scholarly journals Suppression of Fusarium moniliforme in Rice by Rice-Associated Antagonistic Bacteria

Plant Disease ◽  
1997 ◽  
Vol 81 (1) ◽  
pp. 49-52 ◽  
Author(s):  
A. M. Rosales ◽  
T. W. Mew
Keyword(s):  
Seed Germination ◽  
Fusarium Moniliforme ◽  
Mycelial Growth ◽  
Field Trials ◽  
The Philippines ◽  
The Other ◽  
Antagonistic Bacteria ◽  
Seedling Vigor ◽  
Bacterial Strains

The potential of antagonistic bacteria from paddy water, rhizosphere soils, sclerotia, and rice plants to control “bakanae” caused by Fusarium moniliforme was assessed. Experiments were conducted to determine the in vitro antibiosis and effect of bacteria on seed germination. Out of 441 isolates, 113 were inhibitory to mycelial growth of the pathogen. Bacterial strains were classified into three groups based on effect on seed germination: (i) those that promoted germination and enhanced seedling vigor; (ii) those that had no effect on germination; and (iii) those that were deleterious and inhibited germination. Bacterization of naturally infected seeds reduced bakanae incidence in seedbox and seedbed tests. In a seedbed experiment with IR 58 seeds soaked in suspensions of bacterial strains, bakanae incidence and disease control ranged from 0.9 to 6.8% and 71.7 to 96.3%, respectively. From the 3 years of field trials, 10 strains reduced bakanae. Five strains consistently reduced bakanae, but the other five exhibited variable effects among trials. Specificity of suppression by antagonistic bacteria against different pathogenic isolates of F. moniliforme from various locations in the Philippines was observed.

scholarly journals Fungicide Seed Treatment Effects on Seedling Damping-off of Pumpkin Caused by Phytophthora capsici

Plant Disease ◽  
2003 ◽  
Vol 87 (1) ◽  
pp. 63-68 ◽  
Author(s):  
M. Babadoost ◽  
S. Z. Islam
Keyword(s):  
Seed Germination ◽  
Untreated Control ◽  
Mycelial Growth ◽  
Seed Treatment ◽  
Culture Medium ◽  
Phytophthora Capsici ◽  
Field Trials ◽  
Seedling Vigor ◽  
Damping Off

Apron XL LS (mefenoxam) and Allegiance FL (metalaxyl) were highly inhibitory to growth of mycelium of Phytophthora capsici in vitro. Effective dose (ED50) of mefenoxam and metalaxyl for 50% inhibition of mycelial growth, for all five isolates of P. capsici tested, was 0.98 and 0.99 μg a.i./ml of culture medium, respectively. For mefenoxam at 200 μg a.i./ml, sporangium and zoospore germination were reduced by 92 and 96%, respectively, and 21 and 24%, respectively, for metalaxyl. In greenhouse studies, seed treatment with mefenoxam (0.42 ml of Apron XL LS/kg of seed) and metalaxyl (0.98 ml of Allegiance FL/kg of seed) significantly reduced pre- and post-emergence damping-off of seedlings caused by P. capsici in three pumpkin cultivars (Dickinson, Hybrid-401, and Hybrid-698) tested. Thirty-one days after seeding, at inoculum levels of 0, 90, 600, 1,400, and 4,000 CFU/g of soil, the average seedling stands for mefenoxam treatment were 98.4, 93.8, 88.3, 77.8, and 64.8%; for metalaxyl, 99.1, 85.3, 85.8, 73.5, and 59.3; and for the untreated control, 97.5, 55.2, 45.7, 37.0, and 22.9%, respectively. In field trials, the average seedling stands 35 days after seeding were 76.7, 74.7, and 44.9% for mefenoxam, metalaxyl, and untreated control, respectively. Seed treatment with mefenoxam or metalaxyl did not have any significant effect on either seed germination or seedling vigor.

scholarly journals Improving the Biocontrol Potential of Bacterial Antagonists with Salicylic Acid against Brown Rot Disease and Impact on Nectarine Fruits Quality

Agronomy ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 209
Author(s):  
Nadia Lyousfi ◽  
Rachid Lahlali ◽  
Chaimaa Letrib ◽  
Zineb Belabess ◽  
Rachida Ouaabou ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Disease Severity ◽  
Mycelial Growth ◽  
Brown Rot ◽  
Antagonistic Bacteria ◽  
Biological Treatments ◽  
Rot Disease ◽  
The Impact

The main objective of this study was to evaluate the ability of both antagonistic bacteria Bacillus amyloliquefaciens (SF14) and Alcaligenes faecalis (ACBC1) used in combination with salicylic acid (SA) to effectively control brown rot disease caused by Monilinia fructigena. Four concentrations of salicylic acid (0.5%, 2%, 3.5%, and 5%) were tested under in vitro and in vivo conditions. Furthermore, the impact of biological treatments on nectarine fruit parameters’ quality, in particular, weight loss, titratable acidity, and soluble solids content, was evaluated. Regardless of the bacterium, the results indicated that all combined treatments displayed a strong inhibitory effect on the mycelial growth of M. fructigena and disease severity. Interestingly, all SA concentrations significantly improved the biocontrol activity of each antagonist. The mycelial growth inhibition rate ranged from 9.79% to 88.02% with the highest reduction rate recorded for bacterial antagonists in combination with SA at both concentrations of 0.5% and 3.5%. The in vivo results confirmed the in vitro results with a disease severity varying from 0.00% to 51.91%. A significant biocontrol improvement was obtained with both antagonistic bacteria when used in combination with SA at concentrations of 0.5% and 2%. The lowest disease severity observed with ACBC1 compared with SF14 is likely due to a rapid adaptation and increase of antagonistic bacteria population in wounded sites. The impact of all biological treatments revealed moderate significant changes in the fruit quality parameters with weight loss for several treatments. These results suggest that the improved disease control of both antagonistic bacteria was more likely directly linked to both the inhibitory effects of SA on pathogen growth and induced fruit resistance.

scholarly journals Selection of phytotoxin producing rhizobacteria

2011 ◽  
Vol 83 (3) ◽  
pp. 1091-1096 ◽  
Author(s):  
Daniel D.C. Carvalho ◽  
Denilson F. Oliveira ◽  
Vicente P. Campos ◽  
Moacir Pasqual
Keyword(s):  
Seed Germination ◽  
Sucrose Solution ◽  
Triticum Aestivum L ◽  
In Vitro Assays ◽  
Lettuce Seed ◽  
Bacterial Strains ◽  
Coleoptile Growth ◽  
Liquid Phases ◽  
Freeze Dried

In order to select phytotoxin producing rhizobacteria to control weed plants, twenty five bacterial strains previously isolated from the rhizospheres of various plants were grown in a liquid medium and, after cell removal by centrifugation, the liquid phases were freeze-dried and the products were extracted with ethyl acetate/methanol. The extracts were concentrated to dryness under vacuum and dissolved in water and sucrose solution to be submitted to in vitro assays of lettuce (Lactuca sativa L.) seed germination and wheat (Triticum aestivum L.) coleoptile growth. Although most samples affected coleoptile growth, only those from four strains reduced lettuce seed germination. Two strains of Bacillus cereus, one strain of B. pumilus and one of Stenotrophoonas altophilia were the most promising microorganisms for producing phytotoxin and, consequently, for the development of new weed control products.

Effect of Imazapic and 2,4-DB on Peanut Yield, Grade, and Seed Germination

2010 ◽  
Vol 37 (1) ◽  
pp. 78-82 ◽  
Author(s):  
W. H. Faircloth ◽  
E. P. Prostko
Keyword(s):  
Seed Germination ◽  
Tomato Spotted Wilt Virus ◽  
Seed Quality ◽  
Field Trials ◽  
The Other ◽  
Peanut Seed ◽  
Stand Establishment ◽  
South Georgia ◽  
Tomato Spotted Wilt ◽  
Wilt Virus

Abstract Recurrent problems with peanut seed germination and stand establishment have raised concerns about the potential effects of herbicides on peanut seed quality. Field trials were conducted in south Georgia in 2005 and 2006 to evaluate the effects of imazapic and 2,4-DB on peanut yield, grade, incidence of tomato spotted wilt virus (TSWV), and seed germination. Imazapic at 71 g ai ha−1, applied at 30 and 40 days after planting (DAP), and 2,4-DB at 270 g ai ha−1, applied at 75 or 90 DAP, had no effect on peanut yield, grade, incidence of TSWV, and seed germination when averaged over two locations (Dawson and Tifton) and three cultivars (Georgia Green, Georgia-01R, and C-99R). Normal cultivar yield variations were observed; however, Georgia-01R had reduced standard (25 C) and cold (15 C) germination when compared to the other cultivars.

scholarly journals CONTROL OF Bipolaris oryzae (Breda de Haan) USING Curcuma longa (Linnaeus) EXTRACT AND EFFECT OF THIS EXTRACT ON RICE SEED PHYSIOLOGY

2018 ◽  
Vol 31 (1) ◽  
pp. 99-105
Author(s):  
KEILOR DA ROSA DORNELES ◽  
PAULO CESAR PAZDIORA ◽  
FÁBIO JÚNIOR ARAÚJO SILVA ◽  
RENATA MOCCELLIN ◽  
CÂNDIDA RENATA JACOBSEN FARIAS
Keyword(s):  
Seed Germination ◽  
Mycelial Growth ◽  
Curcuma Longa ◽  
Control Treatment ◽  
Rice Seed ◽  
Germination Test ◽  
Bipolaris Oryzae ◽  
Seed Physiology ◽  
Seed Germination Test

ABSTRACT This study was conducted to evaluate the use of Curcuma longa (Linnaeus) extract in the in vitro control of Bipolaris oryzae (Breda de Haan) and to characterize the effect of this extract on rice seed germination. A completely randomized arranged in a factorial experimental design was used: three isolates of B. oryzae from rice seed from different rice-growing regions of Rio Grande do Sul (Fronteira Oeste, Campanha, and Sul) were tested with three concentrations (20, 40, and 80 mg/mL) of C. longa plus a control treatment (0 mg/mL). Each reaction was repeated in quadruplicate. The effect of the extract upon the disease development was evaluated based on mycelial growth (PMG) and spore production; rice seed germination was evaluated using a germination test (Germitest®). The PMG results demonstrate that the treatments were effective in reducing PMG, with a stronger response observed as the concentration of the extract increased. An average inhibition of 84% of sporulation was observed for the tested strains compared with the control treatment. There were, however, no significant differences in terms of seed germination test with the different C. longa concentrations. Therefore, treatment of rice seeds with C. longa extract does not affect seed germination but positively inhibits mycelial growth and sporulation, affecting the in vitro sporulation of the different isolates of B. oryzae.

VARIABILITY IN SENSITIVITY TO THE FUNGICIDE PYROXYCHLOR WITHIN THE GENERA PHYTOPHTHORA AND PYTHIUM

1976 ◽  
Vol 56 (2) ◽  
pp. 365-369 ◽  
Author(s):  
LLOYD T. RICHARDSON
Keyword(s):  
Mycelial Growth ◽  
The Other ◽  
Individual Species ◽  
Systemic Fungicide ◽  
Damping Off ◽  
Response Curves ◽  
In Vitro Sensitivity ◽  
Pea Seedlings ◽  
Growth Room

A comparative study was made of the innate sensitivity of individual species within the genera Phytophthora and Pythium to the selective systemic fungicide pyroxychlor (2-chloro-6-methoxy-4-(Trichloromethyl)pyridine). In vitro sensitivity was evaluated on the basis of inhibition of mycelial growth on treated V8-juice agar. Little variation was found among the 10 Phytophtora spp. tested, the dosage response curves being linear and generally steep, with ED50 values ranging from 0.4 to 6.2 ppm. Similar steep, linear curves with low ED50 values were obtained with six Pythium spp., but five other species responded quite differently. P. sylvaticum was the most tolerant with no inhibition up to 25 ppm and only 20% at 100 ppm. The dosage response of the other species was irregular. Inhibition of P. irregulare and P. splendens reached a maximum of 50% near 1 ppm. The curve for P. ultimum also reached a maximum near 1 pp, but declined to a lower, constant level. The curve for P. polymastum was distinctly bimodal, ascending with dosage up to 0.5 ppm, descending sharply to 3.1 ppm, then ascending again. The effectiveness of pyroxychlor in controlling preemergence damping-off of pea seedlings caused by four of the Pythium spp. was compared in a growth-room test. P. aphanidermatum and P. ultimum were effectively controlled by postplant drench treatments, but P. irregulare and P. sylvaticum were not.

scholarly journals β-Lactamase inhibition profile of new amidine-substituted diazabicyclooctanes

2021 ◽  
Vol 17 ◽  
pp. 711-718
Author(s):  
Zafar Iqbal ◽  
Lijuan Zhai ◽  
Yuanyu Gao ◽  
Dong Tang ◽  
Xueqin Ma ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Second Generation ◽  
Bacterial Species ◽  
The Other ◽  
Inhibition Activity ◽  
Bacterial Strains ◽  
E Coli ◽  
Mic Value

The diazabicyclooctane (DBO) scaffold is the backbone of non-β-lactam-based second generation β-lactamase inhibitors. As part of our efforts, we have synthesized a series of DBO derivatives A1–23 containing amidine substituents at the C2 position of the bicyclic ring. These compounds, alone and in combination with meropenem, were tested against ten bacterial strains for their antibacterial activity in vitro. All compounds did not show antibacterial activity when tested alone (MIC >64 mg/L), however, they exhibited a moderate inhibition activity in the presence of meropenem by lowering its MIC values. The compound A12 proved most potent among the other counterparts against all bacterial species with MIC from <0.125 mg/L to 2 mg/L, and is comparable to avibactam against both E. coli strains with a MIC value of <0.125 mg/L.

scholarly journals Effects of Genotype and Date of Harvest on Infection of Peanut Seed by Aspergillus flavus and Subsequent Contamination with Aflatoxin1

1986 ◽  
Vol 13 (2) ◽  
pp. 46-50 ◽  
Author(s):  
V. K. Mehan ◽  
D. McDonald ◽  
N. Ramakrishna ◽  
J. H. Williams
Keyword(s):  
Aspergillus Flavus ◽  
Field Trials ◽  
Aflatoxin Contamination ◽  
The Other ◽  
Seed Infection ◽  
Peanut Seed ◽  
Aflatoxin Content ◽  
Peanut Crop ◽  
Increased Susceptibility

Abstract Several peanut genotypes reported as resistant, susceptible or highly susceptible to in vitro colonization of rehydrated, mature, stored, undamaged seed by Aspergillus flavus (IVSCAF) were tested for natural seed infection by A. flavus and other fungi in two or more replicated field trials at ICRISAT Center, Patancheru, India, in 1979–1984. Undamaged pods were sampled before maturity, at optimum maturity (normal harvest) and when over - mature (late harvest) and seed examined for infection by A. flavus and other fungi. In the 1983 and 1984 rainy and 1983/84 postrainy seasons, only four genotypes (one resistant and three susceptible) were tested, and seed were also tested for aflatoxin content. In all seasons the genotypes reported as IVSCAF - resistant had significantly lower levels of seed infection with A. flavus and other fungi than did genotypes reported as IVSCAF - susceptible. Cenotypic differences in levels of seed infection by A. flavus were consistent over seasons. The resistant cultivar J11 had a significantly lower aflatoxin content than the other three IVSCAF - susceptible genotypes tested in the 1983–1984 seasons. Drought stress in the 1984 season apparently increased susceptibility to seed infection by A. flavus and other fungi, and to aflatoxin contamination, in all cultivars. Seed infection by A. flavus and other fungi, and aflatoxin contamination increased with increasing maturity of pods, indicating the importance of lifting the peanut crop at optimum maturity.

scholarly journals Impact of Azoxystrobin, Dimethomorph, Fluazinam, Fosetyl-Al, and Metalaxyl on Growth, Sporulation, and Zoospore Cyst Germination of Three Phytophthora spp.

Plant Disease ◽  
2000 ◽  
Vol 84 (4) ◽  
pp. 454-458 ◽  
Author(s):  
M. E. Matheron ◽  
M. Porchas
Keyword(s):  
Life Cycle ◽  
Disease Control ◽  
Mycelial Growth ◽  
Phytophthora Capsici ◽  
Effective Concentration ◽  
The Other ◽  
In Vitro Activity ◽  
Phytophthora Spp ◽  
Cyst Germination

In vitro activity of azoxystrobin, dimethomorph, and fluazinam on growth, sporulation, and zoospore cyst germination of Phytophthora capsici, P. citrophthora, and P. parasitica was compared to that of fosetyl-Al and metalaxyl. The 50% effective concentration (EC50) values for)inhibition of mycelial growth of the three pathogens usually were lowest for dimethomorph and (metalaxyl, ranging from <0.1 to 0.38 μg/ml. However, the 90% effective concentration (EC90) levels for dimethomorph always were lower than the other four tested compounds, with values ranging from 0.32 to 1.6 μg/ml. Mycelial growth of P. capsici, P. citrophthora, and P. parasitica was least affected by azoxystrobin and fluazinam, with estimated (EC90) values >3,000 μg/ml. Reduction of sporangium formation by P. capsici, P. citrophthora, and P. parasitica in the presence of dimethomorph at 1 μg/ml was significantly greater than that recorded for the same concentration of azoxystrobin, fluazinam, and fosetyl-Al. For the three species of Phytophthora, zoospore motility was most sensitive to fluazinam (EC50 and EC90 values of <0.001 μg/ml) and (least sensitive to fosetyl-Al, with (EC50 and EC90 values ranging from 299 to 334 and 518 to 680 μg/ml, respectively). Germination of encysted zoospores of P. capsici, P. citrophthora, and P. parasitica was most sensitive to dimethomorph (EC50 and EC90 values ranging from 3.3 to 7.2 and 5.6 to 21 μg/ml, respectively), intermediate in sensitivity to fluazinam (EC50 and EC90 from 18 to 108 and 67 to >1,000 μg/ml, respectively) and metalaxyl (EC50 and EC90 from 32 to 280 and 49 to 529 μg/ml, respectively), and lowest in sensitivity to azoxystrobin and fosetyl-Al (EC50 and EC90 from 256 to >1,000 μg/ml). The activity of azoxystrobin, dimethomorph, and fluazinam on one or more stages of the life cycle of P. capsici, P. citrophthora, and P. parasitica suggests that these compounds potentially could provide Phytophthora spp. disease control comparable to that of the established fungicides fosetyl-Al and metalaxyl.

scholarly journals In vitro antifungal activity of endophytic bacteria isolated from date palm (Phoenix doctylifera L.) against fungal pathogens causing leaf spot of date palm

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
H. H. Al-Nadabi ◽  
N. S. Al-Buraiki ◽  
A. A. Al-Nabhani ◽  
S. N. Maharachchikumbura ◽  
R. Velazhahan ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Endophytic Bacteria ◽  
Mycelial Growth ◽  
Fungal Pathogens ◽  
Date Palm ◽  
Dual Culture ◽  
Bacterial Endophytes ◽  
Bacterial Strains ◽  
Culture Filtrates

Abstract Background Date palm ((Phoenix doctylifera L.) suffers from several fungal diseases. The endophytic microorganisms present in higher plants generally offer protection to their host plants against invading phytopathogenic fungi and bacteria. In the present study, endophytic bacteria associated with date palm leaves were isolated and their in vitro antagonistic potential against fungal pathogens causing leaf spots in date palm was demonstrated. Results Endophytic bacteria were isolated from date palm leaves of 3 different cultivars viz., Nighal, Khalas and Khinaizi and evaluated for their inhibitory activity against leaf spot pathogens of date palm viz., Fusarium solani, Alternaria sp., Nigrospora sp., Thieloviopsis sp., Curvularia subpapendrofii and Tilletiopsis minor using an in vitro dual culture assay. Of the 24 endophytic bacterial strains tested, the endophytes designated B1, B7, B8 and B9 obtained from cv. Nighal showed inhibitory activities (more than 55% mycelial growth inhibition) against F. solani and Alternaria sp. None of the bacterial endophytes inhibited the growth of other fungal pathogens tested. These antagonistic bacterial strains were identified as Pantoea septica on the basis of 16S rRNA gene sequence analysis. The hyphae of F. solani and Alternaria sp. exhibited morphological abnormalities such as shrinkage and disintegration when grown in the presence of antagonistic bacterial endophytes. The cell-free culture filtrates of the bacterial endophytes caused inhibition of mycelial growth and induced leakage of electrolytes from the mycelia of F. solani and Alternaria sp. This is the first study that describes inhibition of the date palm pathogens F. solani and Alternaria sp. by P. septica. Conclusion Endophytic Pantoea septica strains isolated from date palm leaves inhibited the mycelial growth of F. solani and Alternaria sp. and induced morphological changes in their mycelia. The culture filtrates of these bacterial strains also inhibited the mycelial growth and caused leakage of electrolytes from the mycelia of F. solani and Alternaria sp. These promising bacterial strains can be exploited as biocontrol agents to control F. solani and Alternaria sp.-induced leaf spot diseases of date palm.

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