Botrytis cinerea induces the formation of free radicals in fruits of Capsicum annuum at positions remote from the site of infection - Rapid communication

Free radical adducts of the spin trap alpha-(4-pyridyl-1-oxide) -N-tert-but ylnitrone have been observed by electron paramagnetic resonance spectroscop y in detached fruits of Capsicum annuum investigated 5 days after infection with Botrytis cinerea. The spectra of these adducts were at a maximum with in the soft rot lesion, but they could also be detected at distances up to 50 min from the edge of the lesion in samples following main vascular bundl es. At distances greater than 40 mm, the spectrum of the ascorbate radical was also seen, and at greater distances from the lesion it was the only rad ical detected. With samples taken from parenchyma tissue adjacent to the va scular bundles there was little adduct formation and the ascorbate radical could be detected, albeit with reduced intensity compared to healthy tissue , at distances as small as 10 mm from the edge of the lesion. This observat ion of chemical changes at considerable distances from the infected tissue is in contrast to previous observations on the behaviour of other markers o f oxidative stress (e.g., 4-hydroxynonenal, malondialdehyde, single-peak fr ee radical, and Fe(III) (g = 4.27) electron paramagnetic resonance signals) , where their levels decreased rapidly outside of the soft rot.