The conserved coat or V2 gene of begomoviruses is responsible for viral movement in the plant cells. RNAi technology was used to silence V2 gene for resistance against these viruses in transgenic plants. The transformation of the RNAi-based gene construct targeting V2 gene of CLCuKoV-Bur, cloned under 35S promoter, was done in two elite cotton varieties MNH-786 and VH-289 using shoot apex cut method of gene transformation. The transformation efficiency was found to be 3.75 and 2.88 % in MNH-786 and VH-289, respectively. Confirmation of successful transformation was done through PCR in T ₀, T ₁, and T ₂ generations using gene-specific primers. Transgenic cotton plants were categorized on the basis of the virus disease index in T ₁ generation. Copy number and transgene location were observed using FISH and karyotyping in T ₂ generation which confirmed random integration of V2 RNAi amplicon at chromosome 6 and 16. Real-time quantitative PCR analyses of promising transgenic lines showed low virus titer compared to wild-type control plants upon challenging them with viruliferous whiteflies in a contained environment. From the results, it was concluded that amplicon V2 RNAi construct was able to limit virus replication and can be used to control CLCuV in the field.

Cotton leaf curl virus disease (CLCuD) is caused by a suite of whitefly-transmitted begomovirus species and strains, resulting in extensive losses annually in India and Pakistan. RNA-interference (RNAi) is a proven technology used for knockdown of gene expression in higher organisms and viruses. In this study, a small interfering RNA (siRNA) construct was designed to target the AC1 gene of Cotton leaf curl Kokhran virus-Burewala (CLCuKoV-Bu) and the βC1 gene and satellite conserved region of the Cotton leaf curl Multan betasatellite (CLCuMB). The AC1 gene and CLCuMB coding and non-coding regions function in replication initiation and suppression of the plant host defense pathway, respectively. The construct, Vβ, was transformed into cotton plants using the Agrobacterium-mediated embryo shoot apex cut method. Results from fluorescence in situ hybridization and karyotyping assays indicated that six of the 11 T₁ plants harbored a single copy of the Vβ transgene. Transgenic cotton plants and non-transgenic (susceptible) test plants included as the positive control were challenge-inoculated using the viruliferous whitefly vector to transmit the CLCuKoV-Bu/CLCuMB complex. Among the test plants, plant Vβ-6 was asymptomatic, had the lowest amount of detectable virus, and harbored a single copy of the transgene on chromosome six. Absence of characteristic leaf curl symptom development in transgenic Vβ-6 cotton plants, and significantly reduced begomoviral-betasatellite accumulation based on real-time polymerase chain reaction, indicated the successful knockdown of CLCuKoV-Bu and CLCuMB expression, resulting in leaf curl resistant plants.