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.     

Differential responses of three fungal species to environmental factors and their role in the mycorrhization of<Emphasis Type="Italic"> Pinus radiata</Emphasis> D. Don

Three ectomycorrhizal (ECM) isolates of Rhizopogon luteolus, R. roseolus and Scleroderma citrinum were found to differ markedly in their in vitro tolerance to adverse conditions limiting fungal growth, i.e. water availability, pH and heavy metal pollution. S. citrinum was the most sensitive, R. luteolus intermediate and R. roseolus the most tolerant species. Pinus radiata D. Don seedlings were inoculated in the laboratory and in a containerised seedling nursery with spore suspensions of the three ECM species. Colonisation percentage was considerably lower under nursery conditions, probably due to competition by native fungi. The effects of nursery ECM inoculation on seedling growth depended on the fungal species. Only R. roseolus-colonised plants showed a significantly higher shoot growth than non-mycorrhizal plants. All three fungi induced significantly higher root dry weights relative to control plants. Despite the low mycorrhizal colonisation, mycorrhization with all three species improved the physiological status of nursery-grown seedlings, e.g. enhanced root enzyme activity, shoot nutrient and pigment content, net photosynthesis rate and water use efficiency. Of the three fungal species, R. roseolus was the most effective; this species was also the most adaptable and showed the greatest range of tolerance to adverse environmental conditions in pure culture. It is, therefore, proposed as a promising fungal species for ECM inoculation of P. radiata in the nursery.     

A comparative phylogenetic analysis of full-length<Emphasis Type="Italic">mariner</Emphasis> elements isolated from the Indian tasar silkmoth,<Emphasis Type="Italic">Antheraea mylitta</Emphasis> (Lepidoptera: saturniidae)

Mariner like elements (MLEs) are widely distributed type II transposons with an open reading frame (ORF) for transposase. We studied comparative phylogenetic evolution and inverted terminal repeat (ITR) conservation of MLEs from Indian saturniid silkmoth,Antheraea mylitta with other full length MLEs submitted in the database. Full length elements fromA. mylitta were inactive with multiple mutations. Many conserved amino acid blocks were identified after aligning transposase sequences. Mariner signature sequence, DD(34)D was almost invariable although a few new class of elements had different signatures.A. mylitta MLEs(Anmmar) get phylogenetically classified under cecropia subfamily and cluster closely with the elements from other Bombycoidea superfamily members implying vertical transmission from a common ancestor. ITR analysis showed a conserved sequence of AGGT(2-8N)ATAAGT for forward repeat and AGGT(2-8N)ATGAAAT for reverse repeat. These results and additional work may help us to understand the dynamics of MLE distribution inA. mylitta and construction of appropriate vectors for mariner mediated transgenics.     

Seedling establishment ofCastanopsis cuspidata var.sieboldii andPersea thunbergii on lava and scoria of the 1962 eruption on Miyake-jima Island,the Izu Islands

Seedling establishment ofCastanopsis cuspidata var.sieboldii Nakai andPersea thunbergii Kosterm. (Machilus thunbergii Sieb. et Zucc.) in early succession was studied on the lava and the scoria of the 1962 eruption on Miyake-jima Island of the Izu Islands. While tall individuals (> 1 m) ofP. thunbergii were found on both the lava and the scoria, those ofC. cuspidata (> 1 m) were found only on the lava. The height growth rate ofC. cuspidata was very low on the scoria, and there was no individual ofC. cuspidata taller than 0.4 m on the scoria. The proportion of yellow leaved individuals was much higher (37.1%) inC. cuspidata than inP. thunbergii (4.0%) on the scoria, while it was similar between the two species on the lava.Persea thunbergii seemed to be able to establish on both the lava and the scoria, butC. cuspidata established only on the lava. The differences in growth rate and vigor between the two species on the lava and the scoria in early succession may influence later stages of succession.     

Production of lipase free of citrinin by Penicillium citrinum

Lipase (Glycerol ester hydrolase E.G. 3.1.1.3) from a Brazilian strain of Penicillium citrinum free of the mycotoxin citrinin has been investigated. Citrinin production was inhibited by using culture medium containing olive oil, soybean oil and corn oil as carbon sources. Potassium concentration and pH play an important role in citrinin production. Potassium concentration lower than 30 mM and pH below 4.5 inhibited the mycotoxin production. P. citrinum produced lipase free of extraneous proteins and citrinin when cultured using, as nitrogen source, ammonium sulphate (lipase activity of 7.88 U/mg) and yeast extract (lipase activity of 4.95 U/mg) with olive oil as carbon source. This data is relevant to the larger scale production of lipases for food technology applications, from Penicillium citrinum.     

<Emphasis Type="Italic">Codium fragile</Emphasis>: rhizomatous growth in the<Emphasis Type="Italic"> Zostera</Emphasis> thief of eastern Canada

A rhizomatous growth form of Codium fragile is described for the first time. Plants were collected in the Gulf of St. Lawrence in estuaries dominated by Zostera marina. Rhizomatous plants developed from propagules of whole plants that settled horizontally. Horizontal axes of C. fragile were up to 1 m long in plants collected in situ. Plants developed several to dozens of erect axes at right angle to the base. Horizontal growth of up to 0.2 m was found in field experiments where fragments were tied to plastic mesh and left in situ for 4 months. The unconsolidated filaments at the base of C. fragile often wrapped around the rhizomes of Z. marina and up to five separate attachment sites to eelgrass were found in single plants of C. fragile. In four estuaries, 57–100% of Codium plants with identifiable substratum were attached to shoots and rhizomes of Z. marina. The rhizomatous growth form was found in plants identified as C. fragile ssp. tomentosoides (Nova Scotia and Prince Edward Island) and C. fragile ssp. atlanticum (Prince Edward Island), suggesting that this is a phenotypic response to growth in soft bottom environments.Communicated by K Lüning     

Studies on antagonism betweenFusarium udum Butler and root region microflora of pigeon-pea

Antagonism betweenFusarium udum Butler causing wilt of pigeon-pea (Cajanus cajan (L.) Millsp.) and the saprophytic microflora of the root region of the host was studied with reference to colony interaction, hyphal interference, volatile and non-volatile metabolites and staling growth products. Studies were extended to screen potential antagonists against the wilt pathogen in soil. Aspergillus flavus, A. niger, A. terreus, Penicillium citrinum andMicromonospora globosa (an actinomycete) were antagonistic againstF. udum, whereas the pathogen parasitized and killedAspergillus luchuensis, Cunninghamella echinulata, Curvularia lunata, Mortierella subtilissima andSyncephalastrum racemosum. The pattern of growth of microorganisms on nutrient agar staled by rhizosphere soil inocula of healthy or wilted pigeon-pea plants was found to be different.F. udum colonized and grew on nutrient agar staled by the rhizosphere inoculum of the wilted plants upto 120h of incubation. However, it could not colonise and grow on the nutrient agar staled by rhizosphere microflora of healthy plants after 48h of incubation because of the presence of antagonists likeA. niger, A. flavus, A. terreus and a few species ofPenicillium in the soil inoculum. When pure cultures in soil ofF. udum was mixed with those of antagonists in different ratios,A. niger, A. flavus andM. globosa significantly suppressed the population ofF. udum, whereasA. terreus markedly reduced the population. When inoculated in soil, the antagonists exhibited a high fungistatic activity againstF. udum.     

Nodulation and growth response ofAllocasuarina andCasuarina species to phosphorus fertilization

To examine how soil phosphorus status affects nitrogen fixation by the Casuarinaceae —Frankia symbiosis,Casuarina equisetifolia and two species ofAllocasuarina (A. torulosa andA. littoralis) inoculated or fertilized with KNO₃ were grown in pots in an acid soil at 4 soil phosphate levels. InoculatedC. equisetifolia nodulated well by 12 weeks after planting and the numbers and weight of nodules increased markedly with phosphorus addition. Growth ofC. equisetifolia dependent on symbiotically fixed nitrogen was more sensitive to low levels of phosphorus (30 mg kg^–1 soil) than was growth of seedings supplied with combined nitrogen; at higher levels of phosphorus, the growth response curves were similar for both nitrogen fertilized and inoculated plants. The interaction between phosphorus and nitrogen treatments (inoculated and nitrogen fertilized) demonstrated that there was a greater requirement of phosphorus for symbiotic nitrogen fixation than for plant growth when soil phosphorus was low.WithAllocasuarina species, large plant to plant variation in nodulation occurred both within pots and between replicates. This result suggests genetic variation in nodulation withinAllocasuarina species. Nodulation ofAllocasuarina species did not start until 16 weeks after planting and no growth response due toFrankia inoculation was obtained at the time of harvest. Addition of nitrogen starter is suggested to boost plant growth before the establishment of the symbiosis. Growth ofAllocasuarina species fertilized with nitrogen responded to increasing levels of phosphorus up to 90 mg P/kg soil after which it declined by 69% forA. littoralis. The decrease in shoot weight ofA. littoralis, A. torulosa, C. equisetifolia andC. cunninghamiana at high phosphorus was confirmed in a sand culture experiment, and may be atributable to phosphorus toxicity.     

Survival of inoculated Laccaria bicolor in competition with native ectomycorrhizal fungi and effects on the growth of outplanted Douglasfir seedlings

The survival, development and mycorrhizal efficiency of a selected strain of Laccaria bicolor along with naturally occurring ectomycorrhizal fungi in a young plantation of Douglas fir was examined. Symbionts were identified and their respective colonization abilities were determined. Eight species of symbiotic fungi, which may have originated in adjacent coniferous forests, were observed on the root systems. Mycorrhizal diversity differed between inoculated (5 taxa) and control (8 taxa) seedlings. Ectomycorrhizal fungi which occurred naturally in the nursery on control seedlings (Thelephora terrestris and Suillus sp.) did not survive after outplanting. Both inoculated and naturally occurring Laccaria species, as well as Cenococcum geophilum, survived on the old roots and colonized the newly formed roots, limiting the colonization by other naturally occurring fungi. Other fungi, such as Paxillus involutus, Scleroderma citrinum and Hebeloma sp. preferentially colonized the old roots near the seedling's collar. Russulaceae were found mainly in the middle section of the root system. Mycorrhizal colonization by Laccaria species on inoculated seedlings (54%) was significantly greater than on controls (13%) which were consequently dominated by the native fungi. Significant differences (up to 239%) were found in the growth of inoculated seedlings, especially in root and shoot weight, which developed mainly during the second year after outplanting. Seedling growth varied with the species of mycorrhizae and with the degree of root colonization. Competitiveness and effectiveness of the introduced strain on improving growth performances of seedlings are discussed.     

Selective effect of the herbicide DCMU on unicellular algae — a potential tool to maintain monoalgal mass culture ofNannochloropsis

The selective effect of DCMU on photosynthetic activity and growth rate was examined in several marine unicellular algae:Nannochloropsis sp. (Eustigmatohyceae),Dunaliella salina (Chlorophyceae)Isochrysis galbana (Prymnesiophyceae) andChaetoceros sp. (Bacillariophyceae). DCMU at 10^–7 M caused an immediate decrease in the photosynthetic rate ofDunaliella andIsochrysis (about 50% inhibition), whereas 10^–6 M imposed 80% inhibition in the photosynthetic rate ofChaetoceros. InNannochloropsis the rate was affected only when DCMU concentration exceeded 10^–6M. Cellular growth rate of all studied algae was affected by DCMU in a similar manner to photosynthesis. The differential effect of DCMU was further examined in mixed cultures in whichNannochloropsis was cultivated together with an additional species simulating a contamination situation of aNannochloropsis culture. When DCMU was added at concentrations higher than 10^–7 M, the growth of the competing algae significantly decreased, whileNannochloropsis maintained a relatively high growth rate. Consequently, after a growth period of 4 to 7 days a clear domination ofNannochloropsis was observed. These results demonstrate that DCMU and probably other herbicides of similar characteristics can be used effectively as a selective tool to suppress contaminating unicellular algae in open ponds in order to maintain a monoculture ofNannochloropsis.     

Genetic Variability and Genetic Structure of Wild and Semi-domestic Populations of Tasar Silkworm (Antheraea mylitta ) Ecorace Daba as Revealed through ISSR Markers

The genetic diversity in the wild and semi-domestic populations of Daba ecorace of Antheraea mylitta was studied to ascertain the distribution of variability within and among populations of semi-domestic bivoltine (DB), trivoltine (DT) and nature grown wild populations (DN) with inter-simple sequence repeat (ISSR) markers. A total of 138 markers were produced among 56 individuals of the three populations, of which 98% were polymorphic. For the individual populations, the percentage polymorphism was 58.69, 52.9 and 77.54 for DB, DT and DN, respectively. Average number of observed (1.791 ± 0.408) and effective alleles (1.389 ± 0.348) was also high in the wild populations in comparison to the bivoltine and trivoltine semi-domestic populations. Genetic diversity (H_t) in DB, DT and DN was 0.180 ± 0.033, 0.153 ± 0.032 and 0.235 ± 0.033, respectively and within-population genetic diversity (H_s) ranged from 0.166 to 0.259 with a mean of 0.189. Mean gene differentiation (G_ST) was found to be 0.25. Shanon’s diversity index was 0.278, 0.237 and 0.361 for DB, DT and DN and overall it was 0.391. Gene flow (N_m) among the populations was 1.509. The dendrogram produced by UPGMA with Dice’s genetic distance matrices resulted in the formation of three major clusters separating the three populations. Considerable intra- and inter-population variability is found in all three populations. The population structure analysis further suggests that the semi-domestic populations of Daba ecorace are at the threshold of differentiating themselves. The high genetic variability present within wild Daba population of A. mylitta is of much importance for conservation as well as utilization in systematic breeding program.     

Bacteriological tests as an aid in the management of dental caries in Iceland

The activities of three natural coumarins, xanthotoxin and bergapten (fromAmmi majus, Umbelliferae) and psoralene (fromFicus cycomorus, Moraceae), were tested against mycelial growth and aflatoxin production of a toxigenic strain ofAspergillus flavus grown in a rice/corn steep liquor medium. Two other natural chromones, khellin and visnagin (fromAmmi visnaga) were also compared. Complete inhibition of aflatoxin release occurred with either xanthotoxin or khellin at 5 mM. The other three compounds also at 5 mM reduced aflatoxin to 12 to 16% of its original concentration. The mould growth was only slightly inhibited by all the compounds used.     

Inoculation of pines in a nursery withPisolithus tinctorius andThelephora terrestris in Korea

Summary Mycelial inocula of the two ectomycorrhizal fungi,Pisolithus tinctorius (Pt) andThelephora terrestris (Tt) were artificially introduced into fumigated nursery soil before seed sowing. At the end of the first growing season, Pt stimulated the height growth ofPinus densiflora, P. thunbergii, P. rigida, andP. rigida×taeda by 55, 36, 69, and 37%, respectively, compared with control seedlings (with no fumigation and no inoculation). When growth stimulation was expressed by dry weight, Pt increased dry weight ofP. densiflora andP. rigida×taeda by 143% and 128%, respectively, over control seedlings. Total absorption (per plant top) of nitrogen and phosphorus of inoculatedP. densiflora seedlings was also increased by 188 and 144%, respectively, even though the concentration of these two elements in the tissue was not significantly different from that of control seedlings.Tt failed to stimulate growth of the inoculated plants possibly due to its lower level of infection (40–60% mycorrhizal tips) compared with the relatively high infection (over 80%) of Pt.Pinus koraiensis did not respond to inoculation during the first growing season, probably due to its inherent characteristics of producing a small number of short roots and its slow shoot growth during the first few years after germination.This study was supported by the International Foundation for Science in Stockholm, Sweden.     

Distribution of similar self-incompatibility (<Emphasis Type="Italic">S</Emphasis>) haplotypes in different genera,<Emphasis Type="Italic"> Raphanus</Emphasis> and<Emphasis Type="Italic"> Brassica</Emphasis>

The nucleotide sequences of ten SP11 and nine SRK alleles in Raphanus sativus were determined, and deduced amino acid sequences were compared with those of Brassica SP11 and SRK. The amino acid sequence identity of class-I SP11s in R. sativus was about 30% on average, the highest being 52.2%, while that of the S domain of class-I SRK was 77.0% on average and ranged from 70.8% to 83.9%. These values were comparable to those of SP11 and SRK in Brassica oleracea and B. rapa. SP11 of R. sativus S-21 was found to be highly similar to SP11 of B. rapa S-9 (89.5% amino acid identity), and SRK of R. sativus S-21 was similar to SRK of B. rapa S-9 (91.0%). SP11 and SRK of R. sativus S-19 were also similar to SP11 and SRK of B. oleracea S-20, respectively. These similarities of both SP11 and SRK alleles between R. sativus and Brassica suggest that these S haplotype pairs originated from the same ancestral S haplotypes.     

Studies onMadhuca butyraceae seed proteins

DefattedMadhuca butyraceae seeds contain 24% of crude protein and 10.4% of saponins. The solubility ofMadhuca seed proteins was determined in water and NaCl as a function of pH and minimum solubility occurred at pH 4.0. The proteins consist of three components with S_20,w values of 2.2, 9.8 and 15.4. On gel filtration the proteins gave three peaks and on diethylaminoethyl cellulose chromatography they resolved into two components. Thein vitro digestibility ofMadhuca seed protein was found to be 69% when assayed with a pepsin-pancreatin system.     

Effects of morphology and rheology on neofructosyltransferase production byPenicillium citrinum

In this study, we investigated the relationship between the morphology and the rheological properties ofPenicillium citrinum to improve the production of neo-fructosyltransferase (neo-FTase). In a 2.5 L bioreactor culture ofP. citrinum, it was observed that agitation speed and aeration rate had significant effects on the production of neo-FTase and that maximum cell mass and neo-FTase production obtained at 500 rpm and 1.5 vvm were 8.14 g/L and 53.2×10⁻³ U/mL, respectively. Cell mass and neo-FTase production increased to 91.53 and 25.17%, respectively. In the morphology and rheology studies,P. citrinum showed a typical pellet morphology that was explained by a shaving mechanism; this phenomenon was significantly affected by carbon sources. The rheology of neo-FTase fermentation byP. citrinum was dependent on cell growth and fungal morphology.     

Lagenidium infection in eggs and larvae of mangrove crab (Scylla serrata) produced in Indonesia

A fungal infection occurred in the eggs and larvae of mangrove crab (Scylla serrata) in seed production in Bali, Indonesia. The causative fungus was classified as a member of the genusLagenidium (Oomycetes, Lagenidiales). After comparison of its biological and physiological characteristics with those ofL. callinectes ATCC 24973, a known parasite of various crustaceans, was concluded that the isolate is a new species ofLagenidium, L. thermophilum, because of its rapid and thermotolerant growth and unique discharge process. Fungal growth was observed on PYG agar containing 0–5.0% (w/v) NaCl and 0–2.5% (w/v) KCI. Similar pathogenicity toward the zoeae of swimming crab (Portunus trituberculatus) was demonstrated.     

Biological species ofArmillaria and their mycoparasitic associations withRhodophyllus abortivus in Hokkaido

Specimens of basidiomes and/or rhizomorphs ofArmillaria mellea complex and basidiomes ofRhodophyllus abortivus, developing on the same decaying stumps or stems of forest trees, were collected in three forests in Hokkaido. Normal basidiomes ofR. abortivus were found near to, but free from, the rhizomorphs and/or basidiomes ofArmillaria, while abnormal basidiomes, as carpophoroid forms, were developed on the rhizomorphs ofArmillaria. Of three mycoparasiticArmillaria isolates found withR. abortivus, one was identified asA. gallica and two asA. jezoensis. The isolates ofR. abortivus showed excellent mycelial growth and rhizomorph formation on PDA. However, on MDA, RMDA and BMDA, they showed poor aerial mycelia growth and no rhizomorphs. In the contrapositional cultures, the growth ofA. gallica was completely inhibited byR. abortivus on PDA but only slightly inhibited on MDA and RMDA. On the other hand, mutual inhibition at a distance was observed on BMDA. The mycelial growth and rhizomorph formation inA. jezoensis were severely inhibited by the colony ofR. abortivus on PDA, but only slightly inhibited on MDA. On RMDA and BMDA, the colonies of twoArmillaria species andR. abortivus showed mutual inhibition at a distance and apparent rhizomorph formation by bothArmillaria species.     

Novel cellulases from an extremophilic filamentous fungi <Emphasis Type="Italic">Penicillium citrinum</Emphasis>: production and characterization

The enzymatic hydrolysis of cellulose has potential economical and environment-friendly applications. Therefore, discovery of new extremophilic cellulases is essential to meet the requirements of industry. Penicillium citrinum (MTCC 6489) that was previously isolated from soil in our laboratory, produced alkali tolerant and thermostable cellulases. Endoglucanase and filter paper activity hydrolase (FPAse) production of P. citrinum were studied using wheat bran substrate in solid state and submerged culture. Zymogram analysis of endoglucanase revealed the presence of two isoforms differing in molecular weight. One of them was 90 kDa and other one was 38 kDa. Partially purified endoglucanase showed two different peaks at pH 5.5 and 8.0, respectively, in its pH optima curve. But FPase showed only one peak (at pH 6.5) in its pH optima curve. Cellulase of P. citrinum is thermostable in nature. The present work reports for the first time, the alkali stable cellulase from alkali tolerant fungus Penicillium citrinum. Thermostable endoglucanase from P. citrinum may have potential effectiveness as additives to laundry detergents.     

Phytophthora root-rot of container-grown citrus as affected by foliar sprays and soil drenches of phosphorous and acetyl salicylic acids

Mycelial growth ofPhytophthora nicotianae var.parasitica in vitro was inhibited by phosphorous and acetyl salicylic acids at 10 ppm; mycelial growth ofP. citrophthora was inhibited by phosphorous acid at 10 ppm and acetyl salicylic acid at 100 ppm. Foliar sprays and soil drenches with these chemicals were compared with soil applications of metalaxyl as treatments for Phytophthora root-rot of container-grown citrus (var. Cleopatra mandarin) caused by the aforementioned spp. Foliar sprays with 0.1% phosphorous acid were as effective as the metalaxyl treatment in promoting root growth and phosphorous acid offers considerable potential as an alternative treatment for Phytophthora root-rot of citrus.