The benefit of combining different Ty-genes for resistance to tomato leaf curl begomoviruses
2019
Kenyon, L. | Hanson, P. M. | Nguyen, T. L. H. | Le, T. H. | Dolores, L. | Techawongstein, S. | Shih, S. L. | Chan, Y. L. | Ledesma, D. R. | Lee, L. M. | Ha, V. C.
Leaf curl caused by whitefly-transmitted geminiviruses (begomoviruses) constraints tomato production in many production areas and breeding for durable resistance is an important target. Four of the leaf curl resistance genes (Ty-1/3, Ty-2, ty-5, and ty-6) identified from tomato wild relatives have been extensively studied, but each of these alone generally provides only tolerance to some begomoviruses. Combinations of Ty genes may offer tolerance to a broader range of begomoviruses and increase durability. Marker-assisted selection was used at World Vegetable Center to stack different combinations of these Ty genes into new tomato breeding lines. A set of 15 of these lines carrying different combinations of the Ty genes was screened in the field in Taiwan where Tomato yellow leaf curl Thailand virus (TYLCTHV) and Tomato leaf curl Taiwan virus (ToLCTV) were confirmed as the predominant tomato-infecting begomoviruses, in Thailand where TYLCTHV and Tomato yellow leaf curl Kanchanaburi virus predominated, and in Vietnam where Tomato leaf curl Hainan virus predominated. The same set of lines was also screened in the net-house in the Philippines with an isolate of Tomato leaf curl Philippines virus, and in Vietnam with an isolate of Pepper yellow leaf curl Vietnam virus. The tomato lines reacted slightly differently when challenged with the different begomoviruses in the different countries, though generally, the lines carrying two Ty genes presented milder leaf curl symptoms than those carrying only one Ty gene. However, none of the combinations of Ty genes provided complete resistance (immunity) to any of the challenging viruses.
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