Physiological parameters for early diagnosis of basal stem rot of coconut.

摘要

Preliminary experiments were conducted to determine the usefulness of physiological parameters for the early diagnosis of basal stem rot of coconut, caused by Ganoderma lucidum. Electrical conductivity (EC), relative water content (RWC), transpiration rate (TR) and stomatal diffusive resistance (SDR) were estimated in the tissues of healthy, apparently healthy as well as mild, moderate and severely diseased coconut palms. Electrolyte leakage was higher in leaf and root tissues of diseased palms than the apparently healthy and healthy palms and increased with increase in disease intensity. The relative water content was less in diseased leaves as compared with healthy ones and decreased with increase in disease severity. Basal stem rot affected palms had higher TR and less SDR than the healthy palms. TR increased and SDR decreased with increase in disease intensity. Though there was a significant difference in the physiological parameters between apparently healthy and diseased palms further studies are required to determine the critical point at which expression of visual symptoms takes place. Periodical estimation of electrical conductivity in apparently healthy palms indicated that coconut palms showed higher EC in root tissues 6-13 months before the expression of visual disease symptoms.