Study on using gamma radiation to inactivate Bacillus thuringiensis spores in biopesticide

Nguyen Thi Thom1, Nguyen Van Binh1, Tran Bang Diep1, Hoang Dang Sang1, Tran Xuan An1, Hoang Phuong Thao1, Tran Minh Quynh1
1 Hanoi Irradiation Center, Minh Khai Ward, Bac Tu Liem District, Hanoi

Main Article Content

Abstract

Bacillus thuringiensis (Bt) produces different types of toxin that have potent and specific insecticidal activity. In recent years, Bt toxins have been used as the safe biological control agents to protect crops replacing for chemical insecticides. Bt-based biopesticides that have been commercialized as the alternative products to control pests and insects for sustainable agriculture, contain toxicity crystals and a significant number of spores that affects to the soil microflora. These uncontrollable changes may contaminate the cultivation soil, and eventually cause adverse effects to human and animal health. Therefore, the living cells and spores existing in the Bt-biopesticides should be controlled. This study evaluates the effects of gamma radiation on spore viability, germination and growth of the existing spores after spraying on the soil and the insecticidal effectiveness of a Bt-based biopesticide (VBT) against lepidoptera larvae. We attempted to identify the optimal dose that could inactivate Bt spores but the toxicity of Bt still retain highly. The results revealed that the dose of 20 kGy is enough to control all living cells and spores in the product that consists of approximately 5.2 × 107 spores in the initial VBT. Though the growth of existing spores after spraying on the soil reduced by 85% or more by irradiation, their insecticidal activity against Heliothis armigera larvae reduced by 20-30% only as compared to that of the initial VBT. It suggested that gamma irradiation can be applied as useful way to control the living cells and spores existing in the commercial Bt-based bio-pesticides, and the radiation dose of 20 kGy is enough to kill all spores in VBT, but still kept its insecticidal effect for Heliothis armigera larvae

Article Details

References

[1]. Market Forecasts: Modest growth for synthetic pesticides, global markets for biopesticides CHM029F, 2017.
[2]. M. P. Silva, “Methods of destroying bacterial spores”. Microbial pathogens and strategies for combating them: science, technology and education, 490-49, 2013.
[3]. Nguyen Van Tuat, "Research on the use of multi-function biopesticides for some biotech crops", State Research Project, KC.04.12, 2004.
[4]. N. Becker, “Sterilization of Bacillus thuringiensis var. israelensis products by gamma radiation”, Journal of the American Mosquito Control Association, 18(1), 57– 62, 2002.
[5]. S. Sun, J. Fan, Z. Chen, Y. Cai, G. Li, and Y. Pang, “The effect of gamma sterilization on the insecticidal toxicity of engineered and conventional Bacillus thuringiensis strains”, Journal of Economic Entomology, 106 (1), 36– 42, 2013.
[6]. S. Gupta, A. K. Dikshit, “Biopesticides: An ecofriendly approach for pest control”, Journal of Biopesticides, 3(1), 186 – 188, 2010.
[7]. Tran Dinh Pha, Nguyen Hong Son, Cu Thi Thanh Phuc, Le Xuan Trac, Dang Thi Phuong Lan, Bui Van Tuan, Nguyen Huu Dung, Pham Van Hieu, “Research on using and potential Infiltration of Pesticides Biology in Agriculture, Vietnam Academy of Agricultural Sciences, 2009.
[8]. P. Setlow, “Spore of Bacillus subtilis: their resistance to and killing by radiation, heat and chemicals”, Journal of Applied Bacteriology, 101, 514–525, 2006.
[9]. N. Hayashi, Y. Akiyoshi, Y. Kobayashi, K. Kanda, K. Ohshima, M. Goto, “Inactivation characteristics of Bacillus thuringiensis spore in liquid using atmospheric torch plasma using oxygen”, Vacuum, 88, 173–176, 2013.
[10]. M.L. Garcia, J. Burgos, B. Sanz, J.A. Ordoñez, Effect of heat and ultrasonic waves on the survival of two strains of Bacillus subtilis, Journal of Applied Bacteriology, 67, 619–628, 1989.
[11]. D. Rabczenko, A. Gliniewicz, B. Kluge, S. Piekarski, “An universal tool for the analysis of effectiveness of insecticides”, Pesticides, 1–4, 57–62, 2011.
[12]. R. A. de Maagd, “Bacillus thuringiensis - based products for insect pest control. principles of plant-microbe interactions”, Springer International Switzerland, 20, 185–192, 2015.