Influence of Defoliate Pathotype of Verticillium dahliae on Some Physiological and Biochemical Characteristics of Chrysanthemum (Dendranthema grandiflorum (Ramat.) Kitam)

Verticillium dahliae Kleb. is a soilborne pathogen that causes vascular wilt in chrysanthemum plant (Dendranthema grandiflorum (Ramat.) Kitam). The objective of the present research was to study the levels of some organic solutes, such as total protein, total soluble sugars, starch and proline, relative water content, RNA level, malondialdehyde and H2O2 contents, in the leaves of chrysanthemum inoculated with V. dahliae. Changes in these parameters were measured 0, 10, 20, 30 and 40 days after inoculation by spectrophotometric analysis. No changes were detected in relative water content, RNA, and protein levels and a slight decrease was observed in chlorophyll level in infected leaf tissue before the appearance of visible wilt. The decrease in relative water content coincided with a sharp buildup of proline and total soluble sugars in leaves. The leaf starch and protein levels gradually declined in both healthy and infected plants during the time course of the experiment. However, the decrease was more pronounced in infected plants since the third week after inoculation. A high negative correlation was observed between total soluble sugars and starch contents in leaves of diseased plants (r= 0.764, P<0.001). Changes in malondialdehyde and H2O2 concentration occurred in infected plants between 30-40 days after inoculation, while they did not change in the leaves of control plants. These data suggest the posssible role of senescence during the development of Verticillium wilt syndrome in chrysanthemum.