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

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.

Author(s):  
V.Zh. Nguyen ◽  
◽  
T.O. Dao ◽  
E. A. Kalashnikova ◽  
Th.H. Nguyen

The purpose of this work is to isolate bacteria from the pepper rhizosphere that inhibit Rhizoctoniasolani and evaluate in vitro their phosphate solubilizing activity and production of siderophore. Of the different soil samples taken from the pepper fields of An Thanh, An Ninh, Quynh My, QuynhPhudistrict, ThaiBinh province, 48 bacterial strains were isolated. Of these, 5 strains (AT16, VK 4.7, VK 4.8, VK 4.12, VK 4.13) expressed as higher inhibitory Rhizoctonia solani activity were selected. Their inhibitory activity is from 11.11% to 62.22%.


1994 ◽  
Vol 40 (2) ◽  
pp. 113-119 ◽  
Author(s):  
M. S. Reddy ◽  
R. K. Hynes ◽  
G. Lazarovits

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.


Plant Disease ◽  
2016 ◽  
Vol 100 (12) ◽  
pp. 2427-2433 ◽  
Author(s):  
Sahar Arabiat ◽  
Mohamed F. R. Khan

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.


2021 ◽  
Author(s):  
Suman Sangwan ◽  
Rajvir Singh ◽  
SUSHEEL GULATI ◽  
Suprita Rana

Abstract A green efficient and facile synthesis of pyrazoles is reported via condensation reaction between substituted aldehydes (1a-1i), malononitrile (2) and 2,4-dinitrophenyl hydrazine (3) in presence of acylated Guar-gum as biocatalyst under solvent-free conditions. The progress of reaction was checked by thin layer chromatography and melting points reported are uncorrected. All synthesized compounds (4a-4i) were characterized by using 1HNMR and FTIR spectral techniques and evaluated for in vitro herbicidal activity against Raphanus sativus L. (Radish seeds). All compounds (4a-4i) were also evaluated for their antifungal activity against Rhizoctonia solani and Aspergillus niger by poisoned food techniques method. Antioxidant activity of synthesized compound was also determined. From activity results, it was found that compound 4f was most active against both Raphanus sativus L. (root) and Raphanus sativus L. (shoot) respectively. Compounds 4e and 4h were found most active against Rhizoctonia solani and Aspergillus niger fungus respectively at highest concentration. Compound 4e has shown maximum percentage DPPH free radical scavenging activity 1.e. 61.47% at 100 µg/mL concentration. Less reaction time, excellent yield of products, mild reaction conditions and simple work-up are some merits of present methodology.


2002 ◽  
Vol 51 (1-2) ◽  
pp. 107-114 ◽  
Author(s):  
I. Jevcsák ◽  
Bálint Oldal ◽  
L. Ködöböcz ◽  

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 .


Author(s):  
V.Z. Nguyen ◽  
T.O. Dao ◽  
T.H. Nguyen ◽  
E.A. Kalashnikova

Перец овощной (Capsicum annuum L.) является одной из основных возделываемых культур Вьетнама в связи с широким его использованием в пищевой промышленности в качестве приправы. Это делает данное растение важной сельскохозяйственной культурой, которая приносит значительный доход вьетнамским фермерам. Однако на плантациях перца часто наблюдается появление и развитие болезни ризоктониоз, которую вызывает патогенный гриб Rhizoctonia solani, а также наблюдается бактериальное увядание, вызываемое бактерией Ralstonia solanacearum. Поражение ризоктониозом, одной из самых вредных болезней перца, может наблюдаться в любой фазе развития растений. Известно, что ризобактерии способны не только стимулировать рост растений, но и подавлять развитие болезней. Цель данной работы выделение из ризосферы растений перцев бактерий, ингибирующих развитие Rhizoctonia solani и оценка in vitro их фосфатрастворяющей активности и секреции сидерофора. Из различных почвенных образцов, отобранных с полей коммун Ан Хань, Ан Нинь, Кунь Ми, района Кунь Фу, провинции Тхай Бинь, выделено 48 штаммов бактерий, из которых были отобраны 5 штаммов (АТ 16 VK 4.7 VK 4.8 VK 4.12 VK 4.13), обладающих высокой ингибирующей активностью по отношению к Rhizoctonia solani, которая составила 11,11 62,22. Показано, что эти штаммы обладают способностью синтезировать такой фитогормон, как индолилуксусную кислоту (ИУК) (с 9,54 мг/мл до 31,06 мг/мл), растворять труднорастворимые фосфатные соединения и секрецировать сидерофор. Из 5 выделенных штаммов только у штамма АТ 16 данные способности выражены более сильно. Полученные результаты свидетельствуют о том, что изученные штаммы обладают хорошим потенциалом для использования их в качестве биологических агентов, контролирующих развитие R. solani на растениях перца.Peppers or chilli (Capsicum annuum L.) is widely grown in Vietnam because they bring considerable income to farmers. On pepper fields, diseases such as rhizoctonia, Rhizoctoniasolani caused by fungus, bacterial wilt by Ralstoniasolanacearum are often observed. Rhizoctoniasolani causes a wide range of significant diseases such as collar rot, root rot, damping offin horticultural and field crops.The diseases caused by rhizoctonia are one of the most harmful diseases on peppers, can be observed in any phase of plant development. Rhizobacteria that stimulate plant growth can be used to improve plant growth and suppress plant diseases. The purpose of this work is to isolate bacteria from the pepper rhizosphere that inhibit Rhizoctoniasolani and evaluate in vitro their phosphate solubilizing activity and production of siderophore. Of the different soil samples taken from the pepper fields of An Thanh, An Ninh, Quynh My, QuynhPhudistrict, ThaiBinh province, 48 bacterial strains were isolated. Of these, 5 strains (AT16, VK 4.7, VK 4.8, VK 4.12, VK 4.13) expressed as higher inhibitory Rhizoctoniasolani activity were selected. Their inhibitory activity is from 11.11 to 62.22. These strains have the ability to synthesize phytohormone IAA (from 9.54 g / ml to 31.06g / ml), solubilize the phosphate compounds and productsiderophore. Strain AT16 more effective expresses these abilities in comparison with 4 other strains. These results suggest that the selected strains have excellent potential for use as biologically controlled agents of R. solani on pepper plants (Capsicum annuum L.).


1969 ◽  
Vol 47 (11) ◽  
pp. 1663-1669 ◽  
Author(s):  
D. S. Hayman

Evidence is presented suggesting that increased seed exudation is a major factor contributing to increased preemergence damping-off of cotton seedlings by Rhizoctonia solani at low temperatures.About seven and three times as much total amino acids and sugars were exuded at 18 and 24 °C, respectively, as at 30 °C, by germinating cotton seeds of equivalent physiological age. Sixteen amino acids and five sugars were exuded. Seed exudation is not related to rate of germination or to respiration.Accumulation of seed exudate at low temperatures was related to increased pathogenesis in vitro and in soil. This appeared to be because R. solani competitively used this exudate to increase its inoculum potential near the germinating seed, thereby becoming more virulent on the susceptible juvenile tissues of the seedling.


2015 ◽  
Vol 105 (10) ◽  
pp. 1334-1346 ◽  
Author(s):  
Tanya R. Copley ◽  
Konstantinos A. Aliferis ◽  
Suha Jabaji

Many studies have investigated the effect of biochar on plant yield, nutrient uptake, and soil microbial populations; however, little work has been done on its effect on soilborne plant diseases. To determine the effect of maple bark biochar on Rhizoctonia damping-off, 11 plant species were grown in a soilless potting substrate amended with different concentrations of biochar and inoculated or not with Rhizoctonia solani anastomosis group 4. Additionally, the effect of biochar amendment on R. solani growth and metabolism in vitro was evaluated. Increasing concentrations of maple bark biochar increased Rhizoctonia damping-off of all 11 plant species. Using multivariate analyses, we observed positive correlations between biochar amendments, disease severity and incidence, abundance of culturable bacterial communities, and physicochemical parameters. Additionally, biochar amendment significantly increased R. solani growth and hyphal extension in vitro, and altered its primary metabolism, notably the mannitol and tricarboxylic acid cycles and the glycolysis pathway. One or several organic compounds present in the biochar, as identified by gas chromatography-mass spectrometry analysis, may be metabolized by R. solani. Taken together, these results indicate that future studies on biochar should focus on the effect of its use as an amendment on soilborne plant pathogens before applying it to soils.


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