Influence of calcium nutrition on the susceptibility of N. tabacum to Phytophthora parasitica

Abstract

Summary — Calcium nutrition (0.1-15 meq I-! Ca; hydroponic culture under controlled conditions) had a significant influence on the susceptibility of N. tabacum to Phytophthora parasitica. In inoculated leaf experiments and in inoculated stem experiments; the tobacco plants grown in 2 meq . I-! Ca (total calcium content = 2.5% of the dry matter) were the most resistant to P. parasitica var. nicofianx, i.e., in the compatible interaction. In the incompatible interaction, the tobacco plants grown above 0.5 meq -I-! Ca (total calcium content > 1.5% of the dry matter) were the most resistant to P. parasitica in inoculated leaf experiments.The pathogenesis-related protein (PR) accumulation was determined in the different interactions and compared with that obtained after induction by an abiotic inductor (a by-product of benzoic acid). Firstly, in the inoculated leaf experiments, the rapidity of PR appearance depended upon the inductor type or on its aggressivity and appeared to be correlated with the horizontal resistance in the two types of interactions.