Induced resistance against the Asian citrus psyllid, Diaphorina citri, by β-aminobutyric acid in citrus.

β-Aminobutyric acid (BABA) is known to induce resistance to microbial pathogens, nematodes and insects in several host plant/pest systems. The present study was undertaken to determine whether a similar effect of BABA occurred against the Asian citrus psyllid, Diaphorina citri Kuwayama, in citrus. A 25mM drench application of BABA significantly reduced the number of eggs/plant as compared with a water control, whereas 200 and 100mM applications of BABA reduced the numbers of nymphs/plant and adults/plants, respectively. A 5mM foliar application of BABA significantly reduced the number of adults but not eggs or nymphs when compared with a water control treatment. In addition, leaf-dip bioassays using various concentrations (25–500mM) of BABA indicated no direct toxic effect on 2nd and 5th instar nymphs or adult D. citri. BABA-treated plants were characterized by significantly lower levels of iron, magnesium, phosphorus, sodium, sulfur and zinc as compared with control plants. The expression level of the PR-2 gene (β-1,3-glucanase) in BABA-treated plants that were also damaged by D. citri adult feeding was significantly higher than in plants exposed to BABA, D. citri feeding alone orcontrol plants. Our results indicate the potential for using BABA as a systemic acquired resistance management tool for D. citri.