Moniliforme Var Research Articles

FUNGAL PATHOGENIC COMPLEX OF THE ROOT ZONE OF CULTIVATED SOYBEAN PLANTS

FUNGAL PATHOGENIC COMPLEX OF THE ROOT ZONE OF CULTIVATED SOYBEAN PLANTS

EFFECT OF PROPIONIC ACID AND MIXED WAX (BEE-CARNAUBA WAX) ON TOTAL MICROORGANISM AND QUALITY OF PURPLE PASSION FRUIT AT AMBIENT TEMPERATURE

The effects of propionic acid and mixed wax (bees and carnauba wax; MW) on total microorganisms and quality of purple passion fruit at ambient temperature 25±2°C and 70%–80% relative humidity were studied. The fruits were dipped in propionic acid solution at the concentrations of 0.15%; 0.25%; 0.35% (v/v) and 0.2% carbendazim, then coated with MW 2.5% by hand. After drying, they were stored at 25 ± 2 °C for 18 days. Uncoated fruits were preserved at the same temperature as control. The determination parameters were isolation and identification of microorganisms, total microorganism, percentage of fruit decay, weight loss, total soluble solids content (TSS), total sugars, titratable acidity, and ascorbic acid content; interval time was every 3 days of storage time. The results showed that identified two kinds of microorganism were Fusarium moniliforme var. subglutinans and Fusarium oxysporum Schlecht. The concentration of 0.25% propionic acid solution and MW coating could reduce the percentage of weight loss, fruit decay, and total microorganisms for 18 days of storage time. Moreover, this combination could remain chemical qualities, as TSS, total sugars, titratable acidity, ascorbic acid content in 18 days of storage time.

In vitro screening of fungicides and plant extracts against six pathogenic fungi isolated from cotton (Gossypium arboreum L.) seed

Six pathogenic fungi, namely Aspergillus flavus Link., A. niger van Tieghem (Type-I)., Curvularia lunata (Wakker) Boedijn, Fusarium moniliforme var. subglutinans Wr. & Reink., Fusarium sporotrichioides Sherb., Mem. and Rhizoctonia solani J.G. Kuhn were isolated from cotton seeds. Five fungicides viz., Acrobat MZ, Autostin 50 WDG, Capvit 50 WP, Nativo 75 WP and Thiovit 80 WG were selected to evaluate in vitro efficacy at 100, 200, 300, 400 and 500 ppm concentrations against pathogenic fungi following poisoned food technique. Out of 5 fungicides Nativo 75 WP showed the complete growth inhibition of above mentioned six pathogenic fungi at all the used concentrations. Autostin 50 WDG showed complete growth inhibition of all tested pathogenic fungi except Curvularia lunata. Leaf extract of five angiospermic plants viz., Adhatoda vasica, Aegle mermelos, Azadirachta indica, Datura metel and Psidium guajava were selected to evaluate in vitro fungitoxicity at 5, 10, 15 and 20% concentrations against the test pathogens. At 20% concentration, out of the 5 plants extracts A. indica was found to be most active to inhibit the growth of Aspergillus niger (Type-I) (65.56%) and Fusarium moniliforme var. subglutinans (75.00%), Psidium guajava were most active against A. flavus (81.29%) and Curvularia lunata (72.23%), and Datura metel was most active against Fusarium sporotrichioides (64.77%) and Rhizoctonia solani (42.44%).

ANTAGONISTIC ACTIVITY OF A NEW STRAIN OF TRICHODERMA VIRIDE AND ITS EFFECT ON MICROMYCETES POPULATIONS IN THE ROOT ZONE OF CORN PLANTS

Goal. To investigate the antagonistic activity of a new strain of Trichoderma viride F-100076and its effect on the formation of micromycetes populations in the root zone of corn plants underfield conditions. Methods. The antagonistic activity of T. viride F-100076 was studied by the method of mixed (counter) cultures on wort agar using phytopathogenic fungi, which were isolated andidentified in the Laboratory of Plant-Microbial Interactions. The appearance and type of relationship were registered using a scale modified by Symonian and Mamikonian. The number of micromycetes was determined by the method of soil dilutions. Isolation, accounting and cultivation of fungiwas carried out according to conventional methods. Micromycetes were identified according to thedeterminants appropriate for a specific systematic group of micromycetes. Results. It was foundthat T. viride IMB F-100076 is characterized by high antagonistic activity against a wide range ofphytopathogenic fungi, showing hyperparasitism as early as on the eighth day. The highest antagonistic activity of the strain was found against: Alternaria radicina, Acremonium strictum, Acremonium сucurbitacearum, Fusarium oxysporum var. orthoceras, Fusarium moniliforme var. lactis, Torula expansa (5 points on the corresponding Symonian and Mamikonian scale). Data from the mycological analysis of the sod-podzolic soil of the corn rhizosphere showed that the mycocenosis ofthe sod-podzolic soil of the corn rhizosphere was formed by micromycetes belonging to the generaAcremonium Link, Cladosporium Corda, Fusarium Link:Fr, Gliocladium Corda, Mucor Mich, Penicillium Link:Fr, Rhizopus Ehrenb, Trichoderma Hers, among which the most represented were micromycetes of the genus Penicillium (59 %). The total number of fungi in the control variant was291.00 ± 79.67 thousand CFU/g of soil. The introduction of straw affected both the total number ofmicromycetes and the genus composition of fungi. The total number of fungi in the variant withstraw increased 2.6 times and amounted to 744.00 ± 114.67 thousand CFU/g of soil. The number ofrepresentatives of all studied genera of micromycetes also increased. In addition, the introductionof straw provoked the development of fungi of Bipolaris and Fusarium genera, which can be considered a negative outcome since representatives of these species are commonly recognised as pathogens of root diseases. Application of the fungus antagonist T. viride IMB F-100076 to the soilalong with straw did not significantly affect the total number of micromycetes. At the same time, a displacement of fungi of the genus Bipolaris and Fusarium from the rhizosphere of corn was registered.The number of fusaria decreased from 96.00 ± 5.44 to 23.00 ± 2.32 thousand CFU/g of soil or almost4 times and reached the level of the control variant. Fungi of the genus Bipolaris in the variant withthe introduction of trichoderma were not detected. Conclusion. The antagonist fungus T. virideF-100076, introduced into the soil along with straw, strikes root in the soil and exhibits antagonisticactivity against micromycetes of the genera Bipolaris and Fusarium, which are commonly represented by root rot pathogens of many crops. Thus, the new strain T. viride F-100076 allows increasing theantagonistic potential of the rhizosphere soil of corn and protecting plants from pathogens.

Pathogenic potentiality of fungi isolated from seeds of three hill cotton varieties (Gossypium arboreum L.)

Twelve species of fungi, namely Aspergillus flavus Link., A. fumigatus Fresenius., A. niger van Tiegh (Type-I)., A. niger van Tiegh (Type-II), Chaetomium globosum Kunze ex Fr., Curvularia lunata (Wakker) Boedijn, Fusarium moniliforme var. subglutinans Wr. & Reink, F. sporotrichioides Sherb., Mem., Penicillium Link., Pestalotiopsis guepinii (Desm.) Stay., Rhizoctonia solani J.G. Kühn, Rhizopus stolonifer (Ehrenb.: Fr.) Vuill and Trichoderma viride Pers were isolated from the seeds of three cotton varieties (HC-1, HC-2 and HC-3) following “Tissue planting” and “Blotter” methods. Among the isolated fungi, six, namely A. flavus, A. niger, C. lunata, F. moniliforme var. subglutinans, F. sporotrichioides and Rhizoctonia solani showed pathogenic potentiality following seed inoculation technique. These pathogenic fungi had remarkable effect on seed germination, root shoot length and mortality of cotton seedlings.
 Dhaka Univ. J. Biol. Sci. 28(2): 187-193, 2019 (July)

Diversity of Fungi in Rhizoplane, Rhizosphere and Edaphosphere of Sunflower at Different Stages of its Development

AbstractThe genus and species composition of the micromycete complex in the root zone (rhizoplane, rhizosphere and edaphosphere) of sunflower at the beginning of flowering and full maturity stages during its cultivation on leached chernozem was studied. It was established that representatives of the genera Aspergillus, Botrytis, Gliocladium, Fusarium, Paecilomyces, Penicillium, Rhizopus and Trichoderma formed the complex of typical fungi of the rhizoplane and rhizosphere. At the stage of flowering in the mycocenosis, the species Paecilomyces lilacinus, Paecilomyces variotii and Trichoderma viride dominated, and in the maturity stage Rhizopus nigricans, Penicillium nigricans, Botrytis cinerea and Fusarium moniliforme var. subglutinans prevailed. The phytopathogenic complex at the flowering stage formed the species of the genera Fusarium and Rhizopus, and by the end of the vegetation the variety of potential pathogens was expanded by representatives of the genera Alternaria, Botrytis and Gliocladium. A comparative analysis of the micromycete complex revealed a similarity of the dominant species of the rhizoplane and rhizosphere in different stages of sunflower development. However, by the end of the vegetation in the rhizosphere, compared to rhizoplane, the abundance of fungi of the species Fusarium moniliforme var. subglutinans and Penicillium nigricans increased significantly. As for edaphosphere, Rhizopus nigricans, Trichoderma viride and Penicillium nigricans dominated during sunflower flowering, and by the end of the crop vegetation the number of micromycetes of the genus Fusarium was reduced while the proportion of micromycetes of the genus Rhizopus increased significantly.

Evaluation of fungal and bacterial antagonists for managing phytopathogen Fusarium moniliforme var. subglutinans Sheldon, causing Pokkah Boeng disease of sugarcane

In the present investigation potential fungal and bacterial antagonists were tested under laboratory and field conditions against the phytopathogen Fusarium moniliforme var. subglutinans Sheldon, causing Pokkah Boeng disease of sugarcane. Different strains of fungal anatagonists viz; Trichoderma spp. (strains TCMS36, TCMS43, Th3, TCMS9, Th14) and bacterial antagonists viz; Pseudomonas fluorescens (strains Psf173 and Psf02) and Bacillus sp. were tested against the pathogen under in vitro conditions by employing dual culture technique and volatile assay. The results from dual culture revealed that TCMS36 showed the maximum radial growth inhibition i.e., 73.33 per cent followed by Th14 (69.01%), Psf02 (68.33%), Th3(66.04%),TCMS43 (64.7%), Bacillus sp. (63.95%) and TCMS9(63.74%). Volatile assay depicted that the maximum radial growth inhibition was found in TCMS36(70.01%) followed by TCMS9 (60.10%), Th3 (57.25%), Th14 (55.36%), Psf02 (50.83%) and Bacillus sp. (51.79%), while minimum growth inhibition was observed in Psf173 (40.49%). Further studies were conducted in field, where, Th 14, Psf02 and the consortium of both (Th 14+Psf 02) were tested through sett treatment. The minimum disease incidence was observed in the treatment where setts were treated with P. fluorescens (Psf02) followed by consortium (Th 14+Psf 02) and Th 14 i.e. 0.92%, 1.51% and 5.53%, respectively. The findings from research conclude that the fungal and bacterial antagonist strains can exert an inhibitory effect on the radial growth of Fusariu m sp. as well as reduce the disease incidence in field. Application of these antagonists in field could be a better management tool without having to depend on hazardous chemicals.

HOST PATHOGEN INTERACTION STUDY IN MALFORMED AFFECTED TISSUES OF <i>MANGIFERA INDICA</i> L.

The malformation disease of mango by Fusarium moniliforme var. subglutinan is one of the major causes of huge economical loss every year. Early diagnosis of the pathogens can help cultivators to protect the mango orchid and fruits from successive and secondary inf ection. The molecular detection is one of the bette r choices among available techniques for diagnosis. B ut the farmers or individual cultivars from tropica l and subtropical countries like India, Pakistan, Malaysi a, Vietnam, Philippines, have lots of limitation to use molecular method. Another problem with this pathogen is lack of specific biomarker. Thus the present s tudy was designed to develop a morphological and histopa thological methodology to detect Fusarium moniliforme var. subglutinans and its host-pathogen interaction between fungus a nd hot tissues. Fresh and preserved (Formaldehyde: Acetic Acid: Alcohol (FAA) solution) tissues were used to check the efficacy of the method. The inter and intracellular distributio n of fungal hyphae, in various tissue like cortex, phloem and parenchymatous pith cell, was clearly revealed by this method. The characteristics which were obse rved like detection of the mycelium threads at the junct ure of the shoot tip, axillary buds, petels and sep als axis of the malformed or infected tissues. The Resin acc umulation in the parenchymatous and other cells of vegetative tissue was also found as characteristics of this pathogen infection. This study is being al so important in terms of identification and growth beh avior of the pathogen.

Hisopathological Study of Healthy and Malformed Tissues of Mango (Mangifera indicaL.)

Malformation is a serious threat to mango production in India and other mango growing countries (tropical and subtropical) of the world. The disease is widespread in flowers and vegetative shoots. It has a crippling effect on mango production causing heavy economic losses. Mango Malformation Disease is a fungal disease caused by Fusarium moniliforme var. subglutinans. Symptoms of the disease include loss of the apical dominance and swelling of vegetative buds, proliferation of leaves and flowers, phyllody and hypertrophy of panicle axes. Histopathological observations of malformed shoots and penical reveal occasional inter-and intracellular distribution of fungal hyphae in cortex, phloem and parenchymatous pith cell. Fungal mycelium has also been detected at the juncture of the shoot tip in malformed axillary buds, axes of petels and sepals of malformed buds, and in the degenerating embryos of mustard stage malformed fruits.

Defence-related biochemical changes by elicitor of malformation pathogen, Fusarium mangiferae, in mango

Malformation of mango (Mangifera indica L.) induced by Fusarium moniliforme var. subglutinans is a plant disease of international importance. The paper reports the downstream defence responses at the initial stage in a susceptible host (cultivar Amrapali) after treatment with biotic (isolated from the pathogen cell wall) (BEL) and abiotic (salicylic acid, SA) elicitors, and inoculation of vegetative buds with the pathogen (IVB). The SA was further tested to induce resistance in field trials. The inoculation and application of elicitors increased β-1, 3 glucanase that causes lysis of fungal hyphae by many folds. Hydrogen peroxide (H2O2) (active oxygen species) that induces hypersensitive cell death was reduced to the minimum level after treatment with BEL. The reduction of H2O2 in the inoculated vegetative buds was also substantial; however, comparatively less with SA treatment. Consequently, there was no hypersensitive cell death in the malformed mango. Salicylic acid that enhances H2O2 content by suppressing H2O2-degradation by catalase, increased marginally with the SA treatment and in the IVB, but reduced with the BEL. The reduction of SA in BEL-treated buds concomitantly reduced its H2O2 content. The activity of catalase, suppressor of resistance mechanism, was reduced in all the treatments, but the reduction was not enough to arrest H2O2-degradation. Magiferin (1, 3, 6, 7-tetrahdroxyxanthone C2-β-D glucoside), a defence metabolite of mango, increased substantially in all the treatments; maximum with the BEL. A pathogenesis-related (PR) protein of 20 KDa that resists symptom development appeared in all the treatments except the control. But light colour of the spots for the PR-protein indicated low protein accumulation. The maximum accumulation was with the IVB followed by SA and BEL treatments. The amount of total protein reduced considerably in all the treatments. The SA treatment on healthy plants failed to induce defence against malformation. Contrarily, the treatment on malformed seedlings restored normal growth within two months. Hence, SA acted better over the infected plants in presence of the pathogen. Thus, a signal transduction system involving SA and H2O2 remained nonfunctional and enough defence chemicals could not be synthesised. Defence genes that produce phenolic and β-1, 3 glucanase, however, became activated and saved the plants from death although could not prevent symptom manifestations.

Biocontrol potential of Trichoderma species against mango malformation pathogens

Malformation disease of Mango (Mangifera indica L.) caused by Fusarium moniliforme var. subglutinans is one of the most destructive diseases, which is a major production constraint in the mango-growing regions of India. In this study, The bioagents Trichoderma viride (Tr1), Trichoderma virens (Tr2) and Trichoderma harzianum (Tr3) were evaluated in culture with the pathogens to monitor the antagonistic effect and their volatile compound and culture filtrates (non-volatile compound). It was found that all the three isolates of bioagents significantly checked the growth of F. moniliforme var. subglutinans. In dual culture, the best result was obtained with T. harzianum followed by T. virens and T. viride. A similar result was also observed in the case of culture filtrates ofTrichoderma spp. The results clearly showed that inhibition of the growth of the fusaria isolates by T. harzianum was significantly superior to T. viride andT.virens. In case of antifungal activity of volatile compounds released by Trichoderma isolates, it was also observed that T. virens was more superior to T.harzianum and T. viride.

Ginsenoside F1 production from ginsenoside Rg1 by a purified β-glucosidase from Fusarium moniliforme var. subglutinans

Fusarium moniliforme var. subglutinans was selected from among 100 strains of fungi for producing ginsenoside F(1) from ginsenoside Rg(1). The enzyme responsible was purified as a single 85 kDa band with a specific activity of 136 U mg(-1). It hydrolysed glucose-linked ginsenosides Rb(1), Rd and Rg(1) but not for other monosaccharide-linked ginsenosides, Rb(2), Rc, R(1), and Re. Under the optimum conditions of pH 6.0, 50 °C, 30 U l(-1) of enzyme, and 5 mg Rg(1) ml(-1), 4 mg F(1) ml(-1) was produced after 4 h, with a molar yield of 100% and a productivity of 1 g l(-1) h(-1). This represents the highest productivity and conversion yield of F(1) yet reported.

First report ofFusarium moniliformevar.anthophylumaffectingDieffenbachia pictavar.tropicin Buenos Aires, Argentina

This is the first report of Fusarium moniliforme var. anthophyllum affecting foliage plants of Dieffenbacchia in Argentina. It appears to be the first report of the isolation and description of the causal agent of this disease on this host in the world.

Mango Malformation Disease and the Associated Fusarium Species

ABSTRACT Mango malformation disease (MMD) occurs in Asia, Africa, and the Americas and was first reported in India in 1891. The vegetative form of MMD was first reproduced in 1966 with Fusarium moniliforme and the floral form with isolates of F. moniliforme var. subglutinans from both vegetative shoots and floral tissue. The fungi were subsequently recognized as F. subglutinans. In 2002, a new species, F. mangiferae, was established based on nuclear and mitochondrial DNA sequences; it included strains of F. subglutinans from Egypt, Florida, Israel, Malaysia, and South Africa, some of which had been shown to cause MMD by artificial inoculation. At least three additional taxa have been associated with MMD: F. sterilihyphosum from Brazil and South Africa, and Fusarium sp. nov. and F. proliferatum (teleomorph: Gibberella intermedia) from Malaysia. To date, Koch's postulates have not been completed with them. In the future, gene sequencing will be essential to identify the Fusarium spp. that are associated with MMD. Work remains to be done on the morphology, sexual compatibility, pathogenicity, and toxigenicity of these taxa.

Gibberella circinata

<i>Gibberella circinata</i>

Responses of conifer species of the Great Lakes region of North America to inoculation with the pitch canker pathogen Fusarium circinatum

SummaryFive conifer species grown in the Great Lakes region of North America were examined for their susceptibility to Fusarium circinatum, (syns. Fusarium subglutinans f. sp. pini and F. moniliforme var. subglutinans), the causal agent of pitch canker. Three‐year‐old (3‐0) seedlings of red (Pinus resinosa), jack (P. banksiana) eastern white (P. strobus), Scots (P. sylvestris) and Austrian (P. nigra) pine were planted in 4 l pots in a greenhouse at Auburn University in November 1998. In April and June 1999, seedlings were inoculated by removing a needle fascicle approximately 5 cm from the terminal bud and placing a drop containing F. circinatum conidia on the wound. Resin production, canker length and seedling mortality were recorded 12 weeks later. Jack, Scots and eastern white pine were the most susceptible with Austrian and red pine more resistant to the fungus. F. circinatum was re‐isolated from 37% to 96% of inoculated seedlings. The susceptibility of jack, Scots and eastern white pine indicates a potential risk to these important species of the region if F. circinatum were to be introduced into the area.

Effect of aqueous extracts of medicinal plants on growth of Fusarium moniliforme var subglutinans Wollenw. and Reinking.

The growth of Fusarium moniliforme var subglutinans Wollenw. and Reinking was evaluated in chloramphenicol potato dextrose agar (cPDA) containing 20 %aqueous extractsof eight medicinal plants. Mycelia growth, was reduced in unautoclaved extracts of Cassia alata, Baphia nitida, Euphorbia hirta, Vernonia amygdalina, Azadirachta indica, and Zingiber officinale, with B. nitida, V. amygdalina, and C. alata, being the most effective. On the contrary, the unautoclaved extract of Cyathula prostrata did not affect the growth of the fungus. The antifungal activities of B. nitida, A. indica, E. hirta, Z. officinale, and C. alata were affected by autoclave treatment. Unautoclaved extracts of C. alata, B. nitida, A. indica, V. amygdalina, A. cordifolia, E. hirta and Z. officinale significantly (p£0.05) reduced the dry weight of the fungus below the control. Autoclaving the extracts affected the fungitoxic activities of C. alata, B. nitida, and V. amygdalina, on the dry weight of the fungus. Sporulation was completely inhibited in cPDA medium amended with unautoclaved extracts of C. alata, B. nitida, A. indica, V. amygdalina and Z. officinale. However all the autoclaved extracts supported sporulation of the fungus. Conidia germination in full strength (w/v, 1:1) extracts was completely inhibited, whereas 90 % of the conidia germinated in sterile deionised water after 6 h of incubation. These findings suggest the potential role of the extracts in controlling the fungus. Keywords: Fusarium moniliforme var subglutinans, medicinal plants, aqueous extracts, in vitro growth inhibition. [Global Jnl Agric Res Vol.2(1) 2003: 9-16]

Two herbivore-deterrent iridoid glycosides reduce the in-vitro growth of a specialist but not of a generalist pathogenic fungus of Plantago lanceolata L

Many secondary plant compounds are involved in defense against both insect herbivores and pathogens. Two secondary plant compounds of Plantago lanceolata, the iridoid glycosides catalpol and its precursor aucubin, are well known for their deterrent effects on generalist and non-adapted specialist insect herbivores. We tested the effects of these compounds on the in-vitro growth of a specialist and generalist fungal pathogen of this host species. Two chemical forms of these iridoids were tested. The glycosides and their aglycones, the products of enzymatic conversion by specific $/Beta$-glucosidase enzymes. The glycosides enhanced growth of both the specialist fungus Diaporthe adunca and the generalist fungus Fusarium moniliforme var. subglutinans. The positive effect of these glycosides on the generalist fungus is in sharp contrast with the generally negative effects of these glysosides on generalist insect herbivores. The aglycones of aucubin and catalpol reduced the growth of the specialist fungus D. adunca, but, contrary to expectation, enhanced the growth of the generalist fungus F. moniliforme var. subglutinans. Effects of aucubin on D. adunca were stronger than effects of catalpol. This was true both for the growth stimulating effects of the glycosides and for the fungitoxic effects of the aglycones. We therefore expect that the effects of these iridoids in P. lanceolata on the specialist fungus will strongly depend on the ratio between catalpol and its precursor aucubin and the chemical form (glycoside or aglycone) in which these compounds are encountered by the fungus during growth. Our results suggest that iridoid glycosides in P. lanceolata can be used as defense against both herbivores and pathogens, but that their effects are highly specific with respect to the natural enemy species that is encountered.

Interactions between Foliar Pathogens and the Saprophytic Microflora of the Wheat (Triticum aestivum L.) Phylloplane

AbstractHyphal interference between 10 saprophytic micro‐organisms isolated from wheat phylloplane against four target pathogens (Septoria tritici, Alternaria triticimaculans, Bipolaris sorokiniana and Drechslera tritici‐repentis) were studied microscopically. Antagonism was measured as the ability of the saprophytic micro‐organisms to induce morphological changes of hyphae and spores of the pathogens and to reduce conidial germination. Typical reactions included formation of chlamydospores, encircled hyphae, plasmolysis, vacuolation and granulation of hyphae. Ungerminated malformed conidia, lysis, and the formation of inflated germ tubes on germinating conidia were also observed. Paecilomyces lilacinus and Bacillus sp. possessed the greatest capacity for interference. Fusarium moniliforme var. anthophilum, Epicoccum nigrum and Chaetomium globosum were next in order of the range and severity of interference. Spore germination of S. tritici was significantly reduced in the presence of P. lilacinus, F. moniliforme var. anthophilum, E. nigrum, Bacillus sp., Cryptococcus sp. and Nigrospora sphaerica, with levels of inhibition of up to 69%. Paecilomyces lilacinus, Cryptococcus sp., F. moniliforme var. anthophilum and N. sphaerica caused a reduction of spore germination of 47–60% with the greatest effect being against B. sorokiniana. Chaetomium globosum, P. lilacinus, Rhodotorula rubra and Bacillus sp. significantly reduced spore germination of A. triticimaculans. E. nigrum, F. moniliforme var anthophilum, Stemphylium sp., P. lilacinus and Bacillus sp. caused the greatest reduction in D. tritici‐repentis. Greenhouse experiments on pathogen–antagonist interactions on the wheat phylloplane showed the potential value of some of the antagonists for controlling the pathogens. If parasitism occurs in nature, the native micro‐organisms might be useful for biological control by competing with the pathogens and so regulating their colonization of wheat leaves.

Tratamento fungicida de sementes de milho contra fungos do solo e o controle de Fusarium associado às sementes

As sementes de milho infectadas por fungos constitue importantes fontes de inóculos, cujos patógenos podem causar podridões de sementes, morte de plântulas em pré e pós-emergência e podridões radiculares. Ademais, em condição de solo frio e úmido há maior exposição das sementes ao ataque de fungos do solo. Assim, estudou-se a eficiência dos fungicidas captan (120,0; 90,0 e 60,0 g i.a. 100 kg-1 de sementes), thiram (140,0) formulado em PM e SC, thiabendazole (20,0), thiram + thiabendazole (75,0 + 10,0) e carboxin + thiram (75,0 + 75,0) no tratamento de sementes de milho da cultivar BR 106. Foram avaliadas as características : sanidade de sementes; emergência de plântulas no campo, em solo esterilizado; bem como as emergências nos testes de frio em solo de campo, em solo esterilizado, em solo infectado separadamente com Fusarium moniliforme var. subglutinans, Pythium aphanidermatum e Rhizoctonia solani. A eficiência dos fungicidas variou de acordo com as características avaliadas, com exceção do thiabendazole, que foi ineficiente para quase todas as características. A presença de F. moniliforme var. subglutinans em sementes de milho não afetou a germinação, porém em solos frios e úmidos os fungos P. aphanidermatum, F. moniliforme var. subglutinans e R. solani promeveram redução na germinação.