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Microbial Interactions And Biocontrol In The Rhizosphere Pdf

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Biological control of potato black scurf by rhizosphere associated bacteria. The present work was carried out to study the potential of plant rhizosphere associated bacteria for the biocontrol of potato black scurf disease caused by Rhizoctonia solani Khun AG A total of twenty-eight bacteria isolated from diseased and healthy potato plants grown in the soil of Naran and Faisalabad, Pakistan were evaluated for their antagonistic potential.

Microbial interactions and biocontrol in the rhizosphere.

Biological control of potato black scurf by rhizosphere associated bacteria. The present work was carried out to study the potential of plant rhizosphere associated bacteria for the biocontrol of potato black scurf disease caused by Rhizoctonia solani Khun AG A total of twenty-eight bacteria isolated from diseased and healthy potato plants grown in the soil of Naran and Faisalabad, Pakistan were evaluated for their antagonistic potential. Nine bacterial strains were found to be antagonistic in vitro , reduced the fungal growth and caused the lysis of sclerotia of R.

The selected antagonistic strains were further tested for the production and efficacy of volatile and diffusible antibiotics, lytic enzymes and siderophores against R. Selected antagonistic bacteria were also characterized for growth promoting attributes i. Biocontrol efficacy and percent yield increase by these antagonists was estimated in greenhouse experiment. Statistical analysis showed that two Pseudomonas spp.

StT2 and StS3 were the most effective with Potential antagonistic bacterial strain StS3 showed maximum homology to Pseudomonas sp. These results suggest that bacterial isolates StS3 and StT2 have excellent potential to be used as effective biocontrol agents promoting plant growth with reduced disease incidence.

Among biotic stresses, plant pathogenic microorganisms are the serious threat to crop production and ecosystem stability 41, Different methods have been used to control plant pathogens, being the most used cultural practices, resistant cultivars, chemical and biological control.

Biological control is a natural and specific way to control pathogens and enhance crop yield by growth promoting attributes of environment friendly microorganisms This method has been developed successfully during the last few years. It is based on the reduction of inoculum or of pathogenic activity due to the natural presence of one or more organisms, through the management of the environment, the host or antagonists 3.

Black scurf of potato Solanum tuberosum L. Black spots of fungus sclerotia about 1mm to 10mm appears on the potato surface. These sclerotia, also known as black scurf, are difficult to remove by washing and brushing The black scurf stage may often produces tubers that are misshapen, cracked, and discolored by the presence of sclerotia on the tuber surface. Black scurf is found in most of the potato growing areas throughout the world. It can be very severe in eastern Canada and Maine A few areas of Punjab are also affected.

Fungi from Trichoderma genus are among the biological control agents of R. On the other hand, bacteria belonging to genus Pseudomonas and Bacillus have also been used in bioantagonism 2, The present research work was carried out to study the potential of rhizobacteria to control potato black scurf diseases and thus increase crop yield. To control plant diseases, bacteria have some weapons in their extracellular metabolites i. Keeping in view the above facts, our objective was to isolate and select antagonistic bacterial strains that could control R.

Isolation of Rhizoctonia solani and growth condition. Black scurf infected tubers of potato Solanum tuberosum L. Cardinal were surface sterilized by 0.

Grown fungal culture was purified by sub-culturing and identified using stereomicroscope after staining with trypan blue. Pure culture of R.

All isolation steps were performed under aseptic conditions. Five mm 2 mycelial disc from a 5 days old culture of R. The colonies of fungi were developed and produced many sclerotia. Determination of virulence in R. Virulence of R. For pathogenicity test, approximately 1 mL of fungal inoculum mycelium and sclerotia was dropped at the injured stem of one month old potato cv. Cardinal plants grown in pots containing 10 kg soil.

SDW was used as control. The plants were observed for symptoms of black scurf i. In vitro pathogenicity test was also performed on leaves, stem and tuber of potato cv. Cardinal in petri plates under aseptic conditions. PDB broth was used as controls. The samples were supplemented daily with 1 mL SDW to avoid dehydration. The plant samples were observed for symptoms of black scurf i. Isolation of bacteria and growth condition. Bacteria were isolated from soil, rhizosphere, roots and tubers of healthy and diseased potato plants collected from Naran and Faisalabad, Pakistan.

The suspension was vortexed and dilutions were prepared up to 10 A large number of bacterial colonies were developed. Morphologically different colonies were selected and purified by sub-culturing Pure cultures were subjected to growth studies. Primary selection of antagonists. Antagonism of all the 28 rhizosphere associated bacterial isolates was evaluated in two major in vitro tests: dual cultures assay and extracellular metabolites efficacy test against R.

Potential antagonists were selected for further studies. Dual cultures assay: One 5-mm 2 disk of a pure culture of R. Percent inhibition was calculated using the following formula:. Extracellular metabolites efficacy test: These tests were performed in mL flasks containing mL of sterile LB broth. The supernatants were sterilized with 0. Growth diameter of the pathogen fungal growth was measured and compared to control growth where the bacterial extracellular metabolites were replaced with LB broth.

Tentative identification of antagonists. Antagonistic bacterial strains were tentatively identified by gram staining 47 and light microscopy Table 1. Fluorescent pseudomonads were identified on King's B plates Mechanisms involved in antagonism. A 5-mm 2 disk of a four days old pure culture of R. Both half plates were placed face to face preventing any physical contact between the pathogen and the bacterial culture.

Plates were sealed to isolate the inside atmosphere and to prevent loss of volatiles formed. Siderophores: Siderophores production by the bacterial isolates was detected using the universal chrome azurol 'S' CAS assay as described by Schwyn and Neillands The amount of siderophore produced was measured as described by Rachid and Bensoltane Bacterial growth was estimated turbidimetrically at nm, the amount of siderophore secreted into the culture medium was determined by removing bacteria by centrifugation and measuring the absorbance of the supernatant at nm.

Dual culture assay was carried out using these modified KB plates. Media contained chitin as the sole carbon source. Concentrated supernatants from liquid cultures of each bacteria were analyzed for the presence of chitinase as described by Zaldivar et al. The bacterial isolates that produced protease were identified by halo zone around the bacterial colony and were measured 6, Growth promoting characteristics of antagonists.

Nitrogenase activity was measured as described by Yasmin et al. Indol acetic acid IAA production: For detection and quantification of IAA production by the bacterial isolates, cultures were grown in Okon's malate medium The plates were observed for clear phosphate solubilization around colonies Phosphate solubilization was quantified by Phospho-molybdate blue color method Evaluation of antagonists in greenhouse.

To evaluate in vivo biocontrol potential of primarily selected antagonistic bacterial, sterilized soil was infested with R. Ten days old R. The experiment was conducted in completely randomized design CRD with three replicates and eleven treatments including two control treatments. There were nine treatments of antagonistic bacteria; T.

Potato cv. Cardinal tuber seeds having about five eyes buds were surface sterilized with 0. One seed from each treatment was then sown in fungal infected soil in each pot. Plants were regularly watered after every three days. Plants were harvested after days and the data was taken for parameters i. Experiment was conducted in autumn growing season, from September to December. The disease incidence was measured at the time of harvest by counting number of sclerotia at tuber skin. The results expressed as biocontrol efficacy, were calculated using the following formula 15, 16 ;.

Yield of potato tuber was also determined at the time of harvest. The results expressed as yield increase percentage were calculated using the following formula 16 ;. Standard Errors were also calculated Statistical operations were performed on CoStat version 6. Total genomic DNA of bacterial strain StS3 was isolated by the alkaline lysis method 26 with slight modifications.

Plasmid isolation of recombinant transformants was performed using Promega mini prep kit. So fungal culture was highly pathogenic to plant.

Mycorrhizal interactions in the rhizosphere

The Rhizosphere and Plant Growth pp Cite as. Mycorrhizal fungi form a symbiotic association with the roots of most plants, and significantly alter the morphology and physiology of the plant. Among other physiological changes, root exudation is qualitatively and quantitatively altered, and thus the microbial composition of the rhizosphere changes. Mycorrhiza-microbial interactions may be direct between organisms, or indirect as mediated by the host plant. For example, plant growth and health may be influenced when mycorrhizal fungi interact with the general microflora, or with specific microbes such symbiotic and free-living nitrogen-fixing bacteria, nutrient solubilizing bacteria, fungal and bacterial biocontrol agents, and other fungi.

It publishes original research papers and reviews, covering all aspects of Microbiology. The journal has a severe policy of manuscript evaluation, and each manuscript is evaluated carefully by at least two selected referees. The Impact Factor measures the average number of citations received in a particular year by papers published in the journal during the two receding years. CiteScore measures average citations received per document published. Read more. SRJ is a prestige metric based on the idea that not all citations are the same.

Either your web browser doesn't support Javascript or it is currently turned off. In the latter case, please turn on Javascript support in your web browser and reload this page. Read article at publisher's site DOI : Appl Environ Microbiol, 12 Phytopathology

Microbial interactions and biocontrol in the rhizosphere.

Plant rhizosphere is the soil nearest to the plant root system where roots release large quantity of metabolites from living root hairs or fibrous root systems. These metabolites act as chemical signals for motile bacteria to move to the root surface but also represent the main nutrient sources available to support growth and persistence in the rhizosphere. Some of the microbes that inhabit this area are bacteria that are able to colonize very efficiently the roots or the rhizosphere soil of crop plants. These bacteria are referred to as plant growth promoting rhizobacteria PGPR. They fulfil important functions for plant growth and health by various manners.

Trichoderma has been used as an alternative to synthetic pesticides to control a variety of phytopathogenic fungi, oomycetes, and nematodes. Although its mechanism of pathogen suppression has been extensively studied, how Trichoderma interacts with non-target microbes is not well understood. Here, we investigated how two Trichoderma biological control agents BCAs interact with rhizosphere bacteria isolated from a tomato plant via secreted proteins, metabolites, and volatile compounds VCs. Culture filtrates CFs of T.

E-mail: john. John M. The loss of organic material from the roots provides the energy for the development of active microbial populations in the rhizosphere around the root.

E-mail: john. John M. The loss of organic material from the roots provides the energy for the development of active microbial populations in the rhizosphere around the root.

Major losses of crop yield and quality caused by soil-borne plant diseases have long threatened the ecology and economy of agriculture and forestry. Biological control using beneficial microorganisms has become more popular for management of soil-borne pathogens as an environmentally friendly method for protecting plants. Two major barriers limiting the disease-suppressive functions of biocontrol microbes are inadequate colonization of hosts and inefficient inhibition of soil-borne pathogen growth, due to biotic and abiotic factors acting in complex rhizosphere environments. Use of a consortium of microbial strains with disease inhibitory activity may improve the biocontrol efficacy of the disease-inhibiting microbes. The mechanisms of biological control are not fully understood. In this review, we focus on bacterial and fungal biocontrol agents to summarize the current state of the use of single strain and multi-strain biological control consortia in the management of soil-borne diseases.


PDF; Split View Multiple microbial interactions involving bacteria and fungi in the rhizosphere are shown to provide enhanced Interest in biological control has increased recently fuelled by public concerns over the use of chemicals in the.


Створки стали стремительно сближаться. Стратмор попытался их удержать, но не сумел. За мгновение до того, как они сомкнулись, Сьюзан, потеряв равновесие, упала на пол за дверью.

Он сразу же перешел к делу: - Я могу заплатить вам семьсот пятьдесят тысяч песет. Пять тысяч американских долларов.  - Это составляло половину того, что у него было, и раз в десять больше настоящей стоимости кольца. Росио подняла брови. - Это очень большие деньги.

 О! - Старик радостно улыбнулся.  - Так вы говорите на языке цивилизованного мира. - Да вроде бы, - смущенно проговорил Беккер.

Вот бы побывать здесь вместе со Сьюзан. - И, разумеется, Христофора Колумба? - просиял лейтенант.

Он в последний раз взглянул на Клушара. - Капля Росы. Вы уверены. Но Пьер Клушар провалился в глубокое забытье. ГЛАВА 23 Сьюзан, сидя в одиночестве в уютном помещении Третьего узла, пила травяной чай с лимоном и ждала результатов запуска Следопыта.

Когда он начал просматривать отчет и проверять ежедневную СЦР, в голове у него вдруг возник образ Кармен, обмазывающей себя медом и посыпающей сахарной пудрой. Через тридцать секунд с отчетом было покончено. С шифровалкой все в полном порядке - как. Бринкерхофф хотел было уже взять следующий документ, но что-то задержало его внимание. В самом низу страницы отсутствовала последняя СЦР.

Через десять минут Беккер уже сидел в буфете АНБ, жуя сдобную булку и запивая ее клюквенным соком, в обществе очаровательной руководительницы Отделения криптографии АНБ. Ему сразу же стало ясно, что высокое положение в тридцать восемь лет в АНБ нельзя получить за красивые глаза: Сьюзан Флетчер оказалась одной из умнейших женщин, каких ему только доводилось встречать. Обсуждая шифры и ключи к ним, он поймал себя на мысли, что изо всех сил пытается соответствовать ее уровню, - для него это ощущение было новым и оттого волнующим. Час спустя, когда Беккер уже окончательно опоздал на свой матч, а Сьюзан откровенно проигнорировала трехстраничное послание на интеркоме, оба вдруг расхохотались. И вот эти два интеллектуала, казалось бы, неспособные на вспышки иррациональной влюбленности, обсуждая проблемы лингвистической морфологии и числовые генераторы, внезапно почувствовали себя подростками, и все вокруг окрасилось в радужные тона.

Больше никаких мотоциклов, пообещал он .

Еще немного, - повторяла она мысленно.  - Северная Дакота - это Хейл. Интересно, какие он строит планы.

 - Мою колонку перепечатывают в Соединенных Штатах, у меня отличный английский. - Мне говорили, - улыбнулся Беккер. Он присел на край койки.  - Теперь, мистер Клушар, позвольте спросить, почему такой человек, как вы, оказался в таком месте. В Севилье есть больницы получше.

Кто будет охранять охранников. - Вот. Если мы - охранники общества, то кто будет следить за нами, чтобы мы не стали угрозой обществу. Сьюзан покачала головой, не зная, что на это возразить.

 На маршруте двадцать семь их отсоединяют.

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