Tri Joko

Sugar transporter (MfsX) of the major facilitator superfamily is required for flagella-mediated pathogenesis in Dickeya dadantii 3937

Dickeya dadantii (syn. Erwinia chrysanthemi) is a causal agent of soft-rot diseases on many crops. Here, we characterized a gene belonging to the major facilitator superfamily (MFS), which is involved in the symport, antiport, or uniport of various substrates, and the survival and virulence of many Gram-negative bacterial animal pathogens, for the possible involvement in the plant pathogenicity of D. dadantii. A marker-exchange mutant of this gene (mfsX) was constructed that had decreased maceration ability in Chinese cabbage, potato, and chicory. Observation with electron microscopy showed greatly reduced numbers of flagella per cell. This mutant had a significant reduction in swimming and swarming motility and a severe reduction in formation of biofilm. Because these phenotypes have been shown to be involved in plant pathogenicity of D. dadantii, mfsX seems to play an important role in pathogenesis of D. dadantii 3937 by its involvement in the expression of these pathogenicity-related phenotypes.

Activities of plant cell wall-degrading enzymes by bacterial soft rot of orchid

Soft rot by bacterial pathogens is one of the most widespread and destructive diseases on various plants including orchids throughout the world. The pathogenicity of the pathogens is reported to be mainly determined by massive production of plant cell wall-degrading enzymes (PCDE). In the previous work, we have isolated 20 isolates of bacterial soft rot from orchids collected in Yogyakarta Special Region and West Java province, Indonesia. In this study, we further confirmed them as pathogens by hypersensitive reaction assay on tobacco leaves followed by pathogenicity test on Phalaenopsis sp. The production of four major PCDE by qualitative plate assays including pectate lyase, polygalacturonase, cellulase and protease was also evaluated. Even though all the isolates were able to initiate soft rot symptom, our results showed two distinct groups which clustered as producing and non-producing PCDE. The 16S rDNA analysis revealed that the isolates belonged to the genera Pectobacterium, Klebsiella, Serratia, Enterobacter, Citrobacter, Providencia and Pseudomonas.

A sugar transporter (MfsX) is also required by Dickeya dadantii 3937 for in planta fitness

Previously, we showed that the sugar transporter MfsX in the major facilitator superfamily is involved in the pathogenicity of Dickeya dadantii (syn. Erwinia chrysanthemi). Here, we show that a mutation in this gene resulted in increased susceptibility to several antimicrobial agents, reduced biosynthesis of a blue pigment indigoidine, and reduced chemotaxis towards some sugars and amino acids and in pellicle formation. These phenotypes in D. dadantii have been thought to be important for survival in planta. Thus, this MfsX sugar transporter may contribute to pathogenicity by enhancing in planta survival of the phytopathogen.

Response of rhizobacterial communities in watermelon to infection with cucumber green mottle mosaic virus as revealed by cultivation-dependent RISA

We investigated the rhizobacterial densities and community structure in watermelon rhizosphere under the infection of cucumber green mottle mosaic virus (CGMMV) by artificial inoculation. Rhizobacterial densities and communities were analysed from healthy and infected plants under aerobic and anaerobic culture techniques. The highest total number of aerobic rhizobacteria was counted to be 2.7 × 108 colony forming units per gram (CFU · g−1) and anaerobic rhizobacteria was to be 3.2 × 106 CFU · g−1, in healthy and infected plants, respectively. Cultivation-dependent ribosomal intergenic spacer analysis (RISA) was employed for further analysis on the rhizobacterial community structure. By incorporating the relative abundance of amplicons, the per cent similarity was determined by the similarity coefficients based only upon the absence or presence of DNA bands. The cluster analysis of RISA showed that the community structure of aerobic rhizobacteria exhibited 60% similarity between healthy and infected plant. The highest community structure similarity (50% similarity) of anaerobic rhizobacteria occurred between before planting and infected plant.

Survey and Detection of Pectobacterium atrosepticum in Major Potato-Growing Areas in Central Java Province, Indonesia

Potato ( Solanum tuberosum ) is a seasonal shrub-tuber crop originated from sub-tropical area. Soft-rot is one of the most important diseases of potato. It can be caused by Pectobactorium atrosepticum , a pathogen within a status of quarantine plant pest A1 type I in Indonesia. The objective of this study was to know the incidence of potato soft rot disease and to detect P. atrosepticum in major potato-growing areas in Central Java Province by applying the serology method using DAS-ELISA technique. Survey of soft rot disease was carried out in some regencies in Central Java Province, i.e. Magelang, Banjarnegara, Wonosobo and Karanganyar. The field survey of potato plant in all the regencies indicated symptoms of stem rot which was black in color (blackleg) and foul-smelling, with disease incidence of about 10–90%. The laboratory testing showed that by applying DAS-ELISA method, P. atrosepticum was detected in samples collected from Pandean and Bagongan villages, district of Ngablak,Regency of Magelang, Central Java Province.

Hyperinduction of pectate lyase in Dickeya chrysanthemi EC16 by plant-derived sugars

ABSTRACT Pectate lyase (Pel) synthesis in Dickeya chrysanthemi has been reported to be hyperinduced in planta and also in the medium containing plant extract in addition to polygalacturonate. In this study, the major components of Pel-hyperinducing fractions were found to be glucose, fructose, and sucrose by TLC and NMR. From the analysis of the sugars and their derivatives, it was found that acyclic d-hexoses with the trans relationship between C-3 and C-5 hydroxyl groups were found to be basic structure required for hyperinducing the expression of a major isozyme in infected plants (i.e. pelE). From the fact that some non-metabolizable sugars such as 2-deoxy-d-glucose and d-fucose could lead to hyperinduction and that the hyperinduction was observed only in the medium containing low concentration (<0.25%) but not higher of the sugars was added, these sugars may be considered to participate in hyperinduction as the signal rather than through their metabolism.

Detection of Mycotoxin-Encoding Genes in Fusarium spp. Isolated from Maize Kernels in Indonesia

Fusarium spp. have a significant status as a plant pathogen in maize cultivation and post-harvest handling in Indonesia, for they not only devastate the crop in the field and during storage but also have potential capability to be a mycotoxin contaminant in maize-based food or feed. This research aimed to detect mycotoxin-encoding genes from 24 isolates of Fusarium spp. collected from maize kernels harvested in several maize cultivation center areas in Java and one isolate from Lombok Island, using specific primers. These Fusarium spp. had already been molecularly characterized and grouped as four species: F. verticillioides, F. graminearum, F. proliferatum, and F. asiaticum. The results showed that genes encoding fumonisin, deoxynivalenol, and zearalenone were detected in F. verticillioides, and genes encoding deoxynivalenol and zearalenone were detected in F. graminearum and F. asiaticum, while those mycotoxin-encoding genes were not detected in F. proliferatum on the basis of the specific primers used in this research. This is a principal study to considerably contribute further research in observing conditions that will be favorable for expression of those genes, in order to better manage maize post-harvest handling to avoid mycotoxin contamination.

Peningkatan Ketahanan Tanaman Pisang Kepok Kuning terhadap Penyakit Darah melalui Variasi Somaklonal dan Simbiosis Endofitik

One of the obstacles that was encountered in the banana cultivation is blood disease. Blood diseases is caused by Ralstonia solanacearum that is subsequently revised to become blood disease bacteria (BDB). Until now the control of banana blood disease is very difficult. Control of banana blood disease with chemical injections and soil treatment is not effective. This study was aimed to obtain Kepok Kuning cultivar banana seedlings which was resistant towards blood disease obtained from in vitro selection by using BDB growing filtrate and induced resistance by inoculation of antagonistic endophytic bacteria.The observation of Kepok Kuning banana explants treated with various concentrations of BDB growing filtrate showed that the percentage of living explants decreased to 83.33% when the BDB growing filtrate concentration increased to 15%. Treatment of banana explants with BDB growing filtrate also affected the number of roots, shoots, and leaves. Treatment with a single antagonistic endophytic bacteria suppressed the intensity of banana blood disease to 0% in comparison with the mixture of antagonistic endophytic bacteria if Kepok Kuning banana explants were not treated with BDB growing filtrate. When Kepok Kuning banana explants were treated with BDB growing filtrate, the intensity of banana blood disease suppressed to 0% after the high concentration of BDB growing filtrate and the antagonistic endophytic bacteria mixture were applied. Salah satu kendala yang dihadapi dalam usaha budidaya pisang adalah adanya penyakit darah. Penyakit darah disebabkan oleh bakteri Ralstonia solanacearumyang selanjutnya direvisimenjadi bakteri darah pisang (Blood Disease Bacteria orBDB). Sampai saat ini pengendalian penyakit darah pisang sangatsukar dilakukan. Pengendalian penyakit darah dengan suntikan bahan kimia dan perlakuan tanah tidak efektif untuk diaplikasikan. Penelitian ini bertujuan untukmendapatkan bibit pisang kultivar Kepok Kuning yang tahan penyakit darah yang diperoleh dariseleksi in vitro dengan menggunakan filtrat pertumbuhan BDB dan induksi ketahanan melalui inokulasi jasad renik endofitik yang bersifat antagonis. Hasil pengamatan terhadap eksplan pisang Kepok Kuning yang diperlakukan dengan berbagai konsentrasi filtrat BDB menunjukkan bahwa pada eksplan yang diperlakukan dengan filtrat pertumbuhan BDB, persentase tumbuhnya akan berkurang hingga 83,33% jika konsentrasifiltrat pertumbuhanBDBmencapai 15%. Selain itu perlakuan planlet pisang dengan filtrat pertumbuhan BDB akan mempengaruhi jumlah akar, tunas, dan daun. Perlakuan dengan jasad renik endofitik antagonis secara tunggal mampu menekan intensitas penyakit darah hingga 0% jika dibandingkan dengan perlakuan campuran apabila sebelumnya eksplan pisang Kepok Kuning tidak diperlakukan dengan filtrat pertumbuhan BDB. Apabila sebelumnya planlet pisangKepokKuning diperlakukan dengan filtrat pertumbuhan BDB maka mampu menekan intensitas penyakit darah hingga 0% jika konsentrasi filtrat pertumbuhanBDBsemakin tinggi dan diperlakuan campuran jasad renik endofitik.