Marker-assisted pyramiding of Ty-2, Ty-3, Ph-2, and Ph-3 genes for combined resistance to tomato leaf curl and late blight diseases in tomato (Solanum lycopersicum L.)

The production of tomato (Solanum lycopersicum L.) often suffers a significant yield loss due to the extensive occurrence of leaf curl disease, which is caused by begomoviruses transmitted by whiteflies, and the presence of late blight caused by oomycetes, Phytophthora infestans (Mont.) De Bary. Resistance to begomovirus and late blight disease is an important breeding goal of many tomato breeding programs. The present study was conducted to pyramid Ty-2, Ty-3, Ph-2, and Ph-3 for combined resistance against begomovirus and late blight through marker-assisted selection. Seven stable pyramided lines differing in fruit characteristics and other horticultural traits were developed and assessed for resistance to tomato leaf curl disease using whitefly-mediated virus inoculation. Reaction to late blight resistance in these pyramided lines was examined through the whole plant assay and the detached-leaflet method. Pyramiding of Ty-2, Ty-3, Ph-2, and Ph-3 genes in tomato lines showed a high degree of combined resistance against both diseases, with acceptable yield and other horticultural features. The experiment on the late blight resistance also showed that Ph-3 is crucial to achieving a high degree of resistance to P. infestans prevailing in India. The constraints of utilizing resistance governed by a single gene and the significance of utilizing marker-assisted gene pyramiding are emphasized.