Evaluation of Argemone mexicana for Control of Root-Infecting Fungi in Tomato

Argemone mexicana L. (Papaveraceae), a tropical annual weed, is known to be phytotoxic to many crop species. This study was designed to examine the possible impact of A. mexicana on root‐infecting fungi, changes in fungal community structure and the growth of tomato. A. mexicana decaying shoots in soil provided a marked decrease in the infectivity of Fusarium solani and Rhizoctonia solani but Macrophomina phaseolina remained unaffected. Plant height and shoot growth of tomato plants increased markedly though high concentration of A. mexicana (5% w/w) was deleterious to tomato plants. General species diversity of soil fungal communities increased in the amended soils over the controls and greater increase in diversity occurred at higher concentrations of decaying A. mexicana. Likewise, equitability and richness components of diversity increased in treatments compared to controls but declined with increasing sampling period. Aspergillus nidulans, Cephaliophora irregularis, Drechslera halodes, Paecilomyces lilacinus and Trichoderma viride were isolated exclusively from the amended soils. Aqueous extract of A. mexicana when applied in soil greatly suppressed all three of the above root‐infecting fungi, and at lower concentration actually enhanced plant growth. The influence of different levels of N‐fertilization with NH₄NO₃ on the modification of the effect of decaying A. mexicana on root‐infecting fungi was also investigated. N‐fertilization to some extent alleviated the phytotoxicity to tomato plants while suppressing the root‐infecting fungi. A. mexicana in conjunction with Pseudomonas aeruginosa, a plant growth‐promoting rhizobacterium, significantly suppressed root‐infecting fungi with concomitant increase in plant growth. Whereas P. aeruginosa was reisolated from the rhizosphere and inner root tissues of tomato, its population slightly declined in the amended soil but not to an extent that could reduce the biocontrol and growth promoting potential of the bacterium.     

Combination of Pseudomonas aeruginosa and Pochonia chlamydosporia for Control of Root-Infecting Fungi in Tomato

A plant growth‐promoting rhizobacterium, Pseudomonas aeruginosa strain IE‐6, and a fungal antagonist, Pochonia chlamydosporia, were tested for their ability to inhibit mycelial growth of root‐infecting fungi under laboratory conditions including Macrophomina phaseolina, Fusarium oxysporum, F. solani and Rhizoctonia solani. Biocontrol effectiveness of the bacterium and the fungus alone or in combination was also determined for the control of root‐infecting fungi under field conditions. In a dual‐culture plate assay, the colonies of P. chlamydosporia and P. aeruginosa met each other and no further growth of either organism occurred. Against M. phaseolina, F. solani and R. solani, an ethyl acetate extract of the culture filtrates of P. aeruginosa inhibited fungal growth greater than the hexane extract, but against F. oxysporum the hexane extract caused greater inhibition of fungal growth. By contrast, against M. phaseolina, F. oxysporum and F. solani, the hexane extract of P. chlamydosporia was more effective in the inhibition of fungal growth than the ethyl acetate fraction. Ethyl acetate extracts of P. aeruginosa at 1.0 mg/ml not only inhibited the radial colony growth of R. solani but also lysed the fungal mycelium. P. aeruginosa produced siderophores and hydrogen cyanide under laboratory conditions. Field experiments conducted in 1997 and repeated in 1998 revealed that Pochonia chlamydosporia and P. aeruginosa significantly suppressed the root‐infecting fungi M. phaseolina, F. oxysporum, F. solani and R. solani and that the combination of the two caused greater inhibition of the fungal pathogens than either alone. Application of P. chlamydosporia and P. aeruginosa as a soil drench also resulted in enhanced growth of tomato plants.     

Application of Bacillus species in the control of root rot diseases of crop plants

Bio control potential of three Bacillus spp viz., Bacillus subtilis, B. thuringiensis and B. cereus, against soil borne root-infecting fungi on cowpea and mash bean plants were tested both in vitro and in vivo. All three species showed efficiency and produced nodules on mash bean and cow pea plants. In vitro dual culture plate method showed significant inhibition of Fusarium spp. by all these three species of Bacillus with the appearance of a prominent zone of inhibition while a maximum zone of inhibition of Fusarium spp. was observed by B. thuringiensis, whereas in case of Macrophomina phaseolina and Rhizoctonia solani, the highest zone of inhibition was observed by B. subtilis. Bacillus spp. used as seed dressing and soil drenching showed a significant increase in shoot length, shoot weight, root length and root weight in cow pea and mash bean plants. Maximum shoot length was observed in cow pea plants where Bacillus spp. were drenched in soil, whereas maximum root length and root weight in cow pea was observed when B. thuringiensis used as seed dressing. Seed dressing and soil drenching with species of Bacillus viz., B. subtilis, B. thuringiensis and B. cereus, were found to be an effective method for the control of soil borne root-infecting fungi like M. phaseolina, R. solani and Fusarium spp., on cow pea and mash bean plants.     

Cultivar response against root-infecting fungi and efficacy of Pseudomonas aeruginosa in controlling soybean root rot

Abstract

A study was conducted in the greenhouse to examine the resistance of three soybean cultivars against root-infecting fungi, and to determine the role of five strains of Pseudomonas aeruginosa in protecting the roots from these fungal pathogens. In this study soybean cv RAWAL was found to be less susceptible against charcoal rot fungus Macrophomina phaseolina than cvs PARC and BRAGG. Most of the strains of P. aeruginosa used as seed dressing significantly reduced M. phaseolina and Rhizoctonia solani infection on all three cvs PARC, BRAGG and RAWAL (p < 0.05). Most of the strains of P. aeruginosa were effective on cv PARC against Fusarium solani infection, while on cv BRAGG P. aeruginosa strain Pa₃, and on cv RAWAL strain Pa₅ were effective. Both strains Pa₃ and Pa₂₂ gave maximum plant height and fresh weight of shoots, respectively on cvs PARC and BRAGG than other strains. These characteristics make these P. aeruginosa strains good candidates for use as biocontrol agents against soil-borne plant pathogens.     

Rhizobacterial bioformulation for the effective management of Macrophomina root rot in mungbean

Abstract

Fluorescent pseudomonads based bioformulation was evaluated for their ability to control Macrophomina root rot disease in mungbean (Vigna mungo). P. fluorescens isolate Pf1 showed the maximum inhibition in mycelial growth of Macrophomina phaseolina under in vitro conditions. Bioformulation of Pf1 with chitin was effective in reducing the root rot incidence in green gram both under glasshouse and field conditions. The rhizosphere colonization of P. fluorescens was observed appreciable with the green gram plants. However, Pf1 amended with chitin colonized effectively. Furthermore, the induction of defence-related enzymes and chemicals in plants by Pf1 amended with or without chitin and neem were tested. Increased accumulation of defence enzymes viz., phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenol oxidase (PPO), chitinase, β-1,3-glucanse and phenolics were observed in Pf1 bioformulation amended with chitin, pre-treated plants challenge inoculated with M. phaseolina under glasshouse conditions. The present study reveals that in addition to direct antagonism and plant-growth promotion, PGPR strains amended with chitin bioformulation induced defence-related enzymes and pathogenesis related (PR) proteins which collectively enhance the resistance in green gram against the infection of M. phaseolina.     

Suppression of the root rot–root knot disease complex by Pseudomonas aeruginosa in tomato: The influence of inoculum density,nematode populations,moisture and other plant-associated bacteria

The influence of different application rates of the plant growth-promoting rhizobacterium, Pseudomonas aeruginosa, population densities of the root-knot nematode, Meloidogyne javanica, moisture and other plant-associated bacteria in the suppression of root rot–root knot disease complex of tomato are described. The impact of these factors on bacterial rhizosphere and inner root and shoot establishment are also presented. The highest inoculum level of P. aeruginosa (7.4 × 10⁸ cfu ml^–1) in the presence of the lowest population density of M. javanica (500 J2/plant) caused the greatest reduction in gall formation due to M. javanica. The number of root–knot nematodes recovered from soil and roots treated with P. aeruginosa were also significantly reduced. Root infection caused by the soilborne root-infecting fungi Fusarium oxysporum, F. solani and Rhizoctonia solani was also effectively suppressed following application of P. aeruginosa. A P. aeruginosa-Bacillus subtilis treatment was the most effective in the suppression of root-rot disease complex with enhancement of plant growth. Biocontrol and growth promoting potential of the bacterium was enhanced when soil was kept at 50% or 75% moisture holding capacity, whereas a 25% MHC reduced bacterial efficacy. Rhizosphere population of P. aeruginosa declined drastically in P. aeruginosa-Bradyrhizobium japonicum treatments. Rhizosphere colonisation by P. aeruginosa seems to be governed by two factors: Initial inoculum size of the bacterium and severity of the root-knot disease. Endoroot and endoshoot colonisation of the bacterium was dependent on degree of root-colonisation by Fusarium oxysporum. An inoculum level 2.5 × 10⁸ cfu/ml of P. aeruginosa was optimal for the enhancement of plant growth, whereas inoculum below this level reduced plant growth.     

Enzymes Associated with Defence against Toxic Oxygen Species in PCNB-Tolerant and Sensitive Soil Fungi

The specific activities of enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPOX) and glutathione reductase (GR), which are involved in protection against toxic species of oxygen, were determined in mycelia extracts of pentachloronitrobenzene (PCNB)-tolerant and susceptible soil fungi. The organisms assayed were the highly PCNB-sensitive Rhizoctonia solani and Rhizopus arrhizus; Sclerotium rolfsii and Trichoderma harzianum, which are moderately susceptible to PCNB, and the fungicide-tolerant Fusarium oxysporum f. sp. melonis and Pythium aphanidermatum. No GPOX activity was detected in the six examined fungi. Significant differences in the specific activities of the other enzyme systems among the fungi were evident. Remarkably low levels of CAT activities were measured in R. solani. Except for T. harzianum, no meaningful differences regarding SOD, CAT and GR activities with age of the fungi cultures were observed. The electrophoretic patterns of SOD and CAT displayed dissimilarities among the fungi under study. P. aphanidermatum is more polymorphic with respect to both SOD and CAT enzyme systems as compared to the other fungi. The SOD of F. oxysporum f. sp. melonis, R. arrhizus and T. harzianum is a cuprozinc enzyme, while the mangano-SOD species was detected in S. rolfsii, R. solani and T. harzianum.     

Influence of soil impoverishment on the interaction between Glomus mosseae and saprobe fungi

 The effect of the saprobe fungi Wardomyces inflatus (Marchal) Hennebert, Paecilomyces farinosus (Holm & Gray) A. H. S. Brown & G. Sm., Gliocladium roseum Bain., Trichoderma pseudokoningii Rifai and T. harzianum Rifai, isolated from sporocarps of Glomus mosseae, on arbuscular mycorrhizal (AM) colonisation and plant dry matter of soybean was studied in 2/3 and 1/5 diluted soils in a greenhouse trial. Soil dilution to 1/5 had no effect on shoot dry matter of soybean but decreased AM colonisation and root dry weight of plants. CFU of saprobe fungi, except T. harzianum, were higher in 1/5 than in 2/3 diluted soils. W. inflatus and Gliocladium roseum decreased the shoot dry weight of soybean plant when inoculated together with Glomus mosseae. The saprobe fungi P. farinosus and T. pseudokoningii increased the shoot dry weights of plants grown in 1/5 diluted soil. The shoot dry weight and AM colonisation in 1/5 diluted soil were also increased when T. harzianum was inoculated together with Glomus mosseae. Thus, saprobe fungi increased AM colonisation of soybean plants by indigenous endophytes. The AM colonisation of plants at both soil dilutions was increased by Glomus mosseae. The highest level of AM colonisation was observed when P. farinosus and T. pseudokoningii were inoculated together Glomus mosseae. The dilution of soils influenced the interaction between inoculated microorganisms and their effect on plant growth. Accepted: 7 June 1999     

New Insights in Trichoderma harzianum Antagonism of Fungal Plant Pathogens by Secreted Protein Analysis

Trichoderma harzianum ALL42 were capable of overgrowing and degrading Rhizoctonia solani and Macrophomina phaseolina mycelia, coiling around the hyphae with formation of apressoria and hook-like structures. Hyphae of T. harzianum ALL42 did not show any coiling around Fusarium sp. hyphae suggesting that mycoparasitism may be different among the plant pathogens. In this study, a secretome analysis was used to identify some extracellular proteins secreted by T. harzianum ALL42 after growth on cell wall of M. phaseolina, Fusarium sp., and R. solani. The secreted proteins were analyzed by two-dimensional electrophoresis and MALDI-TOF mass spectrometry. A total of 60 T. harzianum ALL42 secreted proteins excised from the gel were analyzed from the three growth conditions. While seven cell wall-induced proteins were identified, more than 53 proteins spots remain unidentified, indicating that these proteins are either novel proteins or proteins that have not yet been sequenced. Endochitinase, β-glucosidase, α-mannosidase, acid phosphatase, α-1,3-glucanase, and proteases were identified in the gel and also detected in the supernatant of culture.     

Integration of Pythium nunn and Trichoderma harzianum isolate T-95 for the biological control of Pythium damping-off of cucumber

Two biological control agents, Pythium nunn and Trichoderma harzianum isolate T-95, were combined to reduce Pythium damping-off of cucumber in greenhouse experiments lasting 3–4 weeks. T. harzianum T-95, a rhizosphere competent mutant, was applied to seeds and P. nunn was applied to pasteurized and raw soils naturally and artificially infested with Pythium ultimum. Some treatments were also amended with bean leaves to enhance the activity of P. nunn. The biological control of Pythium damping-off was evaluated in a Colorado soil (Nunn sandy loam) and an Oregon soil mix, which were replanted twice after 2 and 3 months. Interactions between P. nunn and T-95 were detected in the Colorado but not the Oregon soil. No consistent evidence of antagonism between P. nunn and T. harzianum was seen, and significant interactions were detected in the Colorado, but not the Oregon soil. In the first planting of some treatments, the combination of P. nunn and T. harzianum gave greater control of damping-off than either applied alone. P. nunn was most effective in soils that were pasteurized or amended with bean leaves. T. harzianum controlled Pythium damping-off in the Colorado, but not the Oregon soil. In both soils, disease declined over time in treatments amended with bean leaves but without P. nunn or T. harzianum added. This suppression was greater in the Colorado soil, which contained an indigenous population of P. nunn. This work demonstrates that two compatible biological control agents can be combined to give additional control of a soil-borne plant pathogen.     

Role of Zinc in Rhizobacteria-Mediated Suppression of Root-Infecting Fungi and Root-Knot Nematode

Understanding the environmental factors that influence the rhizosphere and inner root colonization of the disease‐suppressive strains of fluorescent pseudomonads is an essential step towards improving the level and reliability of their biocontrol activity. Soil amendment with Zn at 0.8 or 1.6 mg/kg of soil alone or in combination with Pseudomonas aeruginosa IE‐6S⁺significantly reduced nematode penetration in tomato roots. Zn applied alone did not reduce root infection caused by Macrophomina phaseolina or Fusarium solani but did reduce when used in combination with IE‐6S⁺. Soil amendment with Zn at 0.8 or 1.6 mg/kg of soil alone or in conjunction with IE‐6S⁺ markedly suppressed Rhizoctonia solani infection. Plant height, fresh weight of shoot and protein contents of the leaves substantially improved when used with Zn, however, plants growing in the soil treated with 1.6 mg/kg of Zn in the absence of IE‐6S⁺ not only reduced plant growth but also showed necrotic symptoms on the leaves. Zn application in the soil decreased populations of IE‐6S⁺ both in the rhizosphere and root. A positive correlation between bacterial rhizosphere and inner root colonization was also observed. With an increase in nematode densities in the soil, nematode penetration and subsequent galling due to Meloidogyne javanica increased. Regardless of the nematode densities, Zn applied alone or in combination with IE‐6S⁺ caused marked suppression of M. javanica. At all the population densities of M. javanica, Zn enhanced the efficacy of IE‐6S⁺ to reduce nematode invasion and subsequent gall development. IE‐6S⁺ caused significant suppression of soil‐borne root‐infecting fungi both in Zn‐sufficient and Zn‐deficient soil although this suppressive effect accentuated in Zn‐sufficient soils. In the absence of IE‐6S⁺ and/or Zn, increased nematode densities in the soil significantly reduced plant height, fresh weight of shoot and protein contents of the shoots. With an increase in nematode densities, populations of IE‐6S⁺ in the rhizosphere and root increased regardless of the Zn application. However, Zn‐deficient soils supported larger populations of IE‐6S⁺ compared with those of Zn‐sufficient soils.     

Influence of beneficial microorganisms during in vivo acclimatization of in vitro-derived tea (<Emphasis Type="Italic">Camellia sinensis</Emphasis>) plants

The effects of native isolates of Pseudomonas fluorescens, Azospirillum brasilense, and Trichoderma harzianum on rooting and acclimatization of in vitro-grown shoots and plantlets of tea were evaluated. In vitro bacterization of P. fluorescens failed to establish, while both T. harzianum and A. brasilense retarded shoot growth, eventually overtaking shoot cultures in in vitro rooting. Acclimatization of rooted plantlets in soil amended with bioinoculants, either individually or in various combinations, promoted plantlet survival. Moreover, efficiency of nutrient uptake of plantlets was higher in the presence of microorganisms. Root rot or wilting of tissue culture-derived plants was not observed in bioinoculant-treated plants, as they possessed relatively higher activities of defense enzymes, including peroxidase and phenylalanine ammonia lyase.     

Evaluation of antifungal activity of food additives against soilborne phytopathogenic fungi

The efficacy of eight food additives as possible alternatives to synthetic fungicides for the control of soilborne pathogens, Fusarium oxysporum f. sp. melonis, Macrophomina phaseolina, Rhizoctonia solani, and Sclerotinia sclerotiorum was evaluated in this study. A preliminary selection of food additives was performed through in vitro tests. The ED₅₀, minimum inhibition concentration (MIC), and minimum fungicidal concentration (MFC) values showed that ammonium bicarbonate and potassium sorbate were more toxic to soilborne pathogens compared to other food additives with few exceptions and, therefore selected for further testing in soil. The inhibitory and fungistatic efficacy potassium sorbate were higher than that of ammonium bicarbonate in in vitro tests. Potassium sorbate completely inhibited F. oxysporum f. sp. melonis, M. phaseolina, and R. solani at 0.6% in soil tests. In contrast ammonium bicarbonate at 0.6% was inferior compared to potassium sorbate. Ammonium bicarbonate achieved to control all fungi at 2% that is the highest concentration used in this study. Potassium sorbate showed higher toxicity to all fungi compared to ammonium bicarbonate in soil tests. Both ammonium bicarbonate and potassium sorbate increased the pH of soil. The rate of pH increase was higher in ammonium bicarbonate.     

Biological control of root-rot disease complex of chickpea by AM fungi

Abstract

Six species AM fungi, namely Glomus fasciculatum, G. constrictum, G. intraradices sp., Gigaspora margarita, Acaulospora sp. and Sclerocystis sp., were used for the biological control of root-rot disease complex of chickpea caused by Meloidogyne incognita and Macrophomina phaseolina. Application of these AM fungi increase plant growth, pod number, chlorophyll, nitrogen, phosphorus and potassium contents in diseased plants and also reduced nematode multiplication and root-rot index. G. fasciculatum caused greater increase in plant growth, pod number, chlorophyll, nitrogen, phosphorus and potassium contents of pathogen inoculated plants followed by G. intaradices, G. constrictum, Sclerocystis, G. margarita and Acaulospora sp. Percent root colonization caused by G. fasciculatum was high followed by G. intaradices, G. constrictum, Sclerocystis sp., G. margarita and Acaulospora sp. Glomus fasciculatum also caused higher reduction in root-rot index, galling and nematodes multiplication while Acaulospora sp. produced the least.     

Impact of biocontrol bacteria with Rhizophora mucronata plant parts in suppression of Meloidogyne javanica (treub) chitwood on crop plants

Germination of seeds, shoot length, shoot weight, root length and root weight on okra and mung bean showed promising results when bacterial antagonists viz., Bacillus subtilis, B. thuringiensis, B. cereus and Rhizobium meliloti after multiplication on Rhizophora mucronata plant parts were used at 1% w/w. Complete suppression of root knots was observed on okra and mung bean when R. meliloti and Bacillus subtilis after multiplication on R. mucronata plant parts viz., leaves and stem.     

Use of Rhizobia in the Control of Root Rot Diseases of Sunflower, Okra, Soybean and Mungbean

Biocontrol potential of Rhizobium and Bradyrbizobium against soilborne root infecting fungi was tested. In vitro tests Rhizobium meliloti inhibited growth of Macrophomina phaseolina, Rhizoctonia solani and Fusarium solani while Bradyrhizobium japonicum inhibited M. phaseolina and R. solani producing zones of inhibition. In field R. meliloti, R. leguminosarum and B. japonicum used either as seed dressing or as soil drench reduced infection of M. phaseolina, R. solani and Fusarium spp., in both leguminous (soybean, mungbean) and non-leguminous (sunflower and okra) plants.     

Analysis of Phaseolus vulgaris Response to Its Association with Trichoderma harzianum (ALL-42) in the Presence or Absence of the Phytopathogenic Fungi Rhizoctonia solani and Fusarium solani

The present study was carried out to evaluate the ability of Trichoderma harzianum (ALL 42-isolated from Brazilian Cerrado soil) to promote common bean growth and to modulate its metabolism and defense response in the presence or absence of the phytopathogenic fungi Rhizoctonia solani and Fusarium solani using a proteomic approach. T. harzianum was able to promote common bean plants growth as shown by the increase in root/foliar areas and by size in comparison to plants grown in its absence. The interaction was shown to modulate the expression of defense-related genes (Glu1, pod3 and lox1) in roots of P. vulgaris. Proteomic maps constructed using roots and leaves of plants challenged or unchallenged by T. harzianum and phytopathogenic fungi showed differences. Reference gels presented differences in spot distribution (absence/presence) and relative volumes of common spots (up or down-regulation). Differential spots were identified by peptide fingerprinting MALDI-TOF mass spectrometry. A total of 48 identified spots (19 for leaves and 29 for roots) were grouped into protein functional classes. For leaves, 33%, 22% and 11% of the identified proteins were categorized as pertaining to the groups: metabolism, defense response and oxidative stress response, respectively. For roots, 17.2%, 24.1% and 10.3% of the identified proteins were categorized as pertaining to the groups: metabolism, defense response and oxidative stress response, respectively.     

Management of disease complex of balsam caused by Meloidogyne javanica and Macrophomina phaseolina by using biofertilisers and pesticides

An investigation was conducted to study the effect of biofertilisers (Glomus fasciculatum, Azospirillum brasilense, Azotobacter chroococcum and Micro Phos) and pesticides (carbofuran and bavistin) on the management of root-rot and root-knot disease complex of balsam. The individual application of biofertilisers (G. fasciculatum, A. brasilense and A. chroococcum) significantly improved the plant growth parameters viz., length, dry weight and number of flowers compared to untreated-uninoculated plants. The simultaneous inoculation of plant with Meloidogyne javanica and Macrophomina phaseolina in the pots treated with either of the biofertilisers (G. fasciculatum, A. brasilense and A. chroococcum) and pesticides (carbofuran/bavistin) significantly improved the plant growth parameters and reduced the reproduction factor, number of galls and intensity of root-rot compared to untreated-inoculated plants. On the other hand, the plants treated with Micro Phos neither significantly improved the plant growth parameters nor reduced the reproduction factor, number of galls and intensity of root-rot. Among the biofertilisers and pesticides, carbofuran was found to be the most effective in the management of disease complex of balsam followed by bavistin, G. fasciculatum, A. brasilense and A. chroococcum.     

A selective medium for isolating Rhizoctonia solani from soil

Ko & Hora's (1971) selective medium (FM) for counting Rhizoctonia solani propagules from soil has been modified. FM medium minus gallic acid and fenaminosulf i.e. mineral antibiotic (MA) medium, was amended with inhibitors and fungicides at different concentrations. The modified medium consisting of MA + gallic acid (400 μg ml^-1) + fosetyl-Al (250μgml^-1) was found most efficient in selective isolation of R. solani from soil even in the presence of Macrophomina phaseolina (Rhizoctonia bataticold) and other soil mycoflora. This amended medium was effective in isolating R. solani from soil even when the number of propagules of M. phaseolina present was 10 times greater. The sensitivity of this medium was five times better than Ko & Hora's medium.     

Bacterial antagonists of Sunflower (Helianthus annuus L.) fungal pathogens

Bacteria isolated on nutrient agar and King's medium B from sunflower leaves, crown and roots inhibited in vitro growth of the leaf spot and wilt pathogens Alternaria helianthi, and Sclerotium rolfsii, respectively, and also the root rot pathogensRhizoctonia solani and Macrophomina phaseolina. Antagonistic bacteria from leaves were mainly actinomycetes and pigmented Gram-positive bacteria, while those from roots and crowns were identified asPseudomonas fluorescens-putida, P. maltophilia, P. cepacia, Flavobacterium odoratum andBacillus sp. In soil bioassays, when used as seed inoculum in the presence ofS. rolfsii, P. cepacia strain N24 increased significantly the percentage of seedling emergence. Bacterial strains which exhibited broad spectrum in vitro antagonistic activity were tested for colonisation of sunflower roots, when used as a seed inoculum. Good colonisers (10⁴ to 10⁶ bacteria/g root) were consistent in their ability to reduce disease and fungal wilt. A seedling having a primary root length < 5 cm with fewer lateral roots, necrosed cotyledons or crown and a wilted shoot indicated its diseased status. On an average, only 30% of seedlings were diseased when treated with the antagonistic strains, in the presence of the pathogen, while 60% of the seedlings were diseased in the presence of the pathogen alone. In microplots treated with strain N24, only 1 to 3% of the seedlings were wilted, while 14% of the seedlings were wilted in the presence of the pathogen alone. The results obtained show that bacterial antagonists of sclerotial fungi can be used as seed inocula to improve plant growth through disease suppression