Verticillium dahliae modifies the concentrations of proline, soluble sugars, starch, soluble protein and abscisic acid in pepper plants

The objective of this research was to study the levels of some organic solutes, such as total protein, total soluble sugars, starch and proline in leaves, as well as abscisic acid concentration in xylem of pepper plants inoculated with Verticillium dahliae Kleb. Healthy and inoculated plants were always kept well watered. Measurements were made at time intervals after inoculation. Leaf water potential rapidly decreased as a consequence of fungal infection. However, relative water content in leaves only changed significantly from day 20 after inoculation, and such decreases coincided with a sharp build up of proline and total soluble sugars in leaves. Starch and protein levels, as well as abscisic acid concentration in xylem, declined in healthy and inoculated peppers as they became older. However, such decreases were more pronounced in infected plants, especially soon after inoculation. Results suggest that proline and total soluble sugars accumulation could be sensors of the damage caused by the fungal infection.