Detection of Viruses Infecting Lettuce (Lactuca sativa L.) in the Derived Savanna of Nigeria and Influence on Proximate Composition

A survey was accomplished in the derived savanna of Oyo State, Nigeria during 2019/2020 cropping season to evaluate the incidence and severity of viruses infecting Lettuce. Laboratory experiments were performed serologically to identify the infecting viruses and to verify possible variations in the proximate composition. A total of 100 symptomatic and asymp­tomatic lettuce leaves were collected from different fields across the study area. Fifty of the leaves which were representative of the locations were then subjected to Antigen Coated Plate (ACP) and Double Antigen Sandwich Enzyme Linked Immunosorbent Assay (DAS ELISA) using specific polyclonal antisera against Cucumber mosaic virus (CMV), broad spectrum potyvirus, Lettuce mosaic virus (LMV) and Lettuce virus X (LeVX). The 50 other samples were subjected to proximate analysis. The incidence of virus infection varied across survey locations from 7.14% to 39.22% with a severity range from 10.33% to 41.32%. ELISA indicated single or multiple virus infection of CMV, LMV and/or Potyvirus while LeVX was not detected in the study. Proximate analysis indicated that the chlorophyll content of infected plants (0.6) was significantly lower than healthy plants (1.4). The total carbohydrate content was also significantly higher in healthy plants (13.8) compared to infected plants (7.7). This study is the first report confirming the infection of Cucumber mosaic virus, Lettuce mosaic virus and Potyvirus in lettuce in the selected agroecological zone. To enhance growth and quality of nutrients derived from lettuce, plant-virus management strategies should be adopted coupled with periodic virus surveys to detect newly emerging virus strains.