An update on the old, new, and emerging viruses infecting sugarcane

At least 24 viruses belonging to 10 different virus families infect sugarcane, and almost all can cause disease. Their impact on sugarcane production varies according to the virus species and the geographical location. Some of these sugarcane-infecting viruses have been found in other cultivated plants (e.g. sorghum and maize) or in non-cultivated hosts (such as grass weeds and ruderal plants). Viruses such as maize striate mosaic virus (MSMV), maize yellow mosaic virus (MaYMV), sugarcane striate virus (SStrV), sugarcane white streak virus (SWSV), sugarcane chlorotic streak virus (SCSV), and a new umbravirus (sugarcane umbra-like virus) were only reported recently. In contrast, other viruses, such as sugarcane Fiji disease virus (FDV) and sugarcane mosaic virus (SCMV), have been known for decades. Up to a few years ago, sugarcane streak mosaic virus (SCSMV) caused yield losses only in Asia, but it was identified in Côte d’Ivoire in 2018 and this virus constitutes a new threat to sugarcane production in Africa. SStrV was only found in germplasm collections in the USA and Guadeloupe but is present in commercial varieties and widespread in China. The effect of the most recently discovered virus species on yields of commercial sugarcane varieties is unknown. Nevertheless, the discovery of new or emerging virus pathogens greatly impacts the movement of sugarcane germplasm around the world and needs to be considered in sugarcane quarantines.