Comparison of the Transmission Efficiency of Two Cucumber Mosaic Virus Isolates by A. spiraecola and M. persicae in Calabar, Nigeria

Abstract

Cucumber mosaic virus (CMV) is transmitted non-persistently by numerous aphid species, but transmission efficiency is strongly influenced by vector abundance and the timing of virus acquisition and inoculation. This study compared two CMV isolate–source-host systems, designated Ocimum and Passiflora, transmitted by Aphis spiraecola and Myzus persicae. Three separate transmission experiments evaluated aphid density (1, 4, 6 and 9 aphids per plant), post-acquisition interval (1, 10, 15 and 20 min), and matched acquisition/inoculation access periods (1/1, 8/8, 10/10 and 15/15 min). Four aphids per plant were maintained in the two time-based experiments, and each experiment was conducted across five independent trials. Transmission generally increased with aphid density but declined progressively with increasing post-acquisition interval and longer acquisition/inoculation access periods. Trial-level analyses showed that these treatment-response patterns were consistent across the five trials, whereas interaction tests provided limited evidence that treatment responses differed systematically between CMV isolate systems or aphid vector species. Dose-response modelling showed higher post-acquisition 50%-transmission intervals (ST50) for the Passiflora system (15.95 min with A. spiraecola and 15.17 min with M. persicae) than for the Ocimum system (10.26 and 6.18 min, respectively). However, because the isolate × post-acquisition interval interaction was not significant and the isolates were maintained in different source hosts, the ST50 difference is interpreted as evidence of potentially longer apparent transmissibility rather than an intrinsic isolate-specific retention mechanism. Overall, vector abundance and the temporal relationship between virus acquisition and inoculation were the most consistent determinants of CMV transmission, emphasising the epidemiological importance of aphid probing and rapid movement between infected and susceptible plants.