Inoculum Quality Research Articles

Factors Affecting Spore Formation of Carrot Leaf Blight Caused by Alternaria dauci In Vitro

In order to examine the pathogenicity of <i>Alternaria dauci</i>, the causal agent of carrot leaf blight, it is necessary to standardize sporulation conditions to ensure the optimal quantity and quality of spore inoculum. Therefore, in this study, the effects of the growth medium, aeration treatment, and UV treatment with 12-hr photoperiod on the sporulation of <i>A. dauci</i> KACC42997 were investigated. <i>A. dauci</i> KACC42997 was pre-cultured for 7 days in a potato dextrose agar medium at 25oC in the dark condition. When the pre-culture, after removing aerial mycelia, was re-incubated for 5 days, with simultaneous aeration treatment and 12-hr cycle UV treatment at 20oC, the largest number of spores was produced. One hundred seventy isolates of <i>A. dauci</i> were isolated from major carrot growing regions such as Pyeongchang, Gumi and Jeju and tested for sporulation under the conditions established in this study. Except for 20 strains, all strains produced spores. Statistically significant differences in the extent of sporulation were found among local populations of <i>A. dauci</i> isolates, but no difference was observed in their pathogenicity on carrots.

Notes on Puccinia graminella, a rust of stipoid grasses in South America and a potential biocontrol agent for Nassella neesiana in New Zealand and Australia

ABSTRACT Puccinia graminella is one of several rusts considered as potential biocontrol agents for the grass weed Nassella neesiana in Australia and New Zealand. While Uromyces pencanus was chosen as the most promising candidate, results of our studies on P. graminella in Argentina (where the rust and grass are native) could be useful if a complementary agent is eventually needed. P. graminella produces aecidioid urediniospores, which morphologically resemble aeciospores but behave like the urediniospores of other rusts i.e. they are repetitive and the main (perhaps only) source of new infections. To improve the consistency of previous laboratory results, we aimed to locate accessible sources of spores in the field, and to determine optimal conditions for their collection, production and storage in the laboratory. Aecidioid urediniospores were found to germinate most readily at temperatures between 10 and 15°C. It was possible to store them in a refrigerator (4°C) or a freezer (−70°C), but already-low germination rates decreased over time using both methods. The appearance of host leaves affected inoculum quality, with green healthy leaves yielding aecidioid urediniospores with good germination rates. Best results in inoculation tests were obtained when spores and plants came from the same site. The presence of qualitative resistance in the pathosystem is suspected. P. graminella is not easy to manipulate in the laboratory, its impact on Nassella neesiana in the field is variable and the nature of its life cycle remains elusive. Remaining gaps in knowledge are identified and future directions for research are discussed.

An Effective Method of Ribes spp. Inoculation with Blackcurrant Reversion Virus under In Vitro Conditions.

Blackcurrant reversion virus (BRV) is the most destructive currant-infecting and mite-transmitted pathogen from the genus Nepovirus. In this work, BRV transmission in the system Ribes ex vitro–Ribes in vitro was applied for the first time. Triple infection of BRV identified in blackcurrant cv. Gojai was used for phylogenetic analysis and inoculation assay. Transmission of BRV was successful due to its stability in the inoculum for up to 8 days at 4 °C; all BRV isolates were infectious. Our suggested inoculation method through roots was applied in six Ribes spp. genotypes with 100.0% reliability, and the expression levels of defence-related gene PR1 to biotic stress was observed. The prevalence of the virus in microshoots after 2–14 days post-inoculation (dpi) was established by PCR. In resistant genotypes, the BRV was identified up to 8 dpi; meanwhile, infection remained constant in susceptible genotypes. We established that BRV transmission under controlled conditions depends on the inoculum quality, post-inoculation cultivation temperature, and host-plant susceptibility to pathogen. This in vitro inoculation method opens possibilities to reveal the resistance mechanisms or response pathways to BRV and can be used for the selection of resistant Ribes spp. in breeding programs.

The methanogenic archaea characteristics and efficacy of aerobic waste sludge in the start-up of anaerobic hybrid reactors treating cassava wastewater

Inoculum is a crucial factor influencing the success of an anaerobic digester start-up. This study evaluated the efficacy of aerobic waste activated sludge (WAS) to start-up anaerobic hybrid reactors (AHR) treating cassava wastewater. The start-up performance and stability of five 6.2 L AHRs inoculated differently by WAS (AHR1) and WAS co-inoculated with pig manure (AHR2), cow dung (AHR3), chicken manure (AHR4), and anaerobic pond sludge (AHR5) were investigated. The results depicted the potential of WAS as starter seed for AHR's start-up. This sludge contained methanogenic populations, mainly Methanomicrobials, Methanosarcinales, and Thermoplasmatales, for 1.5 × 107 MPN/g VS compared to 4.0 × 103-6.0 × 107 MPN/g VS in manures and anaerobic sludge. Co-inoculation of WAS with cow dung (AHR3) and anaerobic sludge (AHR5) promoted a rapid start-up, achieved 4.0 kg COD/m3.d within 1.5-1.7 months, while about 2.5-3.3 months needed for the others. A satisfying performance, stability, microbial development and activity, depicted as high COD removal (CODrem) efficiency and methane productivity, were achieved in all digesters. About 0.32 and 0.21 m3/kg CODrem for biogas and methane yielded in AHR1, whereas 0.41-0.49 m3-biogas/kg CODrem and 0.25-0.32 m3-CH4/kg CODrem obtained in other reactors. This finding confirmed that inoculum's quality is critical for productive gas productivity and system stability maintenance.

Automation of high CHO cell density seed intensification via online control of the cell specific perfusion rate and its impact on the N-stage inoculum quality

Current CHO cell production processes require an optimized space-time-yield. Process intensification can support achieving this by enhancing the productivity and improving facility utilization. The use of perfusion at the last stage of the seed train (N-1) for high cell density inoculation of the fed-batch N-stage production culture is a relatively new approach with few industry applicable examples. Within this work, the impact of the cell-specific perfusion rate (CSPR) of the N-1 perfusion and the relevance of its control for the quality of generated inoculation cells was evaluated using an automated perfusion rate (PR) control based on online biomass measurements. Precise correlations (R² = 0.99) between permittivity and viable cell counts were found up to the high densities of 100⋅106 c·mL−1. Cells from N-1 perfusion were cultivated at a high and low CSPR with 50 and 20 pL·(c·d)−1, respectively. Lowered cell growth and an increased apoptotic reaction was found as a consequence of the latter due to nutrient limitations and reduced uptake rates. Subsequently, batch cultivations (N-stage) from the different N-1 sources were inoculated to evaluate the physiological state of the inoculum. Successive responses resulting from the respective N-1 condition were uncovered. While cell growth and productivity of approaches inoculated from high CSPR and a conventional seed were comparable, low CSPR inoculation suffered significantly in terms of reduced initial cell growth and impaired viability. This study underlines the importance to determine the CSPR for the design and implementation of an N-1 perfusion process in order to achieve the desired performance at the crucial production stage.

EFEKTIVITAS Glomus clorum TERHADAP PERTUMBUHAN TANAMAN CABAI RAWIT (Capsicum frutescens L.), TOMAT (Solanum lycopersicum L.) DAN TERUNG (Solanum melongena L.)

Increasing plant growth by arbuscula mycorrhizal fungi depends on the fungus and plant spesies. The aim of this study was to determine the efectivity of fungal mycorrhizal fungus on the growth of cayenne pepper, tomato and eggplant which are Solanaceae family members. The study was conducted by Completely Randomized Design method.with two factors. The fisrt factor was species of experimental plant consisted of cayenne pepper (Capsicum frutescens L.), tomato (Solanum lycopersicum L.) and eggplant (Solanum melongena L.). The second factor was addition of Glomus clorum inokulum consisted of with and without inoculum addition. The result showed that there was no effect of inoculum addition on plant growth of three experiemal plants. The quality of inoculum used for this experiment was not good enough furthermore fungi could not germinate and colonize plant root.

Improving ecological fitness of Beauveria bassiana conidia to control the sugar cane borer Diatraea saccharalis

ABSTRACTDiatraea species are considered the most important insect pests in sugarcane crops in Colombia and other South America countries. Previous research demonstrated Beauveria bassiana isolate Bv062 to be pathogenic to larvae of Diatraea species under laboratory conditions. However, virulence of the isolate was variable, possibly affected by inoculum quality. The aim of this research was to select an appropriate mass culture medium to produce conidia with consistently high yield, high virulence, and high storage stability. Conidia were produced on three semi-solid media based on rice, oat and potato, which were adjusted to three levels of water activity (aw). Conidia yield, germination, polyols accumulation, enzymatic activity, and virulence to Diatraea saccharalis larvae, before and after 30 days of storage at 30°C, were measured. Conidia produced on potato-based medium were the most virulent, with a median lethal time (LT50) of 8.9 days, compared to 9.7 and 9.1 days for rice and oat media, respectively. Insecticidal activity was stable after one month of storage for conidia produced on potato (LT50 8.0 days) but was reduced for conidia produced on the other media (LT50 13.0 days and 11.7 days for rice and oat, respectively). Mannitol was the predominant polyol in conidia and trehalose was not detected. Maximum yield and storage stability were obtained in the potato-based medium (C:N ratio of 30:1). Based on these results, potato-based medium is superior to the standard rice-based medium for the production of B. bassiana Bv062 conidia with better ecophysiological performance to control the sugar cane borer.

Selection of inocula conditioning methodologies for the anaerobic digestion of food waste

Food waste (FW) has a high potential for use in biological processes such as anaerobic digestion (AD), especially due to its high content of biodegradable organic matter. To inoculate the reactors, sludge is usually used. The sludge should ideally have good sedimentation and specific methanogenic activity (SMA), which is typical for granular sludge. However, in a Latin American context, the most available and accessible sludges are flocculants with low sedimentation and SMA. Applying technological surveillance between 1975 and 2017, using multicriteria analysis techniques such as analytical hierarchy process (AHP), and consulting with international and national experts, we observed that there were few studies, compared to published studies on the substrates that focused on improving inoculum quality through conditioning to improve its characteristics and maximize methane production. The inoculum-conditioning methodologies identified were grouped into five categories, being the main strategy the addition of nutrients followed by anaerobic digestion with an easily degradable substrate. However, extension of technological surveillance is recommended by incorporating the results published from significant events in the field of anaerobic digestion, such as the Latin American Workshop and Symposium on Anaerobic Digestion and the World Congress on Anaerobic Digestion.

Cell Banks Preparation In Biopharmaceuticals Production

Abstract The fast development of the biopharmaceutical market is correlated with the growing number and availability of technologies for the production of so-called biodrugs. One of the main procedures for therapeutic protein production is based on bacterial expression systems. In order to maintain the constant quality and homogeneity of the initial inoculum, the cell bank must be created in full accordance with quality standards. The first step should be the establishment of a Master Cell Bank (MCB), which must be performed in a laboratory that meets high quality standards and according to well-described main procedures. The MCB should be initiated from a single well-characterised bacterial colony. A Working Cell Bank (WCB) is usually prepared as a second step from one or few vials deposited in the MCB. The WCB must be characterised for bacterial strain homology and be free of any biological cross contamination. This paper describes the main requirements and good practises for the preparation of a cell bank suitable for constant and reproducible production of biopharmaceuticals. 1. Introduction. 2. Prokaryotic expression system. 3. Cell banking system. 4. Cell banks characterization. 4.1. Conformation of identity (properties) of the bacterial strain. 4.2. Confirmation of the purity of the bacterial strain. 5. Summary

THE EFFECT OF SOILAGGREGATE SIZE AND P DOSAGE ON AMF SPORES NUMBER IN SHORGUM (Sorghum bicolor L.)

Mycorrhiza is a biological agent to help fertility of soil and plants. Application of mycorrhiza on the land in the form of inoculum is often used in agricultural land in the name of quality of inoculum that also influenced by the content of existing spores. One of them is growing medium. This study aimed to study the effect of soil aggregate size and P dosage on the number of mycorrhizal spores in sorghum plants. The research design used was Randomized Block Design consisting of 2 factors. First factor was soil aggregate size(μm) which consisted of 4 treatments: U1 = < 2000, U2 = 500 - 1000, U3 = 200 - 500, U4 = < 200, and second factor was P dosage: 100 mg/kg and 300mg/kg. Each treatment combination was repeated 3 times so that there were 24 units of experimental unit. Observation parameters included the percentage of the infected root, number of spores, plant height and dry weight of the plant. The research was conducted in Greenhouse and Agronomy Laboratory of Agricultural Faculty of Tadulako University Palu. The various sizes of soil aggregates do not affect the amount of arbuscular mycorrhizal spores in sorghum plants. P 100 mg/kg or f P 300 mg/kg dosage used do not address the effect of the mycorrhizal spores. There is no interaction between soil aggregate size and P dosage to the amount of mycorrhizal spores in sorghum plants.

Toward a Noninvasive, Label-Free Screening Method for Determining Spore Inoculum Quality of Penicillium chrysogenum Using Raman Spectroscopy.

We report on a label-free, noninvasive method for determination of spore inoculum quality of Penicillium chrysogenum prior to cultivation/germination. Raman microspectroscopy providing direct, molecule-specific information was used to extract information on the viability state of spores sampled directly from the spore inoculum. Based on the recorded Raman spectra, a supervised classification method was established for classification between living and dead spores and thus determining spore inoculum quality for optimized process control. A fast and simple sample preparation method consisting of one single dilution step was employed to eliminate interfering signals from the matrix and to achieve isolation of single spores on the sample carrier (CaF2). Aiming to avoid any influence of the killing procedure in the Raman spectrum of the spore, spores were considered naturally dead after more than one year of storage time. Fluorescence staining was used as reference method. A partial least squares discriminant analysis classifier was trained with Raman spectra of 258 living and dead spores (178 spectra for calibration, 80 spectra for validation). The classifier showed good performance when being applied to a 1 µL droplet taken from a 1:1 mixture of living and dead spores. Of 135 recorded spectra, 51% were assigned to living spores while 49% were identified as dead spores by the classifier. The results obtained in this work are a fundamental step towards developing an automated, label-free, and noninvasive screening method for assessing spore inoculum quality.

Microbial Nursery Production of High-Quality Biological Soil Crust Biomass for Restoration of Degraded Dryland Soils.

Biological soil crusts (biocrusts) are slow-growing, phototroph-based microbial assemblages that develop on the topsoils of drylands. Biocrusts help maintain soil fertility and reduce erosion. Because their loss through human activities has negative ecological and environmental health consequences, biocrust restoration is of interest. Active soil inoculation with biocrust microorganisms can be an important tool in this endeavor. We present a culture-independent, two-step process to grow multispecies biocrusts in open greenhouse nursery facilities, based on the inoculation of local soils with local biocrust remnants and incubation under seminatural conditions that maintain the essence of the habitat but lessen its harshness. In each of four U.S. Southwest sites, we tested and deployed combinations of factors that maximized growth (gauged as chlorophyll a content) while minimizing microbial community shifts (assessed by 16S rRNA sequencing and bioinformatics), particularly for crust-forming cyanobacteria. Generally, doubling the frequency of natural wetting events, a 60% reduction in sunlight, and inoculation by slurry were optimal. Nutrient addition effects were site specific. In 4 months, our approach yielded crusts of high inoculum quality reared on local soil exposed to locally matched climates, acclimated to desiccation, and containing communities minimally shifted in composition from local ones. Our inoculum contained abundant crust-forming cyanobacteria and no significant numbers of allochthonous phototrophs, and it was sufficient to treat ca. 6,000 m2 of degraded dryland soils at 1 to 5% of the typical crust biomass concentration, having started from a natural crust remnant as small as 6 to 30 cm2 IMPORTANCE: Soil surface crusts can protect dryland soils from erosion, but they are often negatively impacted by human activities. Their degradation causes a loss of fertility, increased production of fugitive dust and intensity of dust storms with associated traffic problems, and provokes general public health hazards. Our results constitute an advance in the quest to actively restore biological soil covers by providing a means to obtain high-quality inoculum within a reasonable time (a few months), thereby allowing land managers to recover essential, but damaged, ecosystem services in a sustainable, self-perpetuating way as provided by biocrust communities.

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Abstract The quantity and quality of inoculum used in the Anaerobic Digestion (AD), impact seriously on the biodegradability and the amount of methane produced. This research evaluated the effect of the source of inoculum municipal wastewater treatment plant (WWTP) on the production of methane as a source of renewable energy AD from Municipal Biowaste (MB), analyzing the Substrate-Inoculum (S/I) ratio and the buffering capacity of the inoculum as key aspects. The experiments were performed on a laboratory scale by testing Biochemical Methane Potential (BMP) in the mesophilic range with a retention time of solids (RTS) 21 days; two inoculums from UASB reactors and the other of an anaerobic sludge digester. The S/I ratios ranged between 0.5 and 12gVSsubstrate gVS-1 inoculum. Although it was found that there were no statistically signifcant differences between the inoculum (p>0.05), the inoculum from the anaerobic digester presented a better performance because of its greater capacity buffer. The S/I ratio showed statistically signifcant differences (p 70mLCH4 gVS-1 substrate ) hydrolysis rates (from 0,15 to 0,21d-1) and phases of lethargy (2,7-9,3d). Keywords: biowaste; renewable energy, hydrolysis, anaerobic sludge, methane, substrate-inoculum ratio.

At-line determination of spore inoculum quality in Penicillium chrysogenum bioprocesses.

Spore inoculum quality in filamentous bioprocesses is a critical parameter influencing pellet morphology and, consequently, process performance. It is essential to determine the concentration of viable spores before inoculation, to implement quality control and decrease batch-to-batch variability. The ability to assess the spore physiologic status with close-to-real time resolution would offer interesting perspectives enhanced process analytical technology (PAT) and quality by design (QbD) strategies. Up to now, the parameters contributing to spore inoculum quality are not clearly defined. The state-of-the-art method to investigate this variable is colony-forming unit (CFU) determination, which assesses the number of growing spores. This procedure is tedious, associated with significant inherent bias, and not applicable in real time.Here, a novel method is presented, based on the combination of viability staining (propidium iodide and fluorescein diacetate) and large-particle flow cytometry. It is compatible with the complex medium background often observed in filamentous bioprocesses and allows for a classification of the spores into different subpopulations. Next to viable spores with intact growth potential, dormant or inactive as well as physiologically compromised cells are accurately determined. Hence, a more holistic few on spore inoculum quality and early-phase biomass composition is provided, offering enhanced information content.In an industrially relevant model bioprocess, good correlation to CFU counts was found. Morphological parameters (e.g. spore swelling) that are not accessible via standard monitoring tools were followed over the initial process phase with close temporal resolution.

Intra and Inter-Spore Variability in Rhizophagus irregularis AOX Gene.

Arbuscular mycorrhizal fungi (AMF) are root-inhabiting fungi that form mutualistic symbioses with their host plants. AMF symbiosis improves nutrient uptake and buffers the plant against a diversity of stresses. Rhizophagus irregularis is one of the most widespread AMF species in the world, and its application in agricultural systems for yield improvement has increased over the last years. Still, from the inoculum production perspective, a lack of consistency of inoculum quality is referred to, which partially may be due to a high genetic variability of the fungus. The alternative oxidase (AOX) is an enzyme of the alternative respiratory chain already described in different taxa, including various fungi, which decreases the damage caused by oxidative stress. Nevertheless, virtually nothing is known on the involvement of AMF AOX on symbiosis establishment, as well on the existence of AOX variability that could affect AMF effectiveness and consequently plant performance. Here, we report the isolation and characterisation of the AOX gene of R. irregularis (RiAOX), and show that it is highly expressed during early phases of the symbiosis with plant roots. Phylogenetic analysis clustered RiAOX sequence with ancient fungi, and multiple sequence alignment revealed the lack of several regulatory motifs which are present in plant AOX. The analysis of RiAOX polymorphisms in single spores of three different isolates showed a reduced variability in one spore relatively to a group of spores. A high number of polymorphisms occurred in introns; nevertheless, some putative amino acid changes resulting from non-synonymous variants were found, offering a basis for selective pressure to occur within the populations. Given the AOX relatedness with stress responses, differences in gene variants amongst R. irregularis isolates are likely to be related with its origin and environmental constraints and might have a potential impact on inoculum production.

Approach toward an efficient inoculum preparation stage for suspension BHK-21 cell culture.

Mammalian cells are the most frequently used hosts for biopharmaceutical proteins manufacturing. Inoculum quality is a key element for establishing an efficient bioconversion process. The main objective in inoculation expansion process is to generate large volume of viable cells in the shortest time. The aim of this paper was to optimize the inoculum preparation stage of baby hamster kidney (BHK)-21 cells for suspension cultures in benchtop bioreactors, by means of a combination of static and agitated culture systems. Critical parameters for static (liquid column height: 5, 10, 15mm) and agitated (working volume: 35, 50, 65mL, inoculum volume percentage: 10, 30% and agitation speed: 25, 60rpm) cultures were study in T-flask and spinner flask, respectively. The optimal liquid column height was 5mm for static culture. The maximum viable cell concentration in spinner flask cultures was reached with 50mL working volume and the inoculum volume percentage was not significant in the range under study (10-30%) at 25rpm agitation. Agitation speed at 60rpm did not change the main kinetic parameters with respect to those observed for 25rpm. These results allowed for a schedule to produce more than 4×10(9) BHK-21 cells from 4×10(6) cells in 13day with 1,051mL culture medium.

POTENSI BERBAGAI TANAMAN SEBAGAI INANG INOKULUM MIKORIZA ARBUSKULAR DAN EFEKNYA TERHADAP PERTUMBUHAN TANAMAN JAGUNG DAN KEDELAI DI TANAH ULTISOL

The objective of this research would be to examine the micorrhyze inoculum quality of severaltypes of hosts using ultisol as growing medium on maize and soybean growth. The research hasbeen conducted in greenhouse and laboratory of Biotechnology of Soil, Faculty of Agriculture,North Sumatera University. To achieve this objective, a non-factorial group random sampling hasbeen used through some treatments: J J (maize was applied with mycorrhyze inoculum of maize), DJ (maize was apolied with mycorrhyze inoculum of soybeans), S J (maize was applied withmycorrhyze inoculum of setaria grass), T J (maize was appolied with mycorrhyze inoculum ofgroundnuts), J D (soybean was applied with mycorrhyze inoculum of maize), D D (soybean wasapplied with mycorrhyze inoculum of soybeans), S D (soybean was applied with mycorrhyzeinoculum of setaria grass), T D (soybean was applied with myzoerhyze inoculum of groundnuts).The result of research indicated that application of myzorrhyze inoculum of maize, soybean,groundnut and setaria grass to maize and soybean plants has not significant effect of increassing theheight of plants, wet weight of shoot, dry weight of shoot, wet weight of root, degree of rootinfection, uptakes of N and P in plants of maize and soybean plants.Keywords: host, mycorrhyze inocolum, maize, soybean, groundnut, and setaria grass

In vitro water stress bioassays with the nematophagous fungus Pochonia chlamydosporia: Effects on growth and parasitism

The biocontrol potential of Pochonia chlamydosporia, a fungus with parasitic activity against economically important plant-parasitic nematodes, can be influenced by abiotic factors such as water availability. The objective of this study was to evaluate the effects of different water stress regimes on in vitro growth, sporulation, germination and parasitism of P. chlamydosporia isolates. The osmotic water potential of 1.7% corn meal agar (CMA) was modified by addition of potassium chloride (KCl) or glycerol, and the matric water potential was modified using polyethylene glycol (PEG 8000). The fungus was able to grow over a range of potentials but radial growth rates decreased with the increase of osmotic and matric stress. No growth was observed at −10MPa on 1.7% CMA amended with glycerol and at −7.1MPa on medium with PEG 8000 but all isolates were able to resume growth when transferred onto unmodified 1.7% CMA. The production of chlamydospores was repressed in both osmotic and matric modified media. Although the production of conidia increased in medium modified with KCl, the germination rate was lower. Spores/hyphal fragments remained viable in all isolates that were previously inoculated onto media with growth-limiting water potential (−10MPa on 1.7% CMA amended with glycerol and −10MPa on medium with PEG 8000). The percentage of viable conidia produced on 1.7% CMA, after inoculation under osmotic or matric stress conditions for 25days, was over 74.5% in all isolates (osmotic stress) and ranged from 1% (Pc1) to 65.8% (Pc280) (matric stress). The in vitro infection of potato cyst nematodes, Globodera rostochiensis eggs by P. chlamydosporia isolates, grown under these limiting conditions, was studied using a standard bioassay. The percentage of parasitized eggs was significantly higher under osmotic stress except for isolates Pc2 and Pc3. P. chlamydosporia spores/hyphal fragments can remain viable at water potentials limiting for growth, for prolonged periods of time, suggesting that the osmoregulation mechanisms, used to compensate water stress, affect in vitro sporulation and increased pathogenicity. Knowledge on water requirements of P. chlamydosporia enables a better understanding of its survival and growth strategies in the soil environment and could aid the development of effective strategies to increase the production and quality of inoculum, thus contributing to the implementation of biosafe, sustainable management strategies against plant-parasitic nematodes.

Growth response of <i>Pterocarpus soyauxii</i> and <i>Lophira alata</i> seedlings to host soil mycorrhizal inocula in relation to land use types

Deficiency in mycorrhizal inoculum in soils due to land use types (LUT) can be alleviated by inoculum addition. Inoculum effects may depend both on quantity and on quality of inoculum applied. A greenhouse bioassay was carried out to determine the effect of host soil mycorrhizal inoculum on mycorrhizal colonization, carbon allocation and partitioning of seedlings of two native timber species of Cameroon humid forest, raised on surface soils (0-20 cm) collected from early secondary forests, LUT derived from slash-and-burn agriculture and selective logging. Host soil mycorrhizal inoculum was collected from the root zones of con-specific tree species. Mycorrhizal inoculation effect (MIE) was estimated as percent difference of average total biomass between seedlings grown on inoculated and non-inoculated soils. Six months-old seedlings of Pterocarpus soyauxii and Lophira alata were mainly colonized by members of the Glomaceae and Gigasporaceae, respectively, as shown by molecular typing. They generally performed poorly in soils with indigenous inoculum. But addition of soil inoculum from P. soyauxii trees favored nodulation, significantly increased mycorrhizal colonization and total biomass but decreased root-to-shoot ratios, resulting in large and positive MIE, irrespective of LUT. ln contrast, host soil inoculum of L. alata did not affect fractional mycorrhizal colonization but significantly increased total biomass, resulted in high carbon allocation to roots, in low and sometimes negative MIE. Therefore, seedlings' responses to mycorrhizal inoculum depend on host soil inoculum and that could be critical for successful rejuvenation of tropical trees. Key words. Arbuscular mycorrhiza-host soil inoculum-Iand use types- Pterocarpus soyauxii-Lophira alata -Cameroon

Exploring the lag phase and growth initiation of a yeast culture by means of an individual-based model

The performance of fermentation processes is greatly influenced by the size and quality of inocula. The characterization of the replicative age is decided by the number of birth scars each yeast exhibits on its cellular membrane. Yeast ageing and inoculum size are factors that affect industrial fermentation, particularly those processes in which the yeast cells are reused such as the production of beer. This process reuses yeast cropped at the end of one fermentation in the following one, in a process called “serial repitching”. The aim of this study was to explore the effects of inoculum size and ageing on the first stages of the dynamics of yeast population growth. However, only Individual-based Models (IbMs) allow the study of small, well-characterized, microbial inocula. We used INDISIM-YEAST, based on the generic IbM simulator INDISIM, to carry out these studies. Several simulations were performed to analyze the effect of the inoculum size and genealogical age of the cells that made it up on the lag phase, first division time and specific growth rate. The shortest lag phase and time to the first division were obtained with largest inocula and with the youngest inoculated parent cells.