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1.
Soil solarisation was consistently efficacious in reducing inoculum density to undetectable levels in a field naturally‐infested with Sclerotium cepivorum. This treatment delayed epidemic onset of white rot of garlic 2–3 months as compared with the untreated control or the inoculation of planting furrows with Glomus intraradices. Furthermore, significant reductions of disease incidence and of the standardised AUDPC were also observed in solarised plots, resulting in quantitative and qualitative yield improvement. Similar effects were observed in plots planted with tebuconazole‐treated cloves, confirming previous results, whereas Trichoderma harzianum was ineffective as a biocontrol agent, when applied to planting furrows. The inoculation of plots with G. intraradices before planting, in three consecutive years, was neither effective for disease control nor on the development of garlic, although the root systems of garlic plants from all the experimental treatments were heavily mycorrhizal at harvest, indicating the presence of native arbuscular mycorrhizal propagules in the soil and their survival after soil solarisation.  相似文献   

2.
Abstract

The efficiency of two biocontrol agents (Trichoderma harzianum NB and Bacillus subtilis NB) and two commercial biocides (Plant Guard and Rhizo-N) in controlling Fusarium root rot disease on some citrus rootstocks was evaluated under artificially infested soil in green house.

Fusrium root rot on citrus rootstocks seedlings i.e. sour orange (SO), volkamer lime (VL), rangpur lime (RP) and cleopatra mandarin (CL) was successfully controlled by dipping the root system of such seedlings in water suspensions of each biological treatment i.e. Trichoderma harzianum (spore suspension 5×106 spore/ml), Bacillus subtilis (cell suspension 8×107 cell/ml), Plant Guard (3 g/l) and Rhizo-N (4 g/l), then transplanted into artificially infested soil with Fusarium solani and drenched with enough water suspension of such biological treatments. Plant Guard (3 g/l) and Rhizo-N (4 g/l) were highly effective treatments in decreasing infection and severity of the disease, Fusarium density in rhizosphere soil and colonization of Fusarium solani in the roots of all tested seedlings.

Meanwhile, root dipping or soil drenching with the same treatments individually gave the least effect in reducing root rot incidenceon all tested rootstocks compared with application of the two methods together.

It should be noted that using biocontrol agents and commercial biocides could be successfully used in controlling root rot pathogens on citrus in commercial greenhouses or under field conditions before transplanting in new reclaimed lands in the desert.  相似文献   

3.
A range of known biocontrol or plant growth-stimulating species ofTrichoderma orGliocladium were grown on peat-bran substrate to yield between 5×107–3×1010 colony forming units (cfu's)g–1 substrate after 14 days growth. Inocula were incorporated into peat:sand potting compost infested withRhizoctonia solani to give 7–8 × 104 cfu's of antagonist g–1 compost and assessed for biological control activity using lettuce seedlings. Six of the eight antagonists decreased daming-off and three of these consistently increased yield in comparison withR. solani treatment alone.Subsequently, peat-bran inoculum ofT. harzianum isolate TH1 was incorporated at 0.5% w/v intoR. solani infested potting compost. Both autoclaved and nonautoclaved inoculum ofT. harzianum TH1 decreased disease and increased yield. Incorporation of ethyl acetate-extracted autoclaved inoculum ofT. harzianum TH1 resulted in similar levels of biocontrol and improved plant growth as did incorporation of nonautoclaved and autoclavedT. harzianum TH1 inoculum. The need to standardize inocula and controls is emphasized.  相似文献   

4.
Abstract

A study was conducted over two seasons in a marginal soil with an acid saturation of 54%. A plant growth promoting rhizobacterium, Bacillus megaterium, a commercial biocontrol agent, Trichoderma harzianum Strain kd (Eco-T®), and soluble potassium silicate were used in this study. The objective was to control maize yield reduction caused by Rhizoctonia solani AG2 root rot isolated from infected maize. R. solani reduced maize yields significantly by 34% in the first season. However, the losses decreased in the second season from 34% to 10%. In the first season, combination of T. harzianum, B. megaterium and potassium silicate increased maize yields by 130%. The highest yield in the presence of R. solani was treatments with T. harzianum (216%) followed by T. harzianum plus potassium silicate (214%) and lastly T. harzianum plus B. megaterium (178%). However, in the second season, T. harzianum plus potassium silicate treatment resulted in the highest yields.  相似文献   

5.
Summary Inoculum potential ofRhizoctonia solani Kühn was studied in an infested carnation field during two successive growth seasons. This inoculum potential was expressed as diseased carnation plants in the field and diseased bean seedlings planted in soil samples. Disease incidence in the field soil samples increased during the first season, up to 60% and 100%, respectively. Removing the carnation plants and keeping the soil wet for 45 days, resulted in a sharp decline in inoculum potential. Both inoculum potential and disease incidence in carnations were lower after plant removal. The use of either methyl bromide or vapam resulted in complete control of the disease and reduced inoculum potential. Results suggest possible reduction ofR. solani inoculum by maintaining the soil moist between growth periods.  相似文献   

6.
Suppression of root rot diseases of ornamental plants is a potential benefit of formulating soilless container media with compost. A green compost (green nursery compost, GNC), obtained by a circular-economy approach from residues of pruning of woody plants and grass clippings during the nursery activities was analysed for its suppressiveness of root rot diseases using lavender. To this end, a bioassay was develop by formulating potting mixes containing GNC with two rates of peat substitution (25% and 50%) and infested with the root rot pathogens Sclerotinia sclerotiorum, Rhizoctonia solani and Phytophthora nicotianae. Contrasting results were obtained by using both substrates with a significant reduction of root rot by S. sclerotiorum, no effect on the containment of that by P. nicotianae, and an increase of symptoms caused by R. solani. The specific suppressiveness observed may be attributed to the colonisation of compost by specific groups of antagonistic microorganisms. This hypothesis was investigated by the analysis of culturable fungal community, which resulted in the isolation of Trichoderma harzianum and T. atroviride as preponderant fungal species. Trichoderma representative isolates exerted in vitro antagonistic activities against the target pathogens with varying efficiencies indicating the employment of multiple complementary mechanisms, which may have contributed to the observed specific suppressiveness. Both substrates containing GNC resulted suitable for nursery cultivation of lavender, showing a growth performance similar to that obtained with peat-based substrate. Present results indicate that on-farm compost is a suitable component of mixed-peat substrates capable to support plant growth and provide specific disease suppression.  相似文献   

7.
Rhizoctonia damping-off caused by Rhizoctonia solani Kühn, is one of the most damaging sugar beet diseases. It causes serious economic damage wherever sugar beets are grown. Biological control is an efficient and environmentally friendly way to prevent damping-off disease. Suppression of damping-off disease caused by R. solani was carried out by four isolates of Bacillus subtilis (Ehrenberg) Cohn as well as three isolates of each of Trichoderma harzianum Rifai and Trichoderma hamatum (Bonord.) Bainier. The effect of Bacillus and Trichoderma isolates against R. solani was investigated in vitro and tested on sugar beet plants under greenhouse conditions. Isolates of Bacillus and Trichoderma were able to inhibit the growth of R. solani in dual culture. Furthermore, Trichoderma isolates gave high antagonistic effect than isolates of B. subtilis. Under greenhouse conditions, coating seeds by T. harzianum and B. subtilis separately, reduced seedling damping-off significantly. However, applications of T. harzianum increased the percentage of surviving plants more than B. subtilis in comparison to control. The obtained results indicate that T. harzianum and B. subtilis are very effective biocontrol agents that offer potential benefit in sugar beet damping-off and should be harnessed for further biocontrol applications.  相似文献   

8.
Biocontrol agents, viz., Rhizobium meliloti, Pseudomonas aeruginosa, Aspergillus niger and Trichoderma harzianum, are used as seed dressing and soil is amended with Prsosopis juliflora (Swartz) DC. plant parts like stem, leaves and flower at 1% w/w for the control of root-rot fungi. All antagonists suppressed the infection of root-rot fungi viz., Fusarium spp., Rhizoctonia solani and Macrophomina phaseolina whereas the infection of R. solani and M. phaseolina was controlled when cowpea (Vigna unguiculata L.) and mungbean (Vigna radiata L.) seeds were treated with P. aeruginosa and T. harzianum and the soil was amended with P. juliflora leaves’ powder at 1% w/w. However, germination of both the crops was observed in all treatments. Growth parameters like shoot and root length, shoot and root weight, and leaf area significantly increased in all the treatments as compared to the control parameters. P. aeruginosa and T. harzianum in combination with soil amendment with P. juliflora plant parts at 1% w/w were the most effective for the control of root-rot fungi of leguminous plants.  相似文献   

9.
Trichoderma harzianum is a widely distributed soil fungus that antagonizes numerous fungal phytopathogens. The antagonism of T. harzianum usually correlates with the production of antifungal activities including the secretion of fungal cell walls that degrade enzymes such as chitinases. Chitinases Chit42 and Chit33 from T. harzianum CECT 2413, which lack a chitin-binding domain, are considered to play an important role in the biocontrol activity of this strain against plant pathogens. By adding a cellulose-binding domain (CBD) from cellobiohydrolase II of Trichoderma reesei to these enzymes, hybrid chitinases Chit33-CBD and Chit42-CBD with stronger chitin-binding capacity than the native chitinases have been engineered. Transformants that overexpressed the native chitinases displayed higher levels of chitinase specific activity and were more effective at inhibiting the growth of Rhizoctonia solani, Botrytis cinerea and Phytophthora citrophthora than the wild type. Transformants that overexpressed the chimeric chitinases possessed the highest specific chitinase and antifungal activities. The results confirm the importance of these endochitinases in the antagonistic activity of T. harzianum strains, and demonstrate the effectiveness of adding a CBD to increase hydrolytic activity towards insoluble substrates such as chitin-rich fungal cell walls.  相似文献   

10.
Soil solarization in combination with introduction of biocontrol agents (BCA) was evaluated as a potential disease management strategy for tomato damping-off caused by Pythium spp. A rifampicin resistant Pseudomonas fluorescens strain (PfT-8) and a carbendazim resistant Trichoderma harzianum strain (ThM-1) were introduced into soil following solarization. Tomato seeds were planted into treated field plots. The influence of soil solarization and application of biocontrol agents on damping-off incidence, plant biomass, rhizosphere population of introduced antagonists, and native Pythium spp. was assessed by two consecutive field trials. Damping-off incidence was significantly reduced in solarized plots compared to control. Soil inoculation of biocontrol agents into solarized plots resulted in the highest suppression of damping-off incidence (PfT-8 up to 92%; ThM-1 up to 83%), and increase in plant biomass (PfT-8 up to 66%; ThM-1 up to 48%) when compared to un-solarized control plots. Rhizosphere population of introduced biocontrol agents gradually increased (PfT-8 up to 102% and ThM-1 up to 84%) in solarized soils when compared to unsolarized control. The population of Pythium spp in rhizosphere soil was reduced up to 55% in solarized plots; whereas, application of BCA to solarized soils reduced the rhizosphere population of Pythium spp. by 86 and 82% in P. fluorescens and T. harzianum applied plots respectively.  相似文献   

11.
A field study was conducted to evaluate the efficacy of indigenous biocontrol agents such as Streptomyces griseus and Streptomyces lydicus along with Bacillus subtilis and Trichoderma harzianum for controlling red root rot disease of tea plants. In response to biological treatments, disease incidence, green leaf yield, biometric and physiological parameters and organoleptic characters of made tea were assessed. Among the thirteen treatments tested, soil drenching of carbendazim was superior in terms of reducing red root rot incidence followed by combination of S. griseus and T. harzianum recorded in two consecutive field experiments. In contrast, the maximum green leaf yield and plant growth was achieved in soil application of these biocontrol agents. However, the performance of this dual combination of biocontrol agents was on par with systemic fungicide in terms of disease control. Correspondingly, the biometric, physiological and biochemical parameters were also considerably increased in biologically treated plants when compared to untreated control. The disease increased from 38.7% to 47.6% in untreated control plots and those plants were unhealthy in terms of leaf yellowing, stunted growth with heavy flowering, drying of branches and sudden death of bushes. The tea quality parameters such as theaflavin and thearubigin contents were significantly increased in the range of 0.75–1.43% and 10.38–13.22% respectively in biocontrol treated plants. This was also reflected in tea liquor characteristics. Our results suggested that the combination of biocontrol agents represent a promising alternative for effective management of red root rot disease in tea plants.  相似文献   

12.
Interactions between Fusarium solani and Phytophthora parasitica or F. solani and P. citrophthora influenced the development of root rot of citrus but depended on the temporal order of inoculation with F. solani or the two Phytophthora spp. Inoculation of citrus with either Fusarium solani and Phytophthora parasitica or Phytophthora citrophthora increased root rot compared to inoculation with P. parasitica or P. citrophthora alone when plants were inoculated with Phytophthora by dipping their roots in zoospore suspensions and subsequently transplanted into soil infested with F. solani. However, root rot was not increased by simultaneous co-inoculation of P. parasitica and F. solani or when plants were inoculated with F. solani first. Root rot was not increased when heat-stressed or non-stressed plants were inoculated with P. parasitica 30 days after transplanting into soil infested with F. solani. In most but not all experiments, F. solani alone reduced growth of tops or roots a small but significant amount.Co-inoculation of citrus by root-dipping into zoospore suspensions of P. parasitica and transplanting into soil infested with F. solani reduced feeder root length by 62% and root weight by 61% but did not significantly reduce the percentage of living roots when compared to inoculation with P. parasitica alone. When citrus roots were immersed in zoospore suspensions of P. citrophthora and transplanted into soil infested with F. solani, feeder root length was reduced by 68%, but feeder root weight and the percentage of living roots were not significantly reduced when compared to plants inoculated with P. citrophthora alone.Propagule densities of both P. parasitica and P. citrophthora in the rhizosphere of plants inoculated by root-immersion and then transplanting into soil infested with F. solani were not significantly different than propagule densities from plants transplanted into non-infested soil. Propagule densities of P. parasitica were suppressed an average of 41% when citrus was inoculated with P. parasitica 30 days after transplanting into soil infested with F. solani and by 41% when citrus was co-inoculated by transplanting into soil infested with both F. solani and P. parasitica.  相似文献   

13.
Lettuce Fusarium wilt, caused by Fusarium oxysporum f. sp. lactucae, represents a major problem in most lettuce production areas worldwide. In the present study, a number of resistance inducers, organic amendments and biocontrol agents were applied in a preventative way, in experimental and commercial situations, to soils artificially or naturally infested with race 1 of the pathogen, and to moderately susceptible lettuce cultivars. Potassium phosphite, acibenzolar‐S‐methyl, green composts, and Bacillus subtilis Qst713, Trichoderma asperellum + Trichoderma gamsii, and Pseudomonas strains achieved the most consistent disease control under the experimental conditions. Moreover, potassium phosphite, green compost, B. subtilis Qst713 and T. asperellum + T. gamsii, also showed a positive effect on plant development. In general, the results of the different treatments in naturally infested soil were similar to those observed in glasshouse trials under artificial inoculation. Potassium phosphite provided a consistent disease reduction (48%–62% in artificially infested soil and 60%–75% in naturally infested soil). The effects of adding 10% compost to a peat growing medium in the nursery, followed by a soil mixing application when lettuce was transplanted, significantly reduced the severity of Fusarium wilt (50%–59% efficacy) and increased fresh biomass production. Compost enrichment with Trichoderma TW2 generally further increased its efficacy. When tested under field conditions, the commercially available Trichoderma spp. and B. subtilis, together with experimental strains of Pseudomonas and Trichoderma spp., applied at the nursery level, provided a disease reduction of 30%–78%. Early application of the different control measures under nursery conditions and at lettuce transplant is noteworthy because it was carried out at a more localized level, with reduced amounts of products. Their use in practice should be integrated with other control strategies.  相似文献   

14.
Y. Bashan  S. Diab  Y. Okon 《Plant and Soil》1982,68(2):161-170
Summary A population ofXanthomonas campestris pv.vesicatoria developed as endophytes in the leaves and rhizosphere of apparently symptomless plants grown under mist but not under dry conditions. The pathogen survired for long periods on, and could be isolated from, the surface of infested dried seeds, inoculated sandy loam soil, dried leaves, and the rhizosphere of pepper and of other non-host plants. In addition, small numbers of the pathogen survived for 18 months in a field previously cropped with pepper diseased with bacterial scab. Healthy nursery or mature plants developed symptoms while growing in soil containing infested leaves, either buried or placed on the soil surface.  相似文献   

15.
Damping-off disease is caused by Rhizoctonia solani and leads to serious loss in many crops. Biological control is an efficient and environmentally friendly way to prevent damping-off disease. Optical micrographs, scanning electron micrographs, and the determination of hydrolytic enzymes were used to investigate the antagonism of Trichoderma harzianum SQR-T37 (SQR-T37) against R. solani. Experiments were performed in pots to assess the in vivo disease-control efficiency of SQR-T37 and bio-organic fertilizer. The results indicate that the mycoparasitism was the main mechanism accounting for the antagonistic activity of SQR-T37. In one experiment, the population of R. solani was decreased from 106 internal transcribed spacer (ITS) copies per gram soil to 104 ITS copies per gram soil by the presence of the antagonist. In this experiment, 45% of the control efficiency was obtained when 8 g of SQR-T37 hyphae per gram soil was applied. In a second experiment, as much as 81.82% of the control efficiency was obtained when bio-organic fertilizer (SQR-T37 fermented organic fertilizer, BIO) was applied compared to only 27.27% of the control efficiency when only 4 g of SQR-T37 hyphae per gram soil was applied. Twenty days after incubation, the population of T. harzianum was 4.12 × 107 ITS copies per gram soil in the BIO treatment, which was much higher than that in the previous treatment (8.77 × 105 ITS copies per gram soil), where only SQR-T37 was applied. The results indicated that SQR-T37 was a potent antagonist against R. solani in a mycoparasitic way that decreased the population of the pathogen. Applying BIO was more efficient than SQR-T37 application alone because it stabilized the population of the antagonist.  相似文献   

16.
In naturally infested soil containingPythium ultimum, P. acanthicum andPhytophthora megasperma, onlyP. ultimum was associated with root rot and damped-off seedlings. Damping-off was promoted by low soil temperatures and by flooding. Seedling stands were markedly reduced when seed was pre-incubated in soil at 12°C but not at 25°C or 35°C. Dusting carrot seed with metalaxyl significantly increased seedling stands in the field at rates from 1.5–6 g kg−1 seed and in both flooded and unflooded, naturally infested soil at 3.15 g kg−1. In greenhouse experiments using artifically infested soil,P. ultimum andP. paroecandrum caused damping-off of carrot seedlings andRhizoctonia solani reduced root and shoot weights.R. solani caused damping-off in nutrient-enriched soil.P. acanthicum andP. megasperma were not pathogenic to seedlings, although both fungi colonized roots. Soil populations of allPythium spp., particularlyP. ultimum, increased during growth of seedlings and population growth ofP. megasperma was promoted by periodic flooding. Infestation of soil withP. acanthicum did not reduce damping-off of carrot seedlings byP. ultimum orP. paroecandrum, but significantly increased root and shoot weights and decreased root colonization byR. solani P. acanthicum has potential as a biocontrol agent againstR. solani.  相似文献   

17.
The usefulness of vermicompost as a supporting media for growth of bioinoculants was evaluated for successful transfer of sufficient propagules of bioinoculants into the organic fields. The rooted plants after 50 days were pot and field tested for their growth and yield performances when transplanted along with rooting medium into pots/organic fields. The rooting medium, 50 days of inoculation, contained sufficient population of bioinoculants and arbuscular mycorrhizal (AM) fungi. Treatment with bioinoculants (except Trichoderma harzianum) substantially improved the root and shoot biomass of nursery raised rooted cuttings particularly in treatments containing Azotobacter chroococcum (150 and 91.67%, respectively), Glomus intraradices (117 and 91.67%, respectively) and Pseudomonas fluorescens (117 and 83%, respectively). The transplanted rooted plants in pots, over two harvests, yielded higher shoot biomass when rooting medium contained A. chroococcum (147%), G. intraradices (139%) and P. fluorescencs (139%). Although the treatments did not affect the content of essential oil, the quality of essential oil as measured by the content of patchouli alcohol improved with Glomus aggregatum (18%). Similar trends were observed in field trials with significantly higher biomass yield achieved with A. chroococcum (51%), G. intraradices (46%) and P. fluorescencs (17%) compared to control (un-inoculated) plots. Increased in herb yield was found to be related with increased nutrient uptake. The population of bioinoculants in the rhizosphere was observed to be considerably higher in plots receiving vermicompost enriched with bioinoculants. This technology can be a successful way of delivering sufficient propagules of bioinoculants along with vermicompost especially in organic fields.  相似文献   

18.
Thirty-five strains ofTrichoderma viride andT. harzianum were screened for their antagonistic ability against the rice sheath blight pathogen,Rhizoctonia solani. The strains that inhibited/overgrew the phytopathogenic fungus were considered effective. Light microscopic studies showed the antagonism of the hyphae of effectiveTrichoderma strains towards their host hyphae. Chitinase activity ofTrichoderma culture filtrates was enhanced, when colloidal chitin was used as the sole carbon source, instead of glucose. Chitinase pattern differed among the four select strains. The chitinase isoforms are induced differentially by carbon sources. The chitin affinity column fraction ofTrichoderma culture filtrate inhibited,in vitro, the growth ofR. solani.  相似文献   

19.
A system was developed to evaluate the effects of root growth of cotton seedlings on the inoculum dynamics ofGliocladium virens in nonsterile soil. In soil infested withG. virens, inoculum densities of the fungus increased when plants remained alive. After 30 days, shoots were excised and the roots allowed to deteriorate. During this portion of the experiment (30–60 days) soil inoculum densities ofG. virens declined. In infested soil without a seedling, inoculum densities remained constant throughout the duration of the experiments. Colonization of roots byG. virens was found to increase throughout the duration of the experiments. At 60 daysG. virens was recovered from approximately 60% of the root pieces (1-cm) sampled. The percentage of primary, secondary, or tertiary roots colonized was different (P = 0.01), but the total colonization of roots at three depths (0–10, 10–20, and 20–30 cm) was not different (P = 0.64). In noninfested soil, colonization of roots by indigenous propagules ofG. virens was never greater than 3%. Offprint requests to: C. M. Kenerley.  相似文献   

20.
Relative effectiveness of seven different application methods of five native bacterial and fungal biocontrol agents (BCAs) and one fungicide (azoxystrobin) was evaluated against Rhizoctonia solani, under pot and field conditions on rice cultivar Pusa Sugandha-5. Plants grown in pots infected with Rsolani suffered a 30%–49% decrease in plant growth and yield of grain. However, treatment with BCAs reduced the adverse effect of the pathogen but significantly varied with the treatment schemes. Amongst the treatments, soil application (SA) at 20 + 40 days after planting (DAP) followed by foliar application (FA) at 60 DAP was recorded as most efficacious, and reduced the severity of disease by 42–68%, resulting in a 21–36% plant growth promotion and yield enhancement. Treatment comprising SA 20 + FA 40 DAP was next in effectiveness but statistically equal to seed priming (SP) + SA 40 DAP of treatment. Amongst the BCAs, Pseudomonas putida was shown to be the most efficient, trailed by Trichoderma harzianum, P. fluorescens, T. viride and Bacillus subtilis. Field trials under naturally infested fields have also validated the effectiveness of Pputida. The SA 20 + 40 + FA 60 DAP with Pputida and Tharzianum were found quite effective and decreased the disease severity and incidence (40–81%), and improved the grain yield (42–72%). Relatively lower ShB control was recorded with SA 20 + FA 60 DAP, however, it was statistically at par with SA 20 DAP treatment and equal to SA 20 + FA 40 DAP.  相似文献   

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