Nanoformulation of Cartap Hydrochloride and its Effect on Growth and Physiology of Anabaena Variabilis ARM 441

Abstract

Insecticides are extensively applied in crop production to combat crop loss due to pest infestation and sometimes at higher concentration than their recommended doses, which has become an environmental hazard. Sustainable agricultural practices highlight minimal application of insecticides at low concentration. Use of controlled release formulations (CRFs) of pesticides in which active compound is associated with inert materials has emerged as an appealing alternative. Cartap hydrochloride is a moderately hazardous nereistoxin analogue insecticide that is predominantly applied in paddy fields of India, at a recommended dose of 10 µg ml-1 to kill chewing and sucking insect pests of rice crop. Nanoformulation of cartap hydrochloride using two natural polymers chitosan and alginate was done and study its release kinetics under in vitro conditions. Prior to that overall impact of cartap hydrochloride induced stress response and physiology of Anabaena variabilis ARM 441 were studied under pure conditions, a filamentous heterocystous cyanobacterium commonly used as algal biofertilizer in paddy cultivation. Anabaena sp. could tolerate commercial grade insecticide up to 30 µg ml-1. However, at the recommended dose of 10 µg ml-1, it caused reduction in algal growth, total nitrogen and heterocyst frequency by 47.28, 24.29 and 17.72% respectively, as well as photosynthetic pigments under pure culture conditions. Increased concentrations of cartap resulted in a decrease in total protein content while increasing carbohydrate content. Scanning electron micrographs revealed cell rupture and breakage in filaments due to cartap exposure with the formation of akinetes. Cartap hydrochloride induced stress, since levels of superoxide dismutase, peroxidase and catalase were increased by 108.57, 187.5 and 117% respectively. Generation of superoxide radicals and hydrogen peroxide were also increased by 152.48 and 34% respectively. Lipid peroxidation was increased by 31.03%, whereas there was decline in ascorbate content by 48.45%, how