Postharvest β-aminobutyric-acid-primed resistance is not effective in the control of Penicillium expansum Link. on 'Golden delicious' apple fruit

β-Aminobutyric acid primes gene induction and callose accumulation in apple (Malus domestica L. cv. 'Golden delicious') fruit, although the induced resistance by itself does not control apple blue mold caused by Penicillium expansum Link.239