Zimbabwe is Free from Maize Chlorotic Mottle Virus (MCMV):The Chief Virus for Maize Lethal Necrosis

Abstract

Invasive cross-border plant pests such as Maize Chlorotic Mottle Virus (MCMV) introduced through pest-pathway exacerbated by anthropogenic behaviour negatively impact market access, food and nutrition security in Sub-Saharan Africa. Surveillance was carried out from 2020 to 2024 by conducting a census (100% population sampling) of maize pathways entering the country to check their MCMV pest-status and to ascertain the impact of pre-border plant biosecurity control measures in reducing accidental introduction of regulated pests. Double antibody-sandwich enzyme-linked immunosorbent assay (ELISA) and Bioreba-agristrips rapid test kits were used to test for the virus. A simple random sampling was used to pick maize fields for green tissues testing and maize grain and seeds from grain stores, seed stores and agro-dealers in the country. A symmetric analysis was computed to understand the association of samples originating from MCMV endemic and non-MCMV endemic areas Ordinal-by-Ordinal Associations test, (Kendall’s tau-b and tau-c = 0.333; Gamma = 0.333; Spearman’s rho = 0.500; p = 1.000, Monte Carlo 99% confidence interval (CI): [1.000, 1.000]) and Interval-by-Interval association and Chi –square Pearson’s correlation coefficient (Pearson’s r = 0.996; at 99% CI of [0.321, 0.346]) showed positive correlation which was not significant. The interval-level showed a close to perfect linear association between samples collected from MCMV endemic and non-MCV endemic countries. The Pearson’s correlation X2  (1); (p = 0.053) was also non- ignificant. A median (Kruskal–Wallis H) test showed no significant difference on the median values of MCMV endemic and non-MCV endemic (p = 0.223). There were no significance difference on the distribution of samples collected from endemic MCMV and none-endemic MCMV regions (α = 0.05; p = 0.368). All the tested 19106 samples were negative for MCMV. This research revealed that Zimbabwe is currently free from MCMV and it also confirmed the effectiveness of pre-border plant quarantine control measures in reducing the risk of germplasm as pest-pathways in cross border traffic particularly for the MCMV maize pathways approaching Zimbabwe.