Abstract
Insect pests represent a major threat to food crops and human health, and therefore have to be combated in several ways, including chemical methods. However, researchers demonstrated that these molecules are dangerous for the farmers, consumers and the environment in general. For this reason, scientists permanently searched environment friendly alternatives such as the use of the bacterium Bacillus thuringiensis classified as one of the best insect pathogens. This microorganism is known by its ability to produce two types of insecticidal proteins, Vegetative insecticidal proteins (Vip) and delta-endotoxins produced during vegetative and sporulation stages of growth, respectively. In the present study, 15 B. thuringiensis strains were isolated from soil collected from different regions in Saudi Arabia (Al Baha, Jeddah, Khulis and Yanbu). B. thuringiensis isolates were then classified according to the shape of their parasporal crystals identified under microscope and proteins content of these crystals. Delta-endotoxins efficiency of the different isolates was investigated and promising strains were identified as very active. After 5 days-treatment, B. thuringiensis isolates 14 and 7 killed Ephestia kuehniella larvae with low LC50 of about 59.18 and 65.67 mg/cm2, respectively. The results described in the present study proved that the new B. thuringiensis isolates could be of a great interest in the control of lepidopteran pests by using their delta-endotoxins in bioinsecticide formulations.
Highlights
Over the past decades, protecting the environment has increasingly become a major global concern
The results described in the present study proved that the new B. thuringiensis isolates could be of a great interest in the control of lepidopteran pests by using their delta-endotoxins in bioinsecticide formulations
After bacteria isolation from soil samples, about 100 white rough pure colonies were investigated by light microscopy to search the presence of parasporal crystals that confirmed the ability of the isolated strains to produce delta-endotoxins characterizing B. thuringiensis from all the other sporulating bacteria
Summary
Over the past decades, protecting the environment has increasingly become a major global concern. To protect crops and to increase the productivity of the agricultural and forestry sectors, chemical insecticides have been used extensively [3]. Growing public concerns about the potentially harmful effects of these chemical molecules on the environment and humans have led the scientific community to seek alternatives to chemical control [4, 5]. One of the ways of protecting consumers and their environment is the partial or total substitution of chemical pesticides by biopesticides. In this context, the world market for biopesticides continues to increase in parallel with a decline in sales of chemical pesticides, and substances based on Bacillus thuringiensis
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