Histopathological aspects of resistance in wheat to Puccinia triticina, induced by Pseudomonas protegens CHA0 and β-aminobutyric acid

Abstract

After perception of specific biotic or abiotic stimuli, such as root colonization by rhizobacteria or selected chemicals, plants can enhance their basal resistanceagainst pathogens. Due to its likely sustainability, this induced resistance will be valuablefor disease management in agriculture. This study examined resistance againstwheat leaf rust (Puccinia triticina) induced by Pseudomonas protegens CHA0 (CHA0)and β-aminobutyric acid (BABA). Seed dressing with CHA0 reduced the number ofsporulating pustules on leaves, and expression of resistance was visible as necrotic orchlorotic leaf flecks. Beneficial effect of CHA0 on wheat seedlings growth was observedin when they were challenged or not with leaf rust. BABA was tested at 10, 15 or 20mM, and a dose-dependent reduction of leaf rust infections was observed with greatestprotection at 20 mM. However, BABA treatment repressed plant growth at 20 mM.Balancing the BABA impact on plant growth and its protective capacity, 15 mM of thecompound was selected as suitable to protect wheat seedlings against leaf rust, with theleast impact on vegetative host growth. Histological aspects of the pathogen infectionprocess was studied to understand mechanisms of behind the observed resistance. Thepre-entry process was not affected by the two resistance inducers, but both treatmentsreduced fungus penetration and haustorium formation. Timing and amplitude of theresistance reactions were different after bacterial or chemical induction, leading to differentlevels of resistance. During fungal colonization of host tissues, high depositionof callose and accumulation of H2O2 in both CHA0- and BABA-treated plants indicatedimportant contributions to resistance