Standardization of virus inoculation method for cassava mosaic disease

Abstract

The study entitled “Standardization of virus inoculation method for cassava mosaic disease”was carried out at the Division of Crop Protection, ICAR-Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram during 2015-2016. The objective of the study was to optimize the virus inoculation procedures for cassava mosaic disease using different methods viz., agro-inoculation, biolistic delivery of rolling circle amplification (RCA) product and whitefly transmission.In vitro derived virus free cassava plants (H226) was used for the study.Two infectious clones namely SLCMV (TVM 1) DNA A PD (pkkc24) and SLCMV (TVM 2) DNA B PD (pkkc25), were successfully transformed into three different Agrobacterium strains C58, GV3103 and LBA4404. The virus inoculation method for screening of cassava mosaic disease resistance was standardized and the factors that affect the efficiency of agroinoculation and whitefly transmission were investigated. Consequently, an optimal protocol was obtained by the syringe-infiltration method in the leaves of N. benthamiana. The protocol involved inoculation of 4-5 leaf stage N. benthamianaplants with the Agrobacterium strain C58 inoculum, having an initial OD600 0.5-0.8 and final OD600of 4.0 and incubation at 28°C for 6-7 days showed high cassava mosaic virus transmission efficiency in N. benthamiana. Viral symptoms were observed on the leaves of N. benthamianaplants 6 days after inoculation, which indicated that this protocol could be used to screen germplasm for their resistance to cassava mosaic disease.