Relationship between in vitro growth inhibition of pathogens and suppression of preemergence damping-off and postemergence root rot of white bean seedlings in the greenhouse by bacteria

1994 ◽  
Vol 40 (2) ◽  
pp. 113-119 ◽  
Author(s):  
M. S. Reddy ◽  
R. K. Hynes ◽  
G. Lazarovits
Keyword(s):  
Rhizoctonia Solani ◽  
Disease Severity ◽  
Fusarium Solani ◽  
Root Rot ◽  
Culture Media ◽  
Pythium Ultimum ◽  
Damping Off ◽  
Bacterial Strains ◽  
White Bean

One hundred and twenty diverse bacterial strains were screened under greenhouse conditions for their ability to protect white bean seedlings from preemergence damping-off caused by Pythium ultimum and Rhizoctonia solani and postemergence root rot by Fusarium solani f.sp. phaseoli. Preemergence mortality or root rot increased with an increase in the inoculum concentration of fungal isolates. For further testing, 200 propagules/g soil of P. ultimum, 3 propagules/g soil of R. solani, and log 3 conidia/g vermiculite of F. solani f.sp. phaseoli were used, as these rates provided an optimal level (approximately 50%) of disease severity. Bacterial strains suspended in sterile distilled water were added to pathogen-amended soil or vermiculite at log 7 colony-forming units/g soil or vermiculite prior to seeding. Final healthy stand and root rot were recorded 4 weeks after planting. Nine bacterial strains on P. ultimum, five on R. solani, and nine on F. solani f.sp. phaseoli provided significant (P = 0.05) suppression of disease severity compared with the nonbacterized control. Bacterial strains were also tested in vitro against the mycelial growth of the fungi on solid and liquid media. There was no relationship between the ability of bacterial strains to inhibit fungal vegetative growth on solid culture media and their ability to suppress pathogen activity in the greenhouse, but, for a few strains, the reduction in disease was linked to reduced growth of the pathogens in liquid media.Key words: White bean, damping-off, root rot, Pythium ultimum, Rhizoctonia solani, Fusarium solani f.sp. phaseoli.

scholarly journals Testing Methods Affecting the Antagonistic Ability of  Pseudomonas Biocontrol Strains

2002 ◽  
Vol 51 (1-2) ◽  
pp. 107-114 ◽  
Author(s):  
I. Jevcsák ◽  
Bálint Oldal ◽  
L. Ködöböcz ◽  
Keyword(s):  
Rhizoctonia Solani ◽  
Fusarium Solani ◽  
Fungal Pathogens ◽  
Culture Media ◽  
Colony Growth ◽  
Antagonistic Effect ◽  
Bacterial Strains ◽  
Testing Methods ◽  
Selection Of

The antagonistic effect of thirteen Pseudomonas aeruginosa and thirteen strains of other Pseudomonas species was studied on the soil-borne phytopathogenic Rhizoctonia solani and Fusarium solani fungi.  The inhibition of pathogen colony growth was tested with two different in vitro techniques using the same type of culture media. In case of the spread slant technique the antagonists induced a significantly stronger inhibition on the growth of pathogens than in case of spot transfer. Among the 26 investigated Pseudomonas strains, P. aeruginosa strains were generally more effective against the fungal pathogens. Rhizoctonia solani proved to be affected to a greater extent by the bacterial strains studied than the Fusarium solani representative. The possibility of in vitro strain selection of biocontrol microbes is being further discussed .

scholarly journals Sensitivity of Rhizoctonia solani AG-2-2 from Sugar Beet to Fungicides

Plant Disease ◽  
2016 ◽  
Vol 100 (12) ◽  
pp. 2427-2433 ◽  
Author(s):  
Sahar Arabiat ◽  
Mohamed F. R. Khan
Keyword(s):  
Sugar Beet ◽  
Rhizoctonia Solani ◽  
Root Rot ◽  
The United States ◽  
Damping Off ◽  
Growth Assay ◽  
The Mean ◽  
Crown And Root Rot ◽  
Mean Concentration

Rhizoctonia damping-off and crown and root rot caused by Rhizoctonia solani are major diseases of sugar beet (Beta vulgaris L.) worldwide, and growers in the United States rely on fungicides for disease management. Sensitivity of R. solani to fungicides was evaluated in vitro using a mycelial radial growth assay and by evaluating disease severity on R. solani AG 2-2 inoculated plants treated with fungicides in the greenhouse. The mean concentration that caused 50% mycelial growth inhibition (EC50) values for baseline isolates (collected before the fungicides were registered for sugar beet) were 49.7, 97.1, 0.3, 0.2, and 0.9 μg ml−1 and for nonbaseline isolates (collected after registration and use of fungicides) were 296.1, 341.7, 0.9, 0.2, and 0.6 μg ml−1 for azoxystrobin, trifloxystrobin, pyraclostrobin, penthiopyrad, and prothioconazole, respectively. The mean EC50 values of azoxystrobin, trifloxystrobin, and pyraclostrobin significantly increased in the nonbaseline isolates compared with baseline isolates, with a resistant factor of 6.0, 3.5, and 3.0, respectively. Frequency of isolates with EC50 values >10 μg ml−1 for azoxystrobin and trifloxystrobin increased from 25% in baseline isolates to 80% in nonbaseline isolates. Although sensitivity of nonbaseline isolates of R. solani to quinone outside inhibitors decreased, these fungicides at labeled rates were still effective at controlling the pathogen under greenhouse conditions.

Variations in Pathogenicity of Three Different Forms of Rhizoctonia Inoculum and Assessment of Cultivar Resistance of Sugar Beet

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Haque ME ◽  
◽  
Parvin MS ◽  
Keyword(s):  
Seed Germination ◽  
Sugar Beet ◽  
Root Rot ◽  
Large Scale ◽  
Culture Media ◽  
Damping Off ◽  
Require Time ◽  
Time Space ◽  
The Usa

Rhizoctonia solani causes pre-emergence and post-emergence damping-off, as well as crown and root rot of sugar beet (Beta vulgaris L.), which significantly affects the yield returns in the USA and Europe. The pathogen overwinters as sclerotia or melanized mycelium. Traditionally, the resistance of cultivars to R. solani is evaluated by scoring disease reactions at the crowns and roots of older seedlings, thus resistance is not evaluated during seed germination. Moreover, earlier studies evaluated cultivars resistance to R. solani using colonized whole barley or wheat grains which, unlike sclerotia, are artificial inocula of the pathogen that require time, space and technical know-how to produce. Moreover, colonized grains are prone to contamination with other pathogens, consumed by rodents/birds while applied in the field, and are often uneconomic. Considering those limitations, a study was undertaken (1) to develop in vitro methods to generate large-scale sclerotia, (2) to compare pathogenic potentials of sclerotia, mycelia, and colonized barley grains for optimization of dampingoff assays, and (3) to evaluate Rhizoctonia resistance of selected commercial cultivars during the seed germination phase. Comparing six different culture media, we found that R. solani had the highest radial growth (8.9 ± 0.04, cm³) at 8-days and the maximum number of sclerotia produced (203 ± 4.6) at 28-days in CV8 medium. We demonstrated significant differences in pathogenicity of the three different forms of R. solani inocula and susceptibility of cultivars to preand post-emergence damping-off. The highest pre-emergence damping-off and root rot were observed with sclerotia, and the highest post-emergence dampingoff was recorded with both sclerotial and colonized barley inocula. In addition, varietal differences in susceptibility to pre- and post-emergence damping-off were noted. The highest pre-emergence damping-off was recorded on cv Crystal 101RR and lowest in Maribo MA 504. The highest post-emergence damping-off was recorded on BTS 8500 and the lowest in Crystal 467. The maximum mean root rot was observed in BTS 8500, BTS 8606, and Crystal 101R. Our studies demonstrated that sclerotia serve as efficient natural inocula, reemphasized that host-pathogen interactions differ at the early vs. late stages of sugar beet growth, and highlighted the need to reevaluate commercial sugar beet cultivars for resistance at the seed germination stage.

Root-rot resistance in common bean

1993 ◽  
Vol 73 (1) ◽  
pp. 365-367 ◽  
Author(s):  
J. C. Tu ◽  
S. J. Park
Keyword(s):  
Phaseolus Vulgaris ◽  
Rhizoctonia Solani ◽  
Common Bean ◽  
Fusarium Oxysporum ◽  
Key Words ◽  
Fusarium Solani ◽  
Root Rot ◽  
Pythium Ultimum ◽  
Growth Room

A bean (Phaseolus vulgaris) line, A - 300, resistant to Rhizoctonia solani and Fusarium oxysporum was introduced into Ontario from Colombia. The results of tests conducted in a root-rot nursery, in a greenhouse and in a growth room showed that this bean line is resistant to Fusarium solani f. sp. phaseoli and Pythium ultimum. Key words: Bean, Phaseolus vulgaris, root rot resistance

Influence of Glyphosate on Rhizoctonia Crown and Root Rot (Rhizoctonia solani) in Glyphosate-Resistant Sugarbeet

Weed Science ◽  
2012 ◽  
Vol 60 (1) ◽  
pp. 113-120 ◽  
Author(s):  
Kelly A. Barnett ◽  
Christy L. Sprague ◽  
William W. Kirk ◽  
Linda E. Hanson
Keyword(s):  
Rhizoctonia Solani ◽  
Ammonium Sulfate ◽  
Disease Severity ◽  
Root Rot ◽  
Radial Growth ◽  
Field Experiments ◽  
Herbicide Treatments ◽  
Tolerant Variety ◽  
Crown And Root Rot

Previous greenhouse studies with a noncommercial glyphosate-resistant sugarbeet variety indicated that susceptibility to Rhizoctonia crown and root rot could increase after glyphosate was applied. Greenhouse and field experiments were conducted in 2008 and 2009 to determine if glyphosate influenced disease severity in potential commercially available varieties of glyphosate-resistant sugarbeet. In the first greenhouse experiment in 2008, Hilleshög 9027RR, the most tolerant variety to Rhizoctonia crown and root rot, exhibited an increase in disease severity when glyphosate was applied. There were no significant differences between herbicide treatments in Hilleshög 9028RR, and glyphosate decreased disease severity in Hilleshög 9032RR when compared with the no-herbicide treatment. Experiments conducted to determine if glyphosate influenced Rhizoctonia solani growth in vitro indicated that glyphosate did not increase the radial growth of R. solani, except at 10× (190 µg ae ml−1) the normal rate of glyphosate plus ammonium sulfate (AMS). Field and additional greenhouse experiments were conducted using four commercial varieties. Differences in disease severity were observed when comparing varieties, but glyphosate did not significantly influence the severity of Rhizoctonia crown and root rot when compared with the no-herbicide control. Choosing a glyphosate-resistant sugarbeet variety with the best demonstrated tolerance to Rhizoctonia crown and root rot is an important factor in reducing disease severity and maintaining sugarbeet yield.

scholarly journals Rapid Screening of Rhizobacteria for Suppression of Rhizoctonia Damping-off

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 468B-468
Author(s):  
J.O Becker ◽  
U.K. Schuch
Keyword(s):  
Rhizoctonia Solani ◽  
Raphanus Sativus ◽  
Soil Samples ◽  
Rapid Screening ◽  
Agricultural Crops ◽  
Screening System ◽  
Damping Off ◽  
Bacterial Strains ◽  
Second Tier

A rapid screening system was developed to identify plant-beneficial rhizobacteria useful in protecting nursery seedlings against damping-off caused by Rhizoctonia solani. Ornamental and agricultural crops were planted into 100 soil samples that were collected from various fields throughout California. More than 7000 bacterial strains from the rhizosphere of these crops were isolated and tested in vitro for antibiosis against R. solani AG4. In a second tier, 600 active strains were tested in planting trays seeded with radish (Raphanus sativus `Cherry Belle'). Each planting cell filled with commercial potting mix contained millet-grown R. solani inoculum in the center and eight radish seeds at the periphery. Bacteria were cultured for 24 hr at 25°C in 10% tryptic soy broth and were applied as a drench at 1 × 107 cfu/cc to each cell. Trays were incubated in a growth chamber at 21°C and a 10-hr photoperiod. Post-emergence damping-off occurred within 8 to 9 days after planting, and no further losses were observed after 14 days. Approximately 0.5% of the original 7000 bacterial strains tested reduced damping-off significantly. Fifteen bacterial strains controlled Rhizoctonia damping-off by 30% to 60% compared to the non-treated control.

scholarly journals Antifungal Activity of Selected IndigenousPseudomonasandBacillusfrom the Soybean Rhizosphere

2009 ◽  
Vol 2009 ◽  
pp. 1-9 ◽  
Author(s):  
M. León ◽  
P. M. Yaryura ◽  
M. S. Montecchia ◽  
A. I. Hernández ◽  
O. S. Correa ◽  
...  
Keyword(s):  
Antifungal Activity ◽  
Seedling Emergence ◽  
Pythium Ultimum ◽  
Phytopathogenic Fungi ◽  
Soybean Seeds ◽  
Damping Off ◽  
Bacterial Strains ◽  
Protected Plants ◽  
Soybean Plants

The purpose of this study was to isolate and select indigenous soilPseudomonasandBacillusbacteria capable of developing multiple mechanisms of action related to the biocontrol of phytopathogenic fungi affecting soybean crops. The screening procedure consisted of antagonism tests against a panel of phytopathogenic fungi, taxonomic identification, detection by PCR of several genes related to antifungal activity, in vitro detection of the antifungal products, and root colonization assays. Two isolates, identified and designated asPseudomonas fluorescensBNM296 andBacillus amyloliquefaciensBNM340, were selected for further studies. These isolates protected plants against the damping-off caused byPythium ultimumand were able to increase the seedling emergence rate after inoculation of soybean seeds with each bacterium. Also, the shoot nitrogen content was higher in plants when seeds were inoculated with BNM296. The polyphasic approach of this work allowed us to select two indigenous bacterial strains that promoted the early development of soybean plants.

scholarly journals Response of Cover Crops to Phytopythium vexans, Phytophthora nicotianae, and Rhizoctonia solani, Major Soilborne Pathogens of Woody Ornamentals

Agriculture ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 742
Author(s):  
Milan Panth ◽  
Anthony Witcher ◽  
Fulya Baysal-Gurel
Keyword(s):  
Rhizoctonia Solani ◽  
Disease Severity ◽  
Cover Crops ◽  
Production System ◽  
Root Rot ◽  
Phytophthora Nicotianae ◽  
Soilborne Pathogens ◽  
Damping Off ◽  
Root Rot Disease ◽  
Rot Disease

Management of plant diseases is a subject of concern for researchers as well as growers. Different management practices are being developed and used to combat the rising number of plant pathogens, which threaten nursery crop production. Use of cover crops for sustainable management of soilborne diseases is being explored as an alternative strategy to the chemicals. However, the potential threat of these cover crops acting as a secondary host of these devastating soilborne pathogens has not been described. We studied the response of the major cover crops being used by woody ornamental growers in the Southeastern United States to Phytopythium vexans, Phytophthora nicotianae, and Rhizoctonia solani in greenhouse conditions to identify the effective cover crops that can be used in a nursery field production system. Data related to post-emergence damping-off and plant growth parameters (plant height increase and fresh weight) were recorded. Similarly, cover crop roots were assessed for root rot disease severity using a scale of 0–100% roots affected. Among the tested cover crops, the grass cover crops triticale (×Triticosecale Wittm. ex A. Camus.), annual ryegrass (Lolium multiflorum L.), Japanese millet (Echinochloa esculenta (A. Braun) H. Scholz), and the legumes Austrian winter pea (Pisum sativum var. arvense (L.) Poir) and cowpea ‘Iron and Clay’ (Vigna unguiculata (L.) Walp.), showed lower root rot disease severity and post-emergence damping-off in the soil inoculated with P. nicotianae, R. solani, or P. vexans compared to the other crops. Since these cover crops can act as non-host crops and benefit the main crop in one way or another, they can be used in the production system. Further research is recommended to evaluate their performance in a natural field setting.

Isolation, characterization, and formulation of antagonistic bacteria for the management of seedlings damping-off and root rot disease of cucumber

2014 ◽  
Vol 60 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Salah Eddin Khabbaz ◽  
Pervaiz A. Abbasi
Keyword(s):  
Plant Growth ◽  
Root Rot ◽  
Storage Period ◽  
Pythium Ultimum ◽  
In Vitro Tests ◽  
Antagonistic Bacteria ◽  
Damping Off ◽  
Biochemical Tests ◽  
Cucumber Seedlings

Antagonistic bacteria are common soil inhabitants with potential to be developed into biofungicides for the management of seedling damping-off, root rot, and other soil-borne diseases of various crops. In this study, antagonistic bacteria were isolated from a commercial potato field and screened for their growth inhibition of fungal and oomycete pathogens in laboratory tests. The biocontrol potential of the 3 most effective antagonistic bacteria from the in vitro tests was evaluated against seedling damping-off and root rot of cucumber caused by Pythium ultimum. Based on phenotypic characteristics, biochemical tests, and sequence analysis of 16S–23S rDNA gene, the 3 antagonistic bacteria were identified as Pseudomonas fluorescens (isolate 9A-14), Pseudomonas sp. (isolate 8D-45), and Bacillus subtilis (isolate 8B-1). All 3 bacteria promoted plant growth and suppressed Pythium damping-off and root rot of cucumber seedlings in growth-room assays. Both pre- and post-planting application of these bacteria to an infested peat mix significantly increased plant fresh masses by 113%–184% and percentage of healthy seedlings by 100%–290%, and decreased damping-off and root rot severity by 27%–50%. The peat and talc formulations of these antagonistic bacteria applied as seed or amendment treatments to the infested peat mix effectively controlled Pythium damping-off and root rot of cucumber seedlings and enhanced plant growth. The survival of all 3 antagonistic bacteria in peat and talc formulations decreased over time at room temperature, but the populations remained above 108CFU/g during the 180-day storage period. The peat formulation of a mixture of 3 bacteria was the best seed treatment, significantly increasing the plant fresh masses by 245% as compared with the Pythium control, and by 61.4% as compared with the noninfested control. This study suggests that the indigenous bacteria from agricultural soils can be developed and formulated as biofungicides for minimizing the early crop losses caused by seedling damping-off and root rot diseases.

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