Detection of tobacco rattle virus by ELISA and test plants in main sprouts of tulip bulbs during storage at different temperatures

The detectability of tobacco rattle virus (TRV) in the main sprouts of primarily and secondarily infected tulip bulbs of cv. Apeldoorn stored at different temperatures from the lifting in July up to February is described. Detection by ELISA was not affected by the size of the main sprout, nor by the size of the bulbs. The rates of TRV-infected bulbs found by ELISA were highest during storage at 13, 9 or 5°C continuously, and when temperatures were lowered from 20 or 17°C to 5°C in October. The percentages detected via test plants, but undetectable by ELISA were also lowest at these temperatures. The unfavourable effect of continuous storage at 20, 17, or 2°C as expressed in low ELISA absorbances not significantly different from the mean value of healthy bulbs, was largely overcome during long storage by the change of temperature down to 5°C from 20 and 17°C or upwards from 2°C. The reverse from 5°C upwards to 17 and 20°C affected the detectability by ELISA unfavourably. The rate of detection via test plants in the main sprout and in the small sprouts from different positions in bulbs was only possible at low percentages.The effect of some factors, like different temperatures during storage, detectability of different TRV serotypes, interference of irregular occurrence of TRV in the removed scale and basal-plate tissue with the main sprout, and variable recurrence of TRV in progeny bulbs, is discussed in view of its impact on routine testing of bulbs during storage.