African Journal of Biotechnology Vol. 6 (20), pp. 2340-2347, 18 October 2007   

ISSN 1684–5315 © 2007 Academic Journals        

Full Length Research Paper

Limitation in detecting African cassava mosaic geminivirus in the lignified tissues of cassava stems

Njock, T. E.¹* and R. N. Ndip^{2, 3}

¹Department of Plant and Animal Sciences, University of Buea, P. O. 63 Buea, Cameroon.

²Department of Biochemistry and Microbiology, University of Buea, P.O. Box 63 Buea, Cameroon.

³Department of Biochemistry and Microbiology, University of Fort Hare, P/Bag X1314, Alice 5700, Republic of South Africa.

*Corresponding author. Email: tnjockeku@yahoo.com. Tel: (237) 760 52 24. Fax: (237) 332 22 72.

Accepted 15 August, 2007

Field-infected cassava stems whose leaves were identified with differential symptoms of African cassava mosaic geminivirus (ACMV) disease were assessed for index of severity of symptoms (ISS) to determine their infection status by scoring young resultant plants in the laboratory. Extracts of young stem tissues and leaves of emergent shoots from topped stems were also assayed for occurrence of ACMV by the enzyme-linked immunosorbent assay (ELISA). Geminivirus disease incidence and severity of symptoms were most abundant on leaves of plants from cuttings of field-symptomatic (I) stems of the moderately-resistant TMS 4(2)1425 (63.2%) and the susceptible TMS 60506 (51.1%) genotypes while those from apparently symptom-free (H) stems of the resistant genotype TMS 30001 recorded significantly the least disease (0%). Similarly, the index of severity of symptoms on all plants (ISS_AP) and diseased plants only (ISS_DP) were significantly highest on leaves of TMS 4(2)1425 (2.42 and 2.83), and were significantly the least (1) on leaves of TMS 30001, respectively. ACMV was not detected in extracts of all sections of lignified cassava stems by ELISA as all absorbance values were below threshold (0.0890). However, the virus was detected at greater concentrations in leaves of emergent axillary shoots regenerating on topped plants of all node types of TMS 60506 and TMS 4(2)1425 as well as the base (node 1) of TMS 30001 stems but not on those from middle and uppermost nodes (10 and 20, respectively) of the latter genotype. The highest absorbance values were recorded on shoots on node 1 of TMS 60506 (0.1720 ± 0.096), TMS 4(2)1425 (0.1640 ± 0.115) and TMS 30001 (0.1580 ± 0.080) in that order, while the least values were on nodes 10 (0.0298 ± 0.020) and 20 (0.0289 ± 0.019) of TMS 30001.

Key words: African cassava mosaic geminivirus, infection status, cassava genotypes, detection limitations, enzyme-linked-immunosorbent assay.