Reduction of cassava mosaic geminiviruses from infected stem cuttings using salicylic acid, hydrogen peroxide and hot water treatment

Abstract

Cassava mosaic disease (CMD) causes significant losses in cassava production in Africa. The disease is caused by several cassava mosaic geminiviruses (CMGs) and spread through the use of infected plant materials. The infected plants remain infected throughout their vegetative lifecycle as the disease cannot be controlled by standard plant protection measures. Therefore, it is important to develop inexpensive field-based methods that can be easily adopted by small-scale farmers to sanitize geminiviruses-infected stem cuttings used as planting material. This study aimed at eliminating CMGs from infected cassava stem cuttings by use of salicylic acid (SA), hydrogen peroxide (H₂O₂) and hot water (HW) treatments. Eight varieties of CMD-infected stem cuttings were pretreated with SA (1.25, 2.5 and 5 mM), H₂O₂ (0.5%, 1.0% and 1.5%) or hot water (50 and 55°C) at different exposure times before establishment in the glasshouse for evaluation of subsequent plant growth and geminivirus detection. Based on the cassava varieties used for the different treatments, treatment with hot water at 50°C for 5 min and 1.0% H₂O₂ for 12 h were the most effective in eliminating CMGs with an efficiency of 81.7% and 77.8%, respectively. Salicylic acid at a concentration of 5 mM for 6 h eliminated the viruses in 65.1% of the cuttings. The methods tested herein have the potential for producing planting materials with significantly reduced CMD risk for smallholder farmers and the cassava industry to meet their increasing demand. It could also contribute to the global exchange of germplasm for conservation and breeding programs.