Solani In Soil Research Articles

Enrichment of bacteria involved in the nitrogen cycle and plant growth promotion in soil by sclerotia of rice sheath blight fungus

Rice sheath blight pathogen, Rhizoctonia solani, produces numerous sclerotia to overwinter. As a rich source of nutrients in the soil, sclerotia may lead to the change of soil microbiota. For this purpose, we amended the sclerotia of R. solani in soil and analyzed the changes in bacterial microbiota within the soil at different time points. At the phyla level, Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria, Chloroflexi and Firmicutes showed varied abundance in the amended soil samples compared to those in the control. An increased abundance of ammonia-oxidizing bacterium (AOB) Nitrosospira and Nitrite oxidizing bacteria (NOB) i.e., Nitrospira was observed, where the latter is reportedly involved in the nitrifier denitrification. Moreover, Thiobacillus, Gemmatimonas, Anaeromyxobacter and Geobacter, the vital players in denitrification, N2O reduction and reductive nitrogen transformation, respectively, depicted enhanced abundance in R. solani sclerotia-amended samples. Furthermore, asymbiotic nitrogen-fixing bacteria, notably, Azotobacter as well as Microvirga and Phenylobacterium with nitrogen-fixing potential also enriched in the amended samples compared to the control. Plant growth promoting bacteria, such as Kribbella, Chitinophaga and Flavisolibacter also enriched in the sclerotia-amended soil. As per our knowledge, this study is of its kind where pathogenic fungal sclerotia activated microbes with a potential role in N transformation and provided clues about the ecological functions of R. solani sclerotia on the stimulation of bacterial genera involved in different processes of N-cycle within the soil in the absence of host plants.

Bio-management of soil borne pathogens infesting cucumber (Cucumis sativus L.) under protected cultivation system

Trichoderma harzianum, Bacillus subtilis and Pseudomonas fluorescens were tested separately and together under in vivo for their ability to supress soil borne pathogens i.e. Meloidogyne incognita, Fusarium oxysporum and Rhizoctonia solani infesting cucumber (Cucumis sativus L.) cv. Magicstar in two consecutive trials (2018–2020) under protected cultivation system. The initial mean population of M. incognita, F. oxysporum and R. solani was recoded 1.72 J2/g soil, 1.3 × 103 cfu/g soil and 7.8 propagules/50 cc soil respectively. Freshly prepared bio-agents were used as soil and drench application. Tested bio-agents were mixed with FYM and vermicompost for fortification before soil application, whereas for drench application, they were mixed with water at the rate of 5 ml/l. The suppressive effect of bio-agents was significantly (P > 0.05) greatest with combined bio-agents (T. harzianum + B. subtilis + P. fluorescens) application treatment which caused greatest reduction of M. incognita, F. oxysporum and R. solani multiplication which was up to 90% at the end of subsequent second season trial with significant enhancement in plant health. The eggs of M. incognita obtained from plants treated with all tested bio-agents showed least hatching (20%) when subjected to bioassay test after termination of experiments. Fluensulfone did not affect multiplication of F. oxysporum and R. solani in soil but establish the reduction in shoot and root disease severity in the plant system. Tested bio-agents were successfully established in the rhizosphere of cucumber plants which showed compatibility among them, hence may be ideal companions to develop consortia against soil borne diseases under protected cultivation system.

In situ Impact of the Antagonistic Fungal Strain, Trichoderma gamsii T30 on the Plant Pathogenic Fungus, Rhizoctonia solani in Soil.

Rhizoctonia solani is a soil-borne fungus causing a wide range of plants diseases. Trichoderma gamsii strain T30 has previously been reported as antagonistic against R. solani. Although there are a few studies about the influence of Trichoderma strains on the R. solani density in a pathosystem in the presence of plant hosts, this report for the first time comprehensively describes in situ effects of a T. gamsii strain on the population density of R. solani in the soil microcosmic conditions. The population dynamics of R. solani were followed in the autoclaved and non-autoclaved soils in artificially prepared microcosms up to day 25 after co-inoculation with T. gamsii in the variable ratios (R1/T1; R1/T0.1; R1/T0.01 of R. solani/T. gamsii). The population density of R. solani was evaluated by qPCR. In the autoclaved soil, target DNA copies of R. solani increased in the control samples from 1 × 105 to 6.5 × 106. At R1/T0.01, the number of target DNA copies were not significantly changed until day 11; however, it decreased by around five times at day 25. At R1/T0.1 and R1/T1, the number of DNA copies was reduced to 2.1 × 106 and 7.6 × 105 at day 11, respectively and the reduction was as much as 17 times at day 25. In the non-autoclaved soil, the number of the fungal cells decreased at day 25 whether inoculated or not with Trichoderma indicating a general suppression by the soil microbiome. In brief, T. gamsii significantly inhibited the growth of R. solani in the soil in situ and there was a general suppressive effect of the natural microbiome.

Control of Rhizoctonia solani damping-off disease after soil amendment with dry tissues of Brassica results from increase in Actinomycetes population

This study investigated the potential use of leaf residues from Brassica rapa, Brassica napus and Brassica juncea to control Rhizoctonia solani damping-off disease. Fungitoxicity against R. solani of volatiles and water-soluble extracts from tested tissues were evaluated in vitro. To identify the mechanisms of disease control, the dynamics of fungi, bacteria and Actinomycetes populations in soils, soil pH and seedling growth were evaluated in a greenhouse. In three soils tested, amendments with B. rapa achieved the strongest overall suppression of R. solani (96.7–100%), followed by B. napus (86.7–100%) and B. juncea (40–100%). Brassica amendments also significantly impacted soil microbial populations. Disease incidence was strongly correlated with the ratio of Actinomycetes/fungi population in soils. Average disease incidence in soils treated with B. rapa and B. napus amendment was less than 4% when the ratio of Actinomycetes/fungi was higher than 505.6±178.2. In addition, disease suppression in greenhouse conditions was not significantly correlated with the in vitro fungitoxicity of the three Brassica species. The amendments with B. rapa and B. napus showed moderate fungitoxicity in vitro, but achieved significant suppression of R. solani in soil. This indicates that compounds in these two species of Brassica might regulate microbial populations to achieve long-term disease control. Results indicate that alternation of microbial populations by B. rapa and B. napus is the main mechanism involved. The considerable phytotoxicity of these two species suggests that to maximize performance in controlling R. solani, further investigation into their selective phytotoxicity is needed.

Saprotrophic competitiveness and biocontrol fitness of a genetically modified strain of the plant-growth-promoting fungus Trichoderma hamatum GD12

Trichoderma species are ubiquitous soil fungi that hold enormous potential for the development of credible alternatives to agrochemicals and synthetic fertilizers in sustainable crop production. In this paper, we show that substantial improvements in plant productivity can be met by genetic modification of a plant-growth-promoting and biocontrol strain of Trichoderma hamatum, but that these improvements are obtained in the absence of disease pressure only. Using a quantitative monoclonal antibody-based ELISA, we show that an N-acetyl-β-d-glucosaminidase-deficient mutant of T. hamatum, generated by insertional mutagenesis of the corresponding gene, has impaired saprotrophic competitiveness during antagonistic interactions with Rhizoctonia solani in soil. Furthermore, its fitness as a biocontrol agent of the pre-emergence damping-off pathogen Sclerotinia sclerotiorum is significantly reduced, and its ability to promote plant growth is constrained by the presence of both pathogens. This work shows that while gains in T. hamatum-mediated plant-growth-promotion can be met through genetic manipulation of a single beneficial trait, such a modification has negative impacts on other aspects of its biology and ecology that contribute to its success as a saprotrophic competitor and antagonist of soil-borne pathogens. The work has important implications for fungal morphogenesis, demonstrating a clear link between hyphal architecture and secretory potential. Furthermore, it highlights the need for a holistic approach to the development of genetically modified Trichoderma strains for use as crop stimulants and biocontrol agents in plant agriculture.

Abiotic soil properties and the occurrence of Rhizoctonia crown and root rot in sugar beet

AbstractSince 1993, Rhizoctonia crown and root rot (Rhizoctonia solani AG 2–2 IIIB) has represented an increasing problem for sugar beet production in Germany. Up to now, the outbreak of the infection and the spread of the disease within a field cannot be predicted and effective countermeasures are not available. Although little is known about the living conditions of R. solani in soils, abiotic soil properties are likely to influence the disease occurrence. Investigations were carried out based on 60 pairwise comparisons, each consisting of a disease‐affected and an adjacent nonaffected patch on farmers' fields in 2002 and 2003. Soil samples from the top soil layer (0–30 cm) were collected before harvest, and eight of the most frequently mentioned soil properties potentially influencing Rhizoctonia crown and root rot infection were examined: bulk density, texture, carbonate carbon, potassium, phosphorus, organic carbon, total nitrogen, and pH. The occurrence of the disease was significantly related to the soil C : N ratio, indicating the influence of soil organic matter on the disease occurrence. Examinations of soil thin sections showed that organic‐matter particles in the soil serve as a substrate for R. solani. All other soil physical and chemical properties examined did not differ between the disease‐affected and nonaffected patches and seem to be of minor importance.

Demonstration of the biofumigation activity of Muscodor albus against Rhizoctonia solani in soil and potting mix

This research demonstrates the role of antimicrobial volatiles produced by Muscodor albus in disease control in soil and potting mix. The volatiles controlled damping-off of broccoli seedlings when pots containing soil or soilless potting mix infested with Rhizoctonia solani were placed in the presence of active M. albus culture without physical contact in closed containers. Conversely, plugs of R. solani on potato dextrose agar were inhibited when they were placed in the presence of M. albus incorporated into garden soil or soilless potting mix. Gas chromatographic analysis with solid-phase micro extraction showed that isobutyric acid and 2-methyl-1-butanol were released from the treated substrates. There was a significant relationship between the production of isobutyric acid in soil and damping-off control (P = 0.0415). Production of isobutyric acid was short-lived in treated substrates, peaking at 24 h in potting mix and 48 h in soil. Amounts of isobutyric acid released from soil were several times higher than those released from potting mix. Also, higher rates of M. albus rye grain culture were required to control damping-off in potting mix than in soil. This suggests that the soil used in this study is a better environment than soilless potting mix for the biological activity or viability of M. albus and components from the potting mix might bind the volatiles. The release of volatiles from soil during the biofumigation process suggests that containment measures such as tarping could be used to improve the control of soil-borne diseases and reduce use rate of the biocontrol agent.

Control of fusarium wilt of Solanum melongena by Trichoderma spp.

Biological control of wilt of egg plant (Solanum melongena L.) caused by Fusarium solani was made with the application of five Trichoderma species, T. harzianum, T. viride, T. lignorum, T. hamatum and T. reesei. The effect of volatile and non-volatile antibiotics of Trichoderma origin on growth inhibition of the wilt pathogen was studied. T. harzianum showed maximum growth inhibition (86.44 %) of the pathogen through mycoparasitism. The non-volatiles produced by the Trichoderma species exhibited 100 % growth inhibition of the pathogen under in vitro condition. Production of siderophores and fungal cell wall degrading enzymes, chitinase and β-1,3-glucanase were found. Treatments with two most efficient Trichoderma species, T. harzianum and T. viride resulted in the decreasing population of Fusarium solani in soil thereby deterring disease incidence in field condition.

SUPRESSIVIDADE DE DIFERENTES SOLOS A Rhizoctonia solani, NOS CERRADOS DO ESTADO DE GOIÁS

This study was carried out at greenhouse in order to evaluate the occurrence of natural suppressiveness to Rhizoctonia solani of soils on cerrados. A complete randomized experimental design was used with ten soils and three replications for treatment, evaluating final stand, sick plantets percentage and disease severity in common beans ( Phaseolus vulgaris L.). Results indicated suppressiveness to R. solani in soils from Goianesia growed with sugar cane and two soils from Orizona with natural vegetation and pasture respectively. KEY-WORDS: Supressive soils; Phaseolus vulgaris .

Trichoderma Mitogen-Activated Protein Kinase Signaling Is Involved in Induction of Plant Systemic Resistance

The role of a mitogen-activated protein kinase (MAPK) TmkA in inducing systemic resistance in cucumber against the bacterial pathogen Pseudomonas syringae pv. lacrymans was investigated by using tmkA loss-of-function mutants of Trichoderma virens. In an assay where Trichoderma spores were germinated in proximity to cucumber roots, the mutants were able to colonize the plant roots as effectively as the wild-type strain but failed to induce full systemic resistance against the leaf pathogen. Interactions with the plant roots enhanced the level of tmkA transcript in T. virens and its homologue in Trichoderma asperellum. At the protein level, we could detect the activation of two forms reacting to the phospho-p44/42 MAPK antibody. Biocontrol experiments demonstrated that the tmkA mutants retain their biocontrol potential against Rhizoctonia solani in soil but are not effective against Sclerotium rolfsii in reducing disease incidence. Our results show that, unlike in many plant-pathogen interactions, Trichoderma TmkA MAPK is not involved in limited root colonization. Trichoderma, however, needs MAPK signaling in order to induce full systemic resistance in the plant.

Biocontrol of Rhizoctonia Damping‐off of Tomato by Bacillus subtilis Combined with Burkholderia cepacia

Abstract Bacillus subtilis strain RB14‐C and Burkholderia cepacia strain BY were used in combination to control damping‐off of tomato plants caused by Rhizoctonia solani. Microcosm tests showed complete inhibition of R. solani growth on filter disks buried in soil added with the mixture of both bacteria. Single BY inhibited the fungus, but not completely, and RB14‐C had only slight inhibitory effect on pathogen growth. The efficacy of this combining treatment was checked in pot experiments, where bacteria were applied to the soil in several combinations: RB14‐C and BY together 4 days before seed planting, RB14‐C 4 days and BY 2 days before seed planting, RB14‐C 4 days and BY immediately before seeds. The effect of these treatments on population of R. solani in soil and infection of plants was compared with the activity of single application of each agent. All bacterial treatments significantly decreased damping‐off of tomato plants. The best control was obtained when BY was added 2 days after RB14‐C. In this treatment plant protection was significantly higher than that obtained in other combined applications and obtained by single strains, except BY added to the soil 4 days before seed planting. The lowest suppression indicated BY introduced to the soil before seed planting. RB14‐C only slightly decreased number of R. solani in the soil. In contrast, BY drastically reduced population of the pathogen. However, there was not a clear relation between decrease of pathogen density in soil and the rate of plant infection. The results show that combination of B. subtilis RB14‐C with B. cepacia BY can lead to greater damping‐off suppression than biocontrol exhibited by these strains used separately, but the effect of combining bacterial agents was clearly related to the order in which both agents were introduced.

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.

The effect of olive oil mill wastewater (OMW) on soil microbial communities and suppressiveness against Rhizoctonia solani

The effect of olive oil mill wastewater (OMW), an important pollutant of agricultural origin, on soil suppressiveness against the plant pathogenic fungus Rhizoctonia solani was examined. Soil was treated with OMW and the pathogen was introduced into the soil 45 days after the last treatment, while lettuce seeds were planted at four successive time periods after pathogen introduction. The damping-off due to R. solani in soil that has been previously treated with OMW was significantly reduced compared to the control (soil treated with water). The effect on soil suppressiveness of the aerobically treated olive mill wastewater (TOMW) was also examined, but was not found to be significantly different from the control. The OMW treated soil exhibited significantly higher respiration compared to the other treatments during the period of waste addition, which immediately decreased when the additions stopped. The bacterial population of r-strategists in the OMW treated soil was significantly higher compared to the soil that received TOMW or water. A transitory phytotoxic effect of the wastes was also observed, but this did not correlate with soil suppressiveness. Results suggest that addition of OMW and initially TOMW to soil creates a nutrient rich environment that is dominated by r-strategists. Such an environment provides unfavourable growth conditions for R. solani.

Increase in Populations of Rhizoctonia solani and Wirestem of Collard with Velvet Bean Cover Crop Mulch.

Velvet bean has been used traditionally as a summer cover crop in the southeastern United States. We investigated the use of killed velvet bean as a cover crop mulch left on the soil surface before collard was transplanted in the fall. Control treatments were weed-free fallow and velvet bean that was killed and disked into the soil before transplanting. Incidence of wirestem, caused by Rhizoctonia solani, reached a maximum of 25% in 2000 but only 4% in 2001 in cover crop mulch treatments. Nevertheless, in both years, the infection rate, area under the disease progress curve, and final incidence were significantly greater with cover crop mulch than in the fallow or disked treatments. Wirestem incidence did not differ between the disked and fallow treatments in either year. Populations of R. solani in soil were greater after cover crop mulch than in fallow plots in both years and greater in the disked treatment than in fallow soil in 2000 but not 2001. Velvet bean does not appear to be suitable as an organic mulch for fall collard production, but could be used as a summer cover crop if disked into the soil before transplanting collard.

Effect of bulk density on the spatial organisation of the fungus Rhizoctonia solani in soil

Abstract The mycelial growth form of eucarpic fungi allows for a highly effective spatial exploration of the soil habitat. However, understanding mycelial spread through soil has been limited by difficulties of observation and quantification of fungi as they spread through this matrix. We report on a study on the effects of soil structure by altering the soil bulk density, on the spatial exploration of soil by the fungus Rhizoctonia solani using a soil thin-sectioning technique. First we quantified fungal densities in microscopic images (0.44 mm(2)). At this scale, hyphae were either absent, or present as minor fragments, typically occupying less than 1% surface area of the thin section. From contiguous microscopic images we then produced large-scale (6.21 cm(2)) spatial distribution maps of fungal hyphae. These maps were superimposed onto soil structural maps, which quantify the degree of porosity in each microscopic image. Alterations in soil structure by changing the bulk density are shown to affect the distribution of the fungus within the soil. The volume of soil explored by the fungus increased with increasing bulk density. This was associated with a shift from a few large pore spaces to more evenly distributed small-scale pores. Fungal hyphae were present in all porosity classes within each bulk density, including areas that contain less than 5% visible pore space. However, fungal hyphae were more often found in areas with a higher porosity, in particular at low soil bulk densities. The results show that soil structure is a major component in the spatial exploration of soil by fungi.

Effect of bulk density on the spatial organisation of the fungus Rhizoctonia solani in soil

The mycelial growth form of eucarpic fungi allows for a highly effective spatial exploration of the soil habitat. However, understanding mycelial spread through soil has been limited by difficulties of observation and quantification of fungi as they spread through this matrix. We report on a study on the effects of soil structure by altering the soil bulk density, on the spatial exploration of soil by the fungus Rhizoctonia solani using a soil thin-sectioning technique. First we quantified fungal densities in microscopic images (0.44 mm 2). At this scale, hyphae were either absent, or present as minor fragments, typically occupying less than 1% surface area of the thin section. From contiguous microscopic images we then produced large-scale (6.21 cm 2) spatial distribution maps of fungal hyphae. These maps were superimposed onto soil structural maps, which quantify the degree of porosity in each microscopic image. Alterations in soil structure by changing the bulk density are shown to affect the distribution of the fungus within the soil. The volume of soil explored by the fungus increased with increasing bulk density. This was associated with a shift from a few large pore spaces to more evenly distributed small-scale pores. Fungal hyphae were present in all porosity classes within each bulk density, including areas that contain less than 5% visible pore space. However, fungal hyphae were more often found in areas with a higher porosity, in particular at low soil bulk densities. The results show that soil structure is a major component in the spatial exploration of soil by fungi.

A PCR-based method for detection of potato pathogen, Helminthosporiumsolani, in silver scurf infected tuber tissue and soils

Silver scurf caused by Helminthosporium solani causes significant economic losses in table stock, seed and processing potatoes. Specific polymerase chain reaction (PCR) primers, Hs1F1/Hs2R1, from H. solani were used for the amplification of a 447-bp product from 20 tissue samples and 54 single spore H. solani isolates, from eastern Canada (27 isolates), western Canada (13 isolates) and North Dakota in USA (14 isolates), but not from other potato fungal pathogens. In addition to PCR analysis, all 54 isolates were studied using conventional detection methods, visual disease symptoms and/or colony morphology and microscopic examination of the morphology of conidiophores and conidia. The PCR assay successfully detected H. solani and the PCR results correlated well with assessments based on conventional techniques. The detection of H. solani by PCR (1 day) is rapid and offers an alternative to the time consuming conventional diagnostic techniques (4–5 weeks). Nested PCR assay was necessary for the detection of H. solani in soils and thus can provide a sensitive technique to study the epidemiology of silver scurf in soils.

Conventional PCR and Real-time Quantitative PCR Detection of Helminthosporium Solani in Soil and on Potato Tubers

Silver scurf is an economically important blemish disease of potato caused by the fungus Helminthosporium solani. Two sets of PCR primers, Hs1F1/Hs2R1 (outer) and Hs1NF1/Hs2NR1 (nested) were designed to unique sequences of the nuclear ribosomal internal transcribed spacer (ITS1 and ITS2) regions of H. solani. Nested PCR was used to increase the specificity and sensitivity of single round PCR. Each primer set amplified a single product of 447 bp and 371 bp respectively, with DNA from 71 European and North American isolates of H. solani, and the specificity of primers was confirmed by the absence of amplified product with DNA from other fungal and bacterial plant pathogens. A simple and rapid procedure for direct extraction of DNA from soils and potato tubers was modified and developed to yield DNA of a purity and quality suitable for PCR within 3 h. The sensitivity of PCR for the specific detection of H. solani in seeded soils was determined to be 1.5 spores g−1 of soil. H. solani was also detected by PCR in naturally infested soil and from peel and peel extract from infected and apparently healthy tubers. Specific primers and a TaqMan™ fluorogenic probe were designed using the original primer sequences to perform real-time quantitative (TaqMan™) PCR. The same levels of sensitivity for specific detection of H. solani in soil and tubers were obtained during first round mboxTaqMan-based PCR as with conventional nested PCR and gel electrophoresis. This rapid and quantitative PCR assay allows an accurate estimation of tuber and soil contamination by H. solani, thus providing a tool to study the ecology of the organism and to serve as a crucial component for disease risk assessments.

Phytochemical and mycological investigation ofArtemisia monosperma

Both polar and nonpolar fractions ofArtemisia monosperma were found to contain taraxasterol, taraxasterol acetate, pseudotaraxasterol acetate, lupeol, β-sitosterol and 3′,5-dihydroxy-4′,6,7-trimethoxyflavone. None of the isolated compounds except 3′,5-dihydroxy-4′,6,7-trimethoxyflavone provided successful control againstRhizoctonia damping-off of cotton in a greenhouse experiment when used as seed treatment. However, on evaluation ofA. monosperma dried shoot as amendment on controlling soil-borne plant pathogens, it was effective in decreasing the damping-off disease of cotton caused byRhizoctonia solani and provided a firmer plant stand. Higher doses of amendment (2 and 4%) caused a significant drop in the number of propagules ofR. solani in soil when incorporated 3 and 6 weeks before planting. In most cases incorporation ofA. monosperma in the soil caused a distinct increase in the total fungal population.In vitro studies showed toxicity of diffused or extracted substances fromA. monosperma for growth and pectolytic and cellulolytic enzyme activities of the target pathogen.

Nylon netting technique for the study of the three dimensional growth of Rhizoctonia solani in soil

A technique for estimating the three-dimensional growth of Rhizoctonia solani in soil by measurement of growth of Rhizoctonia on intersecting vertical and horizontal planes of nylon netting or nylon cloth is described. The three-dimensional system was compared to a two-dimensional soil sandwich technique using either Millipore filter membranes, or nylon netting. The techniques are also compared to a three-dimensional, pellet soil-sampler technique. There was better adherence of hyphae to the nylon netting (1.7 mm dia pores) than to the Millipore membrane (0.45 μm dia holes) or the Nybolt 21-T nylon screen printing material (32 μm dia holes). The two-dimensional and three-dimensional nylon netting technique resulted in a far more sensitive measure of hyphal growth in soil than the pellet soil-sampler technique. The use of nylon netting to measure growth of hyphae of R. solani in soil would be most appropriate in disturbed soil with the choice of two-dimensional or three-dimensional measurements depending on the aims of the experiment.