Problems of heat spot in fragaria vesca L. when indexing strawberry selections for viruses

Summary In view of the available labour the testing of strawberry selections for viruses by runner grafting is carried out in autumn and winter. In order to obtain sufficient runners on the test plants these tests were carried out at a constant temperature of 23°C. At this temperature, however, the indicator plants (Fragaria vesca) developed heat spot. The symptoms are reminiscent of virus-infection, which makes it difficult to decide whether the test plant carries a virus or not.It was found that heat spot symptoms became less distinct at a constant temperature of 17°C, and were absent on newly developed leaves. Consequently the indicator plants were transferred to 17°C after 2 successful unions had been obtained at 23°C. In this way it was possible to obtain a reliable impression of the state of health of the test plant.