Antifungal activity of berberine iodide, a constituent ofFumaria indica

Berberine iodide, an isoquinoline alkaloid was isolated fromFumaria indica and its efficacy was tested against spore germination of some plant parasitic as well as saprophytic fungi. The alkaloid significantly curbed spore germination ofCurvularia lunata, Erysiphe cichoracearum, E. pisi, Fusarium udum andPenicillium species. Complete inhibition (100%) of spore germination was observed inE. cichoracearum andPenicillium species at 1.5 g/L.Albugo candida andAlternaria species were not affected by the chemical.     

Fungi isolated from Sclerotia ofSclerotium cepivorum and from soil and their effects upon the pathogen

Summary Data are presented on the antagonistic effects of the fungi isolated from sclerotia ofSclerotium cepivorum and from nonrhizosphere soil taken from around the roots of infected onions upon mycelial growth and sclerotial germination ofS. cepivorum. Most of the isolated fungi especiallyPenicillium species were antagonistic to mycelial growth. Sclerotial germination was slightly inhibited by diffusates of these fungal isolates. Testing the antifungal effect of someAllium extracts against the fungal isolates by the inhibition zone method showed that garlic extract has the greatest antifungal effects and onion extract is the least potent. However, spore germination tests indicated that onion extract completely inhibits the spore germination of all test fungi. The role of host-plant extracts in stimulating sclerotial germination is discussed.     

Arbuscular mycorrhizal fungi on adjacent semi-natural grasslands with different vegetation in Japan

Arbuscular mycorrhizal (AM) fungi on Japanese semi-natural grasslands were investigated at three adjacent sites with different vegetation. The predominant grasses at the three sites were 1)Pleioblastus chino, 2)Miscanthus sinensis andArundinella hirta (M. sinensis/A. hirta), and 3)Zoysia japonica, respectively. The degree of colonization was higher inM. sinensis/A. hirta than inP. chino andZ. japonica. AM fungi were recovered by spore extraction and by pot cultures started from soil inoculum or from transplanting of field plants. Total spore number obtained by the spore extraction method was highest in the rhizosphere ofM. sinensis/A. hirta and lowest in that ofP. chino. AGlomus sp. resemblingG. geosporum predominated in association withM. sinensis/A. hirta andP. chino. FromZ. japonica, three species,Acaulospora gerdemannii, Glomus leptotichum, and a species resemblingG. clarum, were isolated by pot culture from soil and two species,A. longula andScutellospora cerradensis, by pot culture from transplanting ofZ. japonica. FromM. sinensis/A. hirta, one species,A. longula, was found by pot culture from soil. FromP. chino, no AM fungus was detected by either method. Single-spore culture confirmed thatG. leptotichum andA. gerdemannii are conspecific.     

Effect of berberine and (±)-bicuculline isolated from<Emphasis Type="Italic">Corydalis chaerophylla</Emphasis> on spore germination of some fungi

Berberine and (±)-bicuculline were isolated from roots and leaves, respectively, ofCorydalis chaerophylla. Both were effectivein vitro against spore germination of some plant pathogenic fungi (Alternaria brassicicola, A. brassicae, A. cheiranthi, A. melongenae, A. solani, Colletotrichum musae, C. falcatum, Curvularia penniseti, C. lunata, C. maculans, C. pallescens, Curvularia sp.,Erysiphe pisi, E. cichoracearum, Erysiphe sp.,Fusarium udum, Helminthosporium spiciferum, H. penniseti, H. frumentacei, Heterosporium sp.,Oidium erysiphoides andUstilago cynodontis). Berberine and (±)-bicuculline significantly inhibited spore germination of all the fungi at concentrations of 100–1000 ppm. Berberine was effective against all the fungi at all concentrations; most of the fungi did not germinate at 1000 ppm.H. penniseti conidia did not germinate at any cencentration of (±)-bicuculline.U. cynodontis was the least sensitive fungus at lower concentrations but 800 ppm dose was highly effective.     

Multiple allelopathic activity of the crustose coralline algaLithophyllum yessoenseagainst settlement and germination of seaweed spores

A study was made to investigate possible formation by the crustose coralline algaLithophyllum yessoenseof multiple allelopathic-related substances against the settlement and germination of spores of various seaweeds. Seven different solvents (n-hexane, diethyl ether, acetone, ethyl acetate, acetonitrile, methanol, distilled water) and seawater were used to obtain crude extracts and secretory exudates from the coralline alga. The extracts and the algal conditioned seawater were tested for inhibitory activity against the settlement and germination of spores from 17 species representing 15 genera. Spore settlement of 14 species was inhibited over 90% by one or more extracts of the six organic solvents and conditioned seawater. The germination of spores from 13 species was inhibited by one or more extracts of all seven solvents and conditioned seawater. The species where spore settlement was not significantly affected showed strong inhibition of germination, andvice versa.     

Antifungal activity of Δ3-alstovenine, a plant alkaloid isolated fromAlstonia venenata

A plant quaternary alkaloid Δ³-alstovenine inhibited the spore germination of most of the fungi tested at concentration of 250–1000 mg/L. Saprophytic and biotrophic fungi were equally sensitive to the alkaloid.Cercospora sp. was the most sensitive as 100% inhibition of spore germination was observed at 250 mg/L.Alternaria species,Curvularia species andFusarium udum were not affected even at 1000 mg/L.     

Studies on spore germination and growth of some mycorrhizal-associated basidiomycetes

Summary Aqueous extracts of Western Hemlock roots were tested for the ability to stimulate initiation of growth from carpophore tissue of certain mycorrhizal-associated fungi. Of numerous species tested, onlyRozites caperatus andInocybe napipes responded slightly to this treatment, initiating a feeble mycelial development from gill tissue fragments.To determine whether exogenous NAD or young, excised roots would stimulate the growth of certain mycorrhizal fungi, species ofAmanita, Tricholoma, andXerocomus were subcultured in a rich basal medium, with and without added NAD or excised tomato roots. Spore germination tests on mycorrhizal-associated species not previously subcultured were conducted in a similar fashion.Added NAD stimulated the growth ofLeucopaxillus amarus but inhibited development ofArmillaria zelleri. It was without pronounced effect on the other cultures. In the presence of excised tomato roots, growth of theLeucopaxillus species was also stimulated, butArmillaria zelleri was inhibited slightly andXerocomus chrysenteron almost completely. Both treatments were without essential effect on the other species tested.No positive results were obtained with either added NAD or excised tomato roots in the spore germination studies.     

The selective allelopathic interaction of a pasture-forest intercropping in Taiwan

An allelopathic interaction of a pasture-forest intercropping system was evaluated by field and greenhouse experiments and by laboratory assays. A study site was situated in the farm of Hoshe Forestry Experiment Station at Nantou County, Taiwan. After deforestation of Chinese fir (Cunninghamia lanceolata), a split plot design of 8 treatments was set up: open ground without planting as control, planted with kikuyu grass, planted with kikuyu grass andAlnus formosana, planted with kikuyu grass andZelkova formosana, planted with kikuyu grass andCinnamomum camphora, planted withA. formosana, planted withZ. formosana, and planted withC. camphora. Field measurements showed that weeds grew luxuriantly six months after treatment in plots which had not been planted with kikuyu grass. However, the growth of weeds was significantly retarded but that of woody plants was not affected when the plots were planted with kikuyu grass. As compared with the tap water control, the aqueous leachate of kikuyu grass stimulated the seedling growth ofC. camphora andA. formosana, but the extract stimulated the growth ofC. camphora and inhibited that ofA. formosana. In contrast, the aqueous extracts of three hardwood plants exhibited variable inhibition on the root initiation of kikuyu grass, and the extract ofZ. formosana revealed the highest phytotoxic effect. The aforementioned extracts and leachates were bioassayed against seed germination and radicle growth of four test plants, namely annual rye grass, perennial rye gras, tall fescue, and Chinese cabbage and against seedling growth ofMiscanthus floridulus. The extract ofZ. formosana revealed the highest phytotoxic effect on the test species while that of kikuyu grass showed the least effect. By means of paper chromatography and high performance liquid chromatography, phytotoxic phenolics were identified and the amount of phytotoxins present was highest in the extract ofZ. formosana but was lowest in that of kikuyu grass. The degree of phytotoxicity and amount of phytotoxins was in good correlation, indicating that a selective allelopathic effect was involved. The findings suggest that allelopathy may contribute benefits in the intercropping system to reduce the need for herbicides and to lessen the labour cost for weed control.Paper No. 346 of the Scientific Journal Series of the Institute of Botany, Academia Sinica, Taipei, Taiwan, Republic of China. This study was supported in part by grants of Academia Sinica, Taipei, and Council of Agriculture, Executive Yuan of the Republic of China.     

Seasonal variation of arbuscular mycorrhizal fungi in temperate grasslands along a wide hydrologic gradient

We studied seasonal variation in population attributes of arbuscular mycorrhizal (AM) fungi over 2 years in four sites of temperate grasslands of the Argentinean Flooding Pampas. The sites represent a wide range of soil conditions, hydrologic gradients, and floristic composition. Lotus glaber, a perennial herbaceous legume naturalised in the Flooding Pampas, was dominant at the four plant community sites. Its roots were highly colonised by AM fungi. Temporal variations in spore density, spore type, AM root colonisation, floristic composition and soil chemical characteristics occurred in each site and were different among sites. The duration of flooding had no effect on spore density but depressed AM root colonisation. Eleven different types of spores were recognized and four were identified. Two species dominated at the four sites: Glomus fasciculatum and Glomus intraradices. Spore density was highest in summer (dry season) and lowest in winter (wet season) with intermediate values in autumn and spring. Colonisation of L. glaber roots was highest in summer or spring and lowest in winter or autumn. The relative density of G. fasciculatum and G. intraradices versus Glomus sp. and Acaulospora sp. had distinctive seasonal peaks. These seasonal peaks occurred at all four sites, suggesting differences among AM fungus species with respect to the seasonality of sporulation. Spore density and AM root colonisation when measured at any one time were poorly related to each other. However, spore density was significantly correlated with root colonisation 3 months before, suggesting that high colonisation in one season precedes high sporulation in the next season.     

Antifungal activity of several medicinal plants extracts against the early blight pathogen (Alternaria solani)

The antifungal activity for several medicinal plants against the early blight fungus (Alternaria solani) has been investigated. These plants were Syrian marjoram (Majorana syriaca), rosemary (Rosmarinus officinalis), Greek sage (Salvia fruticosa), roselle (Hibiscus sabdariffa) and cotton lavender (Santolina chamaecyparissus). The inhibitory effect of these extracts on the radial mycelial growth as well as on spore germination was measured in vitro at various concentrations of crude extract (0.5 g dry plant powder/ml medium). Extracts of M. syriaca and H. sabdariffa were most effective causing total inhibition of mycelial growth and spore germination at 8–10% concentration. Extract of R. officinalis also caused total inhibition of the above two parameters but at double the concentration (20%). Extracts of S. fructicosa and S. chamaecyparissus produced relatively moderate antifungal activity. At 25% concentration, these extracts showed an incomplete inhibition in mycelial growth being around 75–85% and 70–90%, respectively. However, at this same concentration both plant extracts produced total inhibition of spore germination. Results of this study indicated that both extracts of M. syriaca and H. sabdariffa were strong inhibitors of this fungus and to levels comparable to standard fungicides. Further studies are required to determine the effect of these extracts in vivo to evaluate their potential as natural treatments for this disease.     

Parasitism ofLygus lineolaris eggs onCoronilla varia,solanum tuberosum,and three host weeds in southeastern Québec

Parasitism ofLygus lineolaris (Palisot de Beauvois) eggs by three species ofMymaridae, Anaphes iole Girault,Erythmelus miridiphagus Dozier andPolynema pratensiphagum Walley and one species ofScelionidae, Telenomus sp., was investigated at Ste-Anne-de-Bellevue, Québec. The maximum level of field parasitism ofL. lineolaris eggs by individual species was 15.4, 53.8, 70.0 and 16,7%, respectively. Parasitoids were retrieved from eggs ofL. lineolaris inserted in stems and branches ofAmaranthus retroflexus L.,Chenopodium album L.,Coronilla varia L.,Rumex obtusifolius L. andSolanum tuberosum L. Amaranthus retroflexus andS. tuberosum sustained a large population ofL. lineolaris and egg parasitism was high enough to consider it as a potential control factor.      

Contribution to the biology of germination of four species ofChenopodium album agg. under different condition

The study investigated various factors stimulating germination of seeds of four species ofChenopodium album agg.—C. album L. s. str.,C. ficifolium Sm.,C. strictum Roth,C. suecicum J. Murr. These factors were: storage in wet and cold, alternating temperature, nitrates mainly in combination with light and, to a lesser degree, the duration of chilling. Germination was inhibited by darkness, which was most marked with seeds ofC. strictum. The effect of alternating temperature was better on the germination ofC. ficifolium andC. suecicum than on that ofC. album andC. strictum. We also discussed several differences in specific reactions of the individual species to the factors under consideration.     

Energetic aspects of spore germination in filamentous fungi

The antifungal activity of substances interfering with the function and biogenesis of mitochondria was studied. Strict anaerobiosis, cyanide, azide, oligomycin, bongkrekic acid and ethidium bromide were found to prevent spore germination ofAspergillus niger andPenicillium italicum in liquid germination medium. The effect of azide, oligomycin and ethidium bromide was fungicidal. Cyanide and azide completely inhibited the incorporation of¹⁴C-leucine and¹⁴C-uracil into germinating conidia ofA. niger. Oligomycin and ethidium bromide reduced the extent of incorporation of both precursors in the first few hours of conidial germination and at later stages stopped it completely. The inhibition of both spore germination and macromolecules synthesis during the germination ofA. niger conidia were in relation to the specific inhibitory effect of the agents on respiratory activity of dormant conidia and mycelial cells. The results indicate that both the function of mitochondrial genetic and protein synthesizing systems and the function of oxidative phosphorylation are essential for normal spore germination and fungal growth.     

Seed germination ofGaleola altissima,an achlorophyllous orchid,with aphyllophorales fungi

Seed germination test ofGaleola altissima was carried out with five aphyllophorales fungi:Erythromyces crocicreas, Ganoderma australe, Loweporus tephroporus, Microporus affinus andPhellinus sp.. All five species were effective for seed germination of the orchid.Erythromyces crocicreas, which has hitherto been regarded as the only endomycorrhizal fungus of the orchid, was confirmed to be effective for further development of the orchid.     

Antagonistic interactions between fungal pathogens and phylloplane fungi of guava

Dominant phylloplane fungi of guava (Psidium guajava L.) were screened for their antagonistic activities against the two pathogens,Colletotrichum gloeosporioides andPestalotia psidii, bothin vitro andin vivo. Culture filtrates ofAspergillus niger, Fusarium oxysporum andPenicillium citrinum caused more than 50% growth inhibition ofC. gloeosporioides. Filtrates ofCephalosporium roseo-griseum andF. oxysporum were most effective in reducing the growth ofP. psidii. Volatiles produced from the cultures ofA. niger, F. oxysporum, P. citrinum andP. oxalicum inhibited the growth ofC. gloeosporioides, whereas volatiles fromC. roseo-griseum, F. oxysporum andTrichoderma harzianum inhibited the growth ofP. psidii. The inhibitory effect of volatiles decreased with increase in incubation time. In general, the maximum effect of volatiles was noticed after 48 h incubation. Different grades of colony interactions in dual cultures were recognised between the two pathogens and the phylloplane fungi examined. Maximum inhibition ofC. gloeosporioides was caused byAureobasidium pullulans, Cladosporium cladosporioides, epicoccum purpurascens, F. oxysporum andMyrothecium roridum, whereasAspergillus terreus, C. roseo-griseum andP. oxalicum significantly reduced the growth ofP. psidii. Application of a spore suspension of each test fungus inhibited lesion development of guava leaves caused by the test pathogensin vitro. Inhibition was more pronounced when the spore concentration was increased.A. pullulans, C. cladosporioides, E. purpurascens, F. oxysporum, andT. harzianum were found to be strongly antagonistic toC. gloeosporioides. A. niger, A. terreus, C. roseo-grisem andT. harzianum were strongly antagonistic toP. psidii.     

Seed treatment with aqueous extract of Viscum album induces resistance to pearl millet downy mildew pathogen

Abstract

Downy mildew (Sclerospora graminicola [Sacc.] Schroet.) is a serious agricultural problem for pearl millet (Pennisetum glaucum [L.] R. Br.) grain production under field conditions. Six medicinally important plant species Azadirachta indica, Argemone mexicana, Commiphora caudata, Mentha piperita, Emblica officinalis and Viscum album were evaluated for their efficacy against pearl millet downy mildew. Seeds of pearl millet were treated with different concentrations of aqueous extract of the plants to examine their efficacy in controlling downy mildew. Among the plant extracts tested, V. album treatment was found to be more effective in enhancing seed quality parameters and also in inducing resistance against downy mildew disease. Germination and seedling vigor was improved in seeds treated with V. album extracts over control. Seeds treated with 10% concentration of V. album showed maximum protection against downy mildew disease under greenhouse and field conditions. The downy mildew disease protection varied from 44–70% with different concentrations. Leaf extract of V. album did not inhibit sporulation and zoospore release from sporangia of Sclerospora graminicola, indicating that the disease-controlling effect was attributed to induced resistance. Seed treatment with V. album extract increased pearl millet grain yield considerably. In V. album, treated pearl millet seedlings increased activities of peroxidase, and phenylalanine ammonia-lyase enzyme was detected. FTIR analysis of V. album extracts showed the presence of amides and other aromatic compounds which are antimicrobial compounds involved in plant defense.     

New or interesting Laboulbeniales (Ascomycetes) on Japanese chlaeniine beetles (Coleoptera,Carabidae)

Four species ofLaboulbenia were isolated from Japanese chlaeniines and are reported.Laboulbenia habui is described as a new species; it is possibly related toL. fasciculata. Laboulbenia habui is characterized by the proliferation and division of cell V, resulting in the formation of an obliquely superposed series of cells from which short, cylindrical cells arise in a double row, whereas there is a single row of cubical cells inL. fasciculata. Laboulbenia humilis is new for the Japanese mycoflora; antheridia of this fungus were observed for the first time; shape of the perithecial apex, persistent antheridia and the spore size suggest thatL. humilis is not closely related toL. exigua and its related taxa. ForL. proliferans andL. fasciculata, new chlaeniine hosts are listed and some supplemental notes are given.     

Mycological studies on the angiosperm root parasiteCynomorium coccineum L. and two of its halophytic hosts

The fungal colonization of the angiosperm root parasiteCynomorium coccineum and the halophytic hostsLimonium delicatulum andArthrocnemum glaucum were investigated in a Mediterranean salt marsh in March 1992. The main fungal inhabitants on the leaves or shoot surface of the test plants wereAspergillus niger, Penicillium chrysogenum andCladosporium herbarum. The qualitative analysis of the fungal species associating the parasite, the hosts and the non-infected plants showed similar pattern. However, the total population exhibited quantitative differences coupled with the amount and the chemical composition of the exudates on plant surface and the quantity of transpired water. The fungal catch from the aerial shoot (inflorescence) of the parasite was higher than that collected from either the leaves or aerial shoots of non-infected or host plants. The fungal density on the leaves ofL. delicatulum was higher than those isolated from the aerial shoots ofA. glaucum. Infection byC. coccineum caused a marked drop in the total fungal population on leaves or shoot surfaces of the hosts as compared to the corresponding non-infected individuals. The stimulative effect of washings on spore germination of some isolated fungal species was matched with the density of fungi on the target plants.     

Influence of plant extracts and microbioagents on physiological traits of faba bean infected with<Emphasis Type="Italic">Botrytis fabae</Emphasis>

Laboratory and greenhouse experiments were conducted to assess the efficacy ofEucalyptus citriodora, Ipomoea carnea, Cuminum cyminum, Allium sativum and Hyoscyamus muticus leaf extracts, and Streptomyces exfloliatus (S) andTrichoderma harzianum (T) for controllingBotrytis fabae causing chocolate spot disease of faba bean. Laboratory study supported the use ofE. citriodora (Ex 1) andI. carnea (Ex 2) extracts than the others for controlling the growth ofB. fabae. S+T was the best for inhibiting spore germination followed by Ex 1 +Ex 2 after 8 h of testing, whereas Ex 1 +Ex 2 produced the lowest percent of germination after 16 h. After 4 days, the inhibiting order of the growth ofB. fabae was S+T > Ex 1 +Ex 2 > T > Ex 2 > Ex 1 =S. Greenhouse experiments showed the highest activities of peroxidase, catalase and pectinase in the infected plants. These activities were markedly reduced in healthy plants and widely changed by the biocontrol treatments. Applying biocontrol agents to the infected plants increased minerals (N, P, K and Mg), and both Chl biosynthesis and the photosynthetic activity, which in turn led to accumulation of metabolites. This served the plant to resist the detrimental effects ofB. fabae on the plant growth and yield. In this concern, the efficiency of test biocontrol agents seemed to be in the order:T+S > Ex 1 +Ex 2 >T >S > Ex 2 > Ex.     

Studies on the rust,Maravalia cryptostegiae,a potential biological control agent of rubber-vine weed,Cryptostegia grandiflora (Asclepiadaceae: Periplocoideae), in Australia,III: Host range

Seventy-one plant species, which were selected using a centrifugal phylogenetic method, were screened againstMaravalia cryptostegiae, an endemic rust of rubber-vine (Cryptostegia grandiflora) in Madagascar. All species and variants of the genusCryptostegia proved to be highly susceptible to the rust under optimum greenhouse conditions. Two other species belonging to the same subfamily Periplocoideae,Gonocrypta grevei from Madagascar andCryptolepis grayi from Australia, developed fertile sori but could still be classified as partially resistant, based on the results of a leaf clearing and staining technique. Fifteen assessment categories and 10 susceptibility ratings were designated by analysing both macro- and microsymptoms. Five resistance mechanisms were identified in the non-hosts and these are described and illustrated. Resistance reactions ranged from complete suppression of spore germination on the plant cuticle to restriction of sorus development due to the collapse of rust haustoria. The significance of host range studies are discussed in relation to the use of rust fungi as classical biological control agents of weeds, and specifically the release ofM. cryptostegiae in Australia.