedings, 2013-09) Uchendu, U.K.; Parkes, Elizabeth Y.; Aina, O.O.; Akoroda, M.O.; Kulakow, Peter A.
Thirty white fleshed cassava genotypes derived from crosses between genotypes from West Africa x East Africa and West Africa x Latin America were evaluated in five major agroecological zones in Nigeria during 2012-2013. The trials were established in a randomized complete block design with four replications. The objectives of the study were (i) to evaluate genotype (G), environment (E), and G X E interaction on cassava mosaic disease (CMD), cassava bacterial blight (CBB), cassava anthracnose disease (CAD), and cassava green spider mite (CGM) in a multi-location uniform yield trial and (ii) to characterize morphological variation to improve a genomic selection training population that includes these genotypes. Combined analysis of variance showed differences (P-<- 0.001) among E for all traits evaluated. Genotypes did not differ significantly in their field reaction to CMD and CBB but showed variation in mild CAD symptoms and more severe, CGM reaction. Environmental variation accounted for 53.09% of the total sum of squares for CMD; 49.53% for CBB; 64.76% for CAD and 59.39% for CGM. The high influence of E demonstrated large differences in disease and pest severity in different locations. Morphological parameters such as levels of branching, angle of branching, height of branching, and plant height varied significantly among genotypes. Genotypes I090488, I090536 and I090590 branched the most, while I090574, I090564 and TMEB 419 (check) branched the least. Our results revealed that genotypes I090506, I090537 and I090609 were either low branching or have a wide angle of branching. This is significant as it helps in suppressing the weed flora, especially spear grass (Imperata cylindrical) by forming a dense canopy.
Progress in screening cassava genotypes for resistance to cassava brown streak Uganda virus
(Conference Proceedings, 2012-02) Kanju, E.; Ntawuruhunga, Pheneas; Otim Okello, F.
Cassava is a key food security crop in sub-Saharan Africa, and is increasingly offering opportunities for income generation from the sale of fresh roots, cuttings and diverse processed products. The total fresh root production is increasingly constrained, by the two principal biotic constraints; cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). Considerable successes have been achieved in mitigating the effects of the CMD pandemic through the multiplication and dissemination of CMD-resistant varieties, but severe CMD continues to spread. In more recent years, there has been a rapid and devastating outbreak of CBSD, especially in the Great Lakes region where it was not prevalent. Outbreaks have been reported in parts of Uganda, Kenya, Rwanda and Tanzania near Lake Victoria, and reports were also received of CBSD-like symptoms in the western part of the Democratic Republic of Congo. Recent reports have confirmed that CBSD is comprised of two distinct species of viruses, Cassava brown streak virus (CBSV) and Cassava brown streak Uganda virus (CBSUV). The most effective and realistic approach to reducing losses to CMD and CBSD is the use of host-plant resistance or the deployment of lesssusceptible cultivars. Cassava trials were therefore, established in Uganda to screen cassava germplasm for resistance to CBSD from 2005/2006 to date. In 2009 fourteen clones that combined dual resistance to CMD and CBSD with good cooking qualities were selected in collaboration with farmers. The fourteen clones were: MM 06/0013, MM 06/0090, MM 06/0130, MM 06/0143, MM 06/0139, MM 06/0082, MM 06/0128, MM 06/0123, MM 06/0083, MM 06/0046, MM 06/0112, MM 06/0074, MM 06/0005 and MM 06/0138. They significantly differed in fresh root yielding ability, which ranged from 3.8 to 25.2 T/ha with a mean 12.3 t/ha. In contrast, the improved check (TME 204) yielded 4.8 t/ha. Their dry matter content ranged from 29.4 to 47.7%. The 14 clones were sent to the Kenya Plant Health Inspectorate Services (KEPHIS), Muguga, Kenya for cleaning and virus indexing ready for regional distribution. However, when the clones were evaluated across three sites during the 2009/2010 season, only three (MM 06/0082, MM 06/ 0123 and MM 06/0128) showed tolerance to CBSD. The three new clones would be the major arsenal against CBSD and specifically CBSUV, in all the midaltitude regions of the Great Lakes region. Most importantly, farmers will need to evaluate these new clones under actual field conditions for dual resistance to CMD and CBSD, as well as for utilization characteristics. The best of them will be used in further disease-resistance breeding among national programs in other countries in the Great Lakes region such as Burundi, Rwanda, Kenya, Tanzania and DR Congo.
Adding value to Africa's cassava in a global environment
(Conference Proceedings, 2012-02) Adebayo, K.; Abayomi, L.; Alacho, O.F.; Dziedzoave, N.T.; Forsythe, L.; Graffham, A.J.; Ilona, Paul; Kleih, Uli K.; Lamboll, R.I.; Mahende, G.; Martin, A.M.; Onumah, G.E.; Posthumus, Helena; Hillocks, R.J.; Sanni, Lateef O.; Sandifolo, V.S.; Sergeant, A.; Westby, Andrew
Based on experiences in the Cassava: Adding Value for Africa (C:AVA) project, this paper examines emerging issues and lessons for adding value to cassava, one of Africa's widely cultivated staples in ways that contribute to the global market environment as well as bring benefits to small holders on the continent. The main issues discussed include: competiveness in the supply of raw material, assisting smallholders to produce value-added products sustainably and competitively, ensuring and maintaining quality of products, selecting appropriate technologies for different circumstances and anticipating negative effects of the market environment on smallholders. One of the main challenges for value addition to a staple crop in Africa is finding 'champions' who are willing to make new investments with knowledge, skill and expertise requirements derived from other nations. The other is increasing the drying capacities for a tropical root crop through appropriate technologies that ensure production of high quality products in required volumes. One focus of the C:AVA project in the near future is to promote transfer of energy efficient Nigerian-made flash drier in collaboration with partners and fabricators from other C:AVA countries (Ghana, Uganda, Malawi and Tanzania). Improved energy efficiency will reduce fuel consumption, reduce operating cost and improve throughput of the dryers. An additional benefit will be reduction in emission of harmful greenhouse gases and their impact on global warming. It is anticipated that the knowledge and skills for further developing the value addition potential for cassava in all five countries will be enhanced. Benchmarking of key variables was used as an approach to understand differences between countries in terms of their abilities to develop high quality cassava flour value chains. It is clear that one strategy does not work in all countries and while positive government support for cassava development is helpful, the real driver is targeting markets according to realisable capacities of the smallholder actors in the value chain.
Evaluation of commercially available herbicides for weed control in cassava
(Conference Proceedings, 2012-02) Moyo, C.C.; Jumbo, S.; Mahungu, N.M.; Benesi, I.R.M.; Ntawuruhunga, Pheneas; Sandifolo, V.S.
A trial was conducted in 2008/09 at Chitedze (31o 59' S; 33o 38' E) and Chitala (13o 40' S; 34o 15' E) Research stations in Malawi to evaluate commercially available pre-emergent herbicides for weed control in cassava (Manihot esculenta Crantz). Four herbicides, Bullet (chloroacetanilide, dimethanamid, triazine), Harness 90 EC (chloroacetanilide), Codal Gold 412-5 EC (prometryn and S-metolachlor) and Metalachlor 960 EC (S-metolachlor; acetamide), were evaluated with and without follow up hand-hoe weeding (check). Panicum maximum, Elusine indica, Rottboellia chochinchinensis and Setaria pumila were the common narrow-leaved weeds while Commelina benghalensis, Bidens pilosa, Nicandra physalodes and Acanthospermum hispidum were the common broad leaved weeds. Herbicide application did not affect crop establishment but significantly (P<0.001) reduced early weed growth by 74.8 to 91.2 % at Chitedze and 53.7 to 97.9 % at Chitala. Bullet was more effective in early weed control (2.8 weeds m-2 at Chitedze and 0.0 weeds m-2 at Chitala) than the other herbicides (38.7 weeds m-2 at Chitedze and 8.8 weeds m-2 at Chitala) and resulted in root yields (12.3 t ha-1 at Chitedze and 18.4 t ha-1 at Chitala) and returns (MK238,844.00 ha-1 at Chitedze and MK360,779.00 ha-1 at Chitala) comparable to or higher than hand weeding (root yield of 10.6 t ha-1 at Chitedze and 16.3 t ha-1 at Chitala and returns of MK2 0 1 , 4 3 8 . 0 0 h a - 1 a t Ch i t e d z e a n d MK310,448.00 ha-1 at Chitala) and other treatments (root yield of 2.2-13.1 t ha-1 at Chitedze and 1.3-23.6 t ha-1 at Chitala and returns of MK44,000.00 to MK249,078 at Chitedze and MK26,000.00 to MK465,100 ha-1 at Chitala), making it a potential alternative to hand hoe weeding in cassava.
Qualité des produits dérivés du manioc prélevés au niveau des sites de fabrication et dans les marchés de Kinshasa, RD Congo
(Conference Proceedings, 2012-02) Mukandila, K.P.; Hell, K.; Hauser, S.; Lamboni, L.; Masimango, J.T.
L'analyse de la qualité microbiologique ont été réalisées sur les produits dérivés du manioc chikwangue, cossettes de manioc et farine de manioc au niveau du site de fabrication (Bas Congo et Bandundu) et dans les marchés de Kinshasa. Les analyses microbiologiques ont révélé la présence de la flore aérobie mésophile et des moisissures appartenant aux genres Penicillium, Aspergillus et Rhizopus sur les produits dérivés du manioc. Dans certains cas, le niveau de contamination était élevé sur les échantillons prélevés au niveau du site de fabrication que sur ceux prélevés dans les marchés de Kinshasa. La contamination élevée par le Penicillium sp (3,34 CFU) et le Rhizopus sp (1,53 CFU) a été constatée sur les échantillons de chikwangue tandis que, la contamination élevée par l'Aspergillus flavus a été observée sur les cossettes de manioc (2,04 CFU) et la farine de manioc (2,48 CFU). Le niveau de contamination élevé par la flore aérobie mésophile a été constaté sur les cossettes de manioc (5,91 CFU). Le pH moyen noté sur les produits dérivés du manioc (4,33 5,39) était favorable à leur contamination que par les microorganismes acidophiles. Le pH noté sur la farine (6,94 7,17) et les cossettes (6,77 7,03) de manioc était favorable à leur contamination par les bactéries pathogènes. La teneur en eau enregistrée sur les produits dérivés du manioc (11,37% - 66,3%) était favorable à leur contamination par les microorganismes. La teneur en eau enregistrée sur les cossettes (11,37% - 15,53%) n'était pas favorable à leur contamination par les bactéries. Le taux moyen des protéines sur la farine (0,82% - 1,48%) et les cossettes (1,01% - 1,52%) de manioc était inférieur au taux moyen des protéines dans les racines fraîches. On a enregistré dans les cossettes de manioc un taux d'acide cyanhydrique (4,9 5,4 mg kg-1) inférieur au seuil limite de 10mg kg-1.
Current status of root and tuber crops improvement, production and utilization in Sierra Leone
(Conference Proceedings, 2012-02) Fomba, S.N.; Massaquoi, F.B.; Norman, P.E.; Samura, A.E.; Mansaray, A.; Jalloh, A.; Dixon, Alfred G.O.; Anthony, N.A.; Benya, M.T.; Fornah, D.S.; Sawi, M.K.; Sartie, A.M.; Onadipe, O.; Sanni, Lateef O.
Cassava (Manihot esculenta Crantz) is the second most important food crop after rice, the staple in Sierra Leone; it is also the most important root and tuber crop. It is followed by sweet potato (Ipomoea batatas L.), yam (Dioscorea spp.), which forms part of the traditional farming system and has only recently been included in the research agenda of NARC/SLARI and potato (Solanum tuberosum L) aka “Irish” potato in Sierra Leone, an introduced crop from neighbouring Republic of Guinea. Genetic improvement of the above crops is mainly through introduction of exotic germplasm from the International Institute of Tropical Agriculture (IITA) at Ibadan, Nigeria; and screening, selection and advancement of promising lines in a participatory manner with farmers and other stakeholders in the crop development process. Breeding objectives of the above crops are aimed at addressing the devastating problem of pests and diseases prevalent in Sierra Leone, cassava mosaic disease (CMD), cassava bacterial blight (CBB), green mite, mealy bug and grasshoppers; sweet potato virus x and scab, and late blight of potato), yield and quality for the various desirable traits of eating, processing and potential industrial uses. Several genotypes of cassava have been released in the recent past (SLICASS 1-6) with yield range of 25-35 mt/ha whilst new and more nutrient-rich genotypes including yellow rooted ones with yield range of 40-50 mt/ha are in the pipeline for release. The yield ranges of sweet potato, yam and potato are 6-10 mt/ha, 10-27 mt/ha and 2-4 mt/ha, respectively. Four potato varieties (SLIPOT 1-4) were recently released to the farming population of Sierra Leone. The current status of cassava, sweet potato (including recent and more nutritious, âcarotene genotypes), yam and potato breeding activities at NARC/SLARI, Sierra Leone is summarized and presented. Yam and potato improvement is new but significant strides have already been made in identifying promising lines of the former with the desirable traits or qualities that are acceptable to both farmers and consumers alike in the country. Production of cassava has increased more than three folds since the end of the civil war in 2002, during which period it served as the most easily cultivated, accessible and affordable food crop, along with sweet potato to the majority of the then internally displaced population (IDP). Recent trends in production of these two crops are also given. Cassava transformation into many useful food products, especially gari, fufu and high quality cassava flour (HQCF) is receiving tremendous boost in many parts of the country by both regional and national projects (CFC/IITA/SLARI) Cassava Value Addition, USAID/IITA-Sierra Leone Unleashing the Power of Cassava in Africa (UpoCA), AfDB/FARA/CORAF/WECARD/ SLARI Promotion of Science and Technology for Agricultural Development (PSTAD) in Africa Project (Dissemination of New Agricultural Technologies in Africa (DONATA) and Regional Agricultural Information Learning Systems (RAILS), Non-Governmental Organizations (NGOs) and the private sector. Strides made in that direction are also summarized and presented. On a lesser scale, processing of sweet potato into more durable and useful by-products such as flour is beginning to receive the necessary attention by scientists at NARC/SLARI, and Njala University (NU), Sierra Leone and the Federal University of Agriculture at Abeokuta (UNAAB) and Association of African Universities (AAU) Regional Food Developers Initiative (FDI) Project, Nigeria. This will hopefully prevent market glut and improve the livelihood of root and tuber crops farmers with a consequent reduction in poverty.
Economic impacts of cassava improvement in Malawi and Zambia
(Conference Proceedings, 2012-02) Alene, Arega D.; Khataza, R.; Ntawuruhunga, Pheneas; Mahungu, N.M.; Jumbo, S.
This paper measures the economic impacts of IITA/SARRNET led cassava improvement research in Malawi and Zambia over the period 1990-2008. The data come from sample household surveys, expert opinion surveys, and a series of cassava improvement experiments conducted in the two countries. Past investments in cassava improvement have led to the development and release of a good number of high-yielding cassava varieties. The results show relatively higher adoption rates for the CMD-free local varieties compared to CMD-resistant modern varieties that have been released in the two countries. The adoption of new varieties has been low and slow largely due to the fact that most of these varieties lacked the consumption attributes highly valued by farmers. The multiplication and distribution of CMD-free planting materials of the recommended local varieties led to greater adoption, but infection with CMD three to four years after adoption meant that the yield gains and economic benefits could not be sustained. Nevertheless, the multiplication and distribution of clean cassava planting materials generated a modest rate of return of 18%, which is actually consistent with an earlier rate of return estimate of 9 to 22% for cassava improvement in developing countries. Analysis of the ex ante impacts of current and future investments in cassava improvement from 2009 to 2050 shows that cassava improvement research that focuses on the development and dissemination of varieties with highly preferred consumption and industrial attributes would yield a greater rate of return of 40%.
Solar drying technology: a pilot design in Benin Republic
(Conference Proceedings, 2012-02) Alenkhe, E.B.; Onadipe, O.O.; Sanni, Lateef O.
An appropriate drying system remains a critical factor for the development of cassava enterprises in Africa, most especially at the rural sector. As part of solving this problem, the Cassava value chain development in West Africa - a project sponsored by the Common Fund for Commodities source information on existing solar drying systems in Nigeria, Ghana, Uganda, Cameroon, and Sierra Leone. Findings from the survey assisted in the design and fabrication of an hybrid solar drying system with less impact on deforestation. The dryer was installed in Hounvi village in Benin republic; one of the project countries. The design, which is a combination of solar and indirect heating of the drying chamber, consists of a drying building roofed with white plastics while the inside contains drying trays on raised platforms. The dryer make use of solar energy during the day while in the evening; heat is supplied from outside the chamber to continue drying. The heating chamber was made of hollow drum inserted from outside of the building. The highest drying temperature attained was 58.55oC with a drying rate of 100-160 kg wet mash/day and an average final moisture content of 11 %. The processors now have opportunity of drying their products any time of the day with less dependence on use of firewood. Wide range of products could be dried hygienically using this drying facility within some hours with little or no quality loss. The functionality, suitability and acceptability by the processors have been confirmed with confidence for replication in other sites and other countries within the tropics.
Scale insects on yams in Benin: diversity, incidence and farmers' knowledge and perceptions
(Conference Proceedings, 2012-02) Goergen, Georg E.; Dossou, R.; Asiedu, Robert; Hanna, R.
Yam (Dioscoreaspp.) is a primary agricultural commodity and a traditional staple food over much of West and Central Africa, where it is highly profitable both for producers and traders especially when production and storage strategies are successful in securing the supply of urban markets throughout the year. Insect pests such as mealybugs of the genus Planococcus Ferris (Hem.: Pseudococcidae) and the scale Aspidiellahartii (Cockerell) (Hem.: Diaspididae) can become major constrains causing significant yield losses both in the field and in storage. Detailed information on the pest status of the scale insects on yams and farmers' knowledge and perceptions of these insects were assessed in two surveys carried out in central and southern Benin in May and December 2009. In the May survey, covering134 sites and 68 villages, scale infestations were found in 68% of yam stores and sales points with in average 41% of the tubers infested. Lower incidence and infestation rates were observed at the main harvest period in December when scale and mealybug infestations were found in 56% of the 102 fields from 68 villages with an average of 23% infested tubers, indicating that scale and mealybug infestations are initiated in the field. Aspidiellahartii tended to become proportionally more important in stores increasing from 9 to 40% of the recovered scale insect pests. In both surveys the percentage of mixed infestations remained relatively low - at 13 and 5% for the first and second survey respectively. Structured questionnaires performed at every site showed that almost all farmers and traders were able to recognize yam scales and mealybugs and ranked both groups equally in importance as pests. The presence of the scale insects was generally regarded as having a negative impact on the quality of stored tubers, especially their germination rate when used as seeds for planting new fields. Whereas all cultivars seemed to be at risk from scale insects, late varieties, appeared to be more susceptible than other varieties. Farmers estimated an average of 22% reduction of the total yield and 23% reduction in planting material due to scale insect infestations. Tuber rot, theft, cattle feed and bush fire were recurrently cited as the most important problems of stored yams. Interestingly, 66% of the questioned farmers believed scale infestations have been on the rise over the last few years, while at the same time the length of fallow periods were on the decline primarily because of increasing pressure on the land which might suggest a relationship between scale infestation and fallow period. Farmers, however, differed considerably in their admission that such a relationship is real. Taken together, both field evidence and farmers perceptions of scale insect infestations on yams are a first and valuable step in the development of appropriate management practices to reduce yam losses due to scale insect infestations. Control options are presently limited to preventive actions such as early harvest, culling of infested tubers, selective early consumption, and production of yam chips.
Using steam to dry food: introducing the (UPoCA) dryer
(Conference Proceedings, 2012-02) Nonie, S.E.B.; James, B.D.; Alpha, S.J.
The production of cassava flour involves drying grated and pressed cassava into pellets that are milled into flour. The drying process is one of the major bottlenecks to expanding the economic value of the crop. The industry looks for fast drying systems with high flour production capacity to meet market demands. Traditional sun-drying is limited by rainfall, and conventional drying systems are based on motorized machinery unsuitable for farm gate use. The UPoCA dryer has been developed to address these constraints in the production of cassava flours by small to medium processing units. In its standard form, drying system comprises a boiler (325 litres) and two drying cabinets constructed of timber/plywood lined with aluminium sheets. The boiler generates steam that circulates through 7 to 11 shelves of copper coils on top of each is placed a sample tray measuring 1.2m x 0.75m. The coil heats the sample tray and steam from mashed cassava in the tray is removed by convection current of ambient air taken into through the vent holes and dampers. In trials, each cabinet produced 14 to 20 kg dried cassava flour in two hours. With two cabinets operating, the production capacity over an eight to ten-hour working day is about 168 kg and 240 kg for the short, and tall version, respectively. Each version required only three (3) people for regular daily operation. The boiler can operate up to four (4) drying chambers to double the production capacity. The major advantage of this system is that its operation does not require moving parts such as blowers and fans that would require regular maintenance. The system is particularly suited to small scale farming communities in the rural setting, utilising firewood, or charcoal as the fuel source. The application of this device to vegetables and other crops has been tested, with promising results.
Genotype by environment interaction effect on beta-carotene of yellow root cassava (Manihot esculenta Crantz) genotypes in Ghana
(Conference Proceedings, 2012-02) Maroya, N.G.; Asante, I.K.; Dixon, A.
Nine yellow root and one white root cassava genotypes were evaluated in ten environments in Ghana for the variability of their beta carotene content in root. The aim was to identify cassava genotypes that have high beta carotene content in storage root to combat the widespread vitamin A deficiency for children under the age of five years and for pregnant and lactating women. This study was conducted in a Randomized Complete Bloc Design with nine yellow root genotypes namely 01/1224; 01/1235; 01/1368; 01/1371; 01/1412; 01/1417; 01/1442; 01/1610; 01/1663 and one white root cassava namely Wenchi009 as check. In 2005-2006 two experiments were conducted at Wenchi in the Forest-Savannah Transition zone and at Bunso in the Deciduous Forest zone and in 2006-2007, one additional location namely Pokuase in the costal savannah zone was added to Wenchi and Bunso to conduct the same field experiment. Each experiment was harvested two times (9 and 12 or 14 months after planting). At each harvest, beta carotene content analyses were carried out on yellow root cassava at the Nutrition Lab of Noguchi Medical Research Centre using High Performance Liquid Chromatography (HPLC) with a mobile phase made of acetonitrile: dichloromethane: methanol in the ratio 70:20:10 at a flow rate of 2.5 ml/min. Data collected were analyzed using the computer software GenStat Discovery Edition Release 4.2DE; MATMODEL 3.0; GGE biplot. Analyses of results showed statistically significant differences between genotypes for beta carotene content per root, beta carotene content in storage root per plant and but no difference for beta carotene concentration. The best genotype for beta carotene content was 01/1417 follow by 01/1371 and 01/1368.The differences between environments were highly significant for all beta carotene traits. The highest value of beta carotene concentration in fresh root was recorded in environments E , E , E and E . 9 1 7 5 These environments were all characterized by harvest at 9 months after planting. For beta carotene concentration, beta carotene content per storage root and beta carotene content in storage roots per plant the best environments were E (9 9 MAP at Pokuase) and E (9 MAP at Wenchi in 1 2005). The IMMI analysis has shown 01/1412 the most stable for beta carotene concentration. The highest average value of beta carotene content per storage root was registered for genotype 01/1253 followed by 01/1417 and 01/1412. The most stable genotype for beta carotene content per storage root was 01/1610 followed by 01/1371. The highest value was registered for genotype 01/1417 (also the most stable) followed by 01/1368 and 01/1235. Based on the above results the yellow root cassava genotypes 01/1368 and 01/1417 which combined high fresh storage root yield, high dry root yield with high beta carotene content in storage root and in storage root per plant were proposed for on farm testing and released to tackle the vitamin A deficiency in Ghana.
Development of mapping populations for genetic analysis in yams (D. rotundata and D. alata)
(Conference Proceedings, 2012-02) Sartie, A.M.; Asiedu, Robert
Progress is being made at the International Institute of Tropical Agriculture to develop molecular tools for marker-assisted selection that would complement and expedite conventional breeding approaches for genetic improvement of yams (Dioscorea spp.). F mapping populations 1 were developed from crossing male and female parents of D. rotundata Poir. and D. alata Lam. that differ in specific traits of interest towards identification of molecular markers linked to those traits. Success in hybridization was validated based on DNA analysis with SSR markers on agarose gel. Traits for which the populations were developed included multiple tuber production, cooking quality and virus disease resistance in D. rotundata, and anthracnose disease, cooking quality and tuber oxidation in D. alata. Death of plants in the field and rotting of tubers in storage, possibly due to pests, diseases and other environmental factors were encountered that led to the reduction in sizes of the populations. Low seed multiplication ratio necessitates two to three cycles of tuber multiplication of mapping population genotypes to achieve adequate numbers of seed tubers for field experimentation. These mapping populations are valuable tools for genetic analysis and molecular marker development in yam improvement programmes.
Development and validation of genomic tools for marker-assisted breeding of cassava mosaic disease resistance in cassava (Manihot esculenta)
(Conference Proceedings, 2012-02) Gedil, Melaku A; Otti, G.; Enok, L.; Kumar, L.
In a bid to fast-track the process of selection of cassava (Manihot esculenta Crantz) genotypes resistant to the cassava mosaic disease (CMD), caused by whitefly-transmitted begomoviruses, a number of molecular markers have been developed to map resistance genes. The simple sequence repeat (SSR) markers, NS158 and SSRY28 and a sequence-characterized amplified region (SCAR) marker, RME-1 have been previously reported to be linked to a CMD2 gene. Other unpublished sources also implicate NS169 and SSRY235 markers as being linked to CMD resistance traits. This study, therefore, aims to verify and validate the utility of these markers including three others - SSRY20, SSRY76 and SSRY238 in marker-assisted selection (MAS) and to test the utility of certain novel approaches in facilitating the use of gene-targeted molecular markers in MAS. It also aims to validate tools for enhancing reliability of marker-trait association. The utility of the markers for MAS were verified by determining their levels of association to CMD resistance in two mapping populations, 1M and 23M and forty elite clones using bulk-segregant analysis (BSA) and simple marker-trait correlation. Candidate R-genes were identified by selecting genes annotated with characteristic resistance domains following sequence homology search of primer sequences of the SSR and SCAR markers on cassava genomic sequences using phytozome (www.phytozome.net). After analyzing all markers, NS158, SSRY28 and RME-1 were found to exhibit significant association to CMD resistance in 1M and 23M populations, both of which involve TME 3 as source of resistance, with percentage association levels of 74%, 75% and 70%, respectively, at a resistance range of 1=R<2 and 88%, 89% and 83% when a disease score of 2 is considered resistant. The tested molecular markers, particularly NS158 and SSRY238 showed good association when tested on 40 elite lines. Two markers SSRY20 and SSRY76 were found to be the closest to any R-gene because their primers were found 58kb downstream and 49.3kb upstream respectively of the closest R-gene. In an effort to improve phenotyping for reliable markertrait association, an expected inverse correlation of cycle threshold (Ct) values to viral quantities was obtained after real time PCR thereby establishing it as a veritable tool for this purpose. Candidate markers could provide useful information for identification of resistance genes for development of gene-targeted molecular markers for molecular breeding of cassava.
Discovery of Single Nucleotide Polymorphisms (SNPs) as a tool for markerassisted breeding of cassava, Manihot esculenta
(Conference Proceedings, 2012-02) Gedil, Melaku A; Igwe, D.
Discovery of single nucleotide polymorphisms, (SNPs) as a tool in marker-assisted breeding of cassava, Manihot esculenta was studied. The principal objective of this study is to discover single nucleotide polymorphisms (SNPs) in some panels of elite lines (ELs) of cassava and in some mapping populations to be used as a tool for marker-assisted breeding in cassava (Manihot esculenta). As a nucleotide base constitutes genetic information for inheritance, SNPs provide the ultimate form of molecular genetic markers. Small insertion or deletion occurrences (indel for insertion/deletion) are other factors that bring about genetic mutations. These mutations may be detected as SNPs as the insertion or deletion of nucleotides changes the sequence read. The rapid advance of the sequencing technology and the steadily declining cost of sequencing prompted the development of a gamut of SNP discovery and genotyping technologies. A panel of ELs and three mapping populations (TME3xTME117, TME3x30555 and TME14x96/1089A) were used. Six full gene sequences (both nuclear and chloroplast genes), involved in starch, sucrose, and cyanogenic glucoside biosynthesis, and three promoter sequences were used for designing primers. Single nucleotide polymorphism analysis of a total of 9,993 base pairs of sequence revealed 184 SNP sites and 43 InDels, giving rise to frequencies of 1 SNP per 54 bp and 1 SNP per 232 bp respectively. Exonic and intronic regions were identified to be 106 and 78 respectively. Synonymous and non-synonymous changes were identified using Codon-based Test of Neutrality. The frequency of SNPs was much higher than that of the InDels. The polymorphisms observed were due to the effects of transitions (C/T or A/G), transversions (C/G, A/T, A/C or G/T), hetero zygosities and the occurrence of InDels within the sequenced samples. A total of 126 polymorphisms (68.5%) were transitions (C/T or A/G) and 58 polymorphisms (31.5%) were transversions (C/G, A/T, A/C, or G/T). Analysis of preference using Z test of selection for estimation of synonymous substitutions per synonymous sites (dS) and n o n s y n o n y m o u s s u b s t i t u t i o n s p e r nonsynonymous sites (dN) was also done on TME14 x 96/1089A. The dN (306.7) > dS (125.5) was noted showing that positive selection is operating within the genes used. Parentage of F1 hybrids of TME14X96/1089A was verified using SNPs generated from four genes out of the aforementioned number of genes used in this study and these highly informative primers not only differentiated the parent genotypes but also confirmed the parentage of their true F1 hybrids.
Improving food security and income and enhancing farmers' livelihoods in Cameroon through the introduction and promotion of improved cassava germplasm
(Conference Proceedings, 2012-02) Njukwe, E.; Nguenkam, A.; Mbairanodji, A.; Ngue-Bissa, T.; Hanna, R.
Cassava is an important staple food for consumption and income generation for farming communities in Cameroon with some estimated 204,548 hectares devoted to it and corresponding annual production of 2.5 million tons. However, most cultivated varieties are susceptible to pest and diseases causing significant yield losses. Major pest and disease constraints include the African root and tuber scale (ARTS), cassava green mite (CGM), cassava mosaic virus disease (CMD), cassava anthracnose disease (CAD), and root rots. More than 200 high yielding cassava varieties, with a range of resistance principally to CMD and suitability for Typhlodromalus aripo, the principal biological control agent of cassava green mite, were introduced into Cameroon from IITA headquarters in Ibadan, Nigeria for testing under several agroecological conditions across Cameroon. At present, five TMS varieties (92/0057, 92/0067, 92/0326, 96/0023, and 96/1414) have been retained on the basis of their high root yield (>20t/ha), high dry matter content (>35%), high CMD resistance, and a combination of suitability to predatory mites (92/0057, 92/0067, and 92/0326), and resistance to CAD and tolerance to ARTS (96/0023). The latter is being largely promoted in the forest zone where the two constraints are most prevalent. These varieties are being propagated through a three-tier multiplication scheme (primary, secondary and tertiary) to ensure equitable, fast and sustainable distribution of healthy planting materials with two IFAD-funded projects, Programme National de Développement des Racines et Tubercules (PNDRT) - implemented by the government of Cameroon, and Cassava IPM implemented by IITA. Through PNDRT, cuttings of the improved varieties (92/0326 and 96/1414) were multiplied and distributed to farmers in 221 villages. The Cassava IPM project emphasized the multiplication and distribution of 96/0023 in the forest zone where ARTS and CAD are major constraints, and 92/0057, 92/0067 and 92/0326 for several regions in Cameroon due to their suitability to the biological control of cassava green mite, in addition to their resistance to CMD. At least 500 farmers in the targeted zones have grown at least 100 plants of each of the varieties in the targeted areas. Presently, more than 550 hectares have been set aside by both projects to produce planting material for distribution. These dissemination schemes have significantly boosted cassava production from 8-10 tons per hectare to 25-30 tons per hectare, and have provoked the need for post-harvest facilities.
Development and dissemination of a manual cassava chipper in Cameroon
(Conference Proceedings, 2012-02) Njukwe, E.; Duindam, J.; Hauser, S.; Maziya-Dixon, B.B.; Amadou Thierno, D.; Onadipe, O.; Mbairanodji, A.; Ngue-Bissa, T.; Kirscht, H.; Hanna, R.
Cassava (Manihot esculenta Crantz) is the main starchy staple in many parts of Cameroon, with 80% of rural and urban households consuming cassava and cassava derived products on a daily basis. Cassava products are commercialized mostly to supply household consumer markets with a total estimated equivalent of 1.1 million ton fresh cassava consumed in 2002 mainly because processing rely highly on family labour. Because of the smallholder nature of farming systems and the low density of producers in more inaccessible areas, investment in immobile, motorized cassava processing equipment is often not economically justified by the production capacity in these areas. Hence, IITA developed manual cassava chipper that are, easily transported and don't rely on electricity or fuel and complex technology. This manual chipper was tested with farmers in several villages. It has a capacity to process up to 260 kg cassava per hour, which is enough for a several farming households to consume in two months. In January 2007, the IFAD-funded project, Programme National de Développement des Racines et Tubercules (PNDRT) embarked on a program to promote and disseminate an IITA manual cassava chipper within the framework of its efforts on value addition to enhance farmers' income in Cameroon. IITA in collaboration with PNDRT identified and trained 13 local fabricators and the chippers disseminated were fabricated locally. 100 machines are currently being used by over 100 groups of cassava growers in 25 villages totalling about 1500 farmers in the 10 regions of Cameroon. Several NGOs, CBOs and farmers' organizations in Cameroon have now engaged in the fabrication and dissemination of IITA manual cassava chipper. Users and beneficiaries of this processing technology are cassava growers and small agricultural machinery manufacturers. The design, specifications and the user's guide for the manual cassava chipper are available. We expect that this technology will improve the accessibility of mechanized processing and increase commercialization and subsequent income of cassava growers in Cameroon.
Proximate composition and physical properties of steamed sour cassava starch bread
(Conference Proceedings, 2012-02) Adegunwa, M.O.; Edema, M.O.; Sanni, Lateef O.; Maziya-Dixon, B.B.
The effects of steaming (10min, 20min and 30min) on the properties of sour cassava starch bread were evaluated. Properties examined include pH, moisture content, protein, ash, starch, sugar, amylose content and sensory analysis. Amylose content ranged between (14.04-15.73%), Amylopectin ranged between (84.27-85.96 %), protein content ranged between (3.85-4.18%), Starch and Sugar content ranged between (68.07- 69.01%) and (10.12-10.34%) respectively. As the level of steaming increases the fat (11.64-12.59%) and protein content (3.85-4.18%) increases. 10min-steamed bread was adjudged the best for sour cassava starch bread production as its bread had the highest score for overall acceptability (6.0) and other sensory parameters evaluated.
Cassava value chain development in West Africa: success stories
(Conference Proceedings, 2012-02) Sanni, Lateef O.; Onadipe, O.O.; Alenkhe, E.B.; Ilona, Paul; Davis-Mussagy, M.; Dixon, Alfred G.O.
The initiative of cassava value chain in West Africa has provided sustainable opportunity for transferring best bet agronomic, processing and marketing practices to less privileged small holder enterprises in Nigeria, Benin and Sierra Leone. This project which started 2008, sponsored by Common Fund for Commodities, supervised by FAO and implemented by IITA has been an avenue to improve key players of cassava enterprise in the selected countries to boost their output qualitatively and quantitatively. The selected beneficiary processors individually and in groups were provided with well equipped renovated processing centers and business plans in 13 locations, thus creating enabling environments for maximum production of cassava products. They also received sound processing trainings on quality and competitive cassava products in addition to the introduction/development of new commercial cassava products for market diversification. The processors were as well provided with storage facility for finished products to enable an all year round access to products. The capacities of local fabricators were enhanced as they were used in fabricating all the equipment at the centers while markets were linked for the processors at all levels. From the assessment of the projects so far, appreciable and sustainable progress had been reported in term of processors' increased productivity, expanded utilization of cassava and capacity enhancement in processing and equipment management. The processing centers are being used as reference for academic and development purposes.

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