The effect of methyl jasmonate (MeJA) sprayed on cotton healthy leaves was evaluated in terms of inherent bioactive chemicals induction. The total phenolic content significantly increased after MeJA 5.0 mM treatments compared to the other tested concentrations (0; 2.5; 10; 15; 20 mM). Among the eleven phenolic compounds which were found except for ferulic acid, gossypetin, gossypol, 3-p-coumaroylquinic acid, and piceatannol were identified as major phenolic constituents of cotton. Their content also significantly increased after the MeJA treatment. In addition, gossypol increased 64 times compared to the control, in the 5.0 mM MeJA treatment. Furthermore, cichoric acid, chlorogenic acid, and pterostilbene are synthesizedde novoin leaves of MeJA-treated plant. Treatment of cotton leaves with MeJA 5.0 mM followed 72 h of incubation hampered the expression ofFusariumwilt caused byFusarium oxysporium f. sp. vasinfectum(FOV). MeJA efficiency was concentration and incubation time dependent. Disease severity on MeJA-treated leaves was significantly lower as compared to the control. Therefore, the high content of gossypetin, gossypol, 3-p-coumaroylquinic acid, ferulic acid, and piceatannol and the presence of cichoric acid, chlorogenic acid, and pterostilbene in plants treated with MeJA, contrary to the control, are essential to equip the cotton compounds with defences or phytoalexins against FOV.

Studies of phenolic compounds were performed during cell suspension cultures in relation with the induction of embryogenic structures in two cultivars of cotton. Coker 312 produced embryogenic structures, unlike R405-2000 which was found to be a non-embryogenic cultivar. Embryogenesis induction in Coker 312 was strongly linked to a higher content of caffeic, ferulic and salicylic acids and to the appearance of p-coumaric acid, benzoic acid, transresveratrol, catechin and naringenin.

For the first time, trans-resveratrol, a stilbene, has been identified in cotton cell suspensions. Cell suspensions of Coker 312, a cultivar which produces embryogenic structures, acccumulate trans-resveratrol contrary to those of cultivar R405-2000, which do not. This stilbene may be a good phenolic marker for induction of somatic embryogenesis in cotton.