Localization of Tomato spotted wilt virus in Chrysanthemum Stock Plants and Efficiency of Viral Transmission from Infected Stock Plants to Cuttings

Localization of Tomato spotted wilt virus (TSWV) in susceptible chrysanthemum stock plants and its efficiency of transmission from latently infected stock plants to cuttings under thrips-free conditions were investigated using double-antibody sandwich enzymelinked immunosorbent assay (DAS-ELISA), reverse transcription polymerase chain reaction (RT-PCR) combined with dot-blot hybridization, and by cultivation. TSWV localized in symptomless stock plants and cuttings taken from them, and its detection frequency, was relatively high in the lower leaves and stems, but low in terminal buds of cuttings. In cv. Seinoyakata, the detection rate of TSWV in cuttings taken from infected stock plants ranged from 26.3 to 38.5% in 2002 and from 16.7 to 39.1% in 2003, and in cv. Jimba from 37.5 to 47.1% from January to May 2003. No fluctuation in detection rate by cutting generation or season was observed. The detection rate of TSWV in the roots of stock plants was >50% in most periods. These results indicate that transmission efficiency from infected chrysanthemum stock plants to cuttings is fairly high (approximately 20–50%) and thus may become a major source of secondary infection in production fields or glasshouses. Our results also suggest that several lower leaves should be combined in ELISA to detect infection in stock plants and cuttings