Sugarcane streak mosaic virus: distribution, prevalence and severity in the integrated farming units of Zuénoula and Borotou-Koro, Côte d'Ivoire

Sugarcane streak mosaic is an emerging viral disease caused by sugarcane streak mosaic virus (SCSMV) recently reported in Ivorian sugar production areas. A 5-year study was performed to determine the spatial distribution, prevalence and severity of SCSMV on commercial varieties in two of the three sugarcane production basins of Côte d'Ivoire. In Zuénoula, 104 plots were evaluated between 2018 and 2021. In Borotou-Koro, 72 plots were evaluated between 2019 and 2022. Disease prevalence and severity were assessed using a 0 to 4 rating scale based on the percentage of symptomatic leaf area. In Zuénoula, overall disease prevalence was 98% in 2018, 100% in 2020 and 98% in 2021. Varieties M1400/86, M2593/92, R570 and SP711406 were monitored during the three years. M1400/86 and M2593/92 showed a moderately susceptible profile, whereas R570 was susceptible to moderately susceptible and SP711406 was susceptible. In Borotou-Koro, overall disease prevalence was 21% in 2019, 48% in 2020 and 61% in 2022. Varieties Co449, M1400/86, R570 and SP711406 were monitored during the three years. Co449 remained moderately susceptible throughout the monitoring, while M1400/86, R570 and SP711406 varied from partially resistant to moderately susceptible. This study showed that SCSMV is highly prevalent in the Zuénoula sugar complex and is rapidly spreading in the Borotou-Koro complex. In this context, varieties showed either a stable or increasing susceptibility profile. In vitro regeneration permitted significant reduction in prevalence and severity but efforts must be maintained to achieve higher levels of resistance.