Abstract. 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.
Abstract. Nurdika AAH, Arwiyanto T, Sulandari S. 2022. Physio-biochemical, molecular characterization, and phage susceptibility of Ralstonia pseudosolanacearum associated with tomato (Solanum lycopersicum) and eggplant (Solanum melongena). Biodiversitas 23: 5149-5158. Ralstonia solanacearum is a plant pathogen that causes bacterial wilt diseases in various plant species. The high diversity of these bacteria strains is the basis for their grouping into the R. solanacearum species complex (RSSC). RSSC associated with tomato and eggplant in Indonesia are commonly known as R. solanacearum. It is necessary to characterize R. solanacearum which infects tomatoes and eggplant according to the latest classification. The high diversity of strains also affects their susceptibility to bacteriophages as host-specific biocontrol agents. This research was conducted by characterizing R. solanacearum isolates from different locations based on their physio-biochemical properties, biovar, virulence, phylotype, sequevar, and susceptibility to 12 bacteriophage isolates. The phylotype identification was carried out using multiplex polymerase chain reaction with several specific primers for R. solanacearum. Amplification and sequencing based on the egl gene region were carried out to determine the sequevar of R. solanacearum isolates. As a result, isolates RS18, RS19, RS23, and RS24 had morphological, physio-biochemical, and biovar characteristics according to Ralstonia pseudosolanacearum phylotype I, biovar 3. The two most virulent isolates, RS19 and RS24 were identified as sequevar 14. RS19 and RS24 isolates were susceptible to 7 of the 12 bacteriophage isolates used in this study. Variations of bacteriophage isolates resulted in different plaque morphology which could be attributed to R. pseudosolanacearum susceptibility and bacteriophage virulence.
Soybean leaf blight (Pseudomonas syringae pv glycinea) is one of the important diseases that has the potential to cause production losses of around 11-20%. This study aims to determine the potential of Pseudomonas fluorescens bacteria that is applied through seed encapsulation methods to stimulate soybean plant growth and surpress the development of leaf blight disease. This research was conducted at the Agrotechnopark Jubung greenhouse, University of Jember using a Completely Randomized Design consisting of 5 treatments namely control (P0), encapsulation of P.fluorescens bacteria with compost (P1) formulation, compost + kaolin (P2), compost + talc (P3), and compost + zeolite (P4). The results showed that seed encapsulation with P.fluorescens bacteria made from compost and inorganic carriers was able to reduce the severity of soybean blight disease by up to 40 HSI. Seed encapsulation with P.fluorescens compost + zeolite formulation can increase seed germination, plant height, and number of leaves. The use of talc carrier materials is able to maintain a bacterial population of 6.0 x 103 cfu / ml for up to 28 days of storage. Keywords: formulation, leaf blight, Pseudomonas fluorescens, Pseudomonas syringae, seed encapsulation
Xanthomonas axonopodis pv glycines (Xag) is a pathogen that causes pustule disease in soybeans. Many techniques for controlling this disease have been widely developed, one of which is the use of biological agents. Bacillus sp. from the soybean phyllosphere is a biological agent that has the potential to suppress the development of pustule disease. One of the biological control mechanisms is through biochemical induction of plant resistance which includes the accumulation of phenols, salicylic acid compounds, and peroxidase enzymes. Bacillus subtilis JB12 and Bacillus velezensis ST32 are two bacteria isolated from the soybean phyllosphere which have previously been known to suppress Xag through an antibiosis mechanism. This study aimed to determine the potential of Bacillus subtilis JB12 and Bacillus velezensis ST32 in inducing soybean resistance against Xag infection. This research was carried out in two stages, the induction of resistance tosoybean germination and an experiment in a greenhouse. This study consisted of 4 treatments and 5 replications, including P0 (Xag inoculation), P1 (Bacillus subtilis JB12 inoculation), P2 (Bacillus velezensisST32), and P3 (Bacillus subtilis JB12 + Bacillus velezensis ST32 inoculation). Observations were made on the content of phenolic compounds, peroxidase enzyme activity, and the development of soybean pustule disease. The results showed differences in phenol content and peroxidase activity at the two stages of the study.Seed treatment with both isolates of Bacillus sp was able to increase the phenol content of soybean sprouts up to 3 - 5 days after inoculation (dai). Phenol content then decreased and was followed by an increase in the peroxidase activity up to 7 dai. The application of Xag and two isolates of Bacillus sp. in soybean plants caused the phenol content to fluctuate and peroxidase activity to decrease. Bacillus subtilis JB12 in general played a better role in increasing phenol content and peroxidase enzyme activity in soybean than Bacillus velezensis ST32. The application of two isolates of Bacillus sp. was not able to prolong the incubation period and reduce the severity of the pustule disease 14 days after inoculation.
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