Ecophysiological and biochemical events associated with the challenge of Verticillium dahliae to eggplant

Verticillium dahliae(Kleb.) is a soil-borne pathogen able to cause yield losses in eggplant,Solanum melongenaL., one of the most important vegetable crops in the Mediterranean basin. In this study, an experiment was conducted to assess physiological and biochemical mechanisms modulating the interactions betweenS. melongenacv. Violetta di Rimini andV. dahliaestrain VdGL16 in leaves at different age (mature, intermediate and young; ML, IL and YL) up to 25 days post artificial root inoculation (dpi). At 8 dpi, infected ML showed a marked reduction of photosynthetic rate (4-fold lower than controls) associated with stomatal (reduced stomatal conductance) and mesophyll (concomitant increase of intercellular CO(2)concentration) limitations. Cell membrane integrity was compromised, and phylloptosis/death occurred. At 8 and 18 dpi, stomatal closure (-40 and - 53%, respectively) and biochemical alterations occurred in IL. At 18 dpi, the consumption of secondary metabolites suggested that antioxidant- and antimicrobial-defence responses were activated. However, photoinhibition, oxidative stress and water deficit were observed at the end of the experiment. These mechanisms were observed also in YL, as confirmed by the strong increase of tannins (+46%) followed by accumulation of other phenylpropanoids. Despite plant growth being maintained, reduction of leaf area and water deficit occurred. This study highlights the capacity of eggplant to activate dynamic biochemical mechanisms in response to fungal infection, even in susceptible genotypes, a starting point for comparisons with resistant material for selection.