Protease Inhibitors from Rhynchosia sublobata (Wild Relative) and BDN1 (Cultivar) Varieties of Cajanus cajan in the Management of Castor Semilooper Achaea janata

Abstract

In agriculture crop production, India is ranked second, with around 4.5 million hectares involved
in vegetable cultivation, producing ~75 million tons each year. Thus, agricultural crops hold an
important position in the Indian economy. However, every year, various abiotic/biotic stresses,
including insect pests, cause significant loss of agricultural crops. In response, plants produce several
defensive molecules, including protease inhibitors (PIs), for their protection from various insect
pests. The wild relatives are known to harbor an important gene pool for biotic stress, while non-host
plants discourage insect invasion. Therefore, PIs from wild relatives and non-host plants are considered
effective candidates for the management of various insect pests. In the present study, serine PIs are
purified from ‘Rhynchosia sublobata’, a wild relative and ‘BDN1’, a cultivar varietyof C. cajan.
Both the varieties are non-hosts to Achaea janata. The PIs from these varieties are tested for their
effect on the growth and development of A. janata larvae. The feeding of the PI to larvae was started
at two different instar stages such as (i) the ‘first instar’ stage for up to 14 days and (ii) actively
feeding ‘third instar’ stage for up to 7 days. This study helps to identify the appropriate larval stage
at which PI should be applied to minimize the infestation of plants in the natural environment. PIs
purified from both varieties caused a significant reduction in the weight of larvae and promoted
mortality. Further, the PI treatment started at the first instar stage and showed a greater insecticidal
impact on A. janata larvae than the PI treatment started at the third instar stage.
KEY WORDS: Achaea janata, Growth and Development, Insecticidal activity, Insect gut
proteases, Protease inhibitors