Showing papers on "Rhizoctonia solani published in 1984"

Role of antibiosis in antagonism of Streptomyces hygroscopicus var. geldanus to Rhizoctonia solani in soil

Abstract: Streptomyces hygroscopicus var. geldanus controlled rhizoctonia root rot of pea in previously sterilized soil if incubated for 2 or more days prior to infesting soil with Rhizoctonia solani and planting. Streptomyces hygroscopicus also reduced saprophytic growth and the population of R. solani in soil. Growth of R. solani was inhibited by geldanamycin, an antibiotic produced by S. hygroscopicus, on nutrient media. Methanol extracts of soils in which the antagonist was incubated for 2 or more days inhibited growth of R. solani. Geldanamycin concentration was 88 μg per gram of soil after 7 days of incubation. Bioautography of soil extracts indicated that the inhibitory compounds were geldanamycin and two other compounds, also found in the geldanamycin standard. The period of incubation necessary for antibiotic production and disease control was similar, with no disease control occurring where no antibiotic was detected. Amending soil with geldanamycin, in amounts equivalent to that produced after 2 or 7 day...

Effects of soil temperature and moisture on the pathogenicity of fungi associated with root rot of subterranean clover

Abstract: The effects of soil temperature (10, 15, 20 and 25¦C) and moisture (45% water holding capacity (WHC), 65% WHC, and flooding) on the pathogenicity of five fungi, both alone and in combinations, were investigated to determine the involvement of these fungi in a severe root rot disorder of subterranean clover in Western Australia. Fusarium avenaceum, Pythium irregulare, and Rhizoctonia solani were highly pathogenic while Fusarium oxysporum and Phoma medicaginis, particularly when used singly, were only weakly pathogenic. Compared with individual fungi, fungal combinations increased the severity of root disease and decreased plant survival and plant fresh weight. While the fungi investigated caused root rot over the range of soil temperatures and moisture conditions of this investigation, the most severe root rot occurred at 10¦C, with less at 15 and 25¦C, and least at 20¦C. Temperature had a marked effect on the disease severity and its effect varied with individual fungi and their combinations, in particular, combinations involving P. irregulare (severest root rot at 10 and 15¦C). The most severe root rotting, compared with the control, occurred at 65% WHC, with less at 45% WHC, and least under flooding conditions. There was often a significant interaction between temperature and moisture for the various fungi and fungal combinations tested.

DNA Base Sequence Homology in Rhizoctonia solani Kühn

Abstract: DNA base sequence homology among AG-6 isolates of Rhizoctonia solani was determined by DNA-DNA reassociation kinetics. Five of 10 isolates examined shared high DNA homology ranging from 91.8 to 97.7%. This group was classified as AG-6 homogeneous group I (HG-I). DNA homology among the remaining 5 isolates was 55.4 to 66.2%. They showed only 47.5 to 62.9% DNA homology with AG-6 HG-I isolates. These isolates were designated AG-6 genotypic variation (GV) isolates. Each of them appeared to have gene structures that differed by nucleotide substitutions. The genetic divergence among AG-6 isolates was also clearly demonstrated by the electrophoretic patterns of proteins and appearances of the cultures. These results suggest that AG-6 consists of strains that are phylogenetically related but have significant genetic polymorphism.

Abscisic acid in phytopathogenic fungi of the genera Botrytis, Ceratocystis, Fusarium, and Rhizoctonia

Abstract: Strains of the phytopathogenic species Botrytis cinerea, Ceratocystis coerulescens, C.fimbriata, Fusarium oxysporum, and Rhizoctonia solani were cultivated on a defined synthetic culture medium. The plant hormone abscisic acid (ABA) was identified by gas chromato- graphy/mass spectrometry and gas chromatography data, and the contents determined in mycelia (15.9-31.9 ng/g mycel) and culture media (1.0-4.6 ng/ml) by scintillation counting.

Isolation of a DNA Plasmid in the Fungus Rhizoctonia solani

Abstract: A DNA plasmid, designated pRS64, was detected in three isolates of anastomosis group 4 (AG-4) of Rhizoctonia solani Kuhn by biophysical methods. The plasmid was a linear double-stranded DNA with a molecular weight of 1.68 ± 0.06 × 106 or 2617 ± 87 bp. Weakly pathogenic isolates of R. solani, 1668 RI-1, 1271 RI-64 and 1272 RI-1, which showed abnormally slow growth, contained the plasmids, but pathogenic isolates, 1668, 1271 and 1272, showing normal growth, contained no detectable plasmid DNA.

Chemical defense of Leguminosae. Are quinolizidine alkaloids part of the antimicrobial defense system of lupins

Abstract: Growth of 6 bacteria (Serratia marcescens, Bacillus megaterium, Bacillus subtilis, Streptococcus viridis, Micrococcus luteus, and Mycobacterium phlei) was inhibited by 50% if the growth medium contained sparteine at concentrations between 0.5-10mᴍ. Total growth inhibition, which was bacteriostatic in nature, was achieved at 20 mᴍ. The growth of 6 phytopathogenic fungi was also affected: at a sparteine concentration of 15 mᴍ the growth of Alternaria porri was reduced by 40% as compared to the untreated control. Respective values were 18% inhibition for Piricularia oryzae, 33% for Helminthosporium carbonum, 15% for Rhizoctonia solani, 5% for Fusarium oxysporum, and 42% for Asperquillus oryzae. Since the concentrations of quinolizidine alkaloids range from 1-200 mᴍ (roots, leaves, or stems) or 10-200 mmol/kg (seeds) in Leguminosae, it is discussed whether quinolizidine alkaloids are involved in the antimicrobial defense of lupins, in addition to their potential role as allelopathic or herbivore repellent defense compounds.

Nursery diseases of eucalyptus in Kerala

Abstract: Survey of Eucalyptus (E, grandis and E. tereticornis) nurseries in Kerala State indicates that the most prevalent diseases are damping-off, web blight and seedling blight in seedbeds and stem canker, leaf and shoot blights and Phaeoseptoria leaf spot in container plants. Cylindrocladium spp., Rbizoctonia solani and Pythium spp. arc the main serious pathogens. Pythium myriotylum, P. deliense, R. scilani, Cylindrocladium camellias, C. clavatum and Sclerotium rolfsii are recorded for the first time on Eucalyptus.

High Frequency of Finding Double-stranded RNA in Naturally Occurring Isolates of Rhizoctonia solani

Abstract: Summary Forty-nine out of 50 field isolates of the basidiomycete Rhizoctonia solani were found to contain dsRNA. The presence of dsRNA appeared to have no consistent association with the degree of pathogenicity (virulence) of the isolates. These findings contradict previous reports correlating the presence of dsRNA with hypovirulence in R. solani.

Antagonists and parasites of Rhizoctonia solani and their efficacy in reducing stem canker of potato under controlled conditions

Abstract: A number of fungi and bacteria isolated from sclerotia on potato tubers were antagonistic to or parasitic on Rhizoctonia solani in vitro . The parasitism of R. solani hyphae by Penicillium cyclopium, P. nigricans, Gliocladium deliquescens, Fusarium culmorum, F. moniliforme, Epicoccum nigrum, Trichothecium roseum, Cylindrocarpon destructans and C. olivaceum are new records. These fungi, Pseudomonas fluorescens , and a Streptomyces sp. were also effective in reducing stem canker under laboratory conditions.

Biological control of Rhizoctonia solani on potatoes by antagonists. 3. Inoculation of seed potatoes with different fungi

Abstract: Inoculation of seed potatoes withVerticillium biguttatum and three other hyperparasitic fungi, alone or in combination, resulted in statistically significant reduction of infestation of potato plants byRhizoctonia solani. Gliocladium roseum, Trichoderma hamatum andHormiactis fimicola did not show prolonged protection againstR. solani under farming conditions.H. fimicola, however, inhibited mycelial growth ofR. solani in vitro, particularly in the lower temperature range whereV. biguttatum did not show any growth. Combining these two antagonistic fungi may be advantageous as they cover the entire temperature range in whichR. solani is active. At the end of the vegetation period,V. biguttatum was superseded byG. roseum. Production of sclerotia on newly formed tubers from seed potatoes inoculated withV. biguttatum (alone or in combination with the other three antagonists) was significantly reduced. Inoculative van pootaardappelen metVerticillium biguttatum, apart of sament met drie andere hyperparasieten, had een gunstig effect op het onderdrukken vanRhizoctonia solani op de plant;Trichoderma hamatum, Gliocaldium roseum enHormiactis fimicola, ieder apart toegediend, boden de plant op lange termijn geen bescherming tegenR. solani onder praktijkomstandigheden.H. fimicola bleek bij lage temperatuur, waarbijV. biguttatum geen groei-activiteit meer vertoonde, op hyfen en sclerotien vanR. solani te kunnen groeien. Toepassing van deze schimmel enV. biguttatum in een gemengde inoculatie zou over een breder temperatuurtraject effectief kunnen zijn. Tegen het einde van het groeiseizoen vond er op de ondergrondse plantedelen een verschuiving plaats, waarbijG. roseum meer op de voorgrond trad. Verondersteld wordt dat de afname vanV. biguttatum op stolonen hiervan een gevolg was. De produktie van sclerotia op nieuwe aardappelen afkomstig van metV. biguttatum behandeld pootgoed (alleen of met andere hyperparasitaire schimmels) bleek sterk verminderd te zijn. Vooral dit gegeven maakt de biologische bestrijding vanR. solani interessant:V. biguttatum blijkt ook op lange termijn effectief te zijn.

Anti-microbial Activity of Phenolic Acids in Pteridium aquilinum

Abstract: All land plants are continually exposed to a wide variety of microorganisms ranging from those which are beneficial to those which are pathogenic. Most plants remain remarkably healthy, and this seems to be especially true of ferns, which reportedly are rarely subject to diseases (Braid, 1940; Hutchinson, 1976; Bandoni, pers. comm.). It is now generally recognized that the resistance of plants to pathogens (and other predators) is mainly due to their containing fungicidal and bactericidal secondary compounds. The few surveys which have been carried out on ferns have confirmed that they do contain such antibiotic substances (Maruzzella, 1961; Khrisagar & Mehta, 1972; Lynch-Brathwaite et al., 1975; Banerjee & Sen, 1980; Cooper-Driver et al., in prep.). One major class of secondary compounds with known antimicrobial activity is the phenolics, which range from simple phenols to complex polymeric tannins (Harbore, 1982, pp. 230-264). Their main role in plants appears to be as protective compounds against fungi, bacteria, and viruses (Friend, 1979; Swain, 1979). For example, the flavonoids present in the farinose exudate on the leaf surfaces of some ferns have antimicrobial properties (Chowdhury et al., 1974; Wollenweber, 1978). Simple phenolics, such as p-hydroxybenzoic, protocatechuic, and vanillic (hydroxybenzoic) acids, and p-coumaric, caffeic, and ferulic (cinnamic) acids (Fig. 1) have been shown to be present in the fronds of ferns (Bohm & Tryon, 1967; Bohm, 1968; Cooper-Driver, 1976) and to play an important role in the ecology of Bracken (Pteridium aquilinum (L.) Kuhn) by inhibiting the germination and growth of neighboring plants (Stewart, 1975; Glass, 1976; Gliessman & Muller, 1978). Such acids are also known to have inhibitory effects on feeding by insects (Jones & Firn, 1979). The concentration of these acids in the leaves is known to vary quantitatively during growth and development (Glass & Bohm, 1969; Cooper-Driver et al., 1977; Jones, 1983), and thus must affect the antimicrobial, allelopathic, and anti-insecticidal properties of the plants differentially during the growing season. Simple phenolic and cinnamic acids must also play a major role in the defense of fern gametophytes against pathogens, particularly since more complex phenols, such as flavonoids, have been shown to be absent during the pre-antheridial stage (Petersen & Fairbrothers, 1980). However, it has been reported that fern prothalli are readily susceptible to several species of "damping off' fungi, like Pythium species (Gregor, 1938, pp. 141-154), and gametophytes grown in pure culture can be readily invaded by Botrytis cinerea, Pythium debaryanum, and Rhizoctonia solani (Hutchinson & Fahim, 1958). Gametophytes grown in pure culture appear to be more susceptible to molds and damping off diseases than to the more specific pathogens of angiosperms, Fusarium solani and Verticillium dahliae (Hutchinson, 1976). In angiosperms, many of these

Screening rapeseed/canola for resistance to damping-off and seedling root rot caused by Rhizoctonia solani

Abstract: (1984). Screening rapeseed/canola for resistance to damping-off and seedling root rot caused by Rhizoctonia solani. Canadian Journal of Plant Pathology: Vol. 6, No. 4, pp. 325-328.

Studies on a new nucleoside antibiotic, dapiramicin. II: Isolation, physico-chemical and biological characterization

Abstract: New nucleoside antibiotics, dapiramicins A and B produced by a Micromonospora sp. SF-1917, have been isolated by column chromatography on Diaion HP-20 and silica gel. Physico-chemical properties suggested that they are disaccharide nucleosides. Dapiramicin A underwent epimerization, under acidic condition, into epidapiramicin A. Although dapiramicin A generally exhibits no in vitro activity, it is very effective against the sheath blight of rice plants caused by Rhizoctonia solani in a green house test.

Crop and pasture rotations at Coonalpyn, South Australia: effects on soil-borne diseases, soil nitrogen and cereal production

Abstract: A crop rotation experiment was conducted at Coonalpyn, South Australia from 1976 to 1979 on a deep, red duplex soil. The experiment compared the productivity of grain legumes and of volunteer and sown annual pastures, and assessed their effects on the mineral nitrogen supply for subsequent wheat and barley crops, and their capabilities for preventing the root diseases of wheat cereal cyst nematode (Heterodera avenae), bare patch (Rhizoctonia solani) and Haydie (Gaeumannomyces graminis). Satisfactory legume dominance of the annual pastures was achieved only in 1979, while the grain legumes grew well and produced more dry matter than the pastures in each season. Wheat and barley yields averaged (1977- 1979) 2.0 t/ha after volunteer and sown pastures, and 2.8 t/ha after grain legumes, with the greatest response in 1979. In that year, wheat produced 11 kg grain/mm of growing season rainfall after grain legumes, but only 6 kg after pastures. The numbers of lesions on the nodal roots caused by R. solani and on the seminal roots by G. graminis varied with the season but both were less after grain legumes than after pasture. Gaeumannomyces graminis had the greatest effect on grain yield and, with soil nitrate at seeding, explained up to 68% of the variation in yield in 1979.

Effect of soil solarization and fungicide soil drenches on crater disease of wheat.

Abstract: for 1 min with 3% sodium hypochlorite, Smith, E. M., Wehner, F. C., and Kotze, J. M. 1984. Effect of soil solarization and fungicide soil rinsed in sterile water, and blot-dried drenches on crater disease of wheat. Plant Disease 68:582-584. aseptically. Fifty randomly selected root segments from each pooled sample were The development and yield of wheat growing in crater disease soil was enhanced significantly by plated out on 1.5% water agar suppletarping with clear polyethylene and by fumigation with methyl- bromide. Soil drenching with mented with 125 mg/L chloramphenicol copper oxychloride, fenarimol, and benomyl also controlled crater disease significantly but to a intd w at 27 C Thlat lesser degree than solarization and methyl bromide. Bipolaris sorokiniana, Fusarium culmorum, F. and incubated at 27 C. The plates equiseti, Rhizoctonia solani, and Sclerotium rolfsii were associated with the wheat roots, but only examined daily for 5 days and again after B. sorokiniana was suppressed by some of the treatments, ie, solarization, methyl bromide, and 5 wk. Fungi that developed from the procymidone. Application of the latter fungicide, however, did not result in enhanced plant growth. segments were isolated and identified. Shoots were dried at 70 C and weighed. At maturity, the wheat was harvested and Cultivation of wheat (Triticum aestivum randomized field experiment in a crater grain yield and 1,000-kernel weight were L.) in dryland fields on the Springbok patch on the Springbok Flats (values in determined. Flats, Republic of South Africa, is parentheses represent g a.i./L applied): seriously threatened by a condition anilazine (0.20), benodanil (0.67), RESULTS referred to as crater disease. The disease is benomyl (0.67), captafol (1.10), copper None of the chemicals applied as soil characterized by patches of chlorotic, oxychloride (0.91), fenarimol (1.00), drenches significantly reduced the stunted plants that appear about 4 wk iprodione (0.6), pencycuron (0.40), number of fungal propagules in the soil; after planting. Affected plants usually die procymidone (0.40), quintozene (1.00), however, solarization and fumigation in the seedling stage, though some remain thiabendazole (0.60), and tolclofos- with methyl bromide resulted in a alive but dwarfed until tillering. Yield methyl (0.40). In addition, formaldehyde significant decrease in the incidence of reduction caused by crater disease can be (15 g/ L) was applied in a similar way, fungi (Table 1). Fungi representing 25 as high as 35% (21). Two fungal species whereas methyl bromide was evaluated as different taxa were isolated from the are implicated as causal organisms of this a fumigant at the rate of 85 g/ m 2 . Soil was variously treated plots. Of these, R. disease, ie, Periconia macrospinosa also covered for 4 wk with 200-/gm-thick solani, Fusarium culmorum (W. G. Sm.) Levebvre & Johnson and Rhizoctonia clear polyethylene sheets. The maximum Sacc., and F. equiseti (Corda) Sacc. are solani Ku*hn, possibly in synergistic temperature recorded under the poly- recognized as wheat root pathogens association with another (20,21). However, ethylene at a depth of 15 cm was 48 C, (5,27). None of the treatments resulted in it has also been hypothesized that whereas the maximum temperature a significant reduction in the propagule phytotoxic aromatic nitroso compounds recorded in uncovered soil was 36 C. Five concentration of any of these pathogens could be involved (23). replicates were used per treatment and in the soil. On the contrary, drenching No work has been done on the plot size was 2 X 4 m. Control plots with benomyl significantly increased the chemical control of P. macrospinosa. received 3.75 L/m 2 of water. number of propagules of R. solani. Information on the chemical control of Four weeks after application of the Trichoderma spp. (mainly T. viride)Pers. R. solani is voluminous, but reports on various chemicals and directly after ex Gray) occurred in significantly greater the application of fungicides to control solarization, a soil sample was taken from numbers in soil treated with formaldehyde this pathogen on wheat are limited each plot at a depth of 0-20 cm. The fungi than in the soil of the control treatment. (6,18,29). Thus far, little attention has present in the samples were determined Five recognized root and crown been given to the control of crater disease by plating out serial dilutions of the soil pathogens of wheat occurred in the roots by chemical means. In this paper we on dextrose-peptone-yeast extract medium of the plants 5 wk after planting, ie, P. report on the effect of soil drenching with (17). After incubation for 5-7 days at 27 solani, F. culmorum, F. equiseti, various fungicides on the disease and the C, colonies that developed were counted Scierotium rolfsii Sacc. (9), and Bipolaris effect of soil solarization, a technique and the fungi were isolated and identified. sorokiniana (Sacc.) Shoem. (27). P. known to control many soilborne The propagule concentration of R. solani macrospinosa did not develop from any pathogens (7). in the various soil samples was determined of the root segments plated out, even after according to the beet seed technique incubation for 5 wk. B. sorokiniana had MATERIALS AND METHODS

Effect of the herbicides EPTC and linuron on cotton diseases caused by Rhizoctonia solani and Fusarium oxysporum f. sp. vasinfectum

Abstract: The herbicides EPTC and linuron applied to soil in the field at three different concentrations X2X, 1X, and 2X of recommended dose) decreased post-emergence, but not pre-emergence daraping-off in cotton incited by Rhizoctonia solani. Both herbicides at the two high concentrations significantly reduced wilt incited by Fusarium oxysporum f. sp. vasinfectum. Both herbicides reduced germination of chlamydospores of Fusarium in natural soil, but not in steamed soil. The 2X concentration of EPTC and linuron reduced the saprophytic activity of R. solani in soil. The effects of EPTC and linuron on post-emergence damping-off and wilt were attributed Ic their ability to suppress the saprophytic ability of R. solani and chlamydospore germinability ofFusarium in soil, respectively.

Effects of Recently Incorporated Organic Amendments on Damping-Off of Conifer Seedlings

Abstract: grow seedlings in the greenhouse for Wall, R. E. 1984. Effects of recently incorporated organic amendments on damping-off of conifer pathogenicity studies with damping-off seedlings. Plant Disease 68:59-60. and root rot fungi. Populations of Fusarium oxysporum Schlect., Rhizoctonia In greenhouse tests, forest nursery soil containing the damping-off fungi Fusarium oxysporum, solani Kihn, Pythium spp. and Rhizoctonia solani, and Pythium spp. was planted to oats (Avena sativa), rye (Secale cereale), ' ' buckwheat (Fagopyrum esculentum), and red clover (Trifolium pratense). After 15 and 20 wk, Cylindrocarpon spp. were therefore these green manure crops were incorporated into the soil, which was then amended with two levels present. each of sphagnum peat or fresh conifer sawdust. Black spruce and jack pine planted on these soils Soils were mixed thoroughly, screened were not significantly affected by the peat or sawdust amendments but the oat, rye, and red clover through a sieve with 0.5-cm openings, green manure crops caused an increase in postemergence damping-off. Jack pine was most affected and placed in wooden flats 30 X 50 X 6 by 15-wk-old oats and rye. Black spruce had the most postemergence damping-off in soil cm, which were placed in the greenhouse containing 15-wk-old red clover. Based on these results and earlier studies, it is suggested that any and watered daily. After 1 wk, half of the green manure crop is potentially damaging if incorporated into soil immediately before planting. flats were planted to green manure crops, and 5 wk later, the remainder were planted (with the exception of the Undecomposed plant residues incor- plant residues have been found to controls, which were left unplanted). The porated into soils before planting can increase for 10-25 days after incorporation green manure crops, oats (Avena sativa have various effects on the ensuing crop. and then decrease (13). Decomposed L. 'Stormont'), rye (Secale cereale L. Beneficial effects include improved soil sawdust is considered superior to fresh 'Kustro'), buckwheat (Fagopyrum escutilth, aeration, moisture-holding capacity, sawdust as an organic amendment in lentum 'Redstraw'), and red clover improved root penetration, and sup- forest nurseries (8,18). (Trifolium pratense L.), were grown pression of pathogenic microorganisms Certain fresh plant residues appear during the summer in a glass greenhouse

Hyphal interactions between Rhizoctonia solani and some Verticillium species

Abstract: The biological control of soil-borne plant pathogens with mycoparasitic fungi (e.g., Trichoderma and Gliocladium spp.) has received considerable attention (Ayers and Adams, 1981; Lumsden, 1981; Papavizas and Lumsden, 1980). Species of Verticillium have been often reported in the literature as mycoparasites but only a few taxa have been cited as parasites of soil-borne plant pathogens. For most common Verticillium species host range studies have not been conducted and their ability to attack soil-borne plant pathogens has not been determined. Hyphal interactions between selected species of Verticillium and the plant pathogen R. solani were examined in this study. Species and isolates of Verticil? lium were chosen to represent the common soil-borne members of the genus. Although most taxa are known as mycoparasites, isolates were not obtained di? rectly from fungal substrates (Table I). A measure ofthe variability within a single species was obtained by including six isolates of V. lecanii from different sources. Identification of the isolates of V. psalliotae and V. lamellicola was verified by determining growth rates on 2% malt extract agar at 20 to 30 C (Gams and Van Zaayen, 1982). All cultures were maintained on Difco potato dextrose agar slants (PDA) and stored at 4 C. Two isolates of R. solani (R-19 and R-33) were tested in combination with each isolate of Verticillium. Both were highly virulent members of anastomosis group AG-4 and isolated from diseased bedding plants (Stephens et al, 1982). Hyphal interactions between Verticillium and R. solani isolates were observed by growing paired cultures from agar discs (5 mm diam) placed at opposite sides of agar plates (9 cm). All results were based on minimum of two plates prepared on two different occasions for each Verticillium/Rhizoctonia combination on at least two media: 2% water agar and Difco potato dextrose agar. In preliminary tests with some isolates, hyphal interactions were also examined on Difco cornmeal agar and 2% agar in an aqueous extract of composted hardwood bark container medium. The extract was prepared by soaking one liter of container media in one liter of distilled water overnight followed by filtering the mixture through cheesecloth. This medium had a final pH of 7.1 and was used to approximate the nutritional conditions of the environment from which two species were isolated. All plates were incubated at 24 C under continuous light and were examined after 5-14 da by direct examination with a compound microscope using either brightfield or Nomarski interference illumination. A coverslip was placed over the zone of contact for examination at high magnification and for photography. In some cases, a small drop of cotton blue in lactophenol was used to stain the hyphae. Replicate plates were prepared with a layer of cellulose dialysis membrane on the

Suppressive effect of Azotobacter chroococcum on Rhizoctonia solani infestation of potatoes

Abstract: Isolates ofAzotobacter chroococcum were found to be promising for the control of infestation of potato plants withRhizoctonia solani. Inoculation with an isolate ofVerticillium biguttatum in combination with isolates ofA. chroococcum effectively protected sprouts, stems and stolons against infestation withR. solani. The effect of inoculation varied with soil temperature.

Rhizoctonia solani damping-off on spring turnip rape and spring rape (Brassica spp.) in Finland

Abstract: Damping-off occurred in 90 % of the spring oilseed rape fields surveyed in 1981—1982. On the average, 10 % of the plants were infected with damping-off. 6 % of the fields were severely infected (> 30 % of the plants affected) by damping-off and 38 % were uninfected or only slightly infected ( < 5% of the plants affected). The incidence of dampingoff was higher in those fields which had been under oilseed rape in earlier years. In a crop rotation experiment, the amount of damping-off increased from 2 % to 20 %, and finally to 38 %, depending upon whether turnip rape had been grown on the same part of the field once, twice or three times. Crops other than Cruciferous ones were grown for 1 or 3 years between the turnip rape crops. Rhizoclonia solani Kiitin was isolated from 76 % of the affected plants. The R. solani isolates produced severe damping-off on rape and turnip rape in pathogenicity tests. R. sotani isolates from barley, potato and lettuce brought about only mild cases of damping-off, or else only a decrease in the growth of the plants. Fusarium avenaceum Sacc. was the only other isolated fungus which was pathogenic.

Resistance in Rhizoctonia solani to tolclofos-methyl

Abstract: Isolates ofRhizoctonia solani were adapted in vitro to grow on a medium amended with tolclofos-methyl at a concentration 500 times that which initially almost completely inhibited growth.

Perforation of Hyphae and Sclerotia of Rhizoctonia solani Kühn by Mycophagous Soil Amoebae from Vegetable Field Soils in Japan

Abstract: Annular depressions and perforations in fungal cell walls were observed on hyphae and sclerotia of Rhizoctonia solani and on conidia of Cochliobolus miyabeanus following burial of these respective fungus propagules for 4 to 8 weeks in vegetable field soils obtained from various locations in Shikoku, Japan. The annular depressions and perforations were 1.0 to 5.5μm in diameter with 1 to 7 perforations per hyphal cell or conidium. Vampyrellid amoebae were isolated from soils and were estimated to number 2.0 to 33.0 per gram of soil. Trophozoites of the amoebae extended 500μm and more with extremely fine filopodia. Plasmotomy was common in large trophozoites before encystment. Digestive cysts were pale yellow, orbicular or elliptic and averaged 33.5×40.1μm in diameter. During excystment, trophozoites emerged through 10 to 20 holes 2.0 to 10.0μm in diameter in the cyst walls. Trophozoites engulfed hyphae in 5 to 20min after attaching to the fungal cell and emptied the contents of the cell within 40 to 90min for hyphae of R. solani and 60 to 120min for conidia of C. miyabeanus. Morphology of the trophozoites and cysts, the mode of encystment and excystment, and the feeding behaviour of the amoebae all match the descriptions for Arachnula impatiens Cienkowski.