Evaluation of Cane Genotypes Under Sprinkler Irrigation at Early Selection Stage for Tolerance to Sugarcane Streak Mosaic Virus (SCSMV) at Ferké Sugar Estates in Ivory Coast

Sugarcane streak mosaic virus (SCSMV) became the major endemic disease of economic importance in Ivorian sugar estates almost two years ago, which spreads very fast across plantations and varieties. The study aimed to determine resistant sugarcane genotypes against SCSMV in Ferké sugar estates. It involved five experiments conducted at first selection stage under sprinkler irrigation, following a randomized complete block design (RCBD) with 20 to 30 different genotypes, two check varieties included, all in 4 replicates. Experiments were planted in October or December 2018, and expected to be harvested in November/December 2019 and 2020 as plant cane and first ratoon, respectively. Disease incidence and severity across all experiments were determined at 3 to 4 months, i.e. at early formative growth stage where symptoms due to SCSMV could be easily observed and recognized in the field. In each of the five selection trials conducted on both Ferké 1 & 2 sugar estates, highly significant differences in disease incidence and severity were observed between genotypes as well as crop cycles (plant cane and first ratoon). Except for one trial (B3-24 in Ferké 1), Genotype x crop cycle interactions were significant or highly significant, which showed that the majority of genotypes tested behaved differently from plant cane to first ratoon towards the disease. Particularly, the percentage of resistant genotypes decreased from 50 to 3.4% whereas that of highly susceptible ones increased from 4.2 to 92.4%. This shows the level of challenge to be tackled in the control of SCSM disease through sugarcane breeding and selection. At the end of the current selection stage under way, i.e. after harvest of first ratoon, only the best yielding genotypes among the resistant ones will undergo the advanced selection stage.