Growth Of Rhizoctonia Solani Research Articles

Seed vectored bacterial endophyte Bacillus pumilus protect sorghum (Sorghum bicolor L.) seedlings from a fungal pathogen Rhizoctonia solani

The goal of this study was to evaluate the role of seed endophytic bacteria (SEB) in fungal disease protection in sorghum seedlings. Total six SEB, including two Bacillus spp. (SM1 and SM6), and four Paenibacillus spp. (SM2, SM3, SM4, and SM5) were isolated from sorghum seeds. All isolates produced auxin while only SM3 isolate showed phosphate solubilization activity. All SEB inhibited the growth of tested fungal pathogens. Bacillus pumilus (SM1) and Bacillus subtilis (SM6) showed positive drop collapse assay, and presence of surfactin gene was also screened in their genomes. Further, lipopeptides extracted from SM1 and SM6 strongly inhibited Rhizoctonia solani growth in disc diffusion assay. Live-dead staining and fluorescence microscopy revealed the structural deformations and cell death in R. solani by lipopeptides. In microcosm assay, seeds inoculated with B. pumilus significantly protected the seedlings from Rhizoctonia infection. B. pumilus inoculated seedlings showed significant increase in the levels of PAL and SOD enzymes and their gene expressions (2.76, 2.00 and 4.61, 2.25 folds, respectively) compared to control. PR1 gene expression was also increased by 2.68 folds compared to the control. Present study concludes that sorghum seeds inhabit SEB like B. pumilus which is crucial in protecting seedlings from R. solani by producing lipopeptides, enhancing antioxidant and defense enzymes level and their gene expressions. This study is significant in terms of its originality which presents a first report on SEB of sorghum roles in seedlings protection against soil borne fungal pathogen like Rhizoctonia solani.

Inhibition Of Rhizoctonia Solani Growth and Its Extracellular Hydrolytic Enzymes by Different Extracts of Cinnamon (Cinnamomum Cassia) and Black Cumin Seeds (Nigella Sativa)

Inhibition Of Rhizoctonia Solani Growth and Its Extracellular Hydrolytic Enzymes by Different Extracts of Cinnamon (Cinnamomum Cassia) and Black Cumin Seeds (Nigella Sativa)

MAPK Cascades Mediating Biocontrol Activity of Trichoderma brevicrassum Strain TC967.

Trichoderma brevicrassum strain TC967 is a novel biological control agent (BCA) against the plant pathogen Rhizoctonia solani and promotes plant growth. Mitogen-activated protein kinase (MAPK) cascades are involved in a variety of physiological functions of Trichoderma, but functions of each MAPK in regulating biocontrol have not been characterized in a single Trichoderma strain. In this study, we assembled and annotated the genome of strain TC967 and identified its three MAPK gene sequences. Functions of Fus3-, Slt2-, and Hog1-MAPK in strain TC967 were dissected. All three MAPKs were involved in hyphal growth. Hog1-MAPK was essential for conidiation and tolerance to saline/osmotic stress. Both Fus3- and Slt2-MAPK deletion mutants reduced cell-wall integrity (CWI) and increased the activities of chitinase and protease. The growth of Rhizoctoniasolani was further inhibited by volatile organic compounds (VOCs) and secondary metabolites produced by Fus3- and Slt2-MAPK deletion mutants, respectively. Biocontrol assays demonstrated that Fus3- and Slt2-MAPK deletion mutants were considerably more effective in disease control than the wild-type strain. RNA-seq analysis revealed that MAPK collectively played a major role in regulating biocontrol-related gene expressions, including the genes in charge of secondary metabolism, fungal cell wall-degrading enzymes (FCWDEs), and small secreted cysteine-rich proteins (SSCPs).

Inhibition of Verticillium Dahliae and Rhizoctonia Solani Growth by Solid Phosphate Sludge Amendments

Background: In Morocco, phosphate processing generates large quantities of sludge which amass, form fillings, reduce arable land and distort the landscape. Phosphate wash sludge is rich in mineral elements. In order to recover some of these mineral elements including phosphorus, we considered using this sludge in a nursery as a substrate. Objective: The aim of the study was to check the effect of solid phosphate sludge amendment on some of the main soil-borne pathogens: Verticillium dahliae Kleb. and Rhizoctonia solani Kühn. Materials and Methods: The pathogens have been isolated and identified in the laboratory of Plant Pathology and Postharvest Quality of INRA-Kenitra. Phosphate wash sludge used was originated from the Khouribga phosphate treatment sludge disposal site. Different concentrations of phosphate sludge (0, 10, 30, 50, and 100 g/l) were tested on a PDA-based medium, in three replicates. The inhibitory effects on mycelial growth were measured and compared with those on the soil used by nurseries (Maamora forest soil). Petri dishes with PDA alone were used as control. The same concentrations (10, 30, 50 and 100 g/kg) were tested in vivo on two varieties of tomato and on Faba Faba bean for Verticillium dahliae and Rhizoctonia solani, respectively. Results: The results of this study showed that there was significant growth inhibition at different concentrations of solid Phosphate sludge amendments in vitro. The highest inhibition percentage was observed at 100 g/l of phosphate sludge amendments with 42% and 75% for Verticillium dahliae and Rhizoctonia solani. The high concentrations of phosphate sludge have shown lower disease severity of Verticillium dahliae on the tomato plants and a disease index of Rhizoctonia solani on the Faba bean plants. Conclusion: Based on these results, we can recommend that solid phosphate sludge can be used or mixed with other substrates in nurseries.

Exemplifying rhizobacteria for growth stimulation and disease suppression in finger millet

Of 111 rhizobacteria isolated from finger millet, 30 isolates exhibiting antagonism against Pyricularia grisea (22.22–44.44%) and Rhizoctonia solani (22.22–38.89%) were selected for functional characterization and in vitro interaction with pathogens. Appraisal of rhizobacteria for antimetabolites revealed HCN production by 3, ammonia production by all (0.80–4.39 µmol/ml) and H2S production by 5 isolates, while all produced siderophore (25.89–93.96%), 20 salicylic acid (3.12–54.46 µg/ml), 19 tested positive for glucanase, 17 for protease and 12 for amylase production. Culture filtrate of all the isolates inhibited growth of Rhizoctonia solani (23.33–81.11%) and Pyricularia grisea (19.35–53.22%). Role of thermostable metabolites in antagonism was observed with 21 isolates against Rhizoctonia solani (11.11–50.0%) and 24 against Pyricularia grisea (8.33–46.66%). Volatile antimetabolites of all the isolates retarded and inhibited growth of Pyricularia grisea (5.88–84.71%) and Rhizoctonia solani (5.5–83.33%), besides affecting mycelial quality and sclerotiation in Rhizoctonia solani. Metabolic extracts of 9 antagonists in ethyl acetate restricted the growth of Pyricularia grisea (8.88–20.80%) and of 10 inhibited Rhizoctonia solani (10.12–23.30%). Enlightening the involvement of bacterial growth regulators in plant growth stimulation, all isolates tested positive for IAA production (1.9–28.8 µg/ml in absence and 9.9–45.7 µg/ml in presence of tryptophan), 19 secreted ACC deaminase and 19 solubilized phosphate, while only 5 exhibited Zn-solubilization potential. Increase in plant height, root length, their fresh weight and chlorophyll content was recorded with seed priming under glasshouse condition.

Inhibition of Mycelial Growth of Rhizoctonia Solani by Chitosan in vitro and in vivo

Objective:Evaluate the antifungal effect of chitosan againstRhizoctonia solani in vitroand the possible mechanisms of its induced activity in potato tubers to control black scurf disease.Methods:Thein vitroinfluence of chitosan at different concentrations on mycelial growth ofR. solaniwas tested by using the poisoned food technique in PDA medium. The effect of these concentrations on the development of lesion diameters in tubers inoculated withR. solanimycelium was assayed for 30 days. The concentration that showed the greatest inhibitory effect on lesion diameters was tested to assess the induced activity of defense-related enzymes in the infected tubers.Results:In the poisoned food technique, chitosan at 1% completely inhibited the growth ofR. solanimycelium.In vivotests showed that chitosan treatment at 0.5% effectively controlled the black scurf in tubers inoculated withR. solanimycelium. Chitosan increased the activities of defense-related enzymes such as Peroxidase (POD), Polyphenol Oxidase (PPO) and Phenylalanine Ammonia-lyase (PAL) in treated tubers of tested cultivars.Conclusion:This work demonstrated that chitosan directly inhibited the growth ofR. solani, and potentially elicited defense reaction in potato tubers.

Characterization of antagonistic‐potential of two Bacillus strains and their biocontrol activity against Rhizoctonia solani in tomato

To investigate the biocontrol mechanism of two antagonistic Bacillus strains (Bacillus subtilis MB14 and Bacillus amyloliquefaciens MB101), three in vitro antagonism assays were screened and the results were concluded that both strains inhibited Rhizoctonia solani growth in a similar manner by dual culture assay, but the maximum percent of inhibition only resulted with MB101 by volatile and diffusible metabolite assays. Moreover, cell free supernatant (CFS) of MB101 also showed significant (p > 0.05) growth inhibition as compared to MB14, when 10 and 20% CFS mix with the growth medium of R. solani. After in vitro-validation, both strains were evaluated under greenhouse and the results concluded that strain MB101 had significant biocontrol potential as compared to MB14. Strain MB101 was enhanced the plant height, biomass and chlorophyll content of tomato plant through a higher degree of root colonization. In field trials, strain MB101 showed higher lessening in root rot symptoms with significant fruit yield as compare to strain MB14 and infected control. Next to the field study, the presence of four antibiotic genes (srfAA, fenD, ituC, and bmyB) also concluded the antifungal nature of both Bacillus strains. Phylogenetic analysis of protein sequences revealed a close relatedness of three genes (srfAA, fenD, and ituC) with earlier reported sequences of B. subtilis and B. amyloliquefaciens. However, bmyB showed heterogeneity in among both strains (MB14 and MB101) and it may be concluded that higher degree of antagonism, root colonization and different antibiotic producing genes may play an important role in biocontrol mechanism of strain MB101.

Eficiência de diferentes moléculas na redução dos sintomas da queima das bainhas em arroz e no crescimento de Rhizoctonia solani in vitro

Este estudo verificou a eficiência da aplicação de diferentes moléculas em reduzir o comprimento relativo da lesão (CRL) da queima das bainhas em arroz. Plantas dos cultivares BR-Irga 409 e Labelle foram cultivadas em solução nutritiva e inoculadas com Rhizoctonia solani, no estádio de máximo perfilhamento. Às 24 horas antes da inoculação, as bainhas das plantas foram pulverizadas com soluções de silicato de potássio (SP), silicato de potássio + fósforo (SP+F), Acibenzolar-S-Metil (ASM), fungicida Carbendazim, quitosana desacetilada (QD), etileno (ET) e fosfito de potássio (FP). Plantas cujas bainhas foram pulverizadas com água destilada serviram como testemunhas. O efeito das moléculas contidas nesses produtos no crescimento micelial de R. solani foi testado in vitro. Para BR-Irga 409, o CRL foi menor com a aplicação do FP, em relação aos demais tratamentos, exceto o Carbendazim. A aplicação do Carbendazim reduziu em 86,1% o CRL, em relação à testemunha. O CRL foi significativamente menor no cultivar BR-Irga 409 do que no 'Labelle', com aplicação do FP. O crescimento micelial de R. solani foi reduzido apenas pelo FP e Carbendazim, em comparação com os demais tratamentos. Não houve diferença significativa entre os tratamentos testemunha, SP e SP+F para a concentração de Si nas bainhas das plantas dos dois cultivares.

Effectiveness of Antagonistic Bacterial Metabolites to Control Rhizoctonia solani on Lettuces and Fusarium oxysporum on Tomatoes

The use of chemical fungicide has seriously damagedenvironmental soils, underground water, air and ecologicalenvironment, etc. Therefore, the use of biological fungi-cides originated from microbial antagonists to protect cropsfrom disease has been increasingly interested in proceedto replace chemical fungicides. High doses of chemical fun-gicides are used to protect crops but makes soils to bebarren, severely affecting the ecological environment.Especially, chemical residues on the agricultural productscause serious impact on human health. The developmentof microbial antagonists for production of plant fungicides isvery urgent and meaningful in organic agriculture. So far,several secondary metabolites producing bacteria havebeen considered as biocontrol agents of plant pathogenicfungi control. For example, Pseudomonas syringae synthe-size syringomycin, syringostatin and syringotoxin whichsuppress effectively pathogenic fungi of Aspergillus flavusand Fusarium oxysporum [4]. Besides, Pseudomonasstrains produce cepacin A and cepacin B [20], phenazine[25] and pyrrolnitrin [12] which inhibit growth of Rhizoctoniasolani, F. oxysporum [8]. Burkholdria cepacia strains pro-duce several antibiotics including cepacin and pyrrolnitrinwhich suppress the growth of both R. solani- and F.oxysporum [2, 13]. In Vietnam, a few papers have pre-sented the use of microbial cells, fungal spores for suppres-sion of plant pathogenic fungi. However, reports of cell freeextracellular compounds (ECs) of antagonists against plantfungal diseases are not much. The aim of this study was to

Composition and Antipathogenic Activities of the Twig Essential Oil of Chamaecyparis formosensis from Taiwan

In this study, antipathogenic activities of the twig essential oil and its constituents from Chamaecyparis formosensis Matsum were evaluated in vitro against six plant pathogenic fungi. The essential oil from the fresh twigs was isolated using hydrodistillation in a Clevenger-type apparatus, and characterized by GC-FID and GC-MS. Twenty-five compounds were identified, representing 98.9% of the oil. The main components were beta-eudesmol (25.1%), tau-muurolol (21.6%), elemol (15.0%), totarol (14.9%), and alpha-cadinol (12.4%). The twig oil (500 mcirog/mL) showed growth inhibitory activity against the phytopathogenic fungi, Fusarium oxysporum, Pestalotiopsis funereal, and Ganoderma austral, with antifungal indices of 92.7%, 71.1%, and 87.7%, respectively. In addition, the oil suppressed totally the growth of Rhizoctonia solani, Colletotrichum gloeosporioides, and Fusarium solani. In order to ascertain the source compounds of these antipathogenic activities, the main components were individually evaluated. Tau-Muurolol and alpha-cadinol exhibited excellent activity against F. oxysporum, R. solani, C. gloeosporioides, and F. solani, with IC50 < 50 microg/mL. These compounds also efficiently inhibited the mycelial growths of P. funereal and G. austral. Thus, alpha-cadinol and tau-muurolol could be considered as potential natural fungicides for controlling fungal pathogens and worth.

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

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.

Effect of Fungal Metabolites and Amendments on Mycelial Growth of Rhizoctonia Solani

Effect of Fungal Metabolites and Amendments on Mycelial Growth ofRhizoctonia SolaniA shift towards organic farming suggests amalgamation of organic resources against soil borne plant pathogens. The influence of metabolites of most ubiquitousAspergillusspp., organic amendment extracts and their combined effect withTrichoderma virenswere evaluatedin vitroagainstRhizoctonia solani.The minimum (36.1 mm) growth was attained byR. solaniin co-culture withA. niger.The maximum (42.3 mm) inhibition of mycelial growth of the test organism was observed with culture filtrate ofA. ochraceousfollowed byA. niger, A. fumigatus, A. flavusandA. terreus.Among organic amendment extractants, castor cake exhibited an additive effect on the growth ofT. virens, however, the maximum (41.8 mm) suppressive effect onR. solaniwas observed with vermicompost. With the advance in time, the effect of organic amendment extracts increased markedly. Inhibition potential of culture filtrate mixturte ofA. niger+T. virensandA. ochraceous+T. virensagainstR. solaniwas significantly higher in comparison to the other combinations.

Screening of bioantagonistic bacteria for biocontrol agent of Rhizoctonia solani and surfactin producer

The objective of this research was to screen 31 of bacteria isolates that have potency to control Rhizoctonia solani growth and isolates capability to produce surfactin. R. solani growth inhibition was performed uses paper discs containing a 5 days cultivation of isolates culture. Surfactin activity assay was performed on LB agar medium. Results of the screening showed that the highest growth inhibition was obtained for isolates code 54 (96.43%), KC4 (93.45%), and 163 (93.19%). All of the isolates were cooproducer of surfactin and iturin, and the highest biosurfactan index was obtained for isolate KB2 (3.91).The four potential isolates were identified, as Bacillus pantotheinticus (isolate 54 and isolate 163), Bacillus brevis (isolateKC4), and Bacillus sp(isolate KB2).© 2008 Jurusan Biologi FMIPA UNS SurakartaKey words: biocontrol, Bacillus pantotheinticus, Bacillus brevis, Bacillus sp., Rhizoctonia solani, surfactin

Effect of label and sublabel rates of metam sodium in combination withTrichoderma hamatum, T. harzianum, T. virens, T. viride on survival and growth ofRhizoctonia solani

This work was undertaken to determine the effects ofTrichoderma spp. combined with label and sublabel rates of metam sodium on survival ofRhizoctonia solani in soil. Soils were infested with wheat bran preparations ofTrichoderma hamatum Tri-4,T. harzianum Th-58,T. virens Gl-3, andT. viride Ts-1-R3. Soil was also infested with sterile beet seeds that were colonized withR. solani. Beet seeds were later recovered, plated onto water agar plus antibiotics, and the growth ofR. solani was recorded. Preliminary experiments showed thatT. hamatum andT. virens reduced survival and saprophytic activity ofR. solani when the biocontrol fungi were incorporated into soil at 1.5% (w:w) or greater. Based on these data, biocontrol fungi in subsequent experiments were incorporated into soil at 2%. Metam sodium at label rate killed all biocontrol fungi andR. solani. At 1:2 and 1:5 dilutions, metam sodium reduced survival ofR. solani and allTrichoderma spp. When biocontrol fungi plus the label rate of metam sodium and 1:5, 1:10, 1:50 or 1:100 dilutions of the label rate were tested together, there were no interactions between any biocontrol agent and the fumigant with respect to colony diameter, reflecting that allTrichoderma isolates tested reacted similarly to increasing concentrations of metam sodium. At the label rate of metam sodium, allTrichoderma spp. significantly reduced colony diameter, but not growth rate, ofR. solani from beet seed. For the levels of metam sodium tested in combination withTrichoderma, it does not appear feasible to use a reduced rate of metam sodium to controlR. solani. However, the combination ofTrichoderma with metam sodium does reduce growth ofR. solani in comparison with that provided by metam sodium at the label rate.

Fungi isolated from soil with quicksets of Chamaecyparis lawsoniana and their influence on the growth of Phytophthora cinnamomi and Rhizoctonia solani

Chamaecyparis lawsoniana is often attacked by other pathogens (from genera: Phytophthora, Pythium, Fusarium, Rhizoctonia) both when the quicksets are taken root and later, when the young plants are planted. The aim of the study was to determine an effect of saprobiotic fungi isolated from soil with quicksets Chamaecyparis lawsoniana on the growth of Phytophthora cinnamomi and Rhizoctonia solani. In our experiment, method series biotic was used (MAŃKA 1974). This method allowed to determine index of impendence for plants by Phytophthora cinnamomi and Rhizoctonia solani with the help of summary biotic effect. The results of observation on the biotic interaction of saprobiotic fungi isolated from soil with quicksets Chamaecyparis lawsoniana, analysed as biotic series and Phytophthora cinnamomi and Rhizoctonia solani showed, that this of fungal community did not limited growth of these pathogens. Summary biotic effects were negative. Environment of saprobiotic fungi more promoted growth of Rhizoctonia solani than Phytophthora cinnamomi. It means, that in the soil under Chamaecyparis lawsoniana crop, Rhizoctonia solani could have a better of conditions for growth than Phytophthora cinnamomi.

Molecular cloning, structural analysis, and expression in Escherichia coli of a chitinase gene from Enterobacter agglomerans.

The gene chiA, which codes for endochitinase, was cloned from a soilborne Enterobacter agglomerans. Its complete sequence was determined, and the deduced amino acid sequence of the enzyme designated Chia_Entag yielded an open reading frame coding for 562 amino acids of a 61-kDa precursor protein with a putative leader peptide at its N terminus. The nucleotide and polypeptide sequences of Chia_Entag showed 86.8 and 87.7% identity with the corresponding gene and enzyme, Chia_Serma, of Serratia marcescens, respectively. Homology modeling of Chia_Entag's three-dimensional structure demonstrated that most amino acid substitutions are at solvent-accessible sites. Escherichia coli JM109 carrying the E. agglomerans chiA gene produced and secreted Chia_Entag. The antifungal activity of the secreted endochitinase was demonstrated in vitro by inhibition of Fusarium oxysporum spore germination. The transformed strain inhibited Rhizoctonia solani growth on plates and the root rot disease caused by this fungus in cotton seedlings under greenhouse conditions.

Control ofRhizoctonia solani andSclerotium rolfsii in the greenhouse using endophyticBacillus spp.

Isolates of different endophytic bacteria were recovered from surface-disinfected seeds obtained from commercial companies, plants in the field and tissue culture. The bacteria were isolated from seeds after stringent surfacedisinfection.Pseudomonas fluorescens (isolate no. 14) from bean inhibited growth of all fungi tested and was fluorescent on King B medium.Bacillus cereus fromSinapis (isolate no. 65) inhibited growth ofRhizoctonia solani, Pythium ultimum andSclerotium rolfsii and also exhibited chitinase activity.Bacillus subtilis from onion tissue culture (isolate no. 72) inhibitedR. solani andP. ultimum growth.B. cereus from cauliflower (isolate no. 78) inhibited growth ofR. solani. B. pumilus from sunflower (isolate no. 85) inhibited growth ofR. solani andS. rolfsii. B. cereus (isolate no. 65) was introduced into cotton, and by using radioactive labelling we found that it was present for 16 days in the root-stem junction. It is most likely that these bacteria were still found 72 days after their introduction in the root and stem, at levels of 2.8·105 and 5·104 cfu g−1 fresh weight, respectively, when selective medium was used. There was no difference between control and treated plants in their height or in the fresh weight of roots, stems and leaves. When cotton seedlings were inoculated withB. cereus (isolate no. 65),B. subtilis (isolate no. 72) orB. pumilus (isolate no. 85), disease incidence caused byRhizoctonia solani was reduced in the greenhouse by 51%, 46% and 56%, respectively. In bean seedlings inoculated withB. subtilis (isolate no. 72),B. cereus (isolate no. 78) orB. pumilus (isolate no. 65), disease incidence caused bySclerotium rolfsii was reduced by 72%, 79% and 26%, respectively, as compared to control. In both cotton and bean seedlings, these endophytes reduced the disease index more than 50%. These results indicate that endophytic bacteria can survive inside cotton plants and are efficient agents for biological control against plant pathogens under greenhouse conditions.

Effect of apiforol and apigeninidin on growth of selected fungi

Selected fungi were grown on agar plates in the presence of naringenin, apiforol, apiforol 7-O-rhamnoglucoside, or apigeninidin. Of the four compounds tested, only apigeninidin inhibited the growth ofFusarium oxysporum, Gibberella zeae, Gliocladium roseum, Altemaria solani, and Phytophthora infestons. In contrast, the growth ofRhizoctonia solani, Sclerotium rolfsii, and Rhizopus stolonifer (- and +) was not effected by any compound. Since apigeninidin is present in seeds ofSorghum sp., we hypothesize that apigeninidin may play a role in mold resistance and that apiforol accumulates as a biosynthetic precursor of apigeninidin, not as a fungal defense compound.

The effect of soil compaction on the saprophytic growth ofRhizoctonia solani

The effect of soil compaction on the saprophytic growth ofRhizoctonia solani

A comparison ofin vitro andin vivo effect of clay minerals, humic acid and micronutrients on the activity of fungicides againstRhizoctonia solani

Activity of nine fungicides against mycelial growth ofRhizoctonia solani in potato dextrose broth and in pot tests as seed treatment against cowpea seedling rot in infested soil was differentially in fluenced by clay minerals, humic acid and micronutrients. Humic acid, extracted from farmyard manure, considerably lowered the activity, bothin vitro andin vivo, of all fungicides except chloroneb. Montmorillonite caused substantial decrease in disease control by fungicides but enhanced the toxicity of 2-methoxyethyl mercury chloride (MEMC), and quintozene in culture. Kaolinite inactivated carbendazim, benomyl and thiophanatemethyl in nutrient broth but had little effect on disease control by these fugicides. The six micronutrients altered the activity of fungicides to varying levels often without definite correlation betweenin vitro andin vivo results. The results ofin vitro growth inhibition tests are largely inapplicable to dieseas control tests in infested soil mainly due to the differences in the ambient conditions of the two systems.