Assessment of the effectiveness ofTygenes in tomato against tomato leaf curl Bangalore virus

Tomato leaf curl Bangalore virus (ToLCBaV), a monopartite begomovirus transmitted by the whiteflyBemisia tabaci, has become a major constraint in tomato production in the Indian subcontinent. Earlier breeding efforts in India led to the adoption of tomato cultivars carrying the resistance geneTy-2. However, it has been observed recently that such cultivars/hybrids are susceptible to begomoviruses. This requires the identification of additional or new sources of resistance against ToLCBaV. The present study was undertaken to assess the effectiveness of severalTygenes in providing resistance against infection by ToLCBaV. The kinetics of virus multiplication in differentTyresistance gene stocks of tomato were estimated and compared using quantitative PCR data. Accumulation of viral genomic units and symptom severity were lower in tomato lines carryingTy-3andTy-2 + Ty-3compared with those carryingTy-2alone. All tested lines carryingTy-2showed typical tomato leaf curl disease symptoms. Tomato lines carryingTy-2 + ty-5andty-5 + Ty-6combinations had a significantly higher disease severity index and viral genomic units compared to those carryingTy-3andTy-2 + Ty-3at 30 days postinoculation. The accumulation level of ToLCBaV genomic units serves as a good indicator for resistance selection along with other parameters of disease. We present here a comprehensive overview of the effectiveness ofTy-2,Ty-3, andty-5alone as well as the combinationsTy-2 + Ty-3andTy-2 + ty-5against ToLCBaV.