Pantoea stewartii (bacterial wilt of maize).

Economic losses in maize due to P. stewartii subsp. stewartii have been inconsequential in North America for the past 50 years except for a few, small sporadic outbreaks and a few extensive epidemics on susceptible sweetcorn hybrids (Pepper, 1967; Anderson, 1986; Anderson and Buzzell, 1986; Pataky et al., 1996; Pataky et al., 2000b). The lack of economic importance of this disease in North America is due primarily to adequate levels of resistance incorporated into maize hybrids that are grown where the disease occurs. Stewart's wilt caused substantial economic losses in the 1930s before the development of resistant cultivars (Pepper, 1967). Severe losses due to Stewart's wilt were reported in Italy in the 1940s and the disease reoccurred there as an important problem in the 1980s (Anon., 1983; Mazzucchi, 1984).

Complete Genome Sequence of Pantoea stewartii subsp. indologenes ZJ-FGZX1, a Lucky Bamboo Pathogen

The phytopathogen Pantoea stewartii subsp. indologenes causes Stewart’s wilt disease in lucky bamboo. Here, we report the complete genome of P. stewartii subsp. indologenes ZJ-FGZX1, which represents the first whole-genome sequence of an isolate from China. The assembled genome consisted of three contigs, with one circular chromosome of 4,550,072 bp and two circular plasmids of 326,337 and 106,454 bp. The complete genome will provide a valuable resource for further studies on bacterial blight worldwide.

Dominant, Heritable Resistance to Stewart’s Wilt in Maize Is Associated with an Enhanced Vascular Defense Response to Infection with Pantoea stewartii

Vascular wilt bacteria such as Pantoea stewartii, the causal agent of Stewart’s bacterial wilt of maize (SW), are destructive pathogens that are difficult to control. These bacteria colonize the xylem, where they form biofilms that block sap flow leading to characteristic wilting symptoms. Heritable forms of SW resistance exist and are used in maize breeding programs but the underlying genes and mechanisms are mostly unknown. Here, we show that seedlings of maize inbred lines with pan1 mutations are highly resistant to SW. However, current evidence suggests that other genes introgressed along with pan1 are responsible for resistance. Genomic analyses of pan1 lines were used to identify candidate resistance genes. In-depth comparison of P. stewartii interaction with susceptible and resistant maize lines revealed an enhanced vascular defense response in pan1 lines characterized by accumulation of electron-dense materials in xylem conduits visible by electron microscopy. We propose that this vascular defense response restricts P. stewartii spread through the vasculature, reducing both systemic bacterial colonization of the xylem network and consequent wilting. Though apparently unrelated to the resistance phenotype of pan1 lines, we also demonstrate that the effector WtsE is essential for P. stewartii xylem dissemination, show evidence for a nutritional immunity response to P. stewartii that alters xylem sap composition, and present the first analysis of maize transcriptional responses to P. stewartii infection.

A Real-Time PCR Differentiating Pantoea stewartii subsp. stewartii From P. stewartii subsp. indologenes in Corn Seed

Stewart’s wilt of corn caused by the bacterium Pantoea stewartii subsp. stewartii is a seed-borne disease of major phytosanitary importance. Many countries have imposed restrictions on corn seed imports from regions where the disease occurs to prevent the potential introduction of the pathogen. Current laboratory testing methods (enzyme-linked immunosorbent assay [ELISA] and polymerase chain reaction [PCR]) cannot readily distinguish P. stewartii subsp. stewartii from the closely related subspecies Pantoea stewartii subsp. indologenes. However, P. stewartii subsp. indologenes, a nonpathogen on corn, is occasionally found on corn seed as part of the resident bacterial population and can yield false positive test results. A real-time PCR targeting the cpsAB intergenic sequence was developed to specifically detect P. stewartii subsp. stewartii from corn seeds and distinguish it from P. stewartii subsp. indologenes. The assay successfully detected P. stewartii subsp. stewartii from corn seed, and P. stewartii subsp. indologenes-contaminated seed lots, which previously yielded false positives by ELISA and published PCR methods, were negative. The absence of P. stewartii subsp. stewartii and the presence of P. stewartii subsp. indologenes in this seed were confirmed by size differentiation of the cpsAB amplicons in a conventional PCR. By distinguishing the two subspecies, the assays described would avoid false positive results and help prevent unnecessary restrictions on international movement of corn seed.

Penyakit Layu Bakteri Stewart pada Jagung di Bali

Stewart’s wilt is a serious disease of sweet corn (Zea mays). The typical symptoms of the disease are pale-green to yellow linear streaks parallel to the veins. The symptoms were observed on sweet corn in Denpasar, Tabanan, Gianyar, and Karangasem areas during a survey in 2015. Pathogen detection based on a polymerase chain reaction was carried out using total DNA obtained from symptomatic leaf samples and the pairs of primers, CPSL1/CPSR2c. The expected sized (~1100 bp) amplicon was detected in samples from Denpasar. Sequence analysis confirmed that Stewart’s wilt disease symptoms are caused by Pantoea stewartii subsp. stewartii. Nucleotide sequence and phylogenetic analysis showed that P. stewartii subsp. stewartii from Bali has high homology (98.97-99.08 %) and placed in the same clade with isolates from Canada, USA and Japan. This is the first report of P. stewarti subsp. stewartii on corn in Bali.

UPAYA PENGGENDALIAN PENYAKIT LAYU STEWART (Pantoea stewartii subsp. stewartii) PADA TANAMAN JAGUNG MENGGUNAKAN RIZOBAKTERIA

<p>Penyakit layu Stewart pada tanaman jagung disebabkan oleh bakteri <em>Pantoea stewartii</em> subsp. <em>stewartii</em>, merupakan penyakit penting karena dapat mengakibatkan kehilangan hasil. Di Indonesia, penyakit layu Stewart masih tergolong baru dan belum ditemukan cara pengendaliannya. Penelitian bertujuan untuk mengupayakan pengendalian penyakit layu Stewart menggunakan Rizobakteria yang berperan sebagai PGPR (<em>Plant Growth Promoting Rizobacteria</em>) agar dapat meningkatkan pertumbuhan tanaman jagung sekaligus mengurangi laju perkembangan penyakit layu Stewart. Penelitian berupa percobaan lapangan di dalam polybag menggunakan RAK (Rancangan Acak Kelompok) dengan 11 perlakuan dan 3 ulangan. Sebagai perlakuan adalah beberapa isolat Rizobakteria yang diperlakukan pada benih jagung. Inokulasi patogen <em>P. stewartii</em> subsp. <em>stewartii</em> dilakukan pada bibit jagung umur 7 hst (hari setelah tanam). Parameter pengamatan antara lain: 1) perkembangan penyakit meliputi: periode inkubasi (hari) dan severitas penyakit (%). 2) pertumbuhan tanaman meliputi: tinggi tanaman (cm), diameter batang (mm), jumlah daun (helai), lebar daun ke-7 (cm), panjang daun ke-7 (cm), muncul bunga jantan (hari), muncul bunga betina (hari), berat buah per tanaman (gr), dan diameter buah tanpa kelobot (mm). Hasil penelitian mendapatkan penggunaan Rizobakteria isolat BRb 251 dapat meningkatkan tinggi tanaman, jumlah daun, dan hasil per tanaman jagung. Dengan demikian, berpotensi sebagai PGPR dalam meningkatkan pertumbuhan tanaman jagung, meskipun belum mampu menunjukkan perannya dalam menurunkan laju perkembangan penyakit layu Stewart.</p><p> </p><p><em>Stewart's wilt disease in corn plants caused by the bacteria Pantoea stewartii subsp. stewartii, that is important because it can cause yield losses. In Indonesia, Stewart’s wilt disease is still relatively new and has not found the way of control. This study aims to seek ways of controlling Stewart's wilt disease by using Rizobakteria which is likely to play a role as PGPR (Plant Growth Promotes Rizobakteria) in order to increase the growth of corn plants while reducing the rate of progression of Stewart’s wilt disease. This research trials in polybag using RAK (Group Random Design) with 11 treatments and 3 replications. As a treatment is several isolates rizobactria treat to seedcorn. Bacterial inoculation was performed on the seeds of maize 7 dap (days after planting). The observation parameters were: 1) disease progression (incubation period (day) and severity of disease (%). 2) plant growth (plant height (cm), stem diameter (mm), number of leaves (strands), width of the leaves of the 7^th (cm), length of the leaves of the 7^th (cm), emerging male flowers (day), female flowers appear (day), weight of ear per plant (gr), and ear diameter without husk (mm). Result from this research, found that using rizobacteria isolate BRB 251 can increase: plant height, number of leaves, and yield per plant, so that potential as PGPR in increasing the growth of corn plants, although not yet able to demonstrate its role in reducing the rate of development of Stewart wilt disease.</em></p>

Integrated downstream regulation by the quorum-sensing controlled transcription factors LrhA and RcsA impacts phenotypic outputs associated with virulence in the phytopathogenPantoea stewartiisubsp.stewartii

Pantoea stewartiisubsp.stewartiiis a Gram-negative proteobacterium that causes leaf blight and Stewart’s wilt disease in corn. Quorum sensing (QS) controls bacterial exopolysaccharide production that blocks water transport in the plant xylem at high bacterial densities during the later stage of the infection, resulting in wilt. At low cell density the key master QS regulator inP. stewartii, EsaR, directly repressesrcsA, encoding an activator of capsule biosynthesis genes, but activateslrhA, encoding a transcription factor that regulates surface motility. Both RcsA and LrhA have been shown to play a role in plant virulence. In this study, additional information about the downstream targets of LrhA and its interaction with RcsA was determined. A transcriptional fusion assay revealed autorepression of LrhA inP. stewartiiand electrophoretic mobility shift assays (EMSA) using purified LrhA confirmed that LrhA binds to its own promoter. In addition, LrhA binds to the promoter for the RcsA gene, as well as those for putative fimbrial subunits and biosurfactant production enzymes inP. stewartii,but not to theflhDCpromoter, which is the main direct target of LrhA inEscherichia coli.This work led to a reexamination of the physiological function of RcsA inP. stewartiiand the discovery that it also plays a role in surface motility. These findings are broadening our understanding of the coordinated regulatory cascades utilized in the phytopathogenP. stewartii.

Complete Genome Assembly of Pantoea stewartii subsp. stewartii DC283, a Corn Pathogen

ABSTRACT The phytopathogen Pantoea stewartii subsp. stewartii DC283 causes Stewart’s wilt disease in corn after transmission from the corn flea beetle insect vector. Here, we report that the complete annotated genome of P. stewartii DC283 has been fully assembled into one circular chromosome, 10 circular plasmids, and one linear phage.

Comparison of Susceptible and Resistant Maize Hybrids to Colonization by Clavibacter michiganensis subsp. nebraskensis

Clavibacter michiganensis subsp. nebraskensis causes Goss’s bacterial wilt and blight on maize and is managed primarily with C. michiganensis subsp. nebraskensis-resistant hybrids. To understand the mechanisms of resistance to infection by C. michiganensis subsp. nebraskensis, leaves of a susceptible and a resistant maize hybrid at the V4 to V5 developmental stage were wound inoculated with the pathogen. Blight lesion length was monitored, C. michiganensis subsp. nebraskensis colonizing ability was determined, and structural changes were observed using microscopy. Bacterial colonization preceded lesion development that occurred 4 to 5 days postinoculation in both hybrids. Lesion expansion in the susceptible hybrid was associated with a faster rate of C. michiganensis subsp. nebraskensis spread and multiplication in the tissues. In the resistant hybrid, spread and multiplication was reduced (P < 0.0001) and, at 16 days postinoculation, became imperceptible. Initially, C. michiganensis subsp. nebraskensis showed a preference for colonization of the metaxylem vessels in both hybrids. Spread from cell to cell was accomplished through disruption of cell walls, presumably from abundance of bacterial cells or enzymatic activity. Morphological responses of the resistant maize hybrid to infection by C. michiganensis subsp. nebraskensis were similar to those reported in maize inbred lines that were resistant to Stewart’s wilt caused by Pantoea stewartii. Resistance to C. michiganensis subsp. nebraskensis was associated with production of a dense matrix in the xylem that deformed and restricted movement of the bacterial cells.

ISOLASI DAN SELEKSI RIZOBAKTERI YANG BERPOTENSI SEBAGAI AGEN PENGENDALI PANTOEA STEWARTII subsp. STEWARTII PENYEBAB LAYU STEWART PADA TANAMAN JAGUNG

Isolation and selection of rhizobacteria potentially as biocontrol agents against Pantoea stewartii subsp. stewartii causing stewart’s wilt disease in maize. Group of bacteria that colonize plant roots were known as Plant Growth Promoting Rhizobacteria (PGPR), in addition to capable of suppressing the development of pathogens also has the ability to improve plant health. This study aims to isolate rhizobacteria from rhizosphere of maize in West Sumatera. Rhizobacteria were characterized and tested for its ability to suppress the bacteria Pantoea stewartii subsp. stewartii causes stewart wilt’s disease on maize. In this research 15 isolates of rizobacteria potential as biological agent were found, i.e. 6 isolates of the fluorescens bacteria group, 5 isolates of non fluorescens bacteria group and 4 isolates of heat-resistant bacteria group.