Expression of the Full‐length Coat Protein Gene of Tomato leaf curl Taiwan virus is Not Necessary for Recovery Phenotype in Transgenic Tomato

Abstract

AbstractTransgenic tomato plants expressing full‐length (CPV1) and truncated coat protein (CP) gene (CPV2) of Tomato leaf curl Taiwan virus (ToLCTWV) were generated by Agrobacterium‐mediated transformation. Transgene integration and expression was confirmed by PCR and Southern blotting and Northern analysis, respectively. Resistance was evaluated both in plants of T0 and T1 progenies using viruliferous whiteflies under two different inoculum pressures (10–15 and 40–50 whiteflies/plant). Upon inoculation with ToLCTWV using viruliferous whiteflies, various levels of phenotypic reaction were observed. No complete resistance was observed in any of the plants tested. The reaction of the transgenic tomato lines carrying full‐length and truncated CP gene to ToLCTWV phenotype was (i) susceptible as non‐transgenic control, (ii) delayed symptom expression, (iii) complete susceptible (from delayed symptom expression phenotype) and (iv) recovered phenotype (either plants from symptom expression as non‐transgenic plants or delayed symptom expression phenotype). Dot blot quantification of the ToLCTWV using the replicase gene as a probe revealed that the recovered phenotypes accumulated a low level of ToLCTWV, and virus concentration was gradually reduced from 10 to 14 weeks postinoculation. The possible mechanisms of CP‐mediated resistance are discussed.