Investigations on cyanide producing pseudomonad bacterial spieces and their potential for application against termite odontotermes obesus

Abstract

Rhizobacteria perform a variety of ecological functions. While some can be deleterious and negatively impact plant growth, others promote plant growth. Rhizobacteria help plants in acquiring scarce and inaccessible nutrients by fixing or mobilizing. They can also protect plants from diseases by releasing a variety of secondary metabolites into the soil which can be toxic to pathogens and pests. HCN producing bacteria are a group of rhizobacteria that can have deleterious effects on a variety of soil borne root pathogens and invertebrate pests. Consequently, they may offer an appealing option for the management of root pathogens and pests. Termites are social insects that perform important ecosystem functions like break down of plant material and initiation of nutrient cycling. They evolved over 150 million years ago and there are more than 3000 species worldwide. They are natural soil engineers, the nests and soil structures that they build help in the aeration of soil and provide food and habitat to a range of animals. Nevertheless, their activities affect human commerce through the damage they cause in agriculture and to infrastructure. For instance, in India termites cause an estimated loss of US$ 35 million in agriculture. Control of termites by strategies employing their natural predators and parasites is appealing from an environmental point of view. However, there are limitations to this approach because of (1) removal of the pathogen by termites when grooming and (2) isolation of infested members of the colony. HCN producing bacteria have a potential to overcome the above limitations as they can potentially kill termites without infection or contact through the release of HCN. In this thesis, I investigated the effectiveness of HCN producing bacteria as biocontrol agents against soil borne insect pests like termites. Odontotermes obesus served as a model termite species for my experiments. The subterranean termite O. obesus is a pest of the Indian subcontinent, causing extensive damage to major agricultur