Effect of temperature and host genotype on the production of inoculum by Phytophthora fragariae var fragariae
A bioassay has been developed in UK to monitor the release of inoculum in drainage water from strawberry plants inoculated with zoospores of Phytophthora fragariae var. fragariae (EPPO A2 quarantine pest). The fungus was detected in drainage water from plants that had been held at temperatures between 2 and 10 °C, but not from plants held at 26 °C. This shows that the production and release of inoculum of P. fragariae var. fragariae from infected strawberry plants is greatly favoured by low temperatures. As the results are consistent with observations previously made on the effect of temperature on zoospore production and on zoospore motility in the laboratory, the authors felt that the inoculum detected in this study mainly consists of motile zoospores. In addition, these results fit with the views that winter conditions of low temperatures and wet soils are the main determinant of damage observed in the following season. Concerning the influence of the host genotype, they observed that more secondary inoculum was produced by host genotype/fungal isolate combinations in which marked root rot symptoms were seen, than in combinations in which the host was resistant.
Sources
Duncan, J.M.; Kennedy, D.M. (1995) Effect of temperature and host genotype on the production of inoculum by Phytophthora fragariae var. fragariae from the roots of infected strawberry plants.
Plant Pathology, 44 (1), 10-21.