Induction of antimicrobial peptides from Bacillus thuringiensis challenged Spodoptera litura larvae and investigation of the antimicrobial properties of hemolymph samples

Antimicrobial peptides constitute key factors in insect humoral immune response against invading microorganisms. In this study, biochemical approach was identified antimicrobial peptides which appeared in larval hemolymph of Spodoptera litura after bacterial challenge. HPLC profile showed two major peaks in two samples, Brassica oleracea and Ricinus communis fed S. litura that were collected at 5 min interval. It was shown to be active against Gram-positive and Gram-negative bacteria. The highest zone of inhibition was observed in Staphylococcus aureus and Escherichia coli in B. oleracea fed S. litura hemolymph fraction II and R. communis fed S. litura hemolymph fraction I and it also contributes the increased antioxidant, lysozyme, and less hemolytic activity were increase in treated groups. TLC activity was tested with hemolymph extract samples, pink color pots was identified the protein present in the samples. An SDS-PAGE result shows that high expression of antimicrobial peptide present in the treated sample. The appearance of peptides with such different properties in insect hemolymph in response to immune challenge indicates the complexity of the insect immune system.

Toxicity of isolated phenolic compounds from Acorus calamus L. to control Spodoptera litura (Lepidoptera: Noctuidae) under laboratory conditions

Background Spodoptera litura (Lepidoptera: Noctuidae), the tobacco cutworm, is an prominent agricultural pest. To reduce the use of chemical pesticides that cause health problems and that leave residue in the environment, some botanical pesticides have been developed. Our research aimed to evaluate the insecticidal efficacy of Acorus calamus L. extract for the control of S. litura under laboratory conditions. Results After 24 h of topical application, the A. calamus methanolic crude extract showed toxicity against secondary instar S. litura larvae (LD50 ~ 7.438 µg/larva). Chrysin (5,7-dihydroxy flavone), one of the isolated phenolic compounds, showed optimal control efficiency (LD50 ~ 2.752 µg/larva) and showed a reduction in carboxylesterase activities, which have detoxification reduction roles in larvae. Conclusion Chrysin in the crude extract of A. calamus may be an active compound to control this pest, and it may be applied as an alternative to minimize the usage of chemical insecticides. Graphical Abstract

Chinese Cabbage Changes Its Release of Volatiles to Defend against Spodoptera litura

Plants respond to herbivorous insect attacks by releasing volatiles that directly harm the herbivore or that indirectly harm the herbivore by attracting its natural enemies. Although the larvae of Spodoptera litura (the tobacco cutworm) are known to induce the release of host plant volatiles, the effects of such volatiles on host location by S. litura and by the parasitoid Microplitis similis, a natural enemy of S. litura larvae, are poorly understood. Here, we found that both the regurgitate of S. litura larvae and S. litura-infested cabbage leaves attracted M. similis. S. litura had a reduced preference for cabbage plants that had been infested with S. litura for 24 or 48 h. M. similis selection of plants was positively correlated with the release of limonene; linalool and hexadecane, and was negatively correlated with the release of (E)-2-hexenal and 1-Butene, 4-isothiocyanato. S. litura selection of plants was positively correlated with the release of (E)-2-hexenal, 1-Butene, 4-isothiocyanato, and decanal, and was negatively correlated with the release of limonene, nonanal, hexadecane, heptadecane, and octadecane. Our results indicate that host plant volatiles can regulate the behavior of S. litura and M. similis.

Eksplorasi Bakteri yang Berpotensi sebagai Pengendali Hama Ulat Grayak (Spodoptera litura) (Exploration of Potential Bacteria as Biological Control of Spodoptera litura)

<p>Usaha pengendalian hama ulat grayak (Spodoptera litura) di tingkat petani masih mengandalkan pestisida sintetik. Tujuan penelitian adalah mengeksplorasi bakteri potensial pengendali hama ulat grayak (S. litura) dan menguji ketahanan bakteri potensial pada bahan pembawa kompos dan zeolit. Isolat tanah diisolasi dari tiga jenis sumber, yaitu sampel tanah daerah rhizosfer (padi, kelapa sawit, terung, jagung), sampel buah busuk (kakao, kelapa sawit, jambu air), dan sampel bangkai serangga (ulat api, belalang, kumbang tahi, kupu-kupu) yang diambil dari kawasan Dramaga dengan metode purposive sampling. Penelitian di laboratorium meliputi isolasi bakteri, uji patogenitas, pewarnaan gram, pengamatan morfologi koloni, uji toksisitas, uji biokimia, dan uji bahan pembawa. Berdasarkan penelitian ini didapatkan dua strain yang berpotensi sebagai agens biokontrol dengan kemampuan membunuh hama yang tinggi pada pengujian toksisitas tahap kedua, yaitu IRJ 10 (tingkat kematian 90%) dan ISU 4 (tingkat kematian 100%). Kedua isolat ini merupakan anggota genus Bacillus. Pada uji bahan pembawa kompos dan zeolit, penurunan jumlah sel bakteri pengendali hama paling tinggi adalah pada bahan pembawa zeolit dibandingkan dengan menggunakan bahan pembawa kompos. Jumlah sel bakteri pengendali hama pada masa penyimpanan 3 minggu masih di atas 108 CFU/g.</p><p><strong>Keywords</strong></p><p>Bakteri; Bahan pembawa; Ekplorasi; Agens pengendali hama; Ulat grayak (Spodoptera litura)</p><p><strong>Abstract</strong></p><p>The effort to control the Spodoptera litura at the farm level still used synthetic pesticides. This research aimed to explore potential bacteria as biological control of S. litura and do viability test of potential bacteria on compost and zeolite carrier. Soil potential bacteria had been isolated from three sources, including rhizosphere soil samples (rice, oil palm, eggplant, corn), rotten fruit samples (cocoa, oil palm, water), and insect samples (fireworms, locusts, dung beetles, butterflies) taken from Dramaga area with the purposive sampling method. Stages of laboratory study include isolation of bacterial isolates, pathogenicity tests, gram staining, colony morphology observation, toxicity test, biochemical test, and viability test. Two strains that have potential as biocontrol agents with a high ability to kill pests in the second stage of toxicity testing are IRJ 10 (90% mortality rate) and ISU 4 (100% mortality rate). Both of these isolates are members of the genus Bacillus. The highest number of viability was found in zeolite carriers. The number of bacterial cells in the three-week storage period is still above 108 CFU/g.</p>