BIODIVERSITAS ISSN: 1412-033X Volume 24, Number 1, January 2023 E-ISSN: 2085-4722 Pages: 33-39 DOI: 10.13057/biodiv/d240105 Effect of micronutrient-enriched media on the efficacy of Bacillus subtilis as a biological control agent against Meloidogyne incognita MUH ADIWENA 1,♥ , ADITYA MURTILAKSONO 1 , SAAT EGRA 1 , MOHAMMAD HOESAIN 2 , IIS NUR ASYIAH 3 , ANKARDIANSYAH PANDU PRADANA 2 , ZIDNA NURUL IZATIKA 2 1 Department of Agrotechnology, Faculty of Agriculture, Universitas Borneo Tarakan. Jl. Amal Lama No. 1, Tarakan 77123, North Kalimantan, Indonesia. ♥ email: wena@borneo.ac.id 2 Department of Plant Protection, Faculty of Agriculture, Universitas Jember. Jl. Kalimantan No. 37, Kampus Tegalboto, Jember 68121, East Java, Indonesia 3 Program of Biology Education, Faculty of Teacher Training and Education, Universitas Jember. Jl. Kalimantan No. 37, Jember 68121, East Java, Indonesia Manuscript received: 2 November 2022. Revision accepted: 25 December 2022. Abstract. Adiwena M, Murtilaksono A, Egra S, Hoesain M, Asyiah IN, Pradana AP, Izatika ZN. 2023. Effect of micronutrient-enriched media on the efficacy of Bacillus subtilis as a biological control agent against Meloidogyne incognita. Biodiversitas 24: 33-39. The root-knot nematodes Meloidogyne incognita poses a serious threat to horticultural food and plantation crops. One of the effective and efficient measures to overcome this nematode is using bacteria as a biological control agent. This study aimed to test the effectiveness of Bacillus subtilis bacteria grown on media with additional micronutrients as a biological control agent for M. incognita. The test was carried out by growing bacteria in 100 mL of nutrient broth (NB) added with FeCl 2, MnCl2, and CuCl2. Each type of micronutrient was administered at concentrations of 35 ppm, 40 ppm, 45 ppm, 50 ppm, and 55 ppm. As a control, NB media was used without the addition of micronutrients. The test results showed that bacteria performed best at 55 ppm MnCl 2, 45 ppm MnCl2, 40 ppm MnCl2, 40 ppm CuCl2, 50 ppm MnCl2, and 35 ppm MnCl2. These six treatments were then used in an antagonism test. A total of 150 J2 M. incognita in 4 mL of suspension was transferred into a petri dish with a diameter of 5 cm. After that, 1 mL of each bacterial suspension was poured into a petri dish following the treatment, nutrient broth as control, nutrient broth plus 35 ppm MnCl 2, nutrient broth plus 40 ppm MnCl2, nutrient broth plus 45 ppm MnCl2, nutrient broth plus 50 ppm MnCl 2, nutrient broth plus 55 ppm MnCl 2 and nutrient broth plus 40 ppm CuCl2. The mortality rate of M. incognita in each treatment was 77.5% in 55 ppm MnCl 2, 74.5% in 45 ppm MnCl2, 77.25% in 40 ppm MnCl2, 73.25% in 40 ppm CuCl2, 78.75% in 50 ppm MnCl2, 79% in 35 ppm MnCl2, and 53.25% in control. The same six treatments were also used to measure the chemotaxis index of M. incognita on tomato roots. The chemotaxis index ranged from 16% to 24% in the treatments, while in control, it was 33%. This study suggests that the addition of micronutrients MnCl 2 and CuCl2 to the growth medium of B. subtilis can increase antagonistic activity against M. incognita and suppress its chemotaxis response in tomato roots soaked in the bacterial suspension. Keywords: Biocontrol, chemotaxis, exudate, mortality, pluronic INTRODUCTION Root-knot nematodes (RKNs) are cosmopolitan pathogens that infect more than 2000 plant species worldwide (Tapia-Vázquez et al. 2022). Of the many species of RKNs, the most problematic species in Indonesia is Meloidogyne incognita (Chaerani 2022). Nematodes can infect horticultural crops, food crops, plantation crops, and spice plants. In Indonesia, M. incognita has been reported to infect tomatoes, celery, pepper, coffee, and eggplant (Taher and Suastika 2012; Kurniawati et al. 2017; Chaerani 2022). Yield losses caused by infection with nematodes vary, depending on environmental conditions, population density, and plant varieties infected. Several studies report that it causes an average yield loss of 35% to 80% (Forghani and Hajihassani 2020). Double infection involving M. incognita and other pathogens, such as fungi or bacteria, can cause total yield loss and plant death (Tapia-Vázquez et al. 2022). For example, tomato and tobacco plants infected with M. incognita and Ralstonia solanacearum simultaneously can cause crop failure (Furusawa et al. 2019; Asghar et al. 2020). Similarly, when M. incognita attacks Solanaceae plants and is followed by infection with Fusarium oxysporum, leading to more severe infection and plant death (Hua et al. 2019). Infection symptoms caused by M. incognita are generally marked by root gall. The gall disturbs the absorption of water and nutrients from the soil and subsequently inhibits nutrient distribution and plant growth (Elling 2013). Insufficient nutrients directly cause stunted plant growth, yellowing leaves, lower yields, and decreased plant freshness. Moreover, this circumstance indirectly makes plants susceptible to other pathogenic infections (Subedi et al. 2020). The disturbances in plant roots caused by M. incognita can also cause plants to wilt despite sufficient water in the soil (Kaloshian and Teixeira 2019). Multiple control measures have been carried out to suppress M. incognita infection in various agricultural commodities. However, to date, M. incognita infection remains unresolved. This nematode has a unique life niche, due to its semi-endoparasite and sedentary natures, making it difficult to control (Singh et al. 2019). The use of