JOURNAL of Soil Biology and Ecology

Effect of soil moisture and duration on the viability of sclerotia of Sclerotinia sclerotiorum

Authors: K. KAMESH KRISHNAMOORTHY, A. SANKARALINGAM AND S. NAKKEERAN

Abstract:

The pathogen Sclerotinia sclerotiorum infects the crucifer cabbage in its mature stage in the field, leading to a head rot disease. Due to this disease, rotting of fully grown cabbage heads is observed, followed by cottony white mycelial growth. In the final stage of the disease, the mycelial growth becomes dense, and the appearance of carbon black coloured structures called sclerotia is observed. The sclerotia serve as resting structures of the pathogen and help in its further perpetuation. In the present study, the effect of soil moisture on the viability of sclerotia was studied. Soil conducive to Sclerotinia sclerotiorum was collected from a cabbage growing field in the Kothagiri area of Nilgiris district, Tamil Nadu. A known quantity of the soil was filled in plastic containers of 14 cm height and 11 cm dia. Nylon mesh pouches containing five sclerotia each six replications were placed in the upper 5 cm soil depth, which was covered by another 5 cm of soil. Four different soil moisture levels, viz., 60, 70, 80 and 90 per cent, were maintained in the containers. Sclerotia were sampled at 15 days’ time intervals for 60 days, and per cent germination of sclerotia was recorded. Results indicated that sclerotia survived better at low soil moisture levels and exhibited maximum germination at 60 per cent soil moisture level, which declined over time. The study demonstrated that higher soil moisture levels inhibited the viability of sclerotia, and viability also decreased with the increasing duration of sclerotia in soil.

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