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

Abstract

<em>Verticillium dahliae</em> Kleb.is a soilborne pathogen that cause vascular wilt in chrysanthemumplant (<em>Dendranthema grandiflorum </em>(Ramat.) Kitam). The objective of this 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 leaves of chrysanthemuminoculated with <em>V. dahliae</em>. Changes of these parameters were measured on 0, 10, 20, 30 and 40 days after inoculation by spectrophotometric analysis. No changes in relative water content, RNA, and protein levels and a slight decrease in chlorophyll level were detected within infected leaf tissue before the appearance of visible wilt. The decrease in relative water content coincided with a sharp build up 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 from 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<em>, </em>P<0.001). Changes in malondialdehyde and H₂O₂concentration 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 psssible role of senescence during the development of <em>Verticillium</em> wilt syndrome in chrysanthemum.