Physiological and Molecular Plant Pathology, Apr 1, 2013
ABSTRACT Compost is used as a peat substitute and soil amendment because of its suppressive prope... more ABSTRACT Compost is used as a peat substitute and soil amendment because of its suppressive properties against soilborne plant diseases. It is also effective in reducing foliar diseases, which suggests that compost systemically affects the plant. The improvement of plant nutrition due to the compost has been suggested as an important factor. In this study, we found higher resistance of Arabidopsis plants grown in an olive marc compost against Botrytis cinerea than in plants grown in perlite. There was no difference in the leaf nutrients of the plants grown in the two substrates. Hence, the compost does not have a nutritional effect on this system. In Col-0 plants, the incidence of diseased leaves was reduced by 30% and an equal reduction in disease was induced in jar1-1 mutants. However, there was no disease reduction in sid2-1. This suggests the need for SA signalling in compost-induced resistance. Furthermore, PR-1 expression was higher in compost-grown plants than in perlite-grown plants before and after pathogen inoculation. VSP2 expression in artificially wounded plants was lower in compost-grown plants than in perlite-grown plants, which suggests that there was negative crosstalk between compost-induced and wound-induced signals.
The soil/substrate that supports plant roots and provides water and nutrients to plants is often ... more The soil/substrate that supports plant roots and provides water and nutrients to plants is often considered a hostile environment that harbours plant pathogens. Moreover, the most common strategy used to control risk of disease from the soil is the eradication or minimization of soil pathogens regardless of the presence of other organisms. Consequently, the extensive use of physical/chemical biocides generates a soil/substrate microbiological vacuum which makes it more susceptible to reinfestation by pathogens, increases disease incidence and in some cases enhances fungal resistance. In Europe, legislation on plant protection products has been re-evaluated since 1991 (Directives 1991/414 and 2009/128), leading to a drastic reduction in the use of chemical compounds. A reduction in fungicides that effectively combat disease is achieved with the use of suppressive composts in pot plants. Suppressive composts similar to suppressive soils are examples of natural biological control of di...
The by-products of palm date (Phoenix dactylifera) contaminated by Fusarium oxysporum f.sp. albed... more The by-products of palm date (Phoenix dactylifera) contaminated by Fusarium oxysporum f.sp. albedinis (Fusarium) were composted with different rates of bovine manure, urea or ammonium nitrogen. Water was added to maintain optimum humidity at 60-70%. During the process of composting and whatever the ratio of the manure or nitrogen in the piles, the pH remained stable and relatively alkaline at values ranging from 8.2 to 8.7. By contrast, electrical conductivity decreased from 25 to 30%. The evolution of the internal temperatures in the piles depended on the volume of the manure added to the mixture, but was characterized by a mesophilic phase showing a fast increase in temperature, then a thermophilic phase, with high temperatures ranging from 50 to 70°C in the piles rich in bovine manure. However, internal temperatures remained unchanged in urea- or ammonium-containing piles. In the piles containing bovine manure, Fusarium was completely eliminated during the thermophilic phase. The...
Pepper (Capsicum annuum L.), one of the most widely grown vegetables worldwide, is susceptible to... more Pepper (Capsicum annuum L.), one of the most widely grown vegetables worldwide, is susceptible to root rot caused by Phytophthora capsici. Many biocides have recently been banned in Europe because of human health and environmental concerns. Integrated pest management is a European priority, where biological control together with other agronomic practices should replace pesticide management of plant diseases in the future. Application of different concentrations of the fungus Trichoderma asperellum strain T34 (the in T34 Biocontrol®) on incidence of disease caused by P. capsici in pepper was studied. Different methods of application of the microbial control agent and inoculation of the pathogen were examined. T34 and etridiazole (Terrazole®) were compared for their ability to suppress P. capsici. T34 reduced disease in most of the assayed situations (up to 71% disease reduction), while etridiazole was effective only when applied at the same time as the pathogen. The results obtained ...
The use of compost tea extracts to control leaf diseases is an alternative that enables the use o... more The use of compost tea extracts to control leaf diseases is an alternative that enables the use of chemicals in agriculture to be reduced. However, little is known about the mechanisms responsible. We examined an aerated compost tea prepared from composted market and garden wastes and tested its effect on naturally occurring powdery mildew disease produced by the foliar pathogen Erysiphe polygoni in tomato plants (Lycopersicon esculentum cv. Roma) grown in perlite in an unheated greenhouse. Untreated plants showed whitish patches of powdery mildew, while in the treated plants the mycelium could hardly be seen and leaves only showed localized yellow spots corresponding to former sites of infection. Tea compost reduced disease incidence by 19% when used as a preventive treatment and eradicated the pathogen on the leaves when applied as a curative treatment. Treatment was not associated with increased peroxidase or chitinase activity in the leaves and induction of local resistance is u...
Verticillium Wilt of Olive, a disease caused by the hemibiotrophic vascular fungus Verticillium d... more Verticillium Wilt of Olive, a disease caused by the hemibiotrophic vascular fungus Verticillium dahliae Kleb. presents one of the most important constraints to olive production in the world, with an especially notable impact in Mediterranean agriculture. This study evaluates the use of RGB vegetation indexes in assessing the effects of this disease during the biotrophic phase of host-pathogen interaction, in which symptoms of wilt are not yet evident. While no differences were detected by measuring stomatal conductance and chlorophyll fluorescence, results obtained from RGB indexes showed significant differences between control and inoculated plants for indexes Saturation, a*, b*, green Area (GA), normalized green-red difference index (NGRDI) and triangular greenness index (TGI), presenting a reduction in plant growth as well as in green and yellow color components as an effect of inoculation. These results were contrasted across two scenarios of mineral fertilization in soil and so...
The microbial disinfestation efficiency of an innovative horizontal-flow slow sand filter (HSSF) ... more The microbial disinfestation efficiency of an innovative horizontal-flow slow sand filter (HSSF) for treating nutrient solution spent from an experimental closed-loop nursery was evaluated by means of a combination of culture-dependent and independent molecular techniques. A dense inoculum of the fungal plant pathogen Fusarium oxysporum f.sp. lycopersici was applied in the fertigation system (10(6) cells per mL). Indigenous and introduced populations of eubacteria and fungi were assessed in the nutrient solution, the HSSF influent/effluent, and a sand bed transect by isolation on selective media, as well as by quantitative qPCR and next-generation sequencing (NGS) on target ribosomal genes. The HSSF effectively reduced viable Fusarium propagules and fungal gene content with an efficiency consistently above 99.9% (5 orders of magnitude down). On the other hand, Fusarium cells accumulated in the sand bed, indicating that physical entrapment was the main removal mechanism. The viabilit...
Physiological and Molecular Plant Pathology, Apr 1, 2013
ABSTRACT Compost is used as a peat substitute and soil amendment because of its suppressive prope... more ABSTRACT Compost is used as a peat substitute and soil amendment because of its suppressive properties against soilborne plant diseases. It is also effective in reducing foliar diseases, which suggests that compost systemically affects the plant. The improvement of plant nutrition due to the compost has been suggested as an important factor. In this study, we found higher resistance of Arabidopsis plants grown in an olive marc compost against Botrytis cinerea than in plants grown in perlite. There was no difference in the leaf nutrients of the plants grown in the two substrates. Hence, the compost does not have a nutritional effect on this system. In Col-0 plants, the incidence of diseased leaves was reduced by 30% and an equal reduction in disease was induced in jar1-1 mutants. However, there was no disease reduction in sid2-1. This suggests the need for SA signalling in compost-induced resistance. Furthermore, PR-1 expression was higher in compost-grown plants than in perlite-grown plants before and after pathogen inoculation. VSP2 expression in artificially wounded plants was lower in compost-grown plants than in perlite-grown plants, which suggests that there was negative crosstalk between compost-induced and wound-induced signals.
The soil/substrate that supports plant roots and provides water and nutrients to plants is often ... more The soil/substrate that supports plant roots and provides water and nutrients to plants is often considered a hostile environment that harbours plant pathogens. Moreover, the most common strategy used to control risk of disease from the soil is the eradication or minimization of soil pathogens regardless of the presence of other organisms. Consequently, the extensive use of physical/chemical biocides generates a soil/substrate microbiological vacuum which makes it more susceptible to reinfestation by pathogens, increases disease incidence and in some cases enhances fungal resistance. In Europe, legislation on plant protection products has been re-evaluated since 1991 (Directives 1991/414 and 2009/128), leading to a drastic reduction in the use of chemical compounds. A reduction in fungicides that effectively combat disease is achieved with the use of suppressive composts in pot plants. Suppressive composts similar to suppressive soils are examples of natural biological control of di...
The by-products of palm date (Phoenix dactylifera) contaminated by Fusarium oxysporum f.sp. albed... more The by-products of palm date (Phoenix dactylifera) contaminated by Fusarium oxysporum f.sp. albedinis (Fusarium) were composted with different rates of bovine manure, urea or ammonium nitrogen. Water was added to maintain optimum humidity at 60-70%. During the process of composting and whatever the ratio of the manure or nitrogen in the piles, the pH remained stable and relatively alkaline at values ranging from 8.2 to 8.7. By contrast, electrical conductivity decreased from 25 to 30%. The evolution of the internal temperatures in the piles depended on the volume of the manure added to the mixture, but was characterized by a mesophilic phase showing a fast increase in temperature, then a thermophilic phase, with high temperatures ranging from 50 to 70°C in the piles rich in bovine manure. However, internal temperatures remained unchanged in urea- or ammonium-containing piles. In the piles containing bovine manure, Fusarium was completely eliminated during the thermophilic phase. The...
Pepper (Capsicum annuum L.), one of the most widely grown vegetables worldwide, is susceptible to... more Pepper (Capsicum annuum L.), one of the most widely grown vegetables worldwide, is susceptible to root rot caused by Phytophthora capsici. Many biocides have recently been banned in Europe because of human health and environmental concerns. Integrated pest management is a European priority, where biological control together with other agronomic practices should replace pesticide management of plant diseases in the future. Application of different concentrations of the fungus Trichoderma asperellum strain T34 (the in T34 Biocontrol®) on incidence of disease caused by P. capsici in pepper was studied. Different methods of application of the microbial control agent and inoculation of the pathogen were examined. T34 and etridiazole (Terrazole®) were compared for their ability to suppress P. capsici. T34 reduced disease in most of the assayed situations (up to 71% disease reduction), while etridiazole was effective only when applied at the same time as the pathogen. The results obtained ...
The use of compost tea extracts to control leaf diseases is an alternative that enables the use o... more The use of compost tea extracts to control leaf diseases is an alternative that enables the use of chemicals in agriculture to be reduced. However, little is known about the mechanisms responsible. We examined an aerated compost tea prepared from composted market and garden wastes and tested its effect on naturally occurring powdery mildew disease produced by the foliar pathogen Erysiphe polygoni in tomato plants (Lycopersicon esculentum cv. Roma) grown in perlite in an unheated greenhouse. Untreated plants showed whitish patches of powdery mildew, while in the treated plants the mycelium could hardly be seen and leaves only showed localized yellow spots corresponding to former sites of infection. Tea compost reduced disease incidence by 19% when used as a preventive treatment and eradicated the pathogen on the leaves when applied as a curative treatment. Treatment was not associated with increased peroxidase or chitinase activity in the leaves and induction of local resistance is u...
Verticillium Wilt of Olive, a disease caused by the hemibiotrophic vascular fungus Verticillium d... more Verticillium Wilt of Olive, a disease caused by the hemibiotrophic vascular fungus Verticillium dahliae Kleb. presents one of the most important constraints to olive production in the world, with an especially notable impact in Mediterranean agriculture. This study evaluates the use of RGB vegetation indexes in assessing the effects of this disease during the biotrophic phase of host-pathogen interaction, in which symptoms of wilt are not yet evident. While no differences were detected by measuring stomatal conductance and chlorophyll fluorescence, results obtained from RGB indexes showed significant differences between control and inoculated plants for indexes Saturation, a*, b*, green Area (GA), normalized green-red difference index (NGRDI) and triangular greenness index (TGI), presenting a reduction in plant growth as well as in green and yellow color components as an effect of inoculation. These results were contrasted across two scenarios of mineral fertilization in soil and so...
The microbial disinfestation efficiency of an innovative horizontal-flow slow sand filter (HSSF) ... more The microbial disinfestation efficiency of an innovative horizontal-flow slow sand filter (HSSF) for treating nutrient solution spent from an experimental closed-loop nursery was evaluated by means of a combination of culture-dependent and independent molecular techniques. A dense inoculum of the fungal plant pathogen Fusarium oxysporum f.sp. lycopersici was applied in the fertigation system (10(6) cells per mL). Indigenous and introduced populations of eubacteria and fungi were assessed in the nutrient solution, the HSSF influent/effluent, and a sand bed transect by isolation on selective media, as well as by quantitative qPCR and next-generation sequencing (NGS) on target ribosomal genes. The HSSF effectively reduced viable Fusarium propagules and fungal gene content with an efficiency consistently above 99.9% (5 orders of magnitude down). On the other hand, Fusarium cells accumulated in the sand bed, indicating that physical entrapment was the main removal mechanism. The viabilit...
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