Effects of allelochemical stress on response of cucumber to UV-B radiation and Botrytis cinerea infection

Using tolerant (Genoype-1) and susceptible (Genoype-14) genotypes of cucumber, which differed in their stress tolerance, we studied the effects of allelochemical stress. The application of ferulic acid (FA) as allelochemical on cucumber enhanced its resistance to UV-B irradiation and B. cinerea infection. Stress was imposed either alone and in combination. FA enhanced the 4-coumarate:CoA ligase (4CL) activity and this was correlated to plant's tolerance but the activity of chalcone synthase was not enhanced. Double stress (FA + UV-B) restricted the 4CL activity but did not affect the accumulation of flavonols. The effect on lignin content was negligible. Inoculation of seedlings with B. cinerea subjected earlier to FA + UV-B irradiation reduced the level of 4CL and flavonols. The results did not suggest cross-tolerance, as both abiotic stresses inhibited the response to B. cinerea.