Abstract:Fluorescent pseudomonads are ubiquitous bacteria that are common inhabitants of the rhizosphere and are the most studied group within the genus Pseudomonas. Strain UTPF61 is a biocontrol agent against Sclerotinia wilt of sunflower, an important disease of sunflower caused by Sclerotinia sclerotiorum. This bacterium was selected out of 47 strains. It was grown in eight culture media containing different carbon sources, such as sucrose, glucose, corn steep liquor, fructose, glycerol, sugar beet molasses, manitol… Show more
“…In practice, dried spores of this antagonist are sprayed either onto pathogen-infested crop debris at the end of a season or onto the soil sur face before planting, and the disease control is economical. Use of micronutrient zinc solely or in combination with molybdenum improves the biocontrol activity of P. fluorescens strain UPPF 61 (Ashofteh et al 2009, Heidari-Tajabadi et al 2011. Another biocontrol agent (Agate-25K) based on Pseudomonas chlororaphis is reported to be effective in the control of Sclerotinia disease of sun flower in Russia (Vinokurova 2000).…”
AgriculturalSciences. He has more than 22 years of research experience in oilseed crop disease management and has significantly contributed in the areas of understanding the host-pathogen interactions, epi demiology, and integrated disease management in sunflower, safflower, sesame, peanut, and rape seed-mustard crops. He has published more than 70 peer-reviewed research papers and 4 books. Dr. Chattopadhyay has to his credit several academic awards and one patent. His significant research achievements include the development of Fusarium wilt-resistant genotypes in safflower, the iden tification of genotypes of Brassica juncea resistant to a mixture of isolates of Albugo candida, the development of a biocontrol agent formulation to reduce the use of fungicides in the management of major diseases of oilseeds (Brassica), and seed treatment (and foliar application) of aqueous bulb extract of Allium sativum for the management of major foliar diseases (Alternaria blight, white rust, powdery mildew, and Sclerotinia stem rot) of mustard. S.J. Kolte, professor of plant pathology (Retd.
“…In practice, dried spores of this antagonist are sprayed either onto pathogen-infested crop debris at the end of a season or onto the soil sur face before planting, and the disease control is economical. Use of micronutrient zinc solely or in combination with molybdenum improves the biocontrol activity of P. fluorescens strain UPPF 61 (Ashofteh et al 2009, Heidari-Tajabadi et al 2011. Another biocontrol agent (Agate-25K) based on Pseudomonas chlororaphis is reported to be effective in the control of Sclerotinia disease of sun flower in Russia (Vinokurova 2000).…”
AgriculturalSciences. He has more than 22 years of research experience in oilseed crop disease management and has significantly contributed in the areas of understanding the host-pathogen interactions, epi demiology, and integrated disease management in sunflower, safflower, sesame, peanut, and rape seed-mustard crops. He has published more than 70 peer-reviewed research papers and 4 books. Dr. Chattopadhyay has to his credit several academic awards and one patent. His significant research achievements include the development of Fusarium wilt-resistant genotypes in safflower, the iden tification of genotypes of Brassica juncea resistant to a mixture of isolates of Albugo candida, the development of a biocontrol agent formulation to reduce the use of fungicides in the management of major diseases of oilseeds (Brassica), and seed treatment (and foliar application) of aqueous bulb extract of Allium sativum for the management of major foliar diseases (Alternaria blight, white rust, powdery mildew, and Sclerotinia stem rot) of mustard. S.J. Kolte, professor of plant pathology (Retd.
“…However, no pyoluteorin was produced in vitro by either of the strains in the growth conditions used. Pyoluteorin inactivity in our experiments was potentially due to the use of a rich growth medium (Heidari‐Tajabadi et al, 2011; Jamali et al, 2009; T. Yang et al, 2018). Pyoluteorin is a chlorinated polyketide antibiotic and its production is regulated by the DAPG precursor, monoacetylphloroglucinol (Kidarsa et al, 2011).…”
Section: Discussionmentioning
confidence: 93%
“…Pyoluteorin inactivity in our experiments was potentially due to the use of a rich growth medium (Heidari-Tajabadi et al, 2011;Jamali et al, 2009;T. Yang et al, 2018).…”
Although plant pathogens are traditionally controlled using synthetic agrochemicals, the availability of commercial bactericides is still limited. One potential control strategy could be the use of plant growth‐promoting bacteria (PGPB) to suppress pathogens via resource competition or the production of antimicrobial compounds. This study aimed to conduct in vitro and in vivo screening of eight Pseudomonas strains against Ralstonia solanacearum (the causative agent of bacterial wilt) and to investigate underlying mechanisms of potential pathogen suppression. We found that inhibitory effects were Pseudomonas strain‐specific, with strain CHA0 showing the highest pathogen suppression. Genomic screening identified 2,4‐diacetylphloroglucinol, pyoluteorin, and orfamides A and B secondary metabolite clusters in the genomes of the most inhibitory strains, which were investigated further. Although all these compounds suppressed R. solanacearum growth, only orfamide A was produced in the growth media based on mass spectrometry. Moreover, orfamide variants extracted from Pseudomonas cultures showed high pathogen suppression. Using the “Micro‐Tom” tomato cultivar, it was found that CHA0 could reduce bacterial wilt disease incidence with one of the two tested pathogen strains. Together, these findings suggest that a better understanding of Pseudomonas–Ralstonia interactions in the rhizosphere is required to successfully translate in vitro findings into agricultural applications.
“…These results are consistent with prior evidence that growth medium can influence bBCA antibiotic activity, with Pseudomonas fluorescens strains AS15 and UTPF61 exhibiting distinct patterns of growth, metabolite secretion, and inhibitory activity against Rhizoctonia solani and Sclerotinia sclerotiorum , respectively, when grown in different types of media. 25 , 28 Figure 2. The inhibitory effect of different F. defendens filtrates on S. melliferum growth in culture at two time points.…”
Frateuria defendens
is a candidate biocontrol agent that has been shown to reduce phytoplasma-related disease symptoms in grapevines and periwinkle plants. While a crude filtrate prepared from
F. defendens
can inhibit mollicute growth, the specific growth parameters for this bacterium, necessary to enhance this protective inhibitory response, remain unknown. Moreover, the separation of filtrate preparations from bacterial cells via centrifugation and filtration is laborious and time-consuming. As such, the present study was conducted to define the optimal growth conditions associated with maximal inhibitory activity of
F. defendens
and to establish a better approach to separating these bacterial cells from their secreted metabolites. To conduct these analyses,
F. defendens
was cultured in a range of media types, while associated inhibitory effects were tested
in vitro
using
Spiroplasma melliferum
as a model mollicute bacterium, and
in planta
using phytoplasma-infected periwinkle plantlets. These analyses revealed
F. defendens
growth patterns change based upon media composition, with filtrates prepared from a specific rich medium (S-medium) exhibiting beneficial activities, including the inhibition of
S. melliferum
and enhanced plant growth. When
F. defendens
cells were grown within semi-permeable, membrane-coated Small Bioreactor Platform (SBP) capsules, they could be more readily separated from the secreted metabolite fraction, obviating the need for filtration and/or centrifugation. This study is the first to have reported the use of SBP capsules to separate bacterial cells from their secreted metabolites under sterile conditions while retaining the ability of these metabolites to inhibit
S. melliferum
growth and to benefit the host plant. The results highlight promising new approaches to the effective biocontrol of phytoplasma-driven diseases in grapevines and other economically important plant species.
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