Twenty-two advanced breeding genotypes of cowpea were evaluated for their responses to infestation by the cowpea aphid, Aphis craccivora Koch. The aim of the study was to identify genotype(s) of cowpea resistant to A. craccivora to be used as breeding line(s). Seedling screening technique and aphid growth and reproduction on each genotype were used to classify the genotypes into resistant and susceptible groups. The cowpea genotypes SARC 1-57-2 and SARC 1-91-1 were found to be the most resistant genotypes, whereas five of the genotypes namely, Apagbaala, IT 97K-499-35, IT 98K-506-1, IT 95K-193-2 and Marfo-Tuya were highly susceptible. The high susceptibility of the IITA lines must be a cause for concern, particularly the IT 97K-499-35 line which is known to be resistant to A. craccivora in Nigeria. This suggests the existence of cowpea aphid biotype in northern Ghana which is more virulent than the biotypes in Nigeria. The results support earlier findings of the development of aphid biotypes that are more aggressive and are not controlled by the aphid resistance varieties of cowpea developed by IITA for Nigeria. pests and diseases (Montimore et al., 1997; Blade et al., 1997). Cowpea is one crop which suffers serious insect pests infestation from the time of planting through harvesting and during storage (Obeng-Ofori, 2007). Cowpea aphid, Aphis craccivora Koch (Homoptera: Aphididae) is a major insect pest of cowpea in Africa, Asia and the Americas (Obeng-Ofori, 2007). Singh and Allen (1980) estimated yield losses of 20% to 40% in cowpea due to A. craccivora infestation in Asia and up to 35% in Africa. The existence of alternative host plants during the crop-free season, intermittent dry periods during the rainy season and favourable tem
Accurate identification of individual genotypes is important for cacao (Theobroma cacao L.) breeding, germplasm conservation and seed propagation. The development of single nucleotide polymorphism (SNP) markers in cacao offers an effective way to use a high-throughput genotyping system for cacao genotype verification. In the present study, high-throughput genotyping with SNP markers was used to fingerprint 160 cacao trees in the germplasm collection at the Cocoa Research Institute of Ghana (CRIG). These accessions had been originally introduced from international germplasm collections. The multilocus SNP profiles, generated by the Sequenom Mass Spectrometry platform, were compared with the SNP profiles of reference trees maintained in the international cacao collections. The comparison unambiguously identified mislabeled trees. For materials introduced as hybrid seeds without an available reference genotype, parentage analysis and model-based assignment were applied to verify their recorded parentage and genetic background. Our study shows that a small set of polymorphic SNP markers can provide a robust and accurate result for cacao genotype identification. This protocol can be applied for large-scale genotyping of cacao as well as for many other crops.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.