Control Of Root Rot Research Articles

Combining potential oomycete and bacterial biocontrol agents as a tool to fight tomato Rhizoctonia root rot

Biological control of Rhizoctonia root rot and growth-promoting potential on two tomato cultivars was performed using Pythium oligandrum in combination, or not, with three tomato-associated rhizobacterial strains of Bacillus subtilis, B. thuringiensis and Enterobacter cloacae. The three bacterial strains displayed antifungal activity against Rhizoctonia solani, with pathogen growth inhibition up to 60%. P. oligandrum also destroyed R. solani cells by antibiosis and mycoparasitism processes. In a three-month greenhouse assays, for all trials and the two tomato cultivars used, disease suppression potential, as compared to the controls, was up to 80% using the microorganisms mixtures and 74% by using P. oligandrum alone. Increased height in disease-free plants was obtained with the microorganism mixtures (59%) compared to P. oligandrum (49%). Plants grown in R. solani inoculated peat and challenged with microorganism mixtures were higher than controls, whereas those amended with P. oligandrum showed 46 to 87% height increase. All treatments with the microorganisms were more effective in suppressing the disease than chemical fungicide. Increment of aerial parts and root fresh weights on disease-free plants were until 51% for those treated with microorganism mixtures compared to 46% recorded using P. oligandrum. On inoculated plants, these parameters were enhanced using the mixed treatment. No differences in the rhizosphere-bacterial populations were observed by Single Strand Conformational Polymorphism (SSCP) when, either the rhizobacteria, with or without P. oligandrum, or the pathogen, were inoculated. This suggests that the native bacterial communities were not significantly impacted by the various microbial-inoculations. Only differences were obtained for the two tomato cultivars that the native bacterial microflora colonize.

Differences in Soil Microbial Community Composition Between Suppressive and Root Rot-Conducive in Tobacco Fields.

Soil microorganism has a profound influence on planting growth and disease suppression. However, the difference in microbial community structure between suppressive and root rot-conducive soil and the mechanism of controlling soil-borne diseases by microorganisms in suppressive soil were not clear. To provide a theoretical foundation for prevention and control of root rot, this paper investigated the change of community structure in rhizosphere soil between suppressive and root rot-conducive tobacco fields. Soil samples were collected during before transplanting, vigorous growing period, and mature period of the tobacco, and bacteria and fungi were analyzed using 16S rRNA and 18S rRNA gene sequencing, respectively. Results showed that bacteria were more sensitive to the change between suppressive and root rot-conducive soil, and fungi were more sensitive to the change of different tobacco growth periods. Compared with conducive soil, tobacco suppressive soil can resist the invasion of pathogens, especially fungi, by regulating soil microbial community structure, and the potential pathogen Boeremia was always lower. Fusarium, the root rot pathogen, decreased rapidly in the mature period in suppressive soil. Moreover, norank_o_Gaiellales and unclassified_f_Trichocomaceae had a critical role in suppressive soil in the process of inhibiting root rot, which was obvious in the mature stage. Overall, the results indicated that the composition and structure of the microbial community significantly altered between suppressive and conducive soil along with the growth of tobacco, and suppressive soil could inhibit the occurrence of soil-borne diseases by boosting beneficial bacteria and inhibiting the potential pathogens.

The Ability of Some Antagonistic Bacteria on Control of Onion Pink Root Rot Compared to Fungicide Efficiency

The Ability of Some Antagonistic Bacteria on Control of Onion Pink Root Rot Compared to Fungicide Efficiency

Effects of biological agents on soil microbiology, enzyme activity and fruit quality of kiwifruit with root rot

Context Root rot is common for kiwifruit (Actinidia chinensis var. diliciosa) plants. It is not easily controlled by chemical methods, and biological agents are an alternative. Aims This study investigated the effects of biological agents on the activity and diversity of soil microorganisms, soil enzyme activity and physicochemical indices during the growth period of kiwifruit plants. Methods There were four treatments: (1) root-rot plants applied with traditional fertiliser (RP); (2) root-rot plants applied with biological agents CY (CY); (3) root-rot plants applied with biological agents CL (CL); and (4) healthy plants with traditional fertiliser (HP). Most samples were taken during the growth period of kiwifruit plants, while activities of defensive-related enzymes and quality of kiwifruits were tested in the fructescence period. Key results CY and CL treatments significantly improved microbial activity, changed microbial structure, increased the diversity, richness and uniformity of microbial species, and altered the relative utilisation ratio of six carbon sources. Soil nutrients of kiwifruit plants with root rot improved with CY and CL compared to RP. Health of kiwifruit plants with CY and CL also improved compared to RP. Activities of defensive-related enzymes in CY and CL treatments were significantly higher than in RP treatment (P < 0.05). Fruit quality indices were also higher than RP. Conclusions CY and CL changed the microbial communities in soil, and improved soil nutrients and plant health. Implications By altering the soil microbial structure, biological agents used to control root rot in kiwifruit plants improved tree health and fruit quality, and provide an alternative to chemical control of root rot.

Biological control of root rot, wilt diseases complex in offshoot date palm and improvement of growth parameters in New Valley Governorate, Egypt

Biological control of root rot, wilt diseases complex in offshoot date palm and improvement of growth parameters in New Valley Governorate, Egypt

The antagonistic activity of certain fungal endophytes against some phytopathogenic fungi through their metabolites and extracellular enzymes

The objectives of this study were to determine the qualitative production of extracellular enzymes produced by ten endophytic fungi and to investigate their antifungal potential against some phytopathogenic fungi namely, Alternaria alternata, Botrytis cinerea, Fusarium oxysporum and Rhizoctonia solani. In addition, the endophytic fungal isolates were screened for enzyme production by plate assay method. All endophytic fungi were able to produce proteases and cellulases with different levels except Alternaria alternata. Meanwhile, Fusarium, Alternaria, Nigrospora and Phoma species produced amylase. None of the tested endophytic fungi showed laccase production. Endophytic fungi filtrates revealed variable antifungal activities against the tested phytopathogenic fungi with Curvularia lunata filtrate being the most effective. This filtrate induced 48% and 80% growth inhibition of B. cinerea and R. solani, respectively. The phytochemical analysis of the endophytic fungi crude extract disclosed the presence of alkaloids and terpenoids. Morphological observations by optical microscope showed uncommon hyphal deformation and enlargement of cytoplasmic vacuoles of R. solani when treated with C. lunata filtrate. Furthermore, C. lunata (hyphal suspension and filtrate) was examined to control root rot caused by R. solani on faba bean plants in vivo. Both antagonistic treatments significantly reduced root rot severity.

Phytophthora Species Differ in Response to Phosphorous Acid and Mefenoxam for the Management of Phytophthora Root Rot in Rhododendron

Phytophthora root rot, caused by many soilborne Phytophthora spp., is a significant disease affecting the $42 million rhododendron nursery industry. Rhododendron growers have increasingly reported failure by two systemic fungicides, phosphorous acid and mefenoxam, to adequately control root rot. Both fungicides may be applied as a foliar spray or soil drench but it is unknown how application method, fungicide chemistry, or pathogen diversity affects disease control. Therefore, two experiments were conducted to (i) determine whether differences in application method or fungicide chemistry affect control of root rot caused by P. cinnamomi and P. plurivora and (ii) evaluate the sensitivity of Phytophthora spp. and isolates from the rhododendron industry to each fungicide. Results demonstrated that soil drenches of either fungicide were more effective than foliar sprays for control of P. cinnamomi but were ineffective for P. plurivora. Furthermore, Phytophthora spp. and isolates varied in sensitivity to phosphorous acid and mefenoxam, and there were multiple fungicide-insensitive isolates, especially within P. plurivora. Differences in sensitivity were also observed among isolates from different nurseries and production systems, with some nurseries having less sensitive isolates than others and with container systems generally having less sensitive isolates than field systems. Our results provide three potential reasons for why fungicide control of Phytophthora root rot might fail: (i) the fungicide can be applied to the wrong portion of the plant for optimal control, (ii) there are differences in fungicide sensitivity among soilborne Phytophthora spp. and isolates infecting rhododendron, and (iii) fungicide-insensitive isolates are present in the rhododendron nursery industry.

INTEGRATED CONTROL OF ROOT ROT AND WILT DISEASES OF PEPPER

This study presented many ways to control the pathogen to save the important economic value of pepper crops. To avoid the dangerous effect of the chemical fungicides, some of (bio-control agents, plant water extracts, essential oils and nano-particles materials) were applied as the chemical fungicides has a dangerous effect on the human health. Collecting the infected pepper samples: Infected pepper samples which showed wilt symptoms previously noticed from different locations in three governorates in Egypt ( Menufia, Kafr El-sheikh and Beheira). Isolation and purification of the pathogen: Isolation and purification of the pathogen were carried out in the department of plant pathology, faculty of agriculture, Menoufia university. 20 purified isolates of Fusariumwere obtained and microscopically identified. Pathogenicity test of the obtained 20 Fusarium isolates: Pathogenicity test of the pathogenic isolates was carried out in department of vegetables pathology, institute of plant pathology, agriculture research center in Giza. In this study four ways with 15 treatments were applied: 1-Bio-control agents {T. asprillium, T.harizianum, T.viride, B. subtilis and B. cereus}. 2- Plant water extracts {sweet pepper, hot pepper, garlic and mint}. 3- Essential oils {clove, mustard, mint and thyme}. 4- Nano-particles materials {Calcium oxide and Zinc oxide}. These control treatments were applied and compared with negative control, blank control and the fungicide (Mon-cut 25%).

Trichoderma Counteracts the Challenge of Phytophthora nicotianae Infections on Tomato by Modulating Plant Defense Mechanisms and the Expression of Crinkler, Necrosis-Inducing Phytophthora Protein 1, and Cellulose-Binding Elicitor Lectin Pathogenic Effectors.

Decoding the mechanisms of plant defense against plant pathogens in a scenario where antagonistic activity and the plant growth-promoting effects of useful organisms intervene simultaneously is a new frontier of plant pathology. Here, we demonstrated that (i) two selected strains of Trichoderma asperellum and Trichoderma atroviride promoted tomato (Solanum lycopersicum) growth and reduced the severity of disease caused by the oomycete Phytophthora nicotianae and (ii) the genetic patterns of the components of the experimental model system tomato–Trichoderma spp.–P. nicotianae were differentially expressed. The beneficial effects in both the promotion of the growth of host plant and the biological control of the pathogen by two selected strains of different Trichoderma species were tested both in planta and in vitro. In both respects, T. atroviride demonstrated to be more effective than T. asperellum. Additionally, the simultaneous transcriptional reprogramming of several plant defense-related genes, pathogen effectors, and mycoparasitism-related genes in tomato, P. nicotianae, and Trichoderma spp., respectively, was evaluated during the three-component interaction. Results support the hypothesis that Trichoderma spp. elicit the expression of plant defense-related genes. As expected, a mycoparasitism-related gene was significantly up-regulated in Trichoderma-colonizing tomato plants infected by P. nicotianae. Finally, a marked up-regulation of the genes encoding two necrosis-inducing effectors was observed in P. nicotianae infecting tomato plants colonized by Trichoderma. In conclusion, this study is a contribution toward understanding the genetic pathways related with the ability of Trichoderma spp. to counteract the challenge of P. nicotianae infections on tomato. Additionally, the experiments revealed the beneficial effects in the tomato growth promotion of a new T. atroviride strain and its good antagonistic effectiveness in the biological control of root and crown rot incited by P. nicotianae, confirming that Trichoderma spp. can be a powerful tool in integrated pest management strategies of Phytophthora diseases of horticultural crops.

Extended control of downy mildew and Phytophthora root rot on ornamentals with the novel fungicide oxathiapiprolin

Extended control of downy mildew and Phytophthora root rot on ornamentals with the novel fungicide oxathiapiprolin

Efficiency of bio-evaporation of Arugula leaves to control root rot disease on cucumber caused by Pythium intermedium in Greenhouse

The efficiency of the Arugula (Eruca vesicaria) leaves extracts against the fungus Pythium intermedium, the root rot disease agent, was evaluated with three concentrations of 2.5, 5, 10 g / kg soil as biofumigation. The fungi around infected root of cucumber plants were isolated and diagnosed from different locations in Baghdad such as Rashidiya, Madaen, Yousifiya and Mahmudiya. The extract of arugula plants significantly reduced the incidence and severity of root rot disease on cucumber plant after 45 days of cultivation compared with control. The highest reduction in incidence and severity of the disease was about 4% and 5% respectively with arugula extract 10 g / kg soil. The study was the first record to evaluate the incidence of P. intermedium on root of cucumber plants in Iraq. Further, all concentrations of arugula extract showed increase on the growth parameters compared with control. In arugula extract 10 g/kg soil the growth parameter such as plant length, leaf length, leaf width, wet weight and dry weight were 35 cm, 5.5 cm, 6 cm, 4 g and 0.28 g respectively. Furthermore, Significant differences in the value of the biological index of arugula plant extract treatments ranging from 2627 to 3433 compared to the treatment of P. intermedium, which was about 1910, while did not differ significantly from the treatment of control with a vital index of 3830.

Research Progress on the Occurrence and Control of Fusarium Crown and Root Rot of Tomato

Research Progress on the Occurrence and Control of Fusarium Crown and Root Rot of Tomato

A pipeline for the genetic improvement of a biological control agent enhances its potential for controlling soil-borne plant pathogens

Use of biopesticides results in a reduction of the worldwide dependence on chemical pesticides, ending in a more sustainable crop protection. For this reason, biological control industry invests in continued research for more effective biocontrol agents (BCAs) using basically two strategies: isolation of new strains from nature or conventional genetic improvement. However, both are highly onerous and time-consuming. Here we show a pipeline for the genetic improvement of fungal BCAs, based on genome shuffling, the most recent and promising non-recombinant DNA technology for the rapid phenotype improvement of microbial strains. The method consisted of the construction of a parent library using mutagenic agents, followed by genome shuffling and high-throughput screening. Sarocladium oryzae BRM 6461, a known cerulenin antifungal producer strain and high biocontrol potential, served as the model fungal BCA. The pipeline aimed to select mutant enhanced strains at least one of these three desirable characteristics: antagonism, UV-B irradiation tolerance and high temperature tolerance. The experiments were conducted in laboratory and green house. After four cycles of genome shuffling we selected the superior S. oryzae GS4-03 strain, showing cerulenin production of 203.3 ± 1.4 µg/mL, 42% higher than the wild-type strain BRM 6461. The GS4-03 strain exhibited good genetic stability for at least five successive subcultivation assays. Antagonism assay showed an increased micelial inhibition of Rhizoctonia solani and Sclerotinia sclerotiorum when using GS4-03 strain compared to the BRM 6461 strain. The bioassays, showed that the superior strain GS4-03 have an increased ability to control root rot (23.4%) and white mold (8.1 times) disease compared to the wild type strain BRM 6461. Assessment of virulence of the superior strain GS4-03 against rice plants showed that improvement procedures did not change the original strain behavior in this subject. Hydrolytic activity of enzymes related to the biocontrol action as chitinase, protease and β-1,3-glucanase did not present statistical difference between GS4-03 and BRM 6461 strains. Results of dual assay culture between GS4-03 and BRM 6461 strains showed that both have different genetic backgrounds, although RAPD and ITS-rDNA tests were not fully efficient to distinguish genetically the strains. Moreover, mutations resulted in S. oryzae strains more tolerant to UV-B irradiation, but with low genetic stability. Our results report for the first time an efficient pipeline for the genetic improvement of fungal BCAs based on genome shuffling.

Control of root rot (Phytophthora cinnamomi) in avocado (Persea Americana) with bioagents

ABSTRACT Despite the favorable edaphoclimatic conditions for avocado production in Brazil, diseases such as root rot caused by the pathogen Phytophthora cinnamomi compromise the crop. With the aim of managing root rot in avocado, the present study aimed to evaluate chemical and biological control with isolates of Trichoderma spp. and Pseudomonas fluorescens. Thus, three assays were conducted to assess: (i) mycelial inhibition of P. cinnamomi by isolates of Trichoderma spp. and P. fluorescens from different crop systems; (ii) effect of autoclaved and non-autoclaved metabolites of P. fluorescens, and (iii) chemical or biological treatment of avocado seedlings on the control of root rot under field conditions. The isolates of Trichoderma spp. from maize cultivation soil and the commercial products formulated with Trichoderma presented greater antagonism (p <0.05) to the pathogen P. cinnamomi in the in vitro tests. Similarly, non-autoclaved metabolites of P. fluorescens presented antagonistic potential to control P. cinnamomi. Under field conditions, the fungicide metalaxyl and the bioagents showed effectiveness in controlling P. cinnamomi, as well as greater root length and mass. Results demonstrated potential for the biological control of avocado root rot with Trichoderma spp. and P. fluorescens.

Isolation and characterization of endophytic bacteria for controlling root rot disease of Chinese jujube.

Fusarium oxysporum is the primary pathogen causing root rot disease that severely affects cultivation of jujube fruit in the Xinjiang province of China. The aim of this study was to identify endophytic bacteria in healthy jujube organs that could effectively suppress F. oxysporum growth. Different plant organs (leaves, twigs and roots) were collected from healthy Chinese jujube cultivated in southern Xinjiang province of China. The endophytic bacterium Brevibacterium halotolerans JZ7 was selected for its strong antagonistic activity and growth-promoting characteristics. Gas-chromatography mass-spectrometry analysis showed that acetoin, 2,3-butanediol and fenretinide were the three dominant volatile organic compounds produced by strain JZ7. Fenretinide strongly suppressed spore germination of F. oxysporum in vitro. Pot experiments showed that strain JZ7 colonized both the roots and rhizosphere soil of Chinese jujube and significantly reduced F. oxysporum level in jujube rhizosphere soil. We demonstrated that B. halotolerans JZ7 can be developed into a biological control agent to combat root rot disease of Chinese jujube in the Xinjiang province of China. The suggested strategy for biological control of jujube root rot disease is fully in accordance with the current principles of sustainability.

Bacterial strains for biological control of Fusarium root rot of soybean in Siberia

Two strains of bacteria isolated from agricultural soil in Yenisey Siberia were tested for their ability to suppress Fusarium root rot of soybean (Glycine max (L.) Merr.) in vitro. The strain RSA-1 statistically significantly (p<0.001) reduced the disease incidence by 25 percentage points in case of naturally infected soybean seeds and by 29 percentage points in case of artificially infected seeds. The strain RSA-13 statistically significantly (p<0.001) reduced the disease incidence by 32 percentage points in case of naturally infected soybean seeds but did not affect the disease incidence in case of artificially infected seeds. Both strains statistically significantly stimulated growth of infected plants. RSA-1 is Gram-positive, motile, aerobic, rod-shaped spore forming bacterium belonging to the Bacillaceae family. RSA-13 is Gram-positive, aerobic, filamentous actinobacterium belonging to the Actinomycetaceae family. Both strains can be recommended for biological control of Fusarium root rot of soybean in Siberia.

Biological control of Fusarium root rot of bean with two Trichoderma species and Pseudomonas fluorescens

Biological control of Fusarium root rot of bean with two Trichoderma species and Pseudomonas fluorescens

Selection of Trichoderma products to enhance the control of loquat white root rot by hot water drip irrigation

Rosellinia necatrix, a soilborne fungus, causes white root rot of loquat trees. Toward preventing the disease by enhancing a 45 °C hot water drip irrigation (HWD) treatment, which activates antagonism by soil fungi, we tested three commercial Trichoderma products and found that a product containing T. harzianum T-22 most enhanced the control efficacy. Field evaluation confirmed the enhanced efficacy of HWD with the product to cure the disease.

Vel1 regulates the growth of Trichoderma atroviride during co-cultivation with Bacillus amyloliquefaciens and is essential for wheat root rot control

Co-cultivation is one of the significant ways to improve the efficacy of biocontrol agents. In the present study, the role of Vel1 on the sporulation, secondary metabolism, mycoparasitism and disease control of Trichoderma atroviride and its influence on B. amyloliquefaciens macrolactin and difficidin gene expressions during co-cultivation have been investigated through the knockout and overexpression of Vel1 gene. Under nutrient stress conditions the T. atroviride Vel1 knockout (T23ΔVel1) exhibited early chlamydospore differentiation, while wild type and over expression strains formed more chlamydospores under nutrient-rich conditions. The differential expression of genes related to sporulation, secondary metabolism, mycoparasitism, and disease control was upregulated by the Vel1 over-expression (T23OVel1), and co-cultivations (T23 + BA and T23OVel1 + BA). The expression of these genes was impaired by the deletion of Vel1 gene and co-culture of B. amyloliquefaciens and T23ΔVel1 strains. Interestingly, macrolactin and difficidin genes of B. amyloliquefaciens were downregulated during co-cultivation with T23OVel1 and upregulated during co-cultivation with T23ΔVel1 strains. The mycoparasitism, plant growth and bio-control activity of T23 + BA and T23OVel1 + BA were superior than other treatments. The T23ΔVel1 showed reduced activity of mycoparasitism, plant growth and biocontrol, but it was increased by the co-culture (T23ΔVel1 + BA) due to the enhanced activity of B. amyloliquefaciens. The results infer that Vel1 of T. atroviride is involved in sporulation, mycoparasitism, disease control and secondary metabolite production. Further, it confirmed that Vel1 downregulates macrolactin and difficidin gene expression of B. amyloliquefaciens and thereby it regulates the compatibility between the T. atroviride and B. amyloliquefaciens to control the wheat root rot disease caused by Fusarium graminearum.

Persistent organic fertilization reinforces soil-borne disease suppressiveness of rhizosphere bacterial community

Soil-borne diseases are an increasingly serious threat to agriculture systems. Organic fertilization would improve soil quality and microbial community as well, and thus is appreciated a promising control strategy for soil-borne diseases. Yet, how soil microbial communities mediate disease control under organic fertilization remains largely unknown. Here, we aimed to explore the microbial mechanism of controlling soil-borne diseases by organic fertilization. We investigated the effects of various fertilization regimes on the soil suppressiveness toward pathogenic fungi in the peanut rhizosphere. The fertilization regimes tested were organic fertilizer, chemical fertilizers, and a combination of both. Uninterrupted application of organic fertilizer in peanut field plots for seven planting seasons resulted in a control of peanut root rot, with a significantly higher peanut yield. Upon organic fertilization, bacterial microbiome assembly in the rhizosphere played a key role in developing soil suppressiveness against peanut root rot; upon chemical fertilization, the potential fungal pathogens dominated the fungal microbiome assembly in the rhizosphere to boost root rot. Further, structural equation model revealed that the rhizosphere bacterial community contributed to the control of root rot. Furthermore, upon organic fertilization, the rhizosphere bacterial community strongly suppressed mycelial growth and spore germination of Fusarium sp. ACCC 36194. Collectively, in a monocropping system, persistent organic fertilization favors the development of a protective microbial shield in the plant rhizosphere, maintaining the rhizosphere health.