Rate of re-infection of tissue culture-derived Latin American and East and Southern African cassava genotypes by mosaic disease

The rate of reinfection by cassava mosaic disease (CMD) in initially virus-free cassava plants of two Latin American and twelve East and Southern African cassava genotypes grown was studied under high disease pressure conditions. An improved clone, TMS 4(2)1425, from the International Institute of Tropical Agriculture was used as check. The virus-free plants had been produced through meristem-tip culture and multiplied in a pest-proof screen house. The genotypes were planted in single row plots of 5 plants each, arranged in a randomized complete block design with 4 replications and spacing of 1 × 1 m2. Incidence and severity of CMD on the genotypes were assessed weekly, from 4 to 16 weeks after planting (WAP). Enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) tests for the cassava mosaic virus were carried out using young leaves collected randomly at 15, 16 and 17 WAP from plants both with and without symptoms. Six genotypes had > 60% CMD incidence at 4 WAP; by 7 WAP, 12 genotypes had > 60% incidence. Only Kigoma red, Kiroba, and UKG-41-6 were notinfected at 4 WAP while Mbudumali had 90% incidence at this time. At 16 WAP, ten genotypes had 100% CMD incidence; Kigoma Red was 39.6% infected. ELISA detected a mean CMD reinfection rate of 66.6%; PCR detected 69%. A high negative and significant (P< 0.01) correlation (r = - 0.70) was established between CMD severity and storage root yield.Keywords: Virus-free cassava genotypes, tissue culture, rate of reinfection, cassava mosaic diseas

Achieving Quality Assurance in Nigeria University System through Strategic Human Resources Development

This paper examines how quality assurance can be attained through Strategic Human Resources Development in Nigerian University system. The purpose is to ensure quality control and maintenance of acceptable standards in the University system. To seek solution to the problem, three research questions were posed. The sample for the study was made up of three hundred and sixty (360) academic staff randomly selected from the various Faculties and Institutes of the University of Calabar, Nigeria. The three research questions were analyzed using descriptive statistics. The results of the analysis revealed a significant relationship between Quality Assurance and Human Resources Development. Keywords: Quality Assurance; Human Resources Development, Quality Education; Higher Education.International Journal of Educational Research Vol. 4 (1) 2008: pp. 161-16

Evaluation of antifungal effect of Parkia biglobosa and Vitellaria paradoxa against selected pathogenic fungi

The aim of this study was to evaluate the antifungal effects of extracts of two plant species namely Vitellaria paradoxa and Parkia biglobosa against growth of some selected fungal species. Aqueous and ethanolic extracts of these plant species were assessed against Aspergillus flavus, Candida albican and Trichophyton mentagrophyte. Phytochemical analysis of these plants showed the presence of alkaloids, flavonoids, tannins, saponins and other secondary metabolites. The minimum fungicidal concentration (MFC) of aqueous extract of P. biglobosa was 150 mg mL-1 against both C. albican and A. flavus. On the other hand, ethanolic extract of this plant species had MFC of 300 mg mL-1 for A. flavus, while there was no MFC for C. albican. Likewise, aqueous extract of V. paradoxa also had same value of MFC against C. albican as well as A. flavus. Ethanolic extract of V. paradoxa had MFC of 150 and 300 mg mL-1 against C. albican and A. flavus, respectively. The combined aqueous extracts of these plant species showed MFC of 300 mg mL-1 against both the C. albican and A. flavus. By contrast, the mixture of ethanolic extracts had MIC of 150 mg mL-1 against C. albican, and no MFC for A. flavus

Crude Oil-Degradation and Plasmid Profile of Nitrifying Bacteria Isolated from Oil-Impacted Mangrove Sediment in the Niger Delta of Nigeria

The crude oil degradability and plasmid profile of autotrophic nitrifying bacteria, Nitrosomonas and Nitrobacter species, isolated from mangrove sediment in the Niger Delta of Nigeria were studied. The effects of temperature, pH and optical density on the utilization of different carbon sources by the bacteria were also investigated. Results showed that nitrifying bacteria could utilize kerosene, diesel oil, jet fuel and engine oil as carbon sources. None utilized hexane and xylene but moderate growth was observed in benzene, phenol and toluene. However, their ability to utilized crude oil varied both in rates of utilization and in growth profiles. Mixed culture of the isolates degrades 52 % of crude oil introduced into the medium followed by Nitrosomonas sp. with 40 % degradation. The least was Nitrobacter sp. with 20 % degradation. The ability of the autotrophs to degrade crude oil was found to be plasmid-mediated through curing experiment and electrophoresis. The size of the plasmid involved was estimated to be 23 kb. The high crude oil utilization of the mixed culture implies that nitrifying bacteria isolated from contaminated ecosystem are excellent crude oil degraders and can be harnessed for bioremediation purposes

Spatially structured genetic diversity of the Amerindian yam (Dioscorea trifida L.) assessed by SSR and ISSR markers in Southern Brazil

Dioscorea trifida L. (Dioscoreaceae) is among the economically most important cultivated Amerindian yam species, whose origin and domestication are still unresolved issues. in order to estimate the genetic diversity maintained by traditional farmers in Brazil, 53 accessions of D. trifida from 11 municipalities in the states of São Paulo, Santa Catarina, Mato Grosso and Amazonas were characterized on the basis of eight Simple Sequence Repeats (SSR) and 16 Inter Simple Sequence Repeats (ISSR) markers. the level of polymorphism among the accessions was high, 95 % for SSR and 75.8 % for ISSR. the SSR marker showed higher discrimination power among accessions compared to ISSR, with D parameter values of 0.79 and 0.44, respectively. Although SSR and ISSR markers led to dendrograms with different topologies, both separated the accessions into three main groups: I-Ubatuba-SP; II-Iguape-SP and Santa Catarina; and III-Mato Grosso. the accessions from Amazonas State were classified in group II with SSR and in a separate group with ISSR. Bayesian and principal coordinate analyzes conducted with both molecular markers corroborated the classification into three main groups. Higher variation was found within groups in the AMOVA analysis for both markers (66.5 and 60.6 % for ISSR and SSR, respectively), and higher Shannon diversity index was found for group II with SSR. Significant but low correlations were found between genetic and geographic distances (r = 0.08; p = 0.0007 for SSR and r = 0.16; p = 0.0002 for ISSR). Therefore, results from both markers showed a slight spatially structured genetic diversity in D. trifida accessions maintained by small traditional farmers in Brazil.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Univ São Paulo, Luiz de Queiroz Coll Agr, Dept Genet, BR-13400970 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Biol Sci, BR-09972270 São Paulo, BrazilUniv Calif Davis, Dept Plant Sci MS1, Sect Crop & Ecosyst Sci, Davis, CA 95616 USAUniversidade Federal de São Paulo, Dept Biol Sci, BR-09972270 São Paulo, BrazilFAPESP: 2007/04805-2Web of Scienc