β-aminobutyric acid-induced resistance in Brassica juncea against the necrotrophic pathogen Alternaria brassicae

beta-Aminobutyric acid (BABA) pretreatment of Brassica plants protected them against the necrotrophic pathogen Alternaria brassicae. The achieved resistance level was much higher than that seen after salicylic acid (SA) and jasmonic acid (JA) pretreatments. BABA pretreatment to the leaves, 1 day before inoculation, led to an inhibition of the oxidative burst and a decrease in SA levels, but did not influence lipoxygenase activity nor cause callose deposition at the site of inoculation. Expression of two marker genes of the SA and JA pathways, namely PR1 and PDF1.2, was enhanced in response to BABA pretreatment. Our results indicate that BABA-induced resistance is mediated through an enhanced expression of pathogenesis-related protein genes, independent of SA and JA accumulation.