Biocontrol Systems Research Articles

Microbial succession in white button mushroom production systems from compost and casing to a marketable packed product

The aim of the study was to investigate microbial succession in the mushroom supply chain from compost, casing to fruit body formation and mushroom growth to the point of harvest, packing and point of sale. The microbial population dynamics of compost, casing and mushrooms were determined using a plate count technique, denaturing gradient gel electrophoresis (DGGE) and sequencing of 16S and 18S rDNA. Plating revealed greater abundance of bacteria, fungi and yeasts in mushroom compost compared to casing and fresh mushroom samples. The viable count method also showed that bacteria and yeasts increased significantly after harvest and during cold storage. Sequencing revealed a more diverse culturable bacterial population in casing and on the mushrooms than in the compost. Phylogenetic analysis revealed a general trend of grouping of species from the same sources. In contrast, a higher microbial diversity was recorded in compost when using the DGGE method, which reflects both cultural and non-culturable microorganisms. For compost and casing bacteria studied using DGGE, several species formed separate lineages, demonstrating highly diverse communities in these samples. Fungi were shown to be less abundant and less diverse compared to bacteria and yeasts. The study provides baseline knowledge of microbial populations and succession trends in mushroom production systems using viable and non-viable methods. The information provided in this study may be useful for microbial ecology studies and to identify and develop biocontrol systems for pathogen control during production or to enhance pinning stimulation by knowing when to apply Pseudomonas spp. to ensure increased yield. Finally, an insight is provided into microbial survival during cold storage and marketing of mushrooms. Potential antagonistic populations known to prevent spoilage, quality deterioration and extend shelf life are listed in this paper.

Nontarget herbivory by a weed biocontrol insect is limited to spillover, reducing the chance of population-level impacts.

Insects approved for classical biocontrol of weeds are often capable of using close relatives of their target weed for feeding, oviposition, or larval development, with reduced preference and performance. When nontarget herbivory occurs and is suspected to reduce survival, growth, or fecundity of individual plants, and insects are capable of reproducing on their nontarget host, characterization of spatial and temporal patterns of the occurrence and intensity of herbivory is valuable for predicting potential population-level effects. Here, we perform a novel post-release manipulative field experiment with a root-feeding biocontrol weevil, Mogulones crucifer, released in Canada to control the rangeland weed Cynoglossum officinale, to test for its ability to establish on the nontarget plant Hackelia micrantha. After Cynoglossum, M. crucifer exhibits its highest preference for and performance on Hackelia spp. We released M. crucifer on Canadian rangeland sites with naturally occurring populations of H. micrantha growing interspersed with the target weed or in the near absence of the target weed. Adult weevil feeding on surrounding plants was monitored for three summers after release (years 0, 1, and 2), and, subsequently, subsets of plants were destructively sampled to determine M. crucifer oviposition levels. Additional oviposition and larval development data were obtained from seven non-experimental sites where weevils were released zero, three, or four years earlier. M. crucifer was not detected on experimental sites without C. officinale after two years, and nontarget herbivory was restricted to rare, low-level spillover. Visible evidence of adult herbivory (i.e., scars on shoots) was associated with oviposition in 90% of targets but only 30% of nontarget plants. We infer, through ecological refuge theory, that nontarget population-level impacts from M. crucifer spillover are unlikely because of temporal, spatial, and probabilistic refuges from herbivory, and make recommendations for monitoring and management of biocontrol systems with similar attributes, such as removing target plants around nontarget populations of interest. Because M. crucifer is among the least host-specific of the modern weed biocontrol agents, and H. micrantha is likely one of its most highly preferred nontargets, these conclusions are, arguably, generally applicable to other nontarget plants and biocontrol systems.

Streptomyces–Aspergillus flavus interactions: impact on aflatoxin B accumulation

The aim of this work was to investigate the potential of Streptomyces sp. as biocontrol agents against aflatoxins in maize. As such, we assumed that Streptomyces sp. could provide a complementary approach to current biocontrol systems such as Afla-guard® and we focused on biocontrol that was able to have an antagonistic contact with A. flavus. A previous study showed that 27 (out of 38) Streptomyces sp. had mutual antagonism in contact with A. flavus. Among these, 16 Streptomyces sp. were able to reduce aflatoxin content to below 17% of the residual concentration. We selected six strains to understand the mechanisms involved in the prevention of aflatoxin accumulation. Thus, in interaction with A. flavus, we monitored by RT-qPCR the gene expression of aflD, aflM, aflP, aflR and aflS. All the Streptomyces sp. were able to reduce aflatoxin concentration (24.0–0.2% residual aflatoxin B1). They all impacted on gene expression, but only S35 and S38 were able to repress expression significantly. Indeed, S35 significantly repressed aflM expression and S38 significantly repressed aflR, aflM and aflP. S6 reduced aflatoxin concentrations (2.3% residual aflatoxin B1) and repressed aflS, aflM and enhanced aflR expression. In addition, the S6 strain (previously identified as the most reducing pure aflatoxin B1) was further tested to determine a potential adsorption mechanism. We did not observe any adsorption phenomenon. In conclusion, this study showed that Streptomyces sp. prevent the production of (aflatoxin gene expression) and decontamination of (aflatoxin B1 reduction) aflatoxins in vitro.

Tailoring biocontrol to maximize top-down effects: on the importance of underlying site fertility.

The degree to which biocontrol agents impact invasive plants varies widely across landscapes, often for unknown reasons. Understanding this variability can help optimize invasive species management while also informing our understanding of trophic linkages. To address these issues, we tested three hypotheses with contrasting predictions regarding the likelihood of biocontrol success. (1) The biocontrol effort hypothesis: invasive populations are regulated primarily by top-down effects, predicting that increased biocontrol efforts alone (e.g., more individuals of a given biocontrol agent or more time since agent release) will enhance biocontrol success. (2) The relative fertility hypothesis: invasive populations are regulated primarily by bottom-up effects, predicting that nutrient enrichment will increase dominance by invasives and thus reduce biocontrol success, regardless of biocontrol efforts. (3) The fertility-dependent biocontrol effort hypothesis: top-down effects will only regulate invasive populations if bottom-up effects are weak. It predicts that greater biocontrol efforts will increase biocontrol success, but only in low-nutrient sites. To test these hypotheses, we surveyed 46 sites across three states with prior releases of Galerucella beetles, the most common biocontrol agents used against invasive purple loosestrife (Lythrum salicaria). We found strong support for the fertility-dependent biocontrol effort hypothesis, as biocontrol success occurred most often with greater biocontrol efforts, but only in low-fertility sites. This result held for early stage metrics of biocontrol success (higher Galerucella abundance) and ultimate biocontrol outcomes (decreased loosestrife plant size and abundance). Presence of the invasive grass Phalaris arundinacea was also inversely related to loosestrife abundance, suggesting that biocontrol-based reductions in loosestrife made secondary invasion by P. arundinacea more likely. Our data suggest that low-nutrient sites be prioritized for loosestrife biocontrol and that future monitoring account for variation in site fertility or work to mitigate it. We introduce a new framework that integrates our findings with conflicting patterns previously reported from other biocontrol systems, proposing a unimodal relationship whereby nutrient availability enhances biocontrol success in low-nutrient sites but hampers it in high-nutrient sites. Our results represent one of the first examples of biocontrol success depending on site fertility, which has the potential to inform biocontrol-based management decisions across entire regions and among contrasting systems.

What does the term microbiome mean? And where did it come from? A bit of a surprise ..

BIOLOGICAL SCIENCES What does the term microbiome mean? And where did it come from? A bit of a surprise .. JONATHAN EISEN READ REVIEWS ✎ WRITE A REVIEW CORRESPONDENCE: jaeisen@ucdavis.edu DATE RECEIVED: “Microbiome” is such a hot term these days. And one key question many ask is “what does it mean?” A related question is – “where did the term come from?” I tried to tackle this many years ago on my blog with a post: The human microbiome – term being used in many ways – but at least it is getting some \npress. Basically my main point was that it seemed that the term “ microbiome” then should be used to refer to the collection of genomes of microbes in a system and that “microbiota” should be used to refer to the collection of organisms. Some key quotes from that post: June 10, 2015 DOI: 10.15200/winn.142971.16196 ARCHIVED: April 22, 2015 CITATION: Jonathan Eisen, What does the term microbiome mean? And where did it come from? A bit of a surprise .., The Winnower 2:e142971.16196 , 2015 , DOI: 10.15200/winn.142971.16196 © Eisen This article is distributed under the terms of the Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and redistribution in any medium, provided that the original author and source are credited. Well, the human microbiome is all over the news recently thanks to a new paper on the diversity and biogeography of microbes in human saliva. My only complaint is that I and Stoneking and many others have unfortunately made a mess of the terminology. The “microbiome” was originally used to refer to the collection of the genomes of the microbes in a particular ecosystem. And the terms “microbiota” was used to refer to the actual organisms. Since Stoneking et al did not survey the genomes, they surveyed rRNA (which really at best tells you about what types of organisms are present) then they should have used microbiota riight? (And if they had I would not have been searching for the genomics component of their work). Not so fast, even the person who coined the term microbiome (Josh Lederberg) who originally seemed to use it to refer to all the genomes of the microbes also used the term ambiguously (e.g., in one paper he sad “the microbiome flora” meaning I guess the microbiota. I note, everyone seems to cite A paper by Lederberg called “Infectious History” in Science (Science 14 April 2000:) as the place he used microbiome but I cannot find the term there. I did however find the term in a paper in 2001 by Lora Hooper and Jeff Gordon (Commensal Host-Bacterial Relationships in the Gut Science 11 May 2001: Vol. 292. no. 5519, pp. 1115 – 1118). The Nobel laureate Joshua Lederberg has suggested using the term “microbiome” to describe the collective genome of our indigenous microbes (microflora), the idea being that a comprehensive genetic view of Homo sapiens as a life-form should include the genes in our microbiome (4). And reference 4 is “Personal communication” Anyway, others have taken the term microbiome and run with it because it does conjure up to many “microbial biome” which could be used to refer to all the microbes in a system. I prefer the original definitions with microbiota being the organisms and microbiome being the collective genomes of all the organisms. EISEN The Winnower APRIL 22 2015

Ecofriendly control of potato late blight causative agent and the potential role of lactic acid bacteria: a review

In times of increasing societal pressure to reduce the application of pesticides on crops, demands for environmentally friendly replacements have intensified. In the case of late blight, a devastating potato plant disease, the historically most widely known plant destroyer has been the oomycete Phytophthora infestans. To date, the most important strategy for control of this pathogen has been the frequent application of fungicides. Due to the aforementioned necessity to move away from traditional chemical treatments, many studies have focused on finding alternative ecofriendly biocontrol systems. In general, due to the different modes of actions (i.e. antagonistic effects or induction of plant defence mechanisms), the use of microorganisms as biological control agents has a definite potential. Amongst them, several species of lactic acid bacteria have been recognised as producers of bioactive metabolites which are functional against a broad spectrum of undesirable microorganisms, such as fungi, oomycetes and other bacteria. Thus, they may represent an interesting tool for the development of novel concepts in pest management. This review describes the present situation of late blight disease and summarises current literature regarding the biocontrol of the phytopathogen P. infestans using antagonistic microorganisms.

Analysis of the Ketosynthase Genes in Streptomyces and Its Implications for Preventing Reinvestigation of Polyketides with Bioactivities

Cucumber wilt by Fusarium oxysporium f sp. cucumarinum is one of the most important soil-borne diseases. Among control strategies for plant soil-borne pathogen, biocontrol systems eliminate neither pathogen nor disease but bring them into natural balance. Polyketides form the largest part of the known natural products, and most of them come from actinomycetes especially streptomyces. Analysis for the ketosynthase genes in streptomyces can implicate new polyketides. In the course of the screening for producers of polyketides with antifungal activities, 117 strains were isolated. The screening program was performed by means of PCR amplification using degenerated primers corresponding to type II ketosynthase (KS) genes. Among 117 isolates, 33 isolates showed antifungal activities and 17 isolates showed positive amplification signal. Antagonism of the 17 isolates against Fusarium oxysporium f sp. cucumarinum, Bacillus subtilis and Erwinia carotovora subsp. carotovora in vitro were analyzed. The diversities of KS-II gene from the 17 isolates were abundant based on phylogenetic tree analysis. The 17 isolates were divided into 6 clades based on KS-II gene sequence. The results showed that different isolates which belong to the same species present different antagonism activities and also the different streptomyces species showed different bioactivities. Among 17 isolates, isolates DQ1, DQ23, GAN1, HVG60 and HVG71 have the potential ability to produce new type polyketides. This method may not only prevent reinvestigation to find bioactive molecules described previously, but also alleviate some of the biases introduced by using conventional cultivation techniques.

An automated plasma D-lactate assay with a new sample preparation method to prevent interference from L-lactate and L-lactate dehydrogenase

Objective. To establish an automated plasma D-lactate assay without interference from L-lactate and L-lactate dehydrogenase (L-LDH). Methods and materials. The D-lactate assay was programmed as a 2-point endpoint assay on the Roche Modular P using the D-lactic acid kit from Biocontrol Systems, USA. In the chemical reaction, D-lactate was oxidized to pyruvate by NAD+ in the presence of D-lactate dehydrogenase. The resultant pyruvate was converted to alanine in the presence of alanine aminotransferase. The amount of NADH formed in the coupled reaction, measured by the change in the absorbance at 340 nm, was proportional to the concentration of D-lactate in the sample. Human serum albumin (HSA) solutions and plasma from pigs with experimentally-induced gut ischemia were used in this study. Blood samples were collected into Venosafe® tubes. Results. The D-lactate assay was linear up to 1.000 mmol/L in HSA solutions and plasma. The detection limit was 0.003 mmol/L. Within-run CVs ≤ 2.0% and total CVs ≤ 3.2% were obtained in the control material. Recovery was 87.1 ± 5.2 % (Mean ± SD). The L-LDH activity was completely inactivated in plasma samples by the addition of 20 µL of a 5 mol/L NaOH solution to 500 µL of plasma (pH 11.5). No interference could be detected from concentrations of bilirubin < 450 µmol/L, haemoglobin < 0.2 mmol/L or Intralipid® < 2.5 g/L. Conclusions. The performance of the established D-lactate assay meets the requirements to be implemented into hospital laboratories. The sample preparation method is simple, cheap and requires minimal labour.

Trait-mediated interactions and lifetime fitness of the invasive plantCentaurea solstitialis

Plants interact with numerous enemies and mutualists simultaneously and sequentially. Such multispecies interactions can give rise to trait-mediated indirect effects that are likely to be common in nature but which are also inherently difficult to predict. Understanding multispecies interactions is also important in the use of biological control agents to control invasive plants because modern approaches to biocontrol rely on releasing multiple agents for each target weed. Centaurea solstitialis is one of the most problematic invasive weeds in California, USA, and the weevil Eustenopus villosus is its dominant biological control agent. We conducted a field experiment to quantitatively assess the direct effect of the recently approved biocontrol pathogen Puccinia jaceae f.s. solstitialis on plant performance and any indirect effects that might arise by altering the plant's interactions with Eustenopus or its pollinators (principally the nonnative Apis mellifera). We documented both synergy and interference between the two biocontrol agents depending on the life stage of the weevil. Puccinia infection increased the impact of bud-feeding by the adult weevils but reduced the impact of seed-feeding by larval weevils. Neither infection nor Eustenopus attack had an effect on pollinator visitation. The net effect was that attack by both the pathogen and the weevil did not reduce plant fitness relative to plants attacked only by the weevil. Because the consequence to the plant of interacting with one species may depend on the presence or absence of other interacting species, a careful consideration of multispecies interactions may be necessary for the selection of biocontrol agents that act in a complementary manner to reduce plant fitness. Likewise, relatively tractable weed–biocontrol systems allow us to examine multispecies interactions that can be difficult to study experimentally in native systems that are composed of numerous species with well-established populations.

An assessment of environmental conditions for control of downy brome by Pseudomonas fluorescens D7

Purpose: We evaluated the conditions that favoured Pseudomonas fluorescens strain D7 (P.f. D7) growth and inhibition of downy brome. Design/methodology/approach: Tn5 mutagenesis and a competitive assay were used to isolate mutants of P.f. D7. Isolates were screened for polysaccharide production and toxin response. Seven mutants were tested under varying pH, temperature and water potential and characterised using Random Amplified Polymorphic DNA analysis. Findings: Temperature, pH, and water potential did not affect weed suppression in bioassays, except at 37°C and with NaCl. Originality and/value: Understanding the genetics of P.f. D7 will help in the development of successful weed biocontrol systems.

Dynamical biocontrol systems: insights through mechanistic modelling

Dynamical biological systems can be modelled mathematically at many levels, from relatively macroscopic, i.e. aggregating many processes or components into subsystem blocks and associated equations characterizing overall behaviour, to microscopic, i.e. focusing on physical mechanisms at the level of individual molecules and associated unit-process equations reflecting such couplings. Here we examine some representative examples within this spectrum of approaches, illustrating the ways in which various investigators handle data-driven modelling problems associated with drug effects–from mostly blood-borne data; switch-like responses in cell signalling subsystems–from molecular biochemistry data; gene network regulation–from pharmacogenomics data; and tumour-suppressor protein regulation mechanisms–also from molecular biochemistry data. Special attention is given to the latter, as modelling of the potential mechanisms involved in this system is an ongoing investigation in our lab. The biosystem model representations described here demonstrate to varying degrees the power of more microscopic methods for discriminating between alternative mechanistic hypotheses of biocontrol system connectivity and dynamics.

A generic theoretical model for biological control of foliar plant diseases

We have developed a generic modelling framework to understand the dynamics of foliar pathogen and biocontrol agent (BCA) populations in order to predict the likelihood of successful biocontrol in relation to the mechanisms involved. The model considers biocontrol systems for foliar pathogens only and, although it is most applicable to fungal BCA systems, does not address a specific biocontrol system. Four biocontrol mechanisms (competition, antibiosis, mycoparasitism and induced resistance) were included within the model rubric. Because of the wide range of mechanisms involved we use Trichoderma/Botrytis as an exemplar system. Qualitative analysis of the model showed that the rates of a BCA colonising diseased and/or healthy plant tissues and the time that the BCA remains active are two of the more important factors in determining the final outcome of a biocontrol system. Further evaluation of the model indicated that the dynamic path to the steady-state population levels also depends critically on other parameters such as the host–pathogen infection rate. In principle, the model can be extended to include other potential mechanisms, including spatio-temporal heterogeneity, fungicide effects, non-fungal BCA and strategies for BCA application, although with a cost in model tractability and ease of interpretation.

Tools and Products

Department editor Dave Kasik highlights some of the new computer graphics tools and products on the market. In this issue the featured tools and products are the "Project Epoc" headset from Emotiv Systems; the BioWave, BioFlex, and BioBeat wearable sensor systems from BioControl Systems; MSI Computer's Wind Notebook; Glucoboy; IBM's Anatomic and Symbolic Mapper Engine; Anark Core Workstation; and nPower Software's version 5.0 of Power NURBS, Power Solids, and Power Translators.

Role of Nutrient Limitation in the Competition between Pseudomonas fluorescens and Escherichia coli O157:H7

Competition between spoilage microorganisms and foodborne pathogens provides a potentially simple approach to limiting the growth of pathogens. A strain of Pseudomonas fluorescens isolated from raw milk repressed growth of Escherichia coli O157:H7 at 22°C in nutrient broth once the maximum population density of the pseudomonad had been reached (9.6 log CFU ml−1). The presence of iron in the growth medium and the parallel inhibitory effect of a siderophore-deficient mutant of P. fluorescens precluded iron limitation as the mechanism of action. Medium depleted by prior growth of P. fluorescens prevented the growth of E. coli, and this effect was reversed by the replenishment of the nutrient broth, its component fractions, or the addition of soy peptones but not peptones derived from milk protein. This is the first report of competition between spoilage microflora and foodborne pathogens in which the mechanism was clearly shown to be nutrient limitation. These results suggest possible improvements in biocontrol systems to prevent pathogen growth on foods.

SEMIQUANTITATIVE EVALUATION OF PROTEIN RESIDUES IN FOODS USING THE FLASH RAPID CLEANING VALIDATION METHOD†

ABSTRACT Cross‐contamination of food contact surfaces in retail foodservice establishments may result in outbreaks of foodborne illness. Traditional microbiological sampling collection methods that use swab tests or agar surface tests to monitor cross‐contamination can be time‐ and cost‐prohibitive to restaurant operators. The purpose of this study was to develop an identification protocol for residual proteins on foodservice contact surfaces using rapid chemical detection methods. The FLASH Rapid Cleaning Validation device (BioControl Systems, Bellevue, WA) was used to detect residual protein traces (exposed for 0, 2, 4, 6 and 8 h) of six different food samples (ground beef, ground turkey, ground pork, catfish, shredded cheddar cheese and shredded vegetables) on plastic cutting boards. Catalase testing was performed concurrently with FLASH validation to add further estimation of potential biological activities. Results showed that meat, cheese and vegetable samples were positive for the FLASH test and could provide semiquantification using a red–green–blue color chart. In addition, catalase testing provided more selective identification of food samples. This study demonstrates the time savings and cost‐effectiveness of using rapid methods of monitoring food safety standards in a foodservice operation.

Stable coexistence of an invasive plant and biocontrol agent: a parameterized coupled plant–herbivore model

Summary Coupled plant–herbivore models, allowing feedback from plant to herbivore populations and vice versa, enable us to predict the impact of biocontrol agents on their target weed populations; however, they are rarely used in biocontrol studies. We describe the population biology of the invasive plant Echium plantagineum and the weevil Mogulones larvatus, a biocontrol agent, in Australia. In order to understand the dynamics of this plant–herbivore system, a series of coupled models of increasing complexity was developed. A simple model was extended to include a seed bank, density‐dependent plant fecundity, competition between weevil larvae and plant tolerance of herbivory, where below a threshold plants could compensate for larval feeding. Parameters and functional forms were estimated from experimental and field data. The plant model, in the absence of the weevil, exhibited stable dynamics and provided a good quantitative description of field densities before the weevil was introduced. In the coupled plant–herbivore model, density dependence in both plant fecundity and weevil larval competition stabilized the dynamics. Without larval competition the model was unstable, and plant tolerance of herbivory exacerbated this instability. This was a result of a time delay in plant response to herbivore densities. Synthesis and applications. The coupled plant–herbivore model allowed us to predict whether stable coexistence of target plant and biocontrol agents was achievable at an acceptable level. We found this to be the case for the Echium–Mogulones system and believe that similar models would be of use when assessing new agents in this and other invasive plant biocontrol systems. Density dependence in new biocontrol agents should be assessed in order to determine whether it is likely to result in the aims of classical biocontrol: low, stable and sustainable populations of plant and herbivore. Further work should be done to characterize the strength of density dependence according to the niche occupied by the biocontrol agent, for example the strength and functional form of density dependence in stem borers may be quite different to that of defoliators.

Formulation of Bacillus spp. for Biological Control of Plant Diseases

ABSTRACT Maximizing the potential for successfully developing and deploying a biocontrol product begins with a carefully crafted microbial screening procedure, proceeds with developing mass production protocols that optimize product quantity and quality, and ends with devising a product formulation that preserves shelf-life, aids product delivery, and enhances bioactivity. Microbial selection procedures that require prospective bio-control agents to possess both efficacy and amenability to production in liquid culture increase the likelihood of selecting agents with enhanced commercial development potential. Scale-up of biomass production procedures must optimize product quantity without compromise of product efficacy or amenability to stabilization and formulation. Formulation of Bacillus spp. for use against plant pathogens is an enormous topic in general terms but limited in published specifics regarding formulations used in commercially available products. Types of formulations include dry products such as wettable powders, dusts, and granules, and liquid products including cell suspensions in water, oils, and emulsions. Cells can also be microencapsulated. Considerations critical to designing successful formulations of microbial biomass are many fold and include preserving biomass viability during stabilization, drying, and rehydration; aiding biomass delivery, target coverage, and target adhesion; and enhancing biomass survival and efficacy after delivery to the target. Solutions to these formulation considerations will not necessarily be compatible. Data from several biocontrol systems including the use of B. subtilis OH 131.1 (NRRL B-30212) to reduce Fusarium head blight of wheat are used to illustrate many of these issues. Using our recently described assay for efficiently evaluating biomass production and formulation protocols, we demonstrate the effectiveness, in vitro, of UV protectant compounds lignin (PC 1307) and Blankophor BBH in reducing OH 131.1 morbidity when cells were exposed to UV light from artificial sunlight.

Whole cells ofBacillus subtilisAF 1 proved more effective than cell-free and chitinase-based formulations in biological control of citrus fruit rot and groundnut rust

In foliar and postharvest biocontrol systems, the use of active metabolites produced by antagonistic microorganisms is advantageous compared with the use of living microorganisms. Chitinases, a major group of hydrolytic enzymes produced by biocontrol agents, are involved in the lysis of cell walls of pathogenic fungi. In the present study, an attempt was made to test the partially purified beta-1,4-N-acetylglucosaminidase (NAGase) of a biocontrol strain Bacillus subtilis AF 1 for control of rust in groundnut (caused by Puccinia arachidis) and soft rot in lemons (caused by Aspergillus niger). Four proteins of molecular mass 67, 40, 37, and 32 kDa were isolated from the culture filtrates of AF 1 by affinity chromatography, of which the 67-kDa protein has detectable chitinolytic ability. This protein (NAGase) effectively inhibited the in vitro growth of A. niger in microtitre plates. In the presence of NAGase, germination of urediniospores of P. arachidis was reduced by 96% compared with the control. In a detached leaf bioassay, NAGase reduced the rust lesion frequency by >60%. NAGase significantly reduced the incidence of soft rot in harvested lemon fruits. However, fresh cells and (or) alginate formulation of AF 1 were more effective than NAGase in control of both of the test plant - pathogen systems.

A Study on the Design of a Biologizing Control System

According to the progress of an information-oriented society, more human friendly systems are required. The systems can be implemented by a kind of intelligent algorithms. In this paper we propose the possibility of the implementation of an intelligent algorithm from gene behavior of human beings, which has some properties such as self organization and self regulation. The regulation of gene behavior is widely analyzed by Boolean network. Also the SORE (Self Organizable and Regulating Engine) is one of those algorithms. This paper does not report detailed research results; rather, it studies the feasibility of gene behavior in biocontrol systems based upon computer simulations.

Transition from Conventional to Organic Farming Systems: I. Challenges, Recommendations, and Guidelines for Pest Management

Conventional agricultural systems increase per-area food production, but deplete natural resources and degrade both crop and environmental quality. Many of these concerns are addressed by sustainable agricultural systems, integrated pest management, biocontrol, and other alternative systems. Environmental and social concerns have escalated the need for alternative agricultural systems in the last decade. One alternative, the organic farming system, substitutes cultural and biological inputs for synthetically made fertilizers and chemicals for crop nutrition and pest management. Practices used for crop and pest management are similar during transition from conventional to organic farming systems, but produce is not certified to be organic during the transition period. During the transition from conventional to organic farming, growers may face pest control difficulties and lower yields when conventional practices are abandoned. The objectives of this paper are to 1) give an overview of the reasons for converting to organic farming and the challenges that growers face during the transition period, 2) outline some potential strategies for crop, soil, and pest management, and 3) list guidelines and recommendations for pest management during the transition to organic farming. Implementation of crop and pest management practices depends on geographical location, climate, available onsite resources, and history of the land. During transition, growers rely on cultural mechanisms and on organic and mineral sources to improve soil fertility, to build a population of natural enemies to suppress pest populations. Pest management practices during the transition period that reduce pest populations to economically manageable levels include crop rotation, cultivation, cover crops, mulches, crop diversification, resistant varieties, and insect traps. These practices also enrich the soil biota and increase crop yields before produce is certified organically grown.