TEMPERATURE AND AGE OF PLANT AFFECT RESISTANCE IN PEACH-ALMOND HYBRID ROOTSTOCK INFECTED WITH MELOIDOGYNE-JAVA']JAVANICA

The influence of temperature and age of the plant was determined on nematode reproduction on a susceptible almond (Prunus amygdalus Batsch.) and on a resistant peach-almond hybrid (P. persica Stok. x P. amygdalus Batsch.) rootstock inoculated with Meloidogyne javanica (Treub) Chitwood. Experiments were conducted under greenhouse conditions in heated and unheated sand beds. 'Garrigues' almond inoculated with 3000 nematodes per plant showed extensive galling, high final nematode population levels, and high counts of nematodes per gram of root at 27 and 32C. The hybrid G x N No. 1 showed minimal galling and reproduction at 27C but higher levels of galling and final population and nematode counts per gram of root at 32C, suggesting a partial loss of resistance with temperature increase. One-month-old and 1-year-old plants of 'Garrigues' were susceptible following inoculation with 2000 nematodes per plant, although plantlets (1-month) were significantly more affected. Plantlets of hybrid G x N No. 1 were also susceptible, but 1-year-old plants were resistant. Resistant genotypes (G x N selections) seem to require root tissue maturation before expressing full resistance.