Abstract:
Plant infochemistry plays crucial role in governing the tritrophic interactions.
Biological pest control is an environmental friendly approach that uses the
natural enemies to control the pest population. To establish a potential
biocontrol agent it’s crucial to understand the natural enemy’s response to the
plant-produced as well as herbivore-metabolized chemicals. Here we tried to
investigate the effect of glucoraphanin and its metabolized forms produced by
the diamondback moth larvae on plant-herbivore-natural enemy interactions
to reveal the ecological significance of plant’s defense and herbivore’s
phytotoxin detoxification mechanisms in the tritrophic interactions. Native
Indian biological control agents for the diamondback moth were collected and
identified based on the available keys. Plant-mediated RNA interference
(PMRi) was used to silence the detoxification gene in Plutella xylostella. PMRi
led to the accumulation of toxic isothiocyanates in gut, hemolymph and frass
of P. xylostella larvae. These toxic isothiocyanates showed detrimental effects
on growth of the herbivore. Three predatory spider species- Hasarius
adansoni, Plexippus paykulli and Wadicosa fidelis were used to evaluate the
effect of gene silencing on the behaviour and choice of the predators. Spiders
showed uniform behavior to the changes in metabolite composition of their
prey. Frass analysis of these spiders revealed that the spiders were able to
detoxify the toxic isothiocyanates via mercapturic pathway. Thus, this case
study demonstrates the ecological significance and metabolism of
glucosinolates in plant-herbivore-natural enemy interaction. This study
contributes valuable inputs towards devising integrated pest management
strategies against the pest P. xylostella.
