First report of Sugarcane Streak Mosaic Virus (SCSMV) infecting sugarcane in Côte d'Ivoire

Sugarcane streak mosaic virus (SCSMV; Poaceavirus; Potiviridae) is the causal agent of streak mosaic disease of sugarcane (Saccharum interspecific hybrids), a major industrial crop that is widely cultivated in tropical and subtropical regions for sugar and ethanol production. was first reported by Hall et al. (1998) from quarantined germplasm material exhibiting mosaic symptoms imported from Pakistan into the USA. Subsequently, the virus was also reported to occur in most of the Asian countries like Bangladesh, India, Indonesia, Iran, Sri Lanka, Thailand, Vietnam and China (Chatenet et al. 2005; Hema et al. 2008, Kasemsin et al. 2016, Putra et al. 2014, Xu et al. 2010, Moradi et al. 2015; Moradi et al. 2018, Zhang et al. 2018). Until now, there is no report of SCSMV outside the Asian continent. From February to October 2018, sugarcane plants exhibiting symptoms such as irregular yellow and green mosaic, interveinal chlorotic specks, and streaks were observed in Bafing (Borotou-Koro), Marahoué (Zuénoula) and Tchologo (Ferkéssédougou) regions of Côte d'Ivoire (Fig. 1a). Varieties under large-scale commercial cultivation such as R570, R579, SP711406, Co997, Co449, M1176/77, M2593/92, M2580/95, and M1400/86 were all symptomatic. A total of 94 sugarcane leaf samples were collected from these regions and, among those, 82 showed disease symptoms and 12 were symptomless. Samples were first tested for the presence of sugarcane mosaic virus (SCMV), which causes mosaic a disease that is already present in Africa. Serological tests with infected sap using a Double Antibody Sandwich (DAS)- Enzyme Linked Immuno Sorbent Assay (ELISA) kit (DSMZ, RT-0166, Braunschweig, Germany) were negative for SCMV and no amplification product was obtained by RT-PCR using primers specific to the coat protein (CP) gene of SCMV (Putra et al. 2003). The 82 symptomatic leaves tested positive by DAS-ELISA with SCSMV antiserum (polyclonal antibodies were graciously provided by Prof. Hema M. of the Sri Venkateswara University, Tirupati, AP, India), whereas the 12 symptomless samples tested negative. To confirm these results, virus free greenhouse-grown sugarcane varieties Co997 and M1176/77, were mechanically inoculated with 10 sap extracts from 10 SCSMV-infected sugarcane leaf samples. Sap was also extracted from DAS-ELISA negative sugarcane leaves and used as negative control. For sap preparation, leaves were homogenized with a mortar in 2 mL of phosphate buffer 0.01 M pH 7.2 (ratio 1:10). Fi