Plant Bacteriology Research Papers - Academia.edu (original) (raw)

Virus and soil borne pathogens negatively impact on the production of potatoes in tropical highland and subtropical environments, limiting supply of an increasingly popular and important vegetable in these regions. It is common for latent disease infected seed tubers or field grown cuttings to be used as potato planting material. We utilised an International Potato Centre technique, using aeroponic technology, to produce low cost mini-tubers in tropical areas. The system has been optimised for increased effectiveness in tropical areas. High numbers of seed tubers of cultivar Sebago (630) and Nicola per m 2 (>900) were obtained in the first generation, and the system is capable of producing five crops of standard cultivars in every two years. Initial results indicate that quality seed could be produced by nurseries and farmers, therefore contributing to the minimisation of soil borne diseases in an integrated management plan. This technology reduces seed production costs, benefiting seed and potato growers. INTRODUCTION Potato production in tropical highland and subtropical environments is often limited due to rapid degeneration of planting material through virus, nematodes and soil borne diseases. Bacterial wilt (Ralstonia solanacearum) (BW) is a disease that has long been recognised as one of the limiting factors in potato production. Warm and wet environmental conditions found in the tropics often result in potatoes with a proliferation of open lenticels, which facilitates entry of the bacteria into the tuber (Kloos and Fernandez, 1985). When present, the bacteria can build up in susceptible plants to create a year round source of inoculum. Historically when this has occurred, farmers have abandoned the land and used slash and burn agriculture to move further into the forests. This can never be a sustainable solution as the newly cleared land is quickly infected, particularly when diseased planting material is used, and thus this land also becomes unproductive. This process threatens soil health, global biodiversity and the future economic prosperity of the people without addressing the problem of disease control. Continually increasing the region's infected land cannot be sustainable. Where farmers have not had the option of moving into clean production areas, many have been forced to abandon potato cropping. An integral part of any control strategy of BW must be the development of farmer available and affordable clean seed potato supplies. While a clean seed production process is important, it is critical that the scheme is not developed in the absence of other agronomic control measures, particularly as there is a very high likelihood that the land on which the farmer wants to plant will already have a level of wilt infection. While this study predominately looks at the feasibility of developing a seed potato production system suitable for bacterial wilt prone lands, it also considers some of the other agronomic techniques that need to be provided to farmers. The studies conducted under ACIAR project Hort./2007/066 showed that in the presence of bacterial wilt, potato yields can be as low as a few kilograms per hectare (Justo et al., 2012). The lack of available clean seed supplies means that famers have no other

- by and +2
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- Plant Bacteriology

Leaf scald caused by Xanthomonas albilineans, had been widely acknowledged by almost all sugarcane growing countries in the world. Its ability to undergo latency period plays a vital role for its spread that made it to be a phytosanitary threat worthy of quarantine regulation (Frison and Putter, 1993). Currently, the disease was already recorded to be present in almost all localities of Negros Occidental, the largest sugarcane growing province in the Philippines, and had infected a number of different cultivars. With the numerous diseases of sugarcane, understanding its symptomatology is a critical and important factor in recognizing the disease. A total of 58 sugarcane genotypes had been evaluated and shows variability of symptom expression under natural condition, varying from white pencil-line streaks in leaves (chronic phase) to wilting of the whole plant (acute phase). Symptoms such as leaf necrosis and “lalas” had been noted to be common among the different genotypes at tillering stage of the crop. This serves as a significant information for the establishment of variety disease screening protocol and refinement of disease rating scale based on Philippine condition.

- by Harold Paniza
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- Plant Bacteriology, Disease Diagnosis, Plant Pathology

A SEGUITO degli importanti disseccamenti riscontrati su olivo nella provincia di Lecce è stata at tivata un'indagine territoriale che ha evidenziato la presenza di tre differenti agenti causali associati al complesso del disseccamento: l'insetto Zeuzera pyrina, i funghi Phaeoacremonium spp. e Phaeomoniella spp. e il batterio Xylella
fastidiosa. Proprio quest'ultimo, essendo un batterio da quarantena
soggetto a lotta obbligatoria, condiziona le strategie di contenimento
che sono finalizzate a evitarne la d iffusione. Tra queste, l'eliminazione delle parti infette e il controllo degli insetti vettori.

- by Franco Nigro
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- Olive and Olive Oil Technology, Plant Bacteriology, Plant Pathology

A survey was conducted in twenty-five cashew (Anacardium occidentale) orchards in five communities in the Dormaa-Central Municipality of Bono Region of Ghana to assess the incidence and severity of anthracnose, gummosis and die-back diseases on cashew. Cashew diseased samples of leaves, stem, inflorescences, twigs, flowers, nuts and apples showing symptoms (e. g. small, water-soaked, circular or irregular yellow, dark or brown spots or lesions on leaves, fruits and flowers, sunken surface, especially on the apples, blight, gum exudates) were collected for isolation of presumptive causative organism. The pathogen was isolated after disinfecting the excised diseased pieces in 70% ethanol, plated on potato dextrose agar (PDA) and incubated at 28 o C for 3 to 7 days. The identity of the putative pathogen was morphologically and culturally confirmed as belonging to Colletotrichum gloeosporioides species complex using standard mycological identification protocols. The pathogen had varied conidia sizes of between 9-15 up to 20 μm in length and diameter of 3-6 μm. The conidia were straight and cylindrically shaped with rounded or obtuse ends. The septate mycelium was whitish-grey, velvety and cotton-like in appearance from the top. The results confirmed the presence of the pathogen in the orchards with incidence ranging from 6.9% and 14.0% for gummosis and averaged 22.9% for anthracnose infected orchards. The result of the pathogenicity test confirmed the isolates to be pathogenic on inoculated cashew seedlings and were consistently re-isolated, thereby establishing the pathogen as the true causal agent of the said diseases in cashew trees and thus completed the Koch's postulate.

- by Dr. Muntala Abdulai and +1
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- Plant Tissue Culture, Mycology and Plant pathology, Plant Bacteriology, Plant Phytopathology

The symposium will include plenary sessions, a field trip and two training workshops. Plenary sessions will be held in Gallipoli (October 21-22, 2014), in the Symposium venue, the Costa Brada Resort located on the white sandy shores of Gallipoli (province of Lecce), just 3 km from the city centre.
A half day field trip (October 22, 2014) will be offered to the delegates with the opportunity to visit the X. fastidiosa outbreaks in the province of Lecce. Two parallel training workshops (October 23-24, 2014) will be held at the Centro di Ricerca, Sperimentazione e Formazione in Agricoltura "Basile Caramia", at Locorotondo (province of Bari). These workshops are designed to provide in-depth technical information
on the current serological and molecular tools for X. fastidiosa detection and on the key characteristics of the main xylem-sap feeders involved in X. fastidiosa transmission. Attendance to the workshops is limited to the 25 delegates who register first.

- by Franco Nigro
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- Olive and Olive Oil Technology, Olea europaea, Plant Bacteriology, Plant Pathology

Isolation of nitrogen fixing rhizobia was made from the root nodules of Cow Pea and Black Gram during July to November 2018. Root nodules were collected from the cultivated field of Anauksu Village, Kyaungkone Township, Ayeyarwady Region, Myanmar. The aim of this research was to isolate nitrogen fixing Rhizobium as starter culture of biofertilizer for peas. Isolation of Rhizobium was made by using Yeast Extract Mannitol agar with Congo red and Bromothymol blue. Identification was based on colony morphology, cell morphology, basic staining reactions and motility. One strain of Rhizobium from Cow Pea and one strain of Bradyrhizobium from Black Gram were isolated. These bacteria could be used as starter culture for the production of rhizobia biofertilizers.

- by Kyaw Myo Naing
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- Rhizobium, Plant Bacteriology
- by Srđan G Aćimović
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- Tree Physiology, Fungal Plant Pathology, Plant Bacteriology, Plant Protection
- by shinta mayasara
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- Bacteriology, Plant Bacteriology

Management of fire blight is complicated by limitations on use of antibiotics in agriculture, antibiotic resistance development, and limited efficacy of alternative control agents. Even though successful in control, preventive antibiotic sprays also affect non-target bacteria, aiding the selection for resistance which could ultimately be transferred to the pathogen Erwinia amylovora. Trunk injection is a target-precise pesticide delivery method that utilizes tree xylem to distribute injected compounds. Trunk injection could decrease antibiotic usage in the open environment and increase the effectiveness of compounds in fire blight control. In field experiments, after 1-2 apple tree injections of either streptomycin, potassium phosphites (PH) or acibenzolar-S-methyl (ASM), significant reduction of blossom and shoot blight symptoms was observed compared to water injected control trees. Overall disease suppression with streptomycin was lower than typically observed following spray applications to flowers. Trunk injection of oxytetracycline resulted in excellent control of shoot blight severity, suggesting that injection is a superior delivery method for this antibiotic. Injection of both ASM and PH resulted in the significant induction of PR-1, PR-2 and PR-8 protein genes in apple leaves indicating induction of systemic acquired resistance (SAR) under field conditions. The time separating SAR induction and fire blight symptom suppression indicated that various defensive compounds within the SAR response were synthesized and accumulated in the canopy. ASM and PH suppressed fire blight even after cessation of induced gene expression. With the development of injectable formulations and optimization of doses and injection schedules, the injection of protective compounds could serve as an effective option for fire blight control.

- by Srđan G Aćimović and +1
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- Gene expression, Host Plant Resistance, Disease Resistance in plants, Plant Bacteriology

In this study, samples were collected from the leaves and stems of healthy wild Pistachio trees (Pistacia atlan-tica L.) from various locations of Baneh and Marivan regions, Iran. In total, 61 endophytic bacteria were isolated and grouped according to phenotypic properties. Ten selected isolates from each group were further identified by partial sequencing of the 16S rRNA gene. Based on the results, isolates were identified as bacteria belonging to Pseudomonas, Stenotrophomonas, Bacil-lus, Pantoea and Serratia genus. The ability of these isolates was evaluated to phytohormone production such as auxin and gibberellin, siderophore production, phosphate solubilization, atmospheric nitrogen fixation, protease and hydrogen cyanide production. All strains were able to produce the plant growth hormone auxin and gibberellin in different amounts. The majority of strains were able to solubilize phosphate. The results of atmospheric nitrogen fixation ability, protease and sid-erophore production were varied among strains. Only Ba66 could produce a low amount of hydrogen cyanide. The results of biocontrol assay showed that Pb78 and Sp15 strains had the highest and lowest inhibition effects on bacterial plant pathogens, Pseudomonas syrin-gae pv. syringae Pss20 and Pseudomonas tolaasii Pt18 under in vitro condition. Pb3, Pb24 and Pb71 strains significantly promote root formation on carrot slices. To our knowledge this is the first report of the isolation of endophytic bacterial strains belonging to Pantoea, Bacillus, Pseudomonas, Serratia and Stenotrophomonas genus from wild pistachio trees with plant growth promoting potential and biocontrol activity.

- by Faegheh Etminani
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- Bacteriology, Plant Bacteriology

Zoltan Klement, Research Professor at the Plant Protection Institute, Hungarian Academy of Sciences, Budapest, Hungary, suddenly and unexpectedly passed away on October 19, 2005.

- by Tamas Komives
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- Bacteriology, Plant Bacteriology

The isolation in pure culture of the Xylella fastidiosa strain associated with the quick decline syndrome of olive, recently observed in Apulia (Salento peninsula, southern Italy) was attempted from symptomatic, naturally infected olive and oleander plants, and a periwinkle seedling that had been exposed to, and was infected by Xylella-positive
spittlebugs. Prior to isolation, the presence of Xylella was ascertained in all donor hosts by PCR, indirect immunofluorescence and electron microscopy. Isolations from olive failed because of the heavy contamination by bacteria other than Xylella. By contrast, pure bacterial cultures were obtained from oleander and periwinkle extracts
plated in periwinkle wilt gelrite (PWG) and buffered cysteine-yeast extract (BCYE) media. In both media, colonies were slow-growing, small-sized (less than 1 mm 25 days from plating), non pigmented, opalescent and exhibited the same morphology, except for the margin that was entire in BCYE and somewhat irregular in PWG. Bacterial
cells were rod-shaped with rounded ends, had a thick and rippled cell wall, an average width of 0.35 μm, and a maximum length of ca. 5 μm. They gave a positive reaction in immunofluorence assays and were clearly decorated by colloidal gold in immunogold labelling tests. Sequenced PCR products amplified from periwinkle and oleander colonies shared 97-99% sequence identity with known X. fastidiosa strains from database and were 100% identical to one another and to comparable sequences obtained from infected olive trees. These sequences grouped in a distinct cluster of a branch comprising X. fastidiosa isolates belonging to the subspecies pauca.

- by Franco Nigro
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- Olive and Olive Oil Technology, Plant Bacteriology, Plant Pathology

Trunk injection is a novel delivery method for plant protective compounds in agriculture, which could increase the sustainability of fruit production through target-precise disease control and thus minimal exposure of the environment to the compounds. We evaluated whether trunk-injected antibiotics, copper and structural plant resistance activator prohexadione-calcium (PC) can significantly reduce fire blight on apples due to translocation of these compounds into the canopy. After 1-2 spring injections of oxytetracycline (OX), kasugamycin (KS) and copper chelate (CC), using four replicates per treatment, we evaluated inoculated apple trees for blossom and shoot blight incidence. In a separate study, after one spray or one injection of PC, we evaluated randomly selected and inoculated apple shoots for shoot blight severity. At high disease pressure, OX, KS and CC significantly reduced blossom blight providing control of 60.6, 31.7 and 15.5-17.8%, respectively. Fire blight has spread ...

Thirty two isolates of fluorescent Pseudomonas and sixteen rhizobia were isolated from the root nodules of mungbean (Vigna radiata) collected from the experimental fields of Karachi University. Pseudomonas isolates and rhizobia were characterized for their growth promoting ability and biocontrol activity in the greenhouse and in the laboratory, through the determination of in vitro activity against root rotting fungi viz., Macrophomina phaseolina, Fusarium solani, F. oxysporum and Rhizoctonia solani and nematacidal activity against the second stage juveniles of Meloidogyne javanica. Pseudomonas isolates NAFP-19, NAFP-21, NAFP-22, NAFP-27, NAFP-31 and NAFP-32, and rhizobia isolates NFB- 103, NFB-107, NFB-109 and NFB-102 inhibited the growth of all the test fungi and showed maximum nematicidal activity against second stage juveniles of M. javanica. Strains of Pseudomonas (NAFP- 19, NAFP- 31 and NAFP- 32) and rhizobia (NFB- 107, NFB- 109 and NFB-103) used as a soil drench significantly reduced root rot disease under greenhouse conditions and thereby enhanced plant growth and yield in mungbean. In field plot experiments mixed or separate application of NAFP and rhizobia showed effective control of M. phaseolina and F. oxysporum with some protection from F. solani and R. solani.

- by Syed Ehteshamul-Haque and +2
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- real time PCR, Pseudomonas, Plant Bacteriology, Mungbean

Soybean is highly important and widely spread farming and industrial crop. Soybean acreage is constantly expanding. Along with acreage expansion many soybean diseases have increased in severity, frequency and intensity. Bacterial diseases of soybean can reduce yield significantly, especially in the years with rainy and cool spring and with rainy summer too. In Serbia the causal agent of Bacterial Blight of soybean - Pseudomonas syringae pv. glycinea has the highest significance. It appears regularly, and in the years with favorable conditions for development and spreading it causes severe damages. Second species Xanthomonas campestrisi pv. glycines, causal agent of Bacterial Pustule of soybean, has been detectet in Serbia but in comparison with P. s. pv. glycinea it has a slightly less economical importance. In favourable conditions this pathogen can reduce yield in some measure. Pseudomonas syringae pv. tabaci, as causal agent of Wildfire of soybean, has not been detected in Serbia but it appears regularly on tobacco as primary host. For all three species of phytopathogenic bacteria detailed survey about: world spread and economical importance, specific symptoms, bacteriological and epidemiological/ecological characteristics, cultivar resistance and recommendations for control has been presented.

- by Srđan G Aćimović
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- Plant Bacteriology, Plant Pathology, Plant Pathogenic Bacteria

To investigate patho-dyanamics of Erwinia tracheiphila on Cucurbita pepo with biochemical, molecular characterization and eco-friendly management approaches. Variability study of Erwinia tracheiphila was done by collecting the isolates from different places in Odisha. Disease severity was calculated and analyzed from 2016-18 to predict trend of emergence and disease progress. Molecular detection of pathogen was done through 16S rRNA sequencing. Biochemical characterization and identification of pathogenic nature of Erwinia tracheiphila was performed through Ortho-Nitrophenyl β-Galactoside, Esculin hydrolysis, Citrate and Malonate utilization in the presence of different carbohydrate molecules. Efficacy of eight different plant oils were tested by in-vitro inhibition zone (IVIZ) assay against Erwinia tracheiphila as eco-friendly management approaches. Analysis of disease severity data from 2016-18 ranged between 29% to 33%. Molecular detection of causal pathogen was further confirmed by 16S rRNA region sequencing with 99% identity of NCBI-GenBank published Erwinia tracheiphila (MK356446 and MK356441) database and phylogenetic analysis. The results of IVIZT revealed that the clove oil treatment showed maximum inhibitory effect on the growth of Erwinia tracheiphila followed by mustard oil and neem oil. Sesamum oil showed the lowest efficacy against Erwinia tracheiphila. Optimum temperature range between 25-28°C, 80-85% relative humidity and 150-180 mm average rainfall triggered the disease progress and turned to be a severe one under experimental agro-climatic situation. Biochemical characterization and molecular detection of causal isolate confirmed the pathogen as Erwinia tracheiphila, causing wilt disease of Cucurbita pepo. This study also revealed the potential efficacy of clove oil and mustard oil against Erwinia tracheiphila as compared to other selected plant oils.

Malakand Division in northwest Pakistan is known for delicious sweet orange, locally called Malta (Citrus sinensis). However, both quality and quantity of the citrus produce has seen a decline over the past few decades. Among production constraints, Huanglongbing (HLB) caused by phloem-limited alpha proteobacterium Candidatus Liberibacter asiaticus (CLas) -an endosymbiont of Asian Citrus Psyllid (Diaphorina citri), is of great economic significance. Therefore, we assessed HLB incidence through symptom-based surveys in major citrus growing areas of Khyber Pakhtunkhwa (KP), Northwest Pakistan. The presence or absence of CLas in the collected citrus samples was confirmed by PCR (Polymerase Chain Reaction) using three set of primers (LSS/LAS606, OI1/OI2C “16S rDNA” and MH353/MH354 “operon “nusG-rplK”). An average disease incidence of 92% and severity of 34% were recorded from main production zones in district Swat, KP. Likewise, in district Lower Dir, HLB had disease incidence and severity of 64% and 24%, respectively. Molecular diagnostics using 16S rDNA-specific primer LSS/LAS606 and OI1/OI2C, yielded characteristic bands of 500 bp and 1160 bp, from all five pooled samples from Swat district, while only two samples of Dir tested positive for both primers. Using an alternative primer MH353/MH354 (nusG-rplK) showed positive amplification for four samples from Swat and two samples of Dir with an amplicon of 631 bp. To assess the molecular diversity of the CLas, Sanger sequencing was carried out based on16S rDNA gene. Sequence analysis of 16S rDNA gene from all samples revealed maximum similarity with C. Liberibacter asiaticus. Among studied isolates, SwKjuPk-5 (MH374503) and SwMtaPk-2 (MH374500) isolates appeared to be more divergent and grouped in separate clad as compared to remaining isolates of Swat and Dir.

- by Plant Protection
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- Plant Bacteriology
- by Nazmul Islam
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- Plant Bacteriology
- by Franco Nigro
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- Olive and Olive Oil Technology, Plant Bacteriology, Plant Pathology

Citrus bacterial canker is one of the most important citrus diseases caused by Xanthomonas citri subsp citri (Xcc). To assess the phenotypic and genotypic diversity of Xcc, 30 strains were isolated from infected areas of Fars province. All isolates were studied for physiological, biochemical and nutritional characters, host range and the existence of rpf gene using XAC02 and XAC01 primers. All strains were compared using seven RAPD primers. All strains were rod-shaped, motile, Gram-negative and obligative aerobic. They were negative in oxidase reaction but positive in catalase and hypersensitive reaction on tobacco. Using NTsys-PC software, numerical analysis of phenotypic characteristics showed that isolates are similar to each other at level 95%. In pathogenicity tests on limes (Citrus aurantifolia), all isolates showed typical symptoms of the disease after two weeks. In RAPD-PCR, using compositional analysis of seven random primers, two main groups at 75% similarity level were ob...

- by Kavous Ayazpour
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- Environmental Biology, Plant Bacteriology
- by Nazmul Islam
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- Plant Bacteriology

An investigation was carried out to evaluate the six selected isolates of three bio-control agents against
foot and root rot pathogens. The pathogens, Fusarium oxysporum and Sclerotium rolfsii were isolated
from foot and root rot infected lentil seedlings. Four isolates of Rhizobium leguminosarum, one isolate
of Pseudomonas fluorescens and one isolate of Trichoderma harzianum were used as bio-control
agents. In dual culture method, highest zone of inhibition of F. oxysporum (57.37%) was measured
against R. leguminosarum isolate 3 and isolate 4. In case of S. rolfsii, 80% and 37.85% inhibition zone
were measured against P. fluorescens and T. harzianum, respectively. In paper towel and water agar
test tube tests, seed treatment with all the bio-control agents showed significantly better germination
than control. It also resulted in significant increase in shoot and root length that gave high vigor index.
In paper towel test, minimum number of deed seeds (9.00), no abnormal and diseased seedlings were
counted from R. leguminosarum treated seeds. In water agar test tube test, minimum number of deed
seed (12.00) and abnormal seedlings (2.00) were counted from R. leguminosarum treated seeds. Here,
no diseased seedling was found from T. harzianum treated seeds.

Bacterial wilt complex disease of tomato (Solanum lycopersicum L.) was incited jointly by bacterial wilt pathogen Ralstonia solanacearum and Meloidogyne incognita worldwide. Bio-efficacy of bacterial antagonists i.e. B. amyloliquefaciens DSBA-11 and P. fluorescens DTPF-3 was studied against the wilt disease complex in tomato at National Phytotran facility Indian Agricultural Research Institute (IARI), New Delhi, at 26 ± 2 °C. Minimum wilt disease incidence (26.00%) with the highest bio-control efficacy (64.15%), less juvenile population (19.33 J 2 /g of soil) of M. incognita was recorded in the combined application of DTPF-3 + DSBA-11 after 30 d of inoculation under glasshouse conditions. In a field study, minimum bacterial wilt disease incidences 19.0% and 20.4% were recorded in the bleaching powder treatment followed by mixed application of DSBA-11 + DTPF-3, 19.6% and 21.2% wilt incidence in 2014 and 2015 respectively. However, a reduction of root-knot gall index was recorded a maximum of 59.76% and 69.62% in DSBA-11 + DTPF-3 treated plants followed by 54.88% and 60.13% over control in DTPF-3 treatment in 2014 and 2015 respectively. The yield of tomato fruit was increased over control by 17.48% and 16.97% in 2014 and 2015 respectively under field conditions. A combination of P. fluorescens DTPF-3 + B. amyloliquefaciens DSBA-11 suppressed bacterial wilt and root-knot diseases and also increased the yield of the tomato fruit significantly (p < 0.05) under field conditions.

- by Saad Ahmed Shah
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- Plant Bacteriology, Plant Protection

- by Saad Ahmed Shah
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- Plant Bacteriology, Plant Protection

Rice blast caused by Magnaporthe grisea is turn to be one of the most severe pathogen under change in climatic condition in coastal region of SouthEastern India. Severity of the pathogen was not overwhelming previously. An investigation was carried out in several villages of different districts of Andhra Pradesh and Odisha under the RAWEP programme of Centurion University of Technology and Management with compared to meteorological data support from IMD, Bhubaneswar, Odisha. Different meteorological factors consider under this study were maximum temperature (T max), minimum temperature (T min), relative humidity maximum (RH max), relative humidity minimum (RH min), rainfall (RF). Among the three cultivated rice varieties, Pooja and Samba mahsuri (BPT-5204) are the most susceptible blast varieties (5.71% and 4.85%) compared to Swarna (MTU 7029) with a disease incidence level of 1.23%. Outcome of this investigation also revealed that the most crucial two (T max and RH max) factors directly involved for the emergence of the disease compared to previous year 2015-16 and 2016-17. The peak disease infestation was observed in the month of October and November with PDI of 27.33 % and 26 %. Farmers based prolonged survey report and our observation concluded with the fact that Tricyclazole 75% WP (trade name-BAAN/ Indofils) and 40% EC formulation of Isoprothiolane (trade name-Fujione / Rallis India Limited) are the two sequential most effective fungicides compared to different market based available fungicides and showed best efficacy against neck, collar and leaf blasts. Weather parameters as well as complex adaptability of the pathogenic nature (showing resistant against different fungicides) turned this Ascomycota member to a severe one. Highlights m The highest rice blast disease incidence was observed in October and November. For epidemiological perspective, the two most crucial factors for the disease development are Maximum temperature, Relative humidity and Rainfall which make a tridirectional pool for disease development. m From the varietal study, it was seen that Pooja and Samba mashuri is the susceptible variety towards rice blast disease while Tricyclazole 75% WP and Isoprothiolane 40% EC is detected as two effective chemical against this disease.

An investigation was carried out to evaluate the efficacy of some selected seed treatments against bacterial leaf blight (BLB) disease of imported hybrid rice during the period from November 2009 to December 2010. Eleven seed treating agents viz. untreated control, sun drying, polythene solarization, brine solution, neem (Azadirachta indica) leaf extract, allamanda (Allamanda cathartica) leaf extract, hot water treatment, Provax 200 (Carboxin), Bavistin 50 WP (Carbendazim), Dithane M 45 (Mancozeb) and Trichoderma harzianum were evaluated. Effect of seed treatments were assessed against the disease incidence and severity at three growth stages (flowering, milking and maturity) and on yield contributing characters under natural epiphytic condition. BLB disease incidence and severity ranged from 13.62% to 23.20% and 5.64 to 8.29 (0-9 scale) respectively at maturity stage where none but hot water treatment was found effective against the disease. Only hot water treatment gave promising result against the BLB disease. It was observed that disease incidence and severity was gradually increased from flowering stage to maturity stage with the age of the plant and minimum incidence and severity gave the maximum yield.

- by Abu Noman Faruq Ahmmed
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- Plant Bacteriology, Plant Pathology

Grapevine is constantly exposed to attacks by different agents of biotic and abiotic nature. Some of biotic inducers appear in this old culture every year, in a higher or lower degree, like for example: Plasmopara viticola, inducer of downy mildew, Uncinula necator, inducer of powdery mildew, Botryotinia fuckeliana, inducer of grey decay. Viruses also accompany grapevine frequently, and phytopathogenous bacteria are not so rare. This significantly complicates struggle against them, since although vine often appears healthy, numerous qualitative and quantitative changes occur inside it, which greatly decreases grape yield and quality. Lately, phytoplasma inducers of grapevine tree redness, and yellowness of grapevine leaves, have significantly endangered this culture. Besides, one group of pathogenes, the so called inducers of grapevine tree diseases, attack mostly vines older than 8 years, causing their drying out and withering. The most frequent inducers are: Phomopsis viticola (inducer of grapevine excoriosis), Eutypa lata (inducer of grapevine eutypa dieback), fungi from the gender Botryosphaeria (inducers of grapevine cancer and drying out) and ESCA (a group of fungi causing drying out-apoplexy or black measles of grapevine), which is discussed in detail here.