BIODIVERSITAS ISSN: 1412-033X Volume 21, Number 4, April 2020 E-ISSN: 2085-4722 Pages: 1287-1294 DOI: 10.13057/biodiv/d210403 Characteristics of Bacillus thuringiensis isolates indigenous soil of South Sumatra (Indonesia) and their pathogenicity against oil palm pests Oryctes rhinoceros (Coleoptera: Scarabaeidae) YULIA PUJIASTUTI 1, , ARSI ARSI 1 , SOFIA SANDI 2 1 Department of Plant Protection, Faculty of Agriculture, Universitas Sriwijaya. Jl. Raya Palembang-Prabumulih Km 32, Indralaya, Ogan Ilir 30662, South Sumatra, Indonesia. Tel.: +62-711-580663, Fax.: +62-711-580276,  email: ypujiastuti@unsri.ac.id 2 Department of Animal Husbandry, Faculty of Agriculture, Universitas Sriwijaya. Jl. Raya Palembang-Prabumulih Km 32, Indralaya, Ogan Ilir 30662, South Sumatra, Indonesia Abstract. Pujiastuti Y, Arsi, Sandi S. 2020. Characteristics of Bacillus thuringiensis isolates indigenous soil of South Sumatra (Indonesia) and their pathogenicity against oil palm pests Oryctes rhinoceros (Coleoptera: Scarabaeidae). Biodiversitas 21: 1287- 1294. Bacillus thuringiensis is a gram-positive, entomopathogenic bacterium that could be isolated from soil and be used to control various plant pests. Oryctes rhinoceros is an important pest in oil palm. Application of B. thuringiensis-based bioinsecticides is an alternative in controlling these pests. The purposes of this study were to isolate and identify B. thuringiensis bacteria from the soil of South Sumatra, production of B. thuringiensis-based bioinsecticides and to test their toxicity to O. rhinoceros larvae. The study was conducted in several cities/districts in the province of South Sumatra. Soil samples were taken from various habitats and B. thuringiensis isolates were grown on NGKG agar media. Among 76 soil samples (6 districts and 2 cities) B. thuringiensis colonies were obtained leading to 24 isolates of B. thuringiensis. Toxicity screening tests for armyworm Spodoptera litura were 55.79% (53 isolates) and their mortality to 25.26% O. rhinoceros larvae (24 isolates). From these isolates whose effectively killed O. rhinoceros larvae, 10 isolates were taken and propagated with Nutrient Broth (NB) and biourine enriched with 5% molasses. Number of spores produced was counted during 24, 48 and 72 hours. Furthermore, a bioassay test was carried out on O. rhinoceros larvae for 7 days. Isolate of KJ3P1 caused the highest mortality of O. rhinoceros larvae after 7 days of observation. SDS Page resulted in KJ3P1 and KJ3R5 isolates showing several bands whose content of various types of protein molecular weight. Isolation of B. thuringiensis in South Sumatra produced 2 isolates potentially to be active ingredients in production of bioinsecticides which were effective in killing O. rhinoceros larvae. Keywords: Bacillus thuringiensis, biological control, Oryctes rhinoceros, toxicity INTRODUCTION Oryctes rhinoceros (Coleoptera: Scarabaeidae) is an important oil palm plant pest both in immature and mature stage of plants (Susanto et al. 2011). The application of zero waste by re-entering empty bunches in oil palm plantations increases O. rhinoceros larvae population. Oil palm empty fruit bunches which decompose into organic matter become suitable breeding sites for these larvae (Santi and Sumaryo 2008). The decline in palm oil yields can occur after the attack. Heavy injury to palm oil leaves (≥ 90%) can reduce production by more than 70% in the first year and continue for the subsequent years (Sudharto and Guritno 2003). Control of O. rhinoceros by using entomopathogens is an alternative when the use of synthetic chemical insecticides is not able to solve pest problems. For example, Bacillus thuringiensis used to pest control has been tried to control Metisa plana caterpillars (Khaeruni and Purnamaningrum 2012; Ahmad et al. 2017; Kamarudin et al. 2017), but to controlling O. rhinoceros is still not much studied. Bacillus thuringiensis works like stomach poison. Proteins and spores of B. thuringiensis produced during sporulation must be ingested and digested in the midgut of insects (Mizuki et al. 1999; Bravo et al. 2015a). The specificity of host is a unique feature of B. thuringiensis. In its grouping, B. thuringiensis is divided into groups based on their insecticidal protein content (Jouzani et al. 2017). The discovery of new isolates is a big chance in producing isolates who is toxic to insect pests (Bravo et al. 2015b). After obtaining B. thuringiensis isolates, their application for controlling insect pest becomes important. Bioinsecticides need to be made with materials that are easily obtained, inexpensive and abundant. Therefore, waste materials such as bio-urine and molasses can be used as media in the propagation of B. thuringiensis (Purnawati et al. 2014; Salazar-Magallon et al. 2015; Pujiastuti et al. 2018). The specificity of the insect pest host of B. thuringiensis can also be explained by its protein content. Wiest et al. (2015) and Osman et al. (2015) explained specifically B. thuringiensis which active against Lepidoptera content a protein molecular weight of 130 kDa, while those active against Coleoptera own a molecular weight of 14-133 kDa (Fernandez and López- Pazos 2011). Therefore it is necessary to investigate B. thuringiensis isolates from soil isolated in South Sumatra province and their toxicity to Oryctes larvae by paying attention to their protein content. Manuscript received: 8 December 2019. Revision accepted: 3 0DUFK 2020.