Bio-production of compost with low pH and high soluble phosphorus from sugar cane bagasse enriched with rock phosphate

Summary Aspergillus niger and Trichoderma viride strains were used together as a fungal activator in the presence or absence of farmyard manure (FM) for composting of bagasse enriched with rock phosphate. Quality of the composts produced was compared with that obtained from non-inoculated bagasse. The composts were evaluated as organic phosphatic fertilizers, for broad bean plants. The results showed that composting of bagasse without microbial inoculation or FM addition was not complete after 105 days of fermentation. An excellent decomposition in a relatively short time however was obtained with the use of A. niger and T. viride as inoculant agents with or without FM. The inoculation with A. niger + T. viridewith or without FM, also represented the most suitable conditions for phosphate solubilization. Acidic conditions (pH 4–5) at the end of the experiment were obtained in all piles receiving Aspergillus niger and there was a correlation between the amounts of soluble phosphorus and the reduction in pH values in the compost piles. There were no phosphate-dissolving fungi present in any composted piles except those treated with Aspergillus niger and Trichoderma viride. The number of phosphate-dissolving bacteria increased only in the treatments that were treated with FM. The non-fertilized sandy soil and the non-inoculated bagasse compost did not provide broad bean plants with phosphorus while the composts produced by inoculation with A. niger + T. viride provided the plants with the highest amounts of phosphorus.     

Screening for fungal antagonists to control black mold disease and to induce the accumulation of antifungal compounds in onion after seed treatment

Twelve isolates belonging to the genera Aspergillus, Penicillium, and Trichoderma, from onion (Allium cepa L.)-growing soils were recently found to have antagonistic features against Aspergillus niger (An) van Tieghem, the cause of black mold disease of onion, in dual culture. In the work reported in this paper, the function of these isolates applied as seed treatment on onion seed germination was investigated. In addition, isolates with no negative effect on seeds were screened for their effect on shoot length, and for their abilities to inhibit colonization of An on seeds, to control black mold disease, to increase set bulb diameter, and to induce production of antifungal compounds in pot-grown onion sets. Application of non-aflatoxigenic A. flavus Link (AS3), T. harzianum Rifai (TRIC7) and (TRIC8) to seeds led to defense reactions with accumulation of antifungal compounds in sets, combined with increased protection against the disease, although they did not enhance bulb diameter.     

Effect of post-irradiation ageing on onion seeds

Seeds of onion (Allium cepa) cv. Ailsa Craig were exposed to various doses of gamma radiation (0, 10, 20, 40, 80 and 100 krad) and subjected to accelerated ageing (RH 100%, 42°C) for 12 h. Radiation doses significantly affected the percentage of normal seedlings, abnormality types (%) and seedling growth. Seed viability, conductivities of seed leachates, final germination (%), germination speed and time to reach 50% germination (T ₅₀) were not affected by the seed irradiation. Accelerated ageing after irradiation had significant influence on seed viability, conductivities of seed leachates, final germination (%) and percentage of normal seedlings. Germination speed, T ₅₀ and seedling growth were not affected by the accelerated ageing. However, all the parameters studied were significantly influenced by the interaction of radiation doses and accelerated ageing. Accelerated ageing generally enhanced the damaging effects of irradiation on seeds. Therefore, it was concluded that onion seeds should not be exposed to adverse environmental conditions after irradiation.     

Stimulation of environmentally controlled mushroom composting by polysaccharidases

Polysaccharidases adsorbed on commercial amylodextrins were added to environmentally controlled composts of straw plus poultry manure. After 5 days of composting at 48°C, microbial enzyme activities and numbers of bacteria were higher in the treated compost than in the control. During the next phase at 80°C, between days 5 and 6, more C and N were solubilized in the treated compost. After introducing a microbial inoculum on day 6, and maintaining the substrate at 48°C, colonization by bacteria was faster in the treated compost and consequently, more fibre was degraded. Differences between composts in yields of Agaricus bisporus after 5 weeks of cropping were not significant (P=0.05).The authors are with INRA, Station de Recherches sur les Champignons, BP 81, 33883 Villenave d'Ornon, France     

Effect of chitin waste-based composts produced by two-phase composting on two oomycete plant pathogens

Biphasic composts were prepared by first mixing peat moss and sawdust with a nitrogen-rich biomass such as chitinous waste or cow manure and composting them until termination of the thermophilic phase. These partially stabilized composts were then amended with shrimp waste inducing a second thermophilic phase. Filter-sterilized water extracts obtained from two mature biphasic composts (SP₂W₂+S and MPW+S) reduced the growth of two oomycete plant pathogens, Phytophthora fragariae var. rubi and Pythium ultimum. Both SP₂W₂+S and MPW+S composts significantly reduce the incidence of cucumber damping-off caused by Pythium ultimum as compared to a commercial brand of compost made from shrimp waste and peat moss. Hydrolysis products of chitin were unlikely to be responsible for growth inhibition since no oligomeric forms of chitin were detected in SP₂W₂+S. The shrimp waste amendment carried out after the first thermophilic phase modified the microbial populations of biphasic composts. Following the amendment, the proportion of branched-chain microbial fatty acids typical of Gram-positive bacteria increased considerably suggesting that this group of bacteria became more prevalent within the total microbial population. These data suggests that the two-phase composting process promotes the proliferation of Gram-positive bacteria antagonistic to oomycete plant pathogens.     

木麻黄浸提液对榄仁树幼苗生长及生理生化的影响

该研究试图将榄仁树引入木麻黄海防林以期形成混交林型的海防林。以15 d榄仁树种子苗为材料,分别采用浓度为125 g·L~-1的木麻黄根、木麻黄凋落物和林下表层土壤的水浸提液胁迫处理榄仁树幼苗60 d,研究木麻黄化感作用对榄仁树幼苗生长、光合作用、膜系统伤害、抗氧化系统酶活性及游离Pro含量的影响。结果表明:木麻黄根、木麻黄凋落物及林下表层土壤的水浸提液都能降低榄仁树幼苗的存活率,影响幼苗株高、叶和根生物量,可以推断不同浸提液中对影响植物生长成分的浓度有所不同。3种浸提液均显著降低处理15~45 d期间幼苗的净光合速率(Pn)、气孔导度(Ccond)、胞间CO_2浓度(Ci)、蒸腾速率(Tr),且显著增加幼苗水分利用率(WUE)。第60天时3种木麻黄浸提液能显著增加幼苗叶片、根的Pro含量,使得幼苗根系组织细胞膜通透性增加,而木麻黄根浸提液能显著增加幼苗Ccond、Ci、叶SOD、根CAT含量,木麻黄凋落物浸提液能显著增加幼苗Ccond和Tr,同时凋落物浸提液会显著降低幼苗根POD含量。榄仁树幼苗通过调整自身的生理生化能适应木麻黄化感胁迫的影响,为此可考虑榄仁树作为沿海防护林建设的树种之一。     

Plant defence and delayed infection of alfalfa pseudonodules induced by an exopolysaccharide (EPS I)-deficient Rhizobium meliloti mutant

Mutants of the symbiotic soil bacterium Rhizobium meliloti that fail to synthesize the acidic exopolysaccharide EPS I were unable to induce infected root nodules on Medicago sativa L. (alfalfa). These strains, however, elicited pseudonodules that contained no infection threads or bacteroids. The cortical cell walls of the pseudonodules were abnormally thick and incrusted with an autofluorescent material. Parts of these cell walls and wall appositions contained callose. Biochemical analysis of nodules induced by the EPS I-deficient R. meliloti mutant revealed an increase of phenolic compounds bound to the nodule cell walls when compared with the wild-type strain. These microscopic and biochemical data indicated that a general plant defence response against the EPS I-deficient mutant of R. meliloti was induced in alfalfa pseudonodules. Following prolonged incubation with the EPS I-deficient R. meliloti mutant, the defence system of the alfalfa plant could be overcome by the rhizobium mutant. In the case of the delayed infections, the mutants colonized lobes of the pseudonodules, but the infection threads in these nodules had an abnormal morphology. They were greatly enlarged and did not contain the typical gum-like matrix inside. The bacteria were tightly packed. Based on the mechanism of phytopathogenic interactions, we propose that EPS I or a related compound may act as a suppressor of the alfalfa plant defence system, enabling R. meliloti to infect the plant.     

Influence of the phenolic compound bearing species Ledum palustre on soil N cycling in a boreal hardwood forest

The effects of the understory shrub Ledum palustre on soil N cycling were studied in a hardwood forest of Interior Alaska. This species releases high concentrations of phenolic compounds from green leaves and decomposing litter by rainfall. Organic and mineral soils sampled underneath L. palustre and at nearby non-Ledum sites were amended with L. palustre litter leachates and incubated at controlled conditions. We aimed to know (i) whether L. palustre presence and litter leachate addition changed net N cycling rates in organic and mineral soils, and (ii) what N cycling processes, including gross N mineralization, N immobilization and gross N nitrification, were affected in association with L. palustre. Our results indicate that N transformation rates in the surface organic horizon were not affected by L. palustre presence or leachate addition. However, mineral soils underneath L. palustre as well as soils amended with leachates had significantly higher C/N ratios and microbial respiration rates, and lower net N mineralization and N-to-C mineralization compared to no Ledum and no leachates soils. No nitrification was detected. Plant presence and leachate addition also tended to increase both gross N mineralization and immobilization. These results suggest that soluble C compounds present in L. palustre increased N immobilization in mineral soils when soil biota used them as a C source. Increases in gross N mineralization may have been caused by an enhanced microbial biomass due to C addition. Since both plant presence and leachate addition decreased soil C/N ratio and had similar effects on N transformation rates, our results suggest that litter leachates could be partially responsible for plant presence effects. The lower N availability under L. palustre canopy could exert negative interactions on the establishment and growth of other plant species.     

Interactions Among Selected Endoparasitic Nematodes and Three Pseudomonads on Alfalfa

Meloidogyne hapla, Pratylenchus penetrans, and Helicotylenchus dihystera, reduced the growth of ''Saranac AR alfalfa seedlings when applied at concentrations of 50 nematodes per plant. All except P. penetrans reduced seedling growth when applied at 25 per seedling. M. hapla reduced growth when applied at 12 per seedling. Nematodes interacted with three pseudomonads to produce greater growth reductions than were obtained with single pathogens, suggesting synergistic relationships. Ditylenchus dipsaci, applied at 25 or 50 nematodes per seedling, reduced plant weight compared with weights of control plants, but did not interact with test bacteria. All of the nematodes except D. dipsaci produced root wounds which were invaded by bacteria.     

Biological activity and chemical isolation of root saponins of six cultivars of alfalfa (Medicago sativa L.)

Wheat, cheat and Trichoderma viride bioassays were used to establish the relationship between the content of biologically active saponins in the roots and the degree of winter dormancy and/or time of six cultivars of alfalfa over the period January to August, 1988. Wheat and cheat bioassay results indicated no significant difforences among cultivars, whereas T. viride was inhibited most by extracts of roots collected during months with high rainfall and rapid growth. Cheast seedling roots were inhibited 8–10% more than those of wheat seedling roots indicating that alfalfa root saponins were more effective as allelopathic compounds in preventing growth of cheat than that of wheat alone. An average of 14 different saponins per cultivar were separated by thin-layer chromatograms. Saponins, and the aglycones produced by acid hydrolysis of the May samples, were separated by thin-layer chromatography. The conclusion is that the amount, structure, and type of saponins present in alfalfa roots vary with time.     

Selective inhibitors of germination of legume seeds in activated sludge compost

Water extracts of the compost produced from activated sludge and coffee residue were found to be selectively inhibitory to seed germination of some legumes. Germination rate of white clover (Trifolium repens L.), red clover (Trifolium pratense L.) and alfalfa (Medicago sativa L.) seeds were reduced to 2, 29 and 73% of the control, respectively, by water extracts of the compost (20 g l^–1). However, the extracts did not show any inhibition to seed germination of sorghum (Sorghum bicolor Moench), African millet (Eleusine coracana Gaertn.), and Komatsuna (Brassica rapa L.) at the same concentration. The inhibitors in the compost extracts were separated by ion-exchange chromatography and reverse-phase high performance liquid chromatography (HPLC) and the inhibitory activities of seed germination were tested with white clover seeds. Five inhibitors were isolated and identified as 3,4-dichlorophenylacetic acid (3,4-DCP), 3,4-dichlorobenzoic acid (3,4-DCB), 3,4,5-trichlorophenylacetic acid, 3,4,5-trichlorobenzoic acid and mono-2-ethylhexylphthalate by ¹H-, ¹³C-NMR spectroscopy and mass spectrometry. The inhibitory activities of some authentic chemicals of the inhibitors and the related compounds were compared. The results indicated that the main inhibitor in the compost could be 3,4-DCB, which was contained at the concentration of 6.58 mg kg^–1 compost and showed the strongest inhibitory effect on seed germination of white clover among the tested compounds.     

Utilization of seaweed Ulva sp. in Paracas Bay (Peru): experimenting with compost

In Paracas Bay (Peru), large quantities of Ulva sp. interfere with various important activities of the zone. In this context, the present study was undertaken to evaluate the effect of adding Ulva sp. in compost piles and the quality of the resulting composts. Six compost piles were prepared using, straw, green material mixture, cow manure and Ulva in different quantities (9, 17 and 28% of volume) and forms. Several variables were monitored during the process and the chemical characteristics of the final composts were determined. Aerial biomass achieved by maize plants was also evaluated for each compost at different compost/sand proportions. Results show that the compost pile made with Ulva powder registered the highest temperature and the longest thermophilic phase. Piles prepared with 28% washed Ulvapresented anoxic conditions at the beginning and had higher electrical conductivity values. Carbon/Nitrogen ratio diminished appropriately in all piles and there was no negative effect observed on the pH of the piles. Compost prepared with Ulva had lower contents of Total Kjeldahl Nitrogen, and produced maize plants aerial biomass.     

Performance evaluation of potent phosphate solubilizing bacteria in potato rhizosphere

Three phosphate solubilizing bacterial isolates identified as Pantoea agglomerans strain P5, Microbacterium laevaniformans strain P7 and Pseudomonas putida strain P13 were assessed for mutual relationships among them, competitiveness with soil microorganisms and associations with plant root using luxAB reporter genes for follow-up studies. Synergism between either P. agglomerans or M. laevaniformans, as acid-producing bacteria, and P. putida, as a strong phosphatase producer, was consistently observed both in liquid culture medium and in root rhizosphere. All laboratory, greenhouse and field experiments proved that these three isolates compete well with naturally occurring soil microorganisms. Consistently, the combinations of either P. agglomerans or M. laevaniformans strains with Pseudomonas putida led to higher biomass and potato tuber in greenhouse and in field trials. It is conceivable that combinations of an acid- and a phosphatase-producing bacterium would allow simultaneous utilization of both inorganic and organic phosphorus compounds preserving the soil structure.     

Beneficial microorganism survival on seed, roots and in rhizosphere soil following application to seed during drum priming

Priming is a technique used to improve seedling establishment of direct-seeded crops such as onion and carrot, resulting in a quick and uniform emergence. This work investigated the application of four selected beneficial microorganisms (Pseudomonas chlororaphis MA342, Pseudomonas fluorescens CHA0, Clonostachys rosea IK726d11 and Trichoderma harzianum T22) to onion and carrot seed during drum priming, and their subsequent survival and establishment in the rhizosphere once the seed was planted. Different application rates of fungi (7 log₁₀ cfu g⁻¹ dry seed) and bacteria (6 log₁₀ cfu g⁻¹ dry seed) were required on onion to achieve the end target of 5 log₁₀ cfu g⁻¹ dry seed, whereas a lower rate (5 log₁₀ cfu g⁻¹ dry seed for both bacteria and fungi) was successful on carrot. Microorganism-treated seed was planted in soil in the glasshouse and root and rhizosphere soil samples were taken at 2, 4 and 8 weeks post-planting. All seed-applied microorganisms were recovered throughout the experiment, although differences in the survival patterns were seen. The bacterial isolates declined in number over time, with P. fluorescens CHA0 showing better overall survival than P. chlororaphis MA342, particularly on the roots and in the rhizosphere soil of carrot. In contrast to the bacteria, the fungal isolate C. rosea IK726d11 showed good survival on both onion and carrot, and increased significantly in number throughout the 8-week period. Trichoderma harzianum T22 remained relatively constant in number throughout the experiment, but showed better survival on carrot than onion roots. Similar results were found in three different soil-types.     

一株高效拮抗向日葵菌核菌的细菌菌株YC16的筛选及其作用效果研究

[目的]筛选高效拮抗向日葵菌核菌的细菌菌株,为开发防治菌核菌病害、提高向日葵产量的生物菌剂提供菌种资源。[方法]以羧甲基纤维素钠(CMC)、小麦秸秆纤维素为唯一碳源的无机盐培养基,分离高效降解纤维素的细菌菌株;采用纤维素降解菌与菌核菌的平板对峙方法,进一步筛选拮抗菌核菌的菌株;利用16S rDNA序列鉴定菌株、PDYA平板对峙实验检验上述所选拮抗菌株的抑菌谱;采用离体向日葵新鲜叶片、草炭土基质盆栽实验,观察拮抗菌菌株抑制菌核菌生长的能力;温室盆栽和田间试验条件下,研究其防治向日葵菌核菌病害、促进生长和提高产量的效果。[结果]筛选了一株高效抑制菌核菌的细菌YC16,经过16S rDNA序列分析,鉴定为解淀粉芽孢杆菌。YC16菌株能够抑制8种病原真菌生长,包括齐整小核菌、腐皮镰孢菌、尖孢镰刀菌、稻梨孢、辣椒疫霉、镰刀菌、尖镰孢黄瓜专化型和向日葵菌核菌;抑制菌核菌感染叶片,抑制率达到了80.42%;抑制盆栽基质中菌核菌的菌丝生长,基质表面菌丝密度比对照减少了50%以上。盆栽接种YC16的向日葵生物量比对照提高54.9%,田间向日葵接种YC16菌剂对菌核菌引发的盘腐病防治效果达39%-100%,产量提高24.4%-30.2%。[结论]YC16生物菌剂施用于土壤,能够有效防治向日葵的茎腐病和盘腐病,展现了防治向日葵菌核病和提高产量的双重效果,是一株具有良好应用前景的高效菌种资源。     

<Emphasis Type="Italic">Penicillium frequentans</Emphasis> isolated from<Emphasis Type="Italic"> Picea glehnii</Emphasis> seedling roots as a possible biological control agent against damping-off

Picea glehnii seedlings are affected by damping-off fungi in nurseries. The aims of this study were (1) to isolate fungi grown in the seedling rhizosphere in forest soil of P. glehnii, (2) to select fungi that produce antifungal compounds against Pythium vexans, and (3) to examine whether or not selected fungi can protect seedlings from P. vexans. Penicillium frequentans from Picea glehnii seedling roots produced antibiotic penicillic acid. Penicillic acid did not cause significant phytotoxicity to the seedlings. Penicillium frequentans increased the average percentage of surviving seedlings when inoculated together with Pythium vexans, but the increase was not significant. Vigorous mycelial growth of P. frequentans around seedling roots seems to be one of the mechanisms for protection, but the amount of penicillic acid was too low to show antifungal activity in the seedling rhizosphere.     

Antifungal activities of actinomycete strains associated with high-altitude sagebrush rhizosphere

The antifungal-producing potential of actinomycete populations from the rhizosphere of low-altitude sagebrush, Artemisia tridentata, has been examined. In a continued investigation of new sources of antifungal-producing microorganisms, this study examined the antifungal-producing potential of actinomycetes from the rhizosphere of high-altitude A. tridentata. With high-altitude sagebrush, rhizosphere soil actinomycete numbers were one to four orders of magnitude higher than those found in nonrhizosphere bulk soils and different from those found with the low-altitude plants. A total of 122 actinomycete isolates was screened against nine fungal species and six bacterial species for the production of antimicrobial compounds. Four rhizosphere isolates, Streptomyces amakusaensis, S. coeruleorubidus, S. hawaiiensis and S. scabies, showed broad-spectrum antifungal activity against three or more fungal species in plate assays. In liquid antagonism assays, mycelium production by Aspergillus niger was reduced by up to 50% by two of the actinomycete isolates. These results demonstrate the potential of rhizosphere microbiology in the search for new antimicrobials.     

Characterization of new bacterial biocontrol agents Acinetobacter,Bacillus, Pantoea and Pseudomonas spp. mediating grapevine resistance against Botrytis cinerea

A collection of 282 bacterial isolates from the rhizosphere and different organs of healthy field-grown grapevine plants was obtained and screened for their ability to protect grapevine leaves against Botrytis cinerea, the causal agent of gray mold. Twenty-six strains effectively controlled B. cinerea infections on leaves. After phenotypic and molecular analysis, seven strains were identified as Pseudomonas fluorescens PTA-268 and PTA-CT2, Bacillus subtilis PTA-271, Pantoea agglomerans PTA-AF1 and PTA-AF2, and Acinetobacter lwoffii PTA-113 and PTA-152. In vitro antifungal experiments showed that from these seven strains, only PTA-AF1 and PTA-CT2 exhibited a direct antagonism against B. cinerea. Furthermore, the biocontrol activity of the seven bacteria was associated with differential induction of defense-related responses lipoxygenase, phenylalanine ammonia-lyase and chitinase in grapevine leaves. Our results show that the selected bacteria can efficiently protect grapevine leaves against gray mold disease through an induction of plant resistance and in some cases by an additional antagonistic activity.     

New trifluoromethyl quinolone derivatives: Synthesis and investigation of antimicrobial properties

A series of quinolone derivatives, containing different heterocyclic amines were prepared. Synthesized compounds were evaluated for their in vitro antimicrobial activities against two Gram-positive bacteria, three Gram-negative bacteria as well as four fungi. All the derivatives showed good activity towards Gram-positive bacteria and less activity towards Gram-negative bacteria. They also showed moderate to comparable activity against Aspergillus niger and Candida albicans and low to moderate antifungal activity against Aspergillus fumigatus and Aspergillus flavus.