Conference Paper

Molecular Characterization and Resistance Screening of Tomato Yellow Leaf Curl Thailand Virus in Taiwan

Conference: The 5th International Bemisia Workshop

ABSTRACT Tomato yellow leaf curl disease caused by begomoviruses (Family Geminiviridae,
Genus Begomovirus) is a major tomato disease worldwide. As of 2003, three tomato
begomoviruses, including the predominant Tomato Leaf Curl Taiwan Virus
(TOLCTWV), have been reported in Taiwan. In 2007, TOLCTWV and a newly
emerged begomovirus, the bipartite Tomato Yellow Leaf Curl Thailand Virus
(TYLCTHV), were determined to be the predominant tomato begomoviruses in Taiwan
by collecting 406 tomato samples from throughout the island and testing all by
polymerase chain reaction using virus specific primers. The TYLCTHV isolates were
highly homologous (>98.0% Nucleotide Identity) based on 1.5 Kb DNA-A sequences
of 76 isolates. However, the TOLCTWV isolates had less homology with the 62
isolates collected island-wide, showing from 78.5 to 99.9% identity to each other. The
pathogenicity of TYLCTHV genomic DNAs was confirmed by co-agroinfection of
infectious DNA-A and B, causing typical yellow leaf curl symptoms on tomato ‘ANT22’.
It was confirmed that TYLCTHV was transmitted by the whitefly Bemisia tabaci
(Biotype B), but it also could be transmitted by mechanical means. Viral DNA-A of
TYLCTHV alone induced typical yellow leaf curl symptoms and was transmitted by
whiteflies, but was not mechanically transmissible. So far, two out of 36 tomato lines
have been determined to be TYLCTHV tolerant by screening in an insect-proof net
house (50 Mesh) with viruliferous whiteflies. Results showed the newly emerged
TYLCTHV should be considered a severe pathogen for tomato culture in Taiwan.

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