Two modern laser-based techniques were synchronously applied to study the dynamics of the trans-resveratrol activity in Botrytis cinerea-infected grapes. Direct analysis of trans-resveratrol in both infected and noninfected grapes (Vitis vinifera, Aledo variety) was performed by using an analytical technique incorporating laser desorption coupled with laser resonant ionization and time-of-flight mass spectrometry. On the other hand, one of the most sensitive on-line methods for trace gas detection, laser photoacoustic spectroscopy, was used to investigate the involvement of the plant hormone ethylene (C 2 H 4 ) in the B. cinerea grapes interaction and its temporal relationship with the trans-resveratrol content upon infection. The trans-resveratrol content and the ethylene released by noninfected grapes showed an opposite behavior. In this case, a high trans-resveratrol content corresponds to a low ethylene emission. For the B. cinerea-infected grapes, ethylene emission rises up after 48 h when the analogous content of trans-resveratrol started to decrease irreversibly. Moreover, the activity of trans-resveratrol as natural pesticide has been investigated by exogenous application on grapes. A short submerge (5 s) of the grapes in 1.6 ϫ 10 Ϫ4 m solution of trans-resveratrol delays the increase of C 2 H 4 emission with about 48 h and produces a decrease of the C 2 H 4 concentration and its emission rate. The treatment has positive effects on fruit conservation during storage; it doubled the normal shelf-life of grapes at room temperature, maintaining their post-harvest quality within 10 d.The fungus Botrytis cinerea is a plant necrotrophic pathogen that colonizes senescent or dead plant tissues and causes softening in fruits. Fungal hyphae can penetrate through wounds or natural openings of the plant tissue and spread from previously colonized dead tissues into healthy tissues. B. cinerea attacks different plant tissues and has a broad host range. It is a major cause of post-harvest rot of perishable plant products, including grapes (Vitis vinifera) at harvest and in storage. Because it is also able to infect at low temperatures, it can result in important economic losses, either in pre-and post-harvest crops (Mansfield, 1980). Under a pathogen attack, plants evolve sophisticated systems of detection and response to decipher the pathogen signals and to induce appropriate defenses. These systems include specific networks that operate through the action of signaling molecules such as salicylate, jasmonate, and ethylene and generate the accumulation of pathogenicity-related proteins, phytoalexins, or other phenolic compounds (Elad, 1997; Dong, 1998; Feys and Parker, 2000).trans-Resveratrol (3,5,4Ј-trihydroxystilbene) is an antioxidant compound naturally produced in a huge number of plants, including grapevine where it is the major component of the phytoalexin response of the plant. It is accumulated in vine leaves and grape skin in response to various fungal infections, UV radiation, or chemicals (Langcake, 1981; Jea...