Vegetos

Abstract

Phyllactinia dalbergiae Piroz. causes powdery mildew on Dalbergia sissoo Roxb. (shisham) in early stages of plants, pathogen takes entry in the host through the stomatal opening later, spread and establish itself in the host. The initial sign of symptom appears as the development of white powdery mass on the leaf surface later it covers the entire shoot finally plant succumbs to death. During survey powdery mildew was detected in the plantlets in the nursery, the infected plantlets were collected to study morphology, histopathology, pathogenicity and disease development under in vivo and in vitro condition. The infected part showed dense mycelial growth with erect conidiophore carrying single terminal conidium and brown-black coloured cleistothecia (fruiting body). The viability of the spore was detected to be 100% within 2–4 days in cavity slide containing nutrient medium through germ tube formation. During pathogenicity studies, healthy plants were inoculated with 15 days old culture of the pathogen to study the disease development. Cleared whole-mount preparation and hand cut sections revealed the presence of intercellular mycelium in the epidermal and sub-epidermal (dorsal and ventral surface) cells of the leaf. Dense mycelial ramification caused lysis and disintegration of cells. The pathogen transmitted through stomata causing heavy losses to tree plantation.