This study investigated the effect of inoculating three Amaranthus hybridus cultivars: NHAM/114, NH84/457-IL and LOCAL GREEN cultivar with Amaranthus mosaic virus (AMV) consecutively for four weeks. Results indicated significant differences between the control and virus inoculated plants. Severity of infection by the virus was more pronounced in plants inoculated at early ages while the effect was very mild on plants inoculated at later stage of growth. Reduced weight values were recorded in plants with early infection compared to plants inoculated at later stages of growth. Mean values of 0.190, 0.250 and 0.218 g were obtained for fresh weights of leaves of NHAM/114, NH84/457-IL and LOCAL GREEN respectively at 2 weeks after planting (WAP) while plants that were inoculated at 5 WAP had average values of 0.516, 0.392 and 0.397 g fresh weights of leaves for the three cultivars respectively. The percentage decrease in fresh weight of stem of the LOCAL GREEN cultivar was above average (56%) and higher than those of NHAM/114 and NH84/457-IL. NHAM/114 produced the least dry weights in stem while the highest dry weights were recorded for NH84/457-IL at all the stages of inoculations. These results indicated that infection at an early age resulted in greater reduction of the parameters assessed.

This study characterized Cucumber mosaic virus (CMV) infecting pepper in Southwestern Nigeria with the aim of providing up-to-date information on the taxonomic subgroup(s) of the parading strains in the study area. Fifty pepper leaf samples with one or more symptoms of mottling, mosaic, necrosis, leaf distortion and stunting were collected from eight commercial farms across Southwestern Nigeria and screened for CMV using antigen coated plate enzyme linked immunosorbent assay (ACP-ELISA). From the seropositive samples, four representative samples were selected, labelled PSWN1-4 before subjected to reverse transcription polymerase chain reaction (RT-PCR) and nucleic acid sequencing using a pair of primers specific for the amplification of RNA 3 genomic fragment of CMV. These were followed by multiple nucleotide sequence alignment and phylogenetic estimations of the isolates alongside selected CMV strains that were reported in previous studies using the molecular evolutionary genetics analysis (MEGA) software. The result of the ACP-ELISA test revealed that 14 (28%) of the samples collected were positive for CMV infection. The resulting nucleotide sequences from RT-PCR revealed 98% nucleotide homologies with several corresponding sequences of CMV strains from the Genbank. Further analysis of the PSWN nucleotide sequences through multiple nucleotide sequence alignment revealed the absence of the EcoR1 restriction site found only within the examined genomic portion of RNA 3 of subgroup II strains. These features defined the detected isolates as subgroup I strains. Phylogenetic analysis and estimations of genetic distances, conclusively distinguished the pepper-infecting CMV isolates from Southwestern Nigeria as members of subgroups IA and IB, which are the most virulent subgroups.