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Joseph W. Kloepper

Bio: Joseph W. Kloepper is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Rhizobacteria & Siderophore. The author has an hindex of 6, co-authored 6 publications receiving 3000 citations.

Papers
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Journal ArticleDOI
01 Aug 1980-Nature
TL;DR: Evidence is presented that PGPR exert their plant growth-promoting activity by depriving native microflora of iron by producing extracellular siderophores (microbial iron transport agents) which efficiently complex environmental iron, making it less available to certain nativemicroflora.
Abstract: Specific strains of the Pseudomonas fluorescens-putida group have recently been used as seed inoculants on crop plants to promote growth and increase yields. These pseudomonads, termed plant growth-promoting rhizobacteria (PGPR), rapidly colonize plant roots of potato, sugar beet and radish, and cause statistically significant yield increases up to 144% in field tests1–5. These results prompted us to investigate the mechanism by which plant growth was enhanced. A previous study indicated that PGPR increase plant growth by antagonism to potentially deleterious rhizoplane fungi and bacteria, but the nature of this antagonism was not determined6. We now present evidence that PGPR exert their plant growth-promoting activity by depriving native microflora of iron. PGPR produce extracellular siderophores (microbial iron transport agents)7 which efficiently complex environmental iron, making it less available to certain native microflora.

1,492 citations

Journal ArticleDOI
TL;DR: These findings suggest that disease suppressiveness is caused in part by microbial siderophores which efficiently complex iron(III) in soils, making it unavailable to pathogens, thus inhibiting their growth.
Abstract: The addition of either fluorescentPseudomonas strain B10, isolated from a take-all suppressive soil, or its siderophore, pseudobactin, to bothFusarium-wilt and take-all conducive soils inoculated withFusarium oxysporum f. sp.lini orGaeumannomyces graminis var.tritici, respectively, rendered them disease suppressive. Our findings suggest that disease suppressiveness is caused in part by microbial siderophores which efficiently complex iron(III) in soils, making it unavailable to pathogens, thus inhibiting their growth. Amendment of exogenous iron(III) to disease-suppressive soils converted them to conductive soils presumably by repressing siderophore production.

581 citations


Cited by
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Journal ArticleDOI
TL;DR: Biocontrol strains of fluorescent pseudomonads produce antifungal antibiotics, elicit induced systemic resistance in the host plant or interfere specifically with fungal pathogenicity factors during root colonization.
Abstract: Particular bacterial strains in certain natural environments prevent infectious diseases of plant roots. How these bacteria achieve this protection from pathogenic fungi has been analysed in detail in biocontrol strains of fluorescent pseudomonads. During root colonization, these bacteria produce antifungal antibiotics, elicit induced systemic resistance in the host plant or interfere specifically with fungal pathogenicity factors. Before engaging in these activities, biocontrol bacteria go through several regulatory processes at the transcriptional and post-transcriptional levels.

2,263 citations

Journal ArticleDOI
TL;DR: Rhizobacteria-mediated induced systemic resistance (ISR) is effective under field conditions and offers a natural mechanism for biological control of plant disease.
Abstract: Nonpathogenic rhizobacteria can induce a systemic resistance in plants that is phenotypically similar to pathogen-induced systemic acquired resistance (SAR). Rhizobacteria-mediated induced systemic resistance (ISR) has been demonstrated against fungi, bacteria, and viruses in Arabidopsis, bean, carnation, cucumber, radish, tobacco, and tomato under conditions in which the inducing bacteria and the challenging pathogen remained spatially separated. Bacterial strains differ in their ability to induce resistance in different plant species, and plants show variation in the expression of ISR upon induction by specific bacterial strains. Bacterial determinants of ISR include lipopolysaccharides, siderophores, and salicylic acid (SA). Whereas some of the rhizobacteria induce resistance through the SA-dependent SAR pathway, others do not and require jasmonic acid and ethylene perception by the plant for ISR to develop. No consistent host plant alterations are associated with the induced state, but upon challenge inoculation, resistance responses are accelerated and enhanced. ISR is effective under field conditions and offers a natural mechanism for biological control of plant disease.

2,146 citations

Journal ArticleDOI
11 Oct 2012
TL;DR: It is envisioned that in the not too distant future, plant growth-promoting bacteria (PGPB) will begin to replace the use of chemicals in agriculture, horticulture, silviculture, and environmental cleanup strategies.
Abstract: The worldwide increases in both environmental damage and human population pressure have the unfortunate consequence that global food production may soon become insufficient to feed all of the world's people. It is therefore essential that agricultural productivity be significantly increased within the next few decades. To this end, agricultural practice is moving toward a more sustainable and environmentally friendly approach. This includes both the increasing use of transgenic plants and plant growth-promoting bacteria as a part of mainstream agricultural practice. Here, a number of the mechanisms utilized by plant growth-promoting bacteria are discussed and considered. It is envisioned that in the not too distant future, plant growth-promoting bacteria (PGPB) will begin to replace the use of chemicals in agriculture, horticulture, silviculture, and environmental cleanup strategies. While there may not be one simple strategy that can effectively promote the growth of all plants under all conditions, some of the strategies that are discussed already show great promise.

2,094 citations

Journal ArticleDOI
TL;DR: The progress to date in using the rhizosphere bacteria in a variety of applications related to agricultural improvement along with their mechanism of action with special reference to plant growth-promoting traits are summarized and discussed in this review.
Abstract: Plant growth-promoting rhizobacteria (PGPR) are the rhizosphere bacteria that can enhance plant growth by a wide variety of mechanisms like phosphate solubilization, siderophore production, biological nitrogen fixation, rhizosphere engineering, production of 1-Aminocyclopropane-1-carboxylate deaminase (ACC), quorum sensing (QS) signal interference and inhibition of biofilm formation, phytohormone production, exhibiting antifungal activity, production of volatile organic compounds (VOCs), induction of systemic resistance, promoting beneficial plant-microbe symbioses, interference with pathogen toxin production etc. The potentiality of PGPR in agriculture is steadily increased as it offers an attractive way to replace the use of chemical fertilizers, pesticides and other supplements. Growth promoting substances are likely to be produced in large quantities by these rhizosphere microorganisms that influence indirectly on the overall morphology of the plants. Recent progress in our understanding on the diversity of PGPR in the rhizosphere along with their colonization ability and mechanism of action should facilitate their application as a reliable component in the management of sustainable agricultural system. The progress to date in using the rhizosphere bacteria in a variety of applications related to agricultural improvement along with their mechanism of action with special reference to plant growth-promoting traits are summarized and discussed in this review.

1,941 citations

Journal ArticleDOI
TL;DR: In some soils described as microbiologi­ cally suppressive to pathogens, microbial antagonism of the pathogen is especially great, leading to substantial disease control, and those identified are excellent examples of the full potential of biological control of soilborne pathogens.
Abstract: Biological control of soilborne pathogens by introduced microorganisms has been studied for over 65 years (9, 49), but during most of that time it has not been considered commercially feasible. Since about 1 965, however, interest and research in this area have increased steadily (9), as reflected by the number of books (10, 47,49, 152) and reviews about it (11,26,30, 106, 143, 153, 173, 174, 183) that have appeared . Concurrently, there has been a shift to the opinion that biological control can have an important role in agriculture in the future, and it is encouraging that several companies now have programs to develop biocontrol agents as commercial products. This renewed interest in biocontrol is in part a response to public concern about hazards associated with chemical pesticides. Microorganisms that can grow in the rhizosphere are ideal for use as biocontrol agents, since the rhizosphere provides the front-line defense for roots against attack by pathogens. Pathogens encounter antagonism from rhizosphere microorganisms before and during primary infection and also during secondary spread on the root. In some soils described as microbiologi­ cally suppressive to pathogens (172), microbial antagonism of the pathogen is especially great, leading to substantial disease control. Although pathogen­ suppressive soils are rare, those identified are excellent examples of the full potential of biological control of soilborne pathogens.

1,775 citations