Virulence and Molecular Detection of Cassava Mosaic and Brown Streak Virus Genes on Elite Mutant Cassava Lines
Lydia Chepkoech Kimno
*
Department of Agriculture and Irrigation, County Government of Elgeyo-Marakwet, P.O. Box 249 - 30700, Iten, Kenya.
Javan Omondi Were
Department of Seed, Crop and Horticultural Sciences, School of Agriculture and Biotechnology, University of Eldoret, P.O. Box 1125 - 30100, Eldoret, Kenya.
Isaac Kofi Bimpong
Plant Breeding and Genetics Section, Joint FAO/IAEA Centre of Nuclear Techniques in Food and Agriculture, Department of Nuclear Sciences and Applications, International Atomic Energy Agency, Vienna International Centre, PO Box 100, 1400 Vienna, Austria.
Miriam Gaceri Kinyua
Department of Agricultural Biotechnology, School of Agriculture and Biotechnology, University of Eldoret, P.O. Box 1125 - 30100, Eldoret, Kenya.
Stephen Kimno
Center of Biotechnology Laboratory, University of Eldoret, P.O. Box 1125 - 30100, Eldoret, Kenya.
*Author to whom correspondence should be addressed.
Abstract
Unavailability of germplasm with Cassava Brown Streak Disease (CBSD) and Cassava Mosaic Disease (CMD) tolerance genes remains the main bottleneck towards management of the two diseases in tropic and sub-tropic regions in Africa. We assessed the pathogenicity of two viruses and established the presence of genes linked to CBSD and CMD among some elite cassava lines using field techniques and PCR methods. The screen-house experiment was arranged in split plot in completely randomized block design replicated thrice. Severity data was done on a scale of 1 - 5 at an interval of 14 days post inoculation. Symptomatic fresh leaves were used in the extraction of genomic deoxyribonucleic acid and amplification done using markers linked to African cassava mosaic virus (ACMV), separated bands scored as present (+) or absent (-) and visualized under UV trans-illuminator. Virulence and pathogenicity results showed higher tolerance to CBSD and CMD under single inoculation. In contrast, dual inoculation synergistically increased severity expression leading defoliation at early stages of growth. DNA amplification found no CBSD and CMD alleles in CAS1. However, some traces of the alleles were amplified on CAS2, CAS3, KME3 and KME4. Mutant cassava lines exhibited low severity compared to parental lines which were genetically different in terms of viral genes detected by the ACMV linked markers.
Keywords: Virulence, gene detection, cassava mosaic virus, cassava brown streak virus, cassava