INFLUENCE OF TEMPERATURE ON THE EXPRESSION OF RESISTANCE IN 6 PRUNUS ROOTSTOCKS INFECTED WITH MELOIDOGYNE-INCOGNITA

The influence of temperature on galling and nematode reproduction was determined for one susceptible and five resistant Prunus rootstocks inoculated with Meloidogyne incognita in two experiments conducted under greenhouse conditions in heated and unheated sand beds. In the first experiment, GF-677 inoculated with 5 000 nematodes per plant became extensively galled and supported about twice as much reproduction at 26 as at 30 degrees C. The higher soil temperature did not alter the expression of resistance substantially in Nemared peach, or in the Marianna GF 8-1 and Citation plums. In the second experiment, GF-677 that had been inoculated with 4 000 nematodes per plant developed similar numbers of galls at 23 and 31 degrees C, but nematode reproduction was about 10 times higher at the higher temperature. On the peach-almond hybrid G x N No 22, reproduction was negligible at 23 degrees C, but a measurable increase in galling and reproduction occurred at 31 degrees C, suggesting a partial loss of resistance with temperature increase. Nemared peach and Myrobalan 29C plum maintained resistance at the higher temperature regimes.