Anti-Quorum Sensing Effects of Some Medicinal and Aromatic Plant Extracts on Xanthomonas axonopodis pv. Phaseoli

Xanthomonas axonopodis pv. phaseoli (Xap) is known as one of the most important seed-borne destructive pathogens on beans worldwide. Nowadays, Xap is considered to acquire resistance to antibiotics and synthetic bactericides which concerns the scientific world for its future management. This has made the use of plant extracts, the best alternative in the control of plant disease pathogens by inhibiting the quorum sensing (QS) mediated virulence factors. This research was designed to investigate the antibacterial activities and the anti-QS effects of the 14 different aromatic and medicinal plants against QS-mediated virulence factors of Xap. The results revealed that Syzgium aromaticum showed the largest inhibition zone diameter and strongest antimicrobial (antibacterial) effect among the 14 plant extracts followed by Thymus vulgaris and Coriandrum sativum. Similarly, the lowest swarming, swimming, and twitching motility values were measured from the Syzgium aromaticum application followed by Coriandrum sativum, Thymus vulgaris, Brassica nigra, Lepidium sativum, and Ruta chalepenis. These results indicated that S. aromaticum, C. sativum, T. vulgaris, B. nigra, L. sativum, and R. chalepenis will be a potential candidates as anti-quorum sensing agents in preventing common bacterial disease of beans caused by Xap. Compounds derived from aromatic and medicinal plants have demonstrated successful control of diseases in crops and the use of these substances provides a valuable tool to the growers around the world for diseases management in organic production.

Inhibition of the Citrus Bacterial Pathogen Xanthomonas axonopodis pv. citri through Aloysia gratissima Essential Oil and Flourensia spp. Extracts and Prenylflavonoids

Background: Xanthomonas axonopodis pv. citri is a gram-negative bacterium that affects citrus crops, causing a disease known as citrus canker. Although essential oils and other compounds isolated from plants represent a natural alternative to treat this disease, they have the disadvantage of having low solubility in the media in which the bioassays to determine antimicrobial activity are performed. This has led several researchers to evaluate the solubility of plant essential oils in alternative solvents. Objectives: The aim of this study was to evaluate the solubility of the essential oil from Aloysia gratissima as well as that of low-polarity extracts and pure compounds of the genus Flourensia in diluted agar/Tween 80 solutions to test and improve their antimicrobial activity against Xanthomonas axonopodis pv. citri. Methods: Antimicrobial activity against Xanthomonas axonopodis pv. citri was determined by bioautography, agar diffusion, and microdilution methods. Results: The A. gratissima oil showed increased activity in the agar (0.15 % m/v)/Tween80 (0.5 % v/v) 1:1 mixture, with MIC values ranging from 75 to 100 µL/mL, while Flourensia spp. extracts were more soluble in agar solution (0.15 % m/v). The pure compounds tested presented MIC values ranging from 50 to 150 µg/mL. Conclusion: The proven antimicrobial activity of both Aloysia gratissima essential oil and Flourensia spp. extracts and pure compounds allows proposing these natural products as potential antimicrobial agents in the control of citrus canker.

Identifikasi Penyakit Daun Jeruk Siam Menggunakan K-Nearest Neighbor

Jeruk siam adalah salah satu jeruk local yang mempunyai nilai jual yang tinggi di Indonesia. Tahun 2020, tingkat produksi jeruk siam mengalami penurunan menjadi 712.585 ton di Jawa Timur. Salah satu faktor utama yang menyebabkan menurunnya tingkat produksi jeruk siam yaitu serangan penyakit pada daun jeruk siam. Dua penyakit yang sering menyerang daun jeruk siam adalah penyakit kanker yang disebabkan oleh patogen Xanthomonas axonopodis pv.citri dan penyakit ulat peliang. Selama ini, pengamatan pada penyakit daun jeruk siam dilakukan secara manual menggunakan mata sehingga penentuan penyakit tersebut bersifat subyektif. Untuk mengatasi masalah tersebut dibuatlah sistem otomatis identifikasi daun jeruk siam sehat dan daun jeruk siam terserang penyakit dengan bantuan teknik computer vision. Tahapan penelitian yaitu pengumpulan citra daun jeruk, konversi warna, ekstraksi fitur warna dan tekstur serta klasifikasi K-Nearest Neighbor (KNN). Parameter fitur yang digunakan yaitu fitur warna GB, fitur tekstur (ASM, entropi dan kontras). Metode KNN mampu mengklasifikasi dan mengidentifikasi penyakit daun jeruk siam dengan akurasi sebesar 70% dengan variasi nilai K = 21.

Diversity of Bacillus spp. from soybean phyllosphere as potential antagonist agents for Xanthomonas axonopodis pv. glycines causal of pustule disease

Nurcahyanti SD, Wahyuni WS, Masnilah R, Nurdika AAH. 2021. Diversity of Bacillus spp. from soybean phyllosphere as potential antagonist agents for Xanthomonas axonopodis pv. glycines causal of pustule disease. Biodiversitas 22: 5003-5011. Pustule disease caused by Xanthomonas axonopodis pv. glycines (Xag) is an important disease in soybean. Bacteria from soybean phyllosphere is one of the potential biological agents against this disease. This is because the microorganisms have similarity. This study aimed to determine the diversity and species of bacteria from the soybean phyllosphere that have potential as biological agents. The research was carried out by morphological observation, physiological - biochemical testing, and molecularly with BOX AIR primer. Molecular identification was carried out by amplifying the 16S-rRNA gene with 27F and 1492R primers. The results showed that 11 isolates could inhibit Xag in vitro which showed morphological, biochemical, and molecular diversity. These bacteria were identified as Bacillus spp. which consisted of 4 groups, namely Bacillus siamensis, B. subtilis. B. amyloliquifaction and B. velezensis. The diversity of phyllosphere bacteria allows them to be used as biological agents because they do not inhibit each other and have diverse living abilities in various environmental conditions.

Anti-bacterial Effect of Aqueous and Ethanolic Extracts of Onion, Garlic and Cinnamon on Xanthomonas Species

Onion (Allium cepa), garlic (Allium sativum) and cinnamon (Cinnamomum zeylanicum) are edible herbs but they contain many chemicals which can be used as medicine. These herbs also contain many antibiotic molecules that are capable to inhibit or reduce growth of many types of microbes including bacteria. Due to the development of resistance of bacteria against synthetic antibiotic now there is a need to have natural antibiotic which must be harmless, cheap and easily available. To know the effectiveness of garlic, onion, and cinnamon on disease causing bacteria such as Xanthomonas campestris pv. malvacearum, Xanthomonas axonopodis pv. citri, Xanthomonas oryzae pv. oryzae, extracts of each sample was made in water and ethanol. Antibacterial potential of plant extracts was observed at two different stages: at the time of inoculation and after growth of pathogen on media. Results showed extracts applied on all the bacteria before growth inhibited maximum bacterial growth as compared to applied after growth. Moreover, cinnamon extract in ethanol effectively control bacterial growth than onion and garlic extracts. Maximum inhibition zone was shown by ethanolic extract of cinnamon before growth of Xanthomonas oryzae pv. oryzae (7.333 mm), Xanthomonas campestris pv. malvacearum (7.83 mm) and Xanthomonas axonopodis pv. citri (5.1 mm). After 24 hours, maximum growth of Xanthomonas oryzae and Xanthomonas axonopodis was inhibited by ethanolic extracts of cinnamon (2.82 and 3.35 mm, respectively) while Xanthomonas campestris was inhibited by ethanolic extract of onion (6.55 mm). Extract diluted from 66mg/ml to 0.01mg/ml showed different minimum inhibitory concentration against pathogens. As concentration decreases inhibition of bacteria also decreases. Ethanolic extracts of cinnamon showed maximum MIC against Xanthomonas campestris pv. malvacearum (3.5 mm to 1.5 mm) and Xanthomonas oryzae pv. oryzae (5 mm to 2 mm) while for Xanthomonas axonopodis pv. citri ethanolic extract of garlic (3 mm to 1 mm) was effective ranging between 66mg/ml to 33 mg/ml. This study highlighted that natural products possess ability to inhibit pathogenic bacterial growth and would also be helpful in medicinal field for further study.

Effect of Different Hormones on Disease Resistance against Bacterial Blight in Pomegranate

Bacterial blight in pomegranate is a major disease caused by Xanthomonas axonopodis pv. punicae, which has resulted in significant economic losses in terms of both quality and quantity. The ineffectiveness of most chemicals in controlling this disease has shifted grower attention to the quest for a new molecule and hence the use of plant growth regulators and signaling molecules is a novel approach to control the disease as well as improving quality and quantity attributes of pomegranate. Hence, the aim of present study was to determine the impact of plant hormones like ethylene, jasmonic acid and salicylic acid on bacterial blight of pomegranate. Among different hormones applied, ethrel application shown maximum disease severity (33.2%) and salicylic acid shown lowest disease severity (15.08%) under greenhouse condition.

Detection and Testing Pathogenicity of Xanthomonas axonopodis pv. punicae Causing Bacterial Blight on Pomegranate

Pomegranate, one of the most important fruit crops, is constantly challenged by Bacterial blight caused by Xanthomonas axonopodispv. punicae, is a prevalent and destructive pomegranate disease. Accurate diagnosis of disease is very important to manage the disease. PCR have been widely used to detect or verify the presence of pathogen in recent decades. These molecular-based methods are rapid, accurate and sensitive for detecting pathogens. In this study, a primer set KKM5 and KKM6 was used and amplification of 491bp of gyrB gene proved the presence of Xap. The pathogenicity of the Xap was confirmed following Koch’s postulates.

PENGUJIAN KONSORSIUM MIKROBA ANTAGONIS UNTUK MENGENDALIKAN PENYAKIT PUSTUL BAKTERI PADA TANAMAN KEDELAI

Salah satu penyakit penting yang menyerang tanaman kedelai adalah penyakit pustul daun yang disebabkan oleh bakteri Xanthomonas axonopodis pv. glycines. Penelitian ini bertujuan untuk mengetahui potensi konsorsium mikroba antagonis yang terdiri dari Bacillus subtillis, Pseudomonas fluorescens, serta Trichoderma sebagai agens hayati untuk mengendalikan penyakit pustul daun pada tanaman kedelai yang disebabkan oleh bakteri X. axonopodis pv. glycines. Hasil penelitian menunjukkan bahwa semua perlakuan aplikasi antagonis baik yang berupa konsorsium mikroba antagonis maupun mikroba antagonis tunggal mampu menghambat pertumbuhan bakteri X. axonopodis pv. glycines pada media dalam cawan Petri. Semua perlakuan mikroba antagonis baik tunggal maupun dalam konsorsium juga menekan perkembangan penyakit pustul bakteri pada tanaman kedelai. Kemampuan konsorsium mikroba antagonis dengan konsentrasi 20ml/l, konsorsium mikroba antagonis dengan konsentrasi 30ml/l, mikroba antagonis tunggal B. subtilis, P. fluorescens, dan Trichoderma, setara dengan bakterisida Streptomisin sulfat dalam menekan perkembangan penyakit pustul bakteri pada tanaman kedelai. Perlakuan mikroba antagonis tunggal P. fluorescens dapat meningkatkan tinggi tanaman kedelai.