Oilseed rape (OSR; Brassica napus L.) is a crop of increasing world importance and suffers yield loss when infected with Heterodera schachtii. The in vitro hatch, in planta root invasion and development of a field population of H. schachtii were investigated in six thermostatically-controlled water baths at temperatures of 5.0, 10.1, 20.5, 27.8, 32.2 and 37.5°C in a glasshouse. The UK winter OSR CVS Flash and Castille were used. Temperature was shown to have a major influence on the development of H. schachtii in OSR. The highest cumulative percentage hatch of second-stage juveniles (J2) observed over an 8-week incubation period occurred between 20.5 and 27.8°C in leachates of both OSR cultivars, indicating that this is the optimum temperature range for hatching of this population. Cumulative hatch was lowest at 37.5 and 5.0°C. Root invasion was inhibited at 5.0 and 37.5°C, whilst the highest number of J2 invaded the roots between 20.5 and 32.2°C, indicating that this is the optimum temperature range for root invasion. The life cycle took between 21 days at 20.5°C and 42 days at 5.0°C from the inoculated J2 to the J2 of the second generation, with the associated accumulated heat units (AHU) of 424 and 203 degree-days with a base temperature (Tb) of 5.0°C. The optimum temperature range (To) for development was between 20.5 and 27.8°C and the maximum (Tm) was 37.5°C. As temperature increased, the AHU required to complete the life cycle increased from 203 degree-days at 5.0°C to 1406 at 37.5°C. Leachates from both OSR cultivars stimulated more J2 to hatch than the distilled water controls. No significant cultivar differences were observed for J2 hatching, root invasion and duration of the life cycle at the different temperatures but significantly more cysts of the second generation (g root)"' were observed in cv. Flash than cv. Castille at 27.8 and 32.2°C, suggesting that the latter cultivar is a poorer host of H. schachtii than cv. Flash. This is the first report of the effect of temperature on H. schachtii development on current winter OSR cultivars in the UK and provides insight into the potential effects of climate change on the nematode-host interaction.

The number of generations completed by a UK field population of Heterodera schachtii on winter and spring oilseed rape (OSR; Brassica napus L.) during the growing season of 2010/2011 was investigated. The experiments were conducted in pots outdoor using UK OSR winter cultivars (cvs) Flash and Castille and spring cvs Belinda and Heros. The results indicated that temperature was crucial in determining the number of generations completed on OSR during the growing season. At least one generation was completed on cv. Castille, whilst two generations were completed on cvs Flash, Belinda and Heros during the growing season. Development of H. schachtii was faster on hybrid OSR cvs Flash and Belinda, suggesting that the hybrids were better hosts of H. schachtii than the conventional cvs Castille and Heros. Cultivar Flash was more susceptible to H. schachtii infection than cv. Castille, while cv. Belinda was more susceptible than cv. Heros. However, no major plant growth differences were observed between the cvs investigated. This is the first report on the number of generations of H. schachtii completed on current cultivars of OSR in the UK.