The Integrated Cassava Project of the International Institute of Tropical Agriculture conducted o... more The Integrated Cassava Project of the International Institute of Tropical Agriculture conducted on-farm, demonstrational, and multilocational trials in 2003/2004 and 2004/2005. From these trials nine new elite genotypes were released to farmers. These trials required working with a lot of stakeholders including farmers and government agencies. Data on several trait variables were obtained from the field trials. This paper presents the last stage in a national breeding program, and the logic behind a decision to release or not release new varieties. It also shows how to arrive at a choice of traits and how to derive appropriate weights in a simulation model.
... not, however, negate the usefulness of NPK fertilizers in cassava tuber production which seve... more ... not, however, negate the usefulness of NPK fertilizers in cassava tuber production which several workers had demonstrated (Okeke et al., 1976; Njoku and Arene, 1980; Odurukwe and Oji, 1984). ... We also thank Mrs Joyce Davidson of the same address for typing the manuscript. ...
Highlights are presented on the status of knowledge about cassava mosaic disease (CMD) and its ca... more Highlights are presented on the status of knowledge about cassava mosaic disease (CMD) and its causal agents in Nigeria. The disease occurs in all the agroecologies where cassava is grown, from the humid forest in the south to the semiarid and arid agroecologies in the north. The severity is generally moderate but can be very severe on susceptible genotypes. A
... International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria and National Root Cro... more ... International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria and National Root Crops Research Institute (NRCRI), Umudike, Umuahia, Nigeria ... sequence of any outbreak of a virulent strain or species of cassava begomovirus and also to minimize the impact of EACMV ...
... First Report of East African Cassava Mosaic Begomovirus in Ghana. SK Offei and M. Owuna-Kwaky... more ... First Report of East African Cassava Mosaic Begomovirus in Ghana. SK Offei and M. Owuna-Kwakye, Department of Crop Science, University of Ghana, PO Box 44, Legon, Ghana; and G. Thottappilly, International Institute of Tropical Agriculture, Ibadan, Nigeria. Open Access. ...
Page 1. RESEARCH, REVIEWS, PRACTICES, POLICY AND TECHNOLOGY Status of Cassava Mosaic Virus Diseas... more Page 1. RESEARCH, REVIEWS, PRACTICES, POLICY AND TECHNOLOGY Status of Cassava Mosaic Virus Diseases and Cassava Begomoviruses in Sub-Saharan Africa GI Atiri FO Ogbe AGO Dixon S. Winter O. Ariyo ABSTRACT. ...
Cassava mosaic disease (CMD) caused by a group of begomoviruses and transmitted by whitefly vecto... more Cassava mosaic disease (CMD) caused by a group of begomoviruses and transmitted by whitefly vector is a serious disease in all the cassava-growing areas of Africa. Field evaluation with replication was conducted in 2003 and 2004 in three agroecologies in Nigeria to study the response of 40 cassava genotypes to CMD and to investigate genotype · environment (GE) interactions on their reactions to CMD, using the rank-sum classification and site regression analysis model. The 40 genotypes were separated into resistant (n = 17), moderately resistant (n = 6), moderately susceptible (n = 2) and susceptible (n = 15) groups. Environments, genotypes and GE interactions were all highly significant (P < 0.0001) for the virus disease contributing 9.5%, 71.36% and 19.14%, respectively to total variation. More than 40% of the genotypes were identified as resistant to the disease. Genotypes TMS 98/0581, TMS 99/3073, TMS 97/4763, TMS M98/0040, TMS 98/0505, TMS 97/0211, TMS 97/4769, TMS 99/2123, TMS M98/0068 and TMS 97/0162 were shown to have high resistance to CMD. The study also identified Umudike, in south-east Nigeria, as having high disease severity and the most appropriate site for CMD resistance screening of genotypes. Most of the genotypes exhibited stable resistance to CMD. The implication that the availability of these resistant genotypes as identified in this study could be a source of CMD resistance for further breeding is discussed.
To determine the occurrence of variants of African cassava mosaic virus, 316 cassava leaf samples... more To determine the occurrence of variants of African cassava mosaic virus, 316 cassava leaf samples were collected from mosaic-affected cassava plants in 254 farmers' fields in 1997 and 1998, covering the humid forest, coastal/derived, southern Guinea and northern Guinea savannas and arid and semiarid agroecologies of Nigeria. The samples were tested in triple antibody sandwich enzyme-linked immunosorbent assay using a panel of 10 monoclonal antibodies (MAbs) against the virus in which 29 reaction patterns were observed. In cluster analysis, nine serotypes were obtained at 0.80 Jaccard similarity coefficient index in which at least 50% of isolates of each serotype reacted alike. The serotypes ranged between two extremes: serotype 1 with 90% isolates reacting with the 10 MAbs and serotype 8 in which 90% of its isolates failed to react with the antibodies. Isolates of serotypes 1, 2, 4 and 8 were widely distributed while those of the other serotypes were restricted to certain agroecologies. Four representative isolates 227 (serotype 1), 231 (serotype 2), 235 and 283 (serotype 8) elicited different responses in Nicotiana benthamiana with isolate 283 not able to infect this and other test plants used. The serological variations did not necessarily reflect the biological variations. In polymerase chain reaction tests, one out of the five pairs of ACMV primers tested distinguished only isolate 283. The humid forest, derived/coastal and southern Guinea savannas where most of the crop is grown in Nigeria had a high number of variants, which makes the agroecologies suitable for the selection of resistant cassava clones against ACMV.
The identification of superior genotypes and mega-environments on the basis of multiple traits is... more The identification of superior genotypes and mega-environments on the basis of multiple traits is a key objective of multi-environment trials in cassava (Manihot esculenta Crantz). The objective of this study was to examine the genetic variation and genotype × environment interaction ...
The Integrated Cassava Project of the International Institute of Tropical Agriculture conducted o... more The Integrated Cassava Project of the International Institute of Tropical Agriculture conducted on-farm, demonstrational, and multilocational trials in 2003/2004 and 2004/2005. From these trials nine new elite genotypes were released to farmers. These trials required working with a lot of stakeholders including farmers and government agencies. Data on several trait variables were obtained from the field trials. This paper presents the last stage in a national breeding program, and the logic behind a decision to release or not release new varieties. It also shows how to arrive at a choice of traits and how to derive appropriate weights in a simulation model.
... not, however, negate the usefulness of NPK fertilizers in cassava tuber production which seve... more ... not, however, negate the usefulness of NPK fertilizers in cassava tuber production which several workers had demonstrated (Okeke et al., 1976; Njoku and Arene, 1980; Odurukwe and Oji, 1984). ... We also thank Mrs Joyce Davidson of the same address for typing the manuscript. ...
Highlights are presented on the status of knowledge about cassava mosaic disease (CMD) and its ca... more Highlights are presented on the status of knowledge about cassava mosaic disease (CMD) and its causal agents in Nigeria. The disease occurs in all the agroecologies where cassava is grown, from the humid forest in the south to the semiarid and arid agroecologies in the north. The severity is generally moderate but can be very severe on susceptible genotypes. A
... International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria and National Root Cro... more ... International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria and National Root Crops Research Institute (NRCRI), Umudike, Umuahia, Nigeria ... sequence of any outbreak of a virulent strain or species of cassava begomovirus and also to minimize the impact of EACMV ...
... First Report of East African Cassava Mosaic Begomovirus in Ghana. SK Offei and M. Owuna-Kwaky... more ... First Report of East African Cassava Mosaic Begomovirus in Ghana. SK Offei and M. Owuna-Kwakye, Department of Crop Science, University of Ghana, PO Box 44, Legon, Ghana; and G. Thottappilly, International Institute of Tropical Agriculture, Ibadan, Nigeria. Open Access. ...
Page 1. RESEARCH, REVIEWS, PRACTICES, POLICY AND TECHNOLOGY Status of Cassava Mosaic Virus Diseas... more Page 1. RESEARCH, REVIEWS, PRACTICES, POLICY AND TECHNOLOGY Status of Cassava Mosaic Virus Diseases and Cassava Begomoviruses in Sub-Saharan Africa GI Atiri FO Ogbe AGO Dixon S. Winter O. Ariyo ABSTRACT. ...
Cassava mosaic disease (CMD) caused by a group of begomoviruses and transmitted by whitefly vecto... more Cassava mosaic disease (CMD) caused by a group of begomoviruses and transmitted by whitefly vector is a serious disease in all the cassava-growing areas of Africa. Field evaluation with replication was conducted in 2003 and 2004 in three agroecologies in Nigeria to study the response of 40 cassava genotypes to CMD and to investigate genotype · environment (GE) interactions on their reactions to CMD, using the rank-sum classification and site regression analysis model. The 40 genotypes were separated into resistant (n = 17), moderately resistant (n = 6), moderately susceptible (n = 2) and susceptible (n = 15) groups. Environments, genotypes and GE interactions were all highly significant (P < 0.0001) for the virus disease contributing 9.5%, 71.36% and 19.14%, respectively to total variation. More than 40% of the genotypes were identified as resistant to the disease. Genotypes TMS 98/0581, TMS 99/3073, TMS 97/4763, TMS M98/0040, TMS 98/0505, TMS 97/0211, TMS 97/4769, TMS 99/2123, TMS M98/0068 and TMS 97/0162 were shown to have high resistance to CMD. The study also identified Umudike, in south-east Nigeria, as having high disease severity and the most appropriate site for CMD resistance screening of genotypes. Most of the genotypes exhibited stable resistance to CMD. The implication that the availability of these resistant genotypes as identified in this study could be a source of CMD resistance for further breeding is discussed.
To determine the occurrence of variants of African cassava mosaic virus, 316 cassava leaf samples... more To determine the occurrence of variants of African cassava mosaic virus, 316 cassava leaf samples were collected from mosaic-affected cassava plants in 254 farmers' fields in 1997 and 1998, covering the humid forest, coastal/derived, southern Guinea and northern Guinea savannas and arid and semiarid agroecologies of Nigeria. The samples were tested in triple antibody sandwich enzyme-linked immunosorbent assay using a panel of 10 monoclonal antibodies (MAbs) against the virus in which 29 reaction patterns were observed. In cluster analysis, nine serotypes were obtained at 0.80 Jaccard similarity coefficient index in which at least 50% of isolates of each serotype reacted alike. The serotypes ranged between two extremes: serotype 1 with 90% isolates reacting with the 10 MAbs and serotype 8 in which 90% of its isolates failed to react with the antibodies. Isolates of serotypes 1, 2, 4 and 8 were widely distributed while those of the other serotypes were restricted to certain agroecologies. Four representative isolates 227 (serotype 1), 231 (serotype 2), 235 and 283 (serotype 8) elicited different responses in Nicotiana benthamiana with isolate 283 not able to infect this and other test plants used. The serological variations did not necessarily reflect the biological variations. In polymerase chain reaction tests, one out of the five pairs of ACMV primers tested distinguished only isolate 283. The humid forest, derived/coastal and southern Guinea savannas where most of the crop is grown in Nigeria had a high number of variants, which makes the agroecologies suitable for the selection of resistant cassava clones against ACMV.
The identification of superior genotypes and mega-environments on the basis of multiple traits is... more The identification of superior genotypes and mega-environments on the basis of multiple traits is a key objective of multi-environment trials in cassava (Manihot esculenta Crantz). The objective of this study was to examine the genetic variation and genotype × environment interaction ...
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