Ecology and Biocontrol Potential of Soil Fungi of a Backwater Environment along the East Coast of India

The soils collected from a backwater environment at Vellapallam in Nagapattinam district of Tamilnadu state along the east coast of India during May 2013 were subjected to the examination of fungi on PDA medium and physicochemical characteristics. The culturable propagules of the fungi were in the range from 6.98 to 106 x 10² CFU/g and the species diversity (number of species) was from 5 to 9.

The pH of the soil was in the range from 7.9 to 8.9; electrical conductivity from 0.04 to 1.31 dSm^-1; cation exchange capacity from 8.01 to 10.11 c.mol proton⁺/kg; organic carbon from 0.04 to 0.21%; available nitrogen from 0.011 to 0.22%; available phosphorus from 0.001 to 0.006%; available potassium from 0.011 to 0.057 ppm; available zinc from 0.36 to 0.57 ppm; available iron from 2.01 to 2.91 ppm; available copper from 0.14 to 0.34 ppm; available manganese from 1.22 to 1.53 ppm; calcium from 3.1 to 5.7 mg/kg; magnesium from 3.1 to 4.2 mg/kg; sodium from 0.29 to 1.73 mg/kg; and potassium 0.01 to 0.08 mg/kg. Among them electrical conductivity and the Organic Matter showed significant positive correlation with the total fungal population.

All the fungal species that were isolated from soils were tested against F. semitectum, a known soil borne fungal pathogen, by dual culture and food poisoning methods. Among them Trichoderma koeningii showed promising activity against the pathogenic fungus for the maximum both in dual culture and in food poisoning techniques. The inhibition was 61.3% at 20% concentration. As the antagonistic fungus was isolated from the environment that showed typical marine conditions, the isolate could better serve as biocontrol agent to control the soil born pathogen, F. semitectum in saline soil crop fields.