The impact of forest encroachment after agricultural land abandonment on passerine bird communities: The case of Greece

Agricultural land abandonment is one of the main drivers of land use change, leading to various responses of farmland ecological communities. In an effort to better understand the effect of agricultural land abandonment on passerine bird communities, we sampled 20 randomly selected sites [1 km × 1 km] in remote Greek mountains, reflecting an abandonment gradient, in terms of forest encroachment. We sampled 169 plots using the point count method of fixed distance (47 passerine species), and we investigated bird diversity and community structure turnover along the gradient. We found that grazing intensity has a beneficial effect hampering forest encroachment that follows progressively land abandonment. Habitat composition changes gradually with forests developing at the expense of open meadows and heterogeneous grasslands. Forest encroachment has a significant negative effect on bird diversity and species richness, affecting in particular typical farmland and Mediterranean shrubland species. Birds form five distinct ecological clusters after land abandonment: species mostly found in pinewoods and cavity-dwelling species; species that prefer open forests forest edges or ecotones; species that prefer shrubland or open habitats with scattered woody vegetation; Mediterranean farmland birds that prefer semi-open habitats with hedges and/or woodlots; and, generalist forest-dwelling or shrubland species. We extracted a set of 22 species to represent the above ecological communities, as a new monitoring tool for agricultural land use change and conservation. We suggest that the maintenance of rural mosaics should be included in the priorities of agricultural policy for farmland bird diversity conservation.     

Molecular dialogues between Trichoderma and roots: Role of the fungal secretome

Trichoderma species are opportunistic fungi residing primarily in soil, tree bark and on wild mushrooms. Trichoderma is capable of killing other fungi and penetrating plant roots, and is commonly used as both a biofungicide and inducer of plant defence against pathogens. These fungi also exert other beneficial effects on plants including growth promotion and tolerance to abiotic stresses, primarily mediated by their intimate interactions with roots. In root–microbe interactions (both beneficial and harmful), fungal secreted proteins play a crucial role in establishing contact with the roots, fungal attachment, root penetration and triggering of plant responses. In Trichoderma–root interactions, the sucrose present in root exudates has been demonstrated to be important in fungal attraction. Attachment to roots is mediated by hydrophobin-like proteins, and secreted swollenins and plant cell wall degrading enzymes facilitate internalization of the fungal hyphae. During the early stage of penetration, suppression of plant defence is vital to successful initial root colonisation; this is mediated by small soluble cysteine-rich secreted proteins (effector-like proteins). Up to this stage, Trichoderma's behaviour is similar to that of a plant pathogen invading root structures. However, subsequent events like oxidative bursts, the synthesis of salicylic acid by the plants, and secretion of elicitor-like proteins by Trichoderma spp. differentiate this fungus from pathogens. These processes induce immunity in plants that help counter subsequent invasion by plant pathogens and insects. In this review, we present an inventory of soluble secreted proteins from Trichoderma that might play an active role in beneficial Trichoderma–plant interactions, and review the function of such proteins where known.     

Influence of vegetation and soil types on the wheatbelt termite,Drepanotermes tamminensis (Hill), in the Western Australian wheatbelt

A survey of the distribution and density of mounds of the harvester termite,Drepanotermes tamminensis (Hill), was carried out in the Durokoppin Nature Reserve, Western Australia in 1990. Vegetation and, to a lesser extent, soil type, appear to be important factors in determining density and distribution of termite mounds within the Reserve. A more detailed study of mounds in Wandoo (Eucalyptus capillosa) woodland and Casuarina (Allocasuarina campestris) shrubland indicated that the total number and size of mounds were significantly higher in the woodland than in the shrubland. The total wet weight biomass ofD. tamminensis was calculated as 3.74 gm⁻² (37.4 kg ha⁻¹) in the woodland and 1.69 gm⁻² (16.9 kg ha⁻¹) in the shrubland. Thus, of the two favored habitats, Wandoo woodland appears to be more optimal for this termite species than the Casuarina shrubland.     

Short-term effects on sheep pastureland due to grazing abandonment in a Western Mediterranean island ecosystem: A multidisciplinary approach

Changes of pasture communities consequent to management practices resulting from land abandonment considerably affect the structure and function of the ecosystem. This study analyses the consequences of grazing abandonment in terms of plant and soil microbial diversity and fertility, on a Mediterranean upland sheep pasture, over a short period (five years). Grazing was experimentally excluded by fencing ten 10×10 m permanent plots within an area that had supported grazing until 2000, by 0.23 sheep ha^?1. Plant and soil microbial communities and physicochemical parameters were monitored within the fenced and unfenced control plots, during three sampling times from 2000 (before the fencing) to 2005. Grazing cessation notably altered the floral composition, with an average dissimilarity of 96.7% between the vegetation communities, over five years. No significant change occurred in the control plots that were grazed throughout the sampling period. This work highlighted that, over a short term, the structural change in the specific plant composition affected only the grass species, confirming that grazing favours the small-sized species over the annual species. Further, it was evident that species groups of conservational and phytogeographic interest, like the endemic and Mediterranean-Atlantic species, tended to disappear with pasture abandonment and were substituted by more widespread species throughout the Mediterranean or even the world. Pasture abandonment was accompanied by an increase of soil pH and a decrease in soil organic matter and soil nitrogen. The microbial parameters recorded at three different sampling times revealed a substantial effect of the plant community, or the time of grazing abandonment, on soil microbial abundance and diversity. Considerable importance is given to the consequences of pasture abandonment on the conservation of plant and microbial diversity and on soil fertility.     

Trichoderma/pathogen/plant interaction in pre-harvest food security

Large losses before crop harvesting are caused by plant pathogens, such as viruses, bacteria, oomycetes, fungi, and nematodes. Among these, fungi are the major cause of losses in agriculture worldwide. Plant pathogens are still controlled through application of agrochemicals, causing human disease and impacting environmental and food security. Biological control provides a safe alternative for the control of fungal plant pathogens, because of the ability of biocontrol agents to establish in the ecosystem. Some Trichoderma spp. are considered potential agents in the control of fungal plant diseases. They can interact directly with roots, increasing plant growth, resistance to diseases, and tolerance to abiotic stress. Furthermore, Trichoderma can directly kill fungal plant pathogens by antibiosis, as well as via mycoparasitism strategies. In this review, we will discuss the interactions between Trichoderma/fungal pathogens/plants during the pre-harvest of crops. In addition, we will highlight how these interactions can influence crop production and food security. Finally, we will describe the future of crop production using antimicrobial peptides, plants carrying pathogen-derived resistance, and plantibodies.     

Mechanism underlying the response of fungi and their Fusarium symbiotic networks to the rotations of soybean and corn

Fusarium oxysporum and Fusarium solani are the main soybean root rot pathogens in northern China. We investigated the distribution and driving factors of Fusarium under different cropping systems to evaluate and regulate soil health. The factors affecting Fusarium in soybean cropping systems were assessed using high-throughput sequencing of ITS1 to identify soil microbial population diversity, and then the soil physicochemical properties were assessed to determine the levels of various elements present in the environment. According to the results, the abundance of Fusarium was obviously reduced in the corn–soybean rotation and uncultivated soil systems. The relative abundance of Fusarium in the soil and the abundance and diversity of fungal communities were significantly positively associated with the abundance of Ascomycota. Additionally, the relative abundance of Fusarium was significantly positively correlated with the zinc (Zn) content. When the Zn content was high, the abundance of Fusarium increased, and the correlations with Chaetomium, Cryptococcus, Penicillium and Trichoderma significantly decreased. Soybean yield was significantly negatively correlated with fungal community abundance and diversity. Based on our results, the uncultivated soil and corn–soybean rotation cropping systems improved the organizational structure of the soil fungal community and were conducive to the health and production of soybean.     

Soil fungal diversity in three nature reserves of Jiuzhaigou County,Sichuan Province,China

Jiuzhaigou County is located at the southern transition zone of Sichuan Basin and the Qinghai–Tibet Plateau and is the site of three famous nature reserves, namely, the Jiuzhaigou Nature Reserve (JZNR), Baihe Nature Reserve (BHNR) and Wujiao Nature Reserve (WJNR). The soil fungal diversity in this region has not yet been investigated. In this study, we collected 25 soil samples from these three nature reserves. Soil fungi were isolated using the soil dilution plate technique and Rose Bengal agar medium. The culturable soil fungal density based on analysis of the 25 samples ranged from 2.18 log to 4.38 log CFU g^?1 dry weight soil, with the fungal density being highest in samples from JZNR and lowest in those from BHNR. Based on morphological characters and the results of phylogenetic analysis of the internal transcribed spacer (ITS) of the rDNA operon, we identified 38 genera (two genera could not be identified) belonging to Ascomycota, Zygomycota and Basidiomycota. The dominant genera were Penicillium, Humicola, Aspergillus and Trichoderma. The species richness index S, biodiversity index H′ and evenness index E of the 25 sampling sites were in the range 10–29, 1.96–3.05 and 0.74–0.95, respectively. The highest mean values of the S, H′ and E indices were in soil samples from BHNR, where the values of these indices were 20.00, 2.66 and 0.90, respectively. These results indicate that the diversity of culturable fungi in these three nature reserves was high. Furthermore, a total 14 Trichoderma isolates were tested for their antagonism activity against mycelium growth of three pathogens: Bipolaris maydis, Curvularia lunata, Rhizoctonia solani. The results showed that six Trichoderma isolates had good antagonistic effects on the three pathogenic fungi.     

Assessing the impact of land abandonment, nitrogen enrichment and fairy-ring fungi on plant diversity of Mediterranean grasslands

Semi-natural calcareous grasslands are of great conservation interest because of their high species richness, but they are threatened by land abandonment and nitrogen eutrophication. These plant communities evolved as a result of a long history of human activity, which generated and maintained these habitats by extensive grazing and mowing. Calcareous grasslands are listed as a priority for conservation in the EC Habitats Directive. However, the effects of different management regimes, nitrogen enrichment, and soil-borne pathogens on plant species diversity are less clear for grasslands of the Mediterranean Basin, compared to meadows in Northern and Central Europe. In this study, we assessed the impact of land abandonment, nitrogen enrichment, and fairy-ring fungi on species diversity in semi-natural grasslands found in the Mediterranean Basin by comparing the available literature with findings from recent studies carried out in Central Italy. In a series of field experiments, the cutting of abandoned grassland consistently reduced the living biomass of the dominant perennial grasses, such as Brachypodium rupestre and Bromus erectus, and promoted a rapid increase in species richness and diversity by allowing the establishment of rare species. There was a similar, but less effective, restoration of species diversity and composition in mowed grassland after litter removal. We also show that nitrogen enrichment at levels comparable to atmospheric deposition depresses species diversity, which also hampers the positive effects of litter removal. Our findings are consistent with previous results achieved in Northern and Central Europe, which however, mainly focused on grasslands with intermediate to high primary productivity levels. The limited availability of data from low-productivity, drought-prone Mediterranean grasslands requires further studies to assess the impact of land abandonment and nitrogen eutrophication in such ecosystems. Finally, we discuss the role of fairy-ring fungi in the maintenance of plant diversity in species-rich grassland. We show that fairy-ring fungi (e.g. Agaricus campestris) critically affect the spatial distribution and diversity of coexisting plant species. By killing the dominant perennial herbs, these radially growing plant pathogens produce empty niches for rare, short-lived species, thus affecting the vegetation pattern. Overall, our results are of interest for environmental managers, as they provide guidelines for the restoration of abandoned areas and the conservation of these species-rich habitats.     

Short Research Report: high level of soil carbon addition causes possible manganese and aluminium phytotoxicity

A restoration trial of grassy woodland on former agricultural land applied carbon at a standard rate (840 g C/m²/year) and at a high rate (4,200 g C/m²/year), to test whether further benefits to native plants and suppression of exotics would emerge. Carbon addition at the high rate reduced plant cover further than the standard rate but led to severe loss of plant species; it also reduced soil pH. Soil Al, Fe and Mn levels increased across the gradient of C addition, which would be consistent with the reduction in soil pH for Al and Mn, and a decrease in soil redox potential for Mn and Fe. Nutrient analysis of leaf tissue confirmed that uptake of Fe and Mn increased over the range of C addition, with the concentration of Mn in the high carbon treatment exceeding the threshold for toxicity for a range of species. The soil and plant tissue data are consistent with the induction of increased soil acidity and of stronger reducing conditions in the soil by high level of carbon addition and localised soil flooding. Plant uptake of Mn to toxic levels occurred subsequently, leading to negative effects on plants; aluminium phytotoxicity may also have occurred.     

Phylogenetic relationships and spatial distributions of putative fungal pathogens of seedlings across a rainfall gradient in Panama

Despite their importance in structuring plant communities, the identities and spatial distributions of the pathogens impacting wild plant communities are largely unknown. To advance our knowledge of plant-pathogen interactions in tropical forests, I identified likely fungal pathogens from forest sites across a rainfall gradient in Panama and compared the communities of fungi inhabiting a wetter, Atlantic and a drier, Pacific forest (∼45 km apart). Seedlings with symptoms of pathogen attack were collected and fungi were isolated from the symptomatic tissue. Based on internal transcribed spacer region sequences, I assigned the fungal isolates to operational taxonomic units (OTUs) and estimated their taxonomic placements. I observed 28 OTUs (defined by 95% sequence similarity); primarily, the genera Mycoleptodiscus, Glomerella, Bionectria, Diaporthe, and Calonectria. The wetter, Atlantic and drier, Pacific forest sites shared 29% of observed and 56% of non-singleton fungal OTUs, suggesting that, in these forests, the common fungal pathogens of seedlings are relatively widespread, habitat generalists.     

Mechanisms of action and biocontrol potential of Trichoderma against fungal plant diseases - A review

Plant diseases are among the major causes of the low productivity of crops, causing yield losses of up to 30%, heralding an enormous threat to global food security. Indiscriminate use of chemical-based fungicides for controlling fungal diseases has raised severe concerns about ecosystem health. Moreover, pathogens have become insensitive against these chemicals necessitating excessive use of chemicals for adequate control. The resulting accumulation of these chemicals in the food chain has provoked numerous health complications. For combating the adversaries of chemical-based fungicides, biological control of fungal pathogens is proposed as an eco-friendly alternative. Among various biological controls, Trichoderma-based biological control agents (BCAs) are widely used in agriculture for controlling soil-borne pathogens. These BCAs are commercialized and known as; stimulators of resistance in plants, growth enhancers, bio-fertilizers, and bio-pesticides. Biological management of plant pathogens has yielded valuable results in the sustainability of ecosystems and compelling improvements in the quality and quantity of agricultural produce. These BCAs exhibit potential against pathogens, remarkably improve photosynthesis, plant growth, and nutrient use efficiency for impressive crop yields. Despite these peculiarities, Trichoderma's mechanisms against pathogens and their growth promotional effects are not thoroughly investigated, hence formulating the prime objective of the current review. Along with these, Trichoderma-based fungicides marketed in different geographical locations are encompassed in this review. Finally, the knowledge gaps and future research directions for improving the efficacy of Trichoderma-based BCAs are discussed.     

The fungal community associated with the ambrosia beetle Xylosandrus compactus invading the mediterranean maquis in central Italy reveals high biodiversity and suggests environmental acquisitions

In summer 2016 a severe infestation of the alien ambrosia beetle Xylosandrus compactus was recorded from the Mediterranean maquis in the Circeo National Park in Central Italy. Trees and shrubs were infested and displayed wilting and necrosis of terminal branches caused by the combined impact of the insect and associated pathogenic fungi. A preliminary screening carried out on captured adults resulted in the isolation of a discrete number of fungal taxa with different life strategies, ranging from true mutualist (e.g. Ambrosiella xylebori) to plant pathogens (Fusarium spp.). In the present study, high-throughput sequencing was applied to determine the total diversity and functionality of the fungal community associated with X. compactus adults collected in the galleries of three Mediterranean woody hosts, Quercus ilex, Laurus nobilis, and Ceratonia siliqua. The effect of season and host in determining the composition of the associated fungal community was investigated. A total of 206 OTUs composed the fungal community associated with X. compactus. Eighteen OTUs were shared among the three hosts, including A. xylebori and members of the Fusarium solani complex. All but two were previously associated with beetles.Sixty-nine out of 206 OTUs were resolved to species level, identifying 60 different fungal species, 22 of which already reported in the literature as associated with beetles or other insects. Functional guild assigned most of the fungal species to saprotrophs and plant pathogens. Effects of seasonality and host on fungal community assemblage were highlighted suggesting the acquisition by the insect of new fungal taxa during the invasion process. The consequences of enriched fungal community on the risk of the insurgence of novel threatful insect–fungus association are discussed considering direct and indirect effects on the invaded habitat.     

Soil Bacterial Community Response to Differences in Agricultural Management along with Seasonal Changes in a Mediterranean Region

Land-use change is considered likely to be one of main drivers of biodiversity changes in grassland ecosystems. To gain insight into the impact of land use on the underlying soil bacterial communities, we aimed at determining the effects of agricultural management, along with seasonal variations, on soil bacterial community in a Mediterranean ecosystem where different land-use and plant cover types led to the creation of a soil and vegetation gradient. A set of soils subjected to different anthropogenic impact in a typical Mediterranean landscape, dominated by Quercus suber L., was examined in spring and autumn: a natural cork-oak forest, a pasture, a managed meadow, and two vineyards (ploughed and grass covered). Land uses affected the chemical and structural composition of the most stabilised fractions of soil organic matter and reduced soil C stocks and labile organic matter at both sampling season. A significant effect of land uses on bacterial community structure as well as an interaction effect between land uses and season was revealed by the EP index. Cluster analysis of culture-dependent DGGE patterns showed a different seasonal distribution of soil bacterial populations with subgroups associated to different land uses, in agreement with culture-independent T-RFLP results. Soils subjected to low human inputs (cork-oak forest and pasture) showed a more stable bacterial community than those with high human input (vineyards and managed meadow). Phylogenetic analysis revealed the predominance of Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes phyla with differences in class composition across the site, suggesting that the microbial composition changes in response to land uses. Taken altogether, our data suggest that soil bacterial communities were seasonally distinct and exhibited compositional shifts that tracked with changes in land use and soil management. These findings may contribute to future searches for bacterial bio-indicators of soil health and sustainable productivity.     

The impact of agricultural land use changes on soil organic carbon dynamics in the Danjiangkou Reservoir area of China

Aims

Over recent decades, a large uncultivated area has been converted to woodland and shrubland plantations to protect and restore riparian ecosystems in the Danjiangkou Reservoir area, a water source area of China’s Middle Route of the South-to-North Water Transfer Project. Besides water quality, afforestation may alter soil organic carbon (SOC) dynamics and stock in terrestrial ecosystems, but its effects remain poorly quantified and understood.

Methods

We investigated soil organic C and nitrogen (N) content, and δ ¹³C and δ ¹⁵N values of organic soil in plant root-spheres and open areas in an afforested, shrubland and adjacent cropped soil. Soil C and N recalcitrance indexes (RIC and RIN) were calculated as the ratio of unhydrolyzable C and N to total C and N.

Results

Afforestation significantly increased SOC levels in plant root-spheres with the largest accumulation of C in the afforested soil. Afforestation also increased belowground biomass. The C:N ratios in organic soil changed from low to high in the order the cropped, the shrubland and the afforested soil. The RIC in the afforested and shrubland were higher than that in cropped soil, but the RIN increased from the afforested to shrubland to cropped soil. The δ¹⁵N values of the organic soil was enriched from the afforested to shrubland to cropped soil, indicating an increased N loss from the cropped soil compared to afforested or shrubland soil. Changes in the δ¹³C ratio further revealed that the decay rate of C in the three land use types was the highest in the cropped soil.

Conclusions

Afforestation increased the SOC stocks resulted from a combination of large C input from belowground and low C losses because of decreasing soil C decomposition. Shifts in vegetation due to land use change could alter both the quantity and quality of the soil C and thus, have potential effects on ecosystem function and recovery.     

Inhibition of net nitrification activity in a Mediterranean woodland: possible role of chemicals produced by Arbutus unedo

Nitrification is a key biological process for the control of soil NO₃ ^? availability and N losses from terrestrial ecosystems. The study investigates the causes for the absence of net nitrification activity in the soil of a Mediterranean monospecific woodland of Arbutus unedo, focusing in particular on the possible role of chemicals produced by this plant. The mineral N pool, net rates of mineralization and nitrification were measured in the soil top 10 cm over 18 months. Raw extracts of leaves and roots of Arbutus unedo and soil underneath Arbutus plant canopy were purified using chromatographic techniques and the structure of chemicals was defined using spectroscopic and spectrometric methods. Leaf extracts (raw, aqueous and organic fractions) were tested for their toxicity on net nitrification, using a test soil. Field and laboratory incubations showed soil NO₃ ^? concentration below the detection limit over the whole study period, despite the significant NH₄ ⁺ availability. Toxicity tests indicated that more than 400 μg of extract g^?1 dry soil were needed to have more than 50% reduction of net NO₃ ^? production. Gallocatechin and catechin were among the most abundant chemicals in the extracts of leaves, roots and soil. Their soil concentration was significantly higher than the annual calculated input via leaf litter, and it was in the range of toxic concentrations, as deduced from the dose-response curve of the toxicity test. Data support the hypothesis that plant produced chemicals might be involved in the limited net nitrate production in this Mediterranean woodland.

     

Biocontrol of aerial plant diseases in agriculture and horticulture: current approaches and future prospects

Until recently, the majority of research on the biological control of aerial plant diseases was focused on control of bacterial pathogens. Such research led to the commercialization of the biocontrol agent Pseudomonas fluorescens A506, as BlightBan A506™, for control of fire blight of pear. In contrast, chemical fungicides typically have provided adequate control of most foliar fungal pathogens. However, fungicide resistance problems, concerns regarding pesticide residues and revocation of registration of certain widely used fungicides have led to increased activity in the development of biocontrol agents of foliar fungal pathogens. Much of this activity has centered around the use of Trichoderma spp and Gliocladium spp to control Botrytis cinerea on grape and strawberry. The biocontrol agent Trichoderma harzianum T39 is commercially available in Israel, as Trichodex ™, for control of grey mold in grapes and may soon be registered for use in the US. Also targeted primarily against a foliar disease of grapes, in this case powdery mildew caused by Uncinula necator, is the biocontrol agent Ampelomyces quisqualis AQ10, marketed as AQ^{10  TM} biofungicide. Another promising development in the area of foliar disease control, though one which is not yet commercialized, is the use of rhizobacteria as seed treatments to induce systemic resistance in the host plant, a strategy which can protect the plant against a range of bacterial and fungal pathogens. Received 06 February 1997/ Accepted in revised form 05 June 1997     

Role and genetic basis of specialised secondary metabolites in Trichoderma ecophysiology

Species of fungal genus Trichoderma are characterized by a versatile lifestyle, high adaptability to the changing environmental conditions and the ability to establish sophisticated interactions with other organisms. Due to their ability to antagonize plant pathogens and to elicit the plant defence responses against biotic/abiotic stresses, Trichoderma spp. are commonly used as commercially biopesticides and biofertilizers. The Trichoderma success in the rhizosphere is supported by a wide arsenal of specialised metabolites (SMs) providing morphological and physiological autoregulation, self-protection and facilitating fungal communication. This review aims to explore the roles of SMs in the biology of fungi, with special emphasis on the genus Trichoderma and on how divergence in the SMs genetic structure determine Trichoderma lifestyles. Trichoderma genomes are endowed with a high number of SMs biosynthetic genes, and understanding the genetic basis of their biosynthesis is crucial for determining the role of these metabolites in Trichoderma ecophysiology and for expanding their application in crop protection. Recent advances on the characterization of the Trichoderma SMs genetic inventory driven by computational biology are discussed.     

Trichoderma spp. tolerance to Brassica carinata seed meal for a combined use in biofumigation

Biofumigation by Brassicaceae green manure or seed meal incorporation into soil is an ecological alternative to chemical fumigation against soil-borne pathogens, based on the release of glucosinolate-derived compounds. This study aimed at investigating the tolerance of the beneficial fungus Trichoderma to these compounds in view to combined utilization with Brassica carinata seed meal (BCSM). Forty isolates of Trichoderma spp. were tested in vitro for tolerance to toxic volatiles released by BCSM and in direct contact with the meal. They were found to be generally less sensitive than the assayed pathogens (Pythium ultimum, Rhizoctonia solani, Fusarium oxysporum), even if a fungistatic effect was observed at the highest dose (10 μmole of sinigrin). Most of them also were able to grow on BCSM and over the pathogens tested. A preliminary experiment of integrating BCSM with Trichoderma in soil was carried out under controlled conditions with the patho-system P. ultimum—sugar beet. BCSM incorporation increased pathogen population, but reduced disease incidence, probably due to indirect mechanisms. The greatest effect was achieved when BCSM was applied in combination with Trichoderma, regardless of meal ability to release isothiocyanate. These findings suggest that disease control can be improved by this integrated approach. This study also highlighted that a reduction of allyl-isothiocyanate concentration in soil could occur due to the activity of some Trichoderma isolates. This effect could protect resident or introduced Trichoderma isolates from depressing effects due to the biocidal compounds, but, on the other hand, could reduce the efficacy of biofumigation against target pathogens.     

Endophytic colonization of Vicia faba and Phaseolus vulgaris (Fabaceae) by fungal pathogens and their effects on the life-history parameters of Liriomyza huidobrensis (Diptera: Agromyzidae)

Ten fungal isolates belonging to the genera Beauveria (3), Hypocrea (1), Gibberella (1), Metarhizium (2), Trichoderma (1) and Fusarium (2) were evaluated in the laboratory to determine whether they could become endophytic in two pea leafminer (Liriomyza huidobrensis) host plants (Vicia faba and Phaseolus vulgaris), and to assess their possible negative effects on leafminers. Beauveria (ICIPE279), Hypocrea, Gibberella, Fusarium and Trichoderma isolates colonized roots, stems and leaves of both host plant species. Beauveria isolates G1LU3 and S4SU1 colonized roots, stems, and leaves of P. vulgaris but only the root and stem of V. faba. Isolates of Metarhizium failed to colonize the two host plants. The effects of endophytically colonized fungal pathogens on mortality, oviposition, emergence and longevity of L. huidobrensis were investigated after endophytic colonization of V. faba plants. All the fungal isolates that succeeded in colonizing the host plant were pathogenic to L. huidobrensis, causing 100 % mortality within 13.2 ± 0.7–15.0 ± 0.6 d. However, Hypocrea outperformed the other isolates (p < 0.0 001) in reducing longevity of the progeny (11.2 ± 1.0 vs. 17.8 ± 1.4 d in the control), the number of pupae (80.0 ± 6.7 vs. 387.0 ± 21.7 pupae in the control), and adult longevity (3.8 ± 1.0 vs. 9.9 ± 1.8 d in the control). Adult emergence was significantly reduced (p < 0.0 001) in Hypocrea (21.4 %) and Beauveria (38.0 %) treatments compared to the control (82.9 %).     

Improvement of the Fungal Biocontrol Agent Trichoderma atroviride To Enhance both Antagonism and Induction of Plant Systemic Disease Resistance

Biocontrol agents generally do not perform well enough under field conditions to compete with chemical fungicides. We determined whether transgenic strain SJ3-4 of Trichoderma atroviride, which expresses the Aspergillus niger glucose oxidase-encoding gene, goxA, under a homologous chitinase (nag1) promoter had increased capabilities as a fungal biocontrol agent. The transgenic strain differed only slightly from the wild-type in sporulation or the growth rate. goxA expression occurred immediately after contact with the plant pathogen, and the glucose oxidase formed was secreted. SJ3-4 had significantly less N-acetylglucosaminidase and endochitinase activities than its nontransformed parent. Glucose oxidase-containing culture filtrates exhibited threefold-greater inhibition of germination of spores of Botrytis cinerea. The transgenic strain also more quickly overgrew and lysed the plant pathogens Rhizoctonia solani and Pythium ultimum. In planta, SJ3-4 had no detectable improved effect against low inoculum levels of these pathogens. Beans planted in heavily infested soil and treated with conidia of the transgenic Trichoderma strain germinated, but beans treated with wild-type spores did not germinate. SJ3-4 also was more effective in inducing systemic resistance in plants. Beans with SJ3-4 root protection were highly resistant to leaf lesions caused by the foliar pathogen B. cinerea. This work demonstrates that heterologous genes driven by pathogen-inducible promoters can increase the biocontrol and systemic resistance-inducing properties of fungal biocontrol agents, such as Trichoderma spp., and that these microbes can be used as vectors to provide plants with useful molecules (e.g., glucose oxidase) that can increase their resistance to pathogens.