Beneficial effects of Rhizophagus irregularis and Trichoderma asperellum strain T34 on growth and fusarium wilt in tomato plants

Fusarium tomato wilt is one of the most prevalent and damaging diseases wherever tomatoes are grown intensively. Progress in agriculture in the twenty-first century is set to be based on lowering agrochemical inputs (implementation of Directive 2009/128/EC on sustainable use of pesticides), which can be achieved to some extent through the use of beneficial microorganisms. This study aimed at comparing the effects of the mycorrhizal fungus Rhizophagus irregularis and the biological control agent Trichoderma asperellum strain T34 on the incidence of fusarium wilt and the growth of tomato plants. Both R. irregularis and T34 lowered disease incidence at similar rates, compared to control plants. R. irregularis added below the seedlings reduced disease incidence more than when it was mixed with the substrate. T34 and R. irregularis increased plant height to the same extent, compared to both control and diseased plants. R. irregularis gave the highest levels of chlorophyll, followed by T34 and control plants; however, the measures for infected plants were slightly better for T34 than for R. irregularis. T34 and R. irregularis had similar effects on Ca, Mg, S, Mn, B and Si uptake in tomato plants, but R. irregularis induced a greater P, K, Zn, Cu and Mo accumulation than T34. Interestingly, at the end of the experiment, the depletion of the substrate was lower on Ca, Mg and S for plants inoculated with either R. irregularis or T34 compared to control plants, while the substrate for T34-treated plants had the lowest levels of Fe, Mn, Zn and Cu

Impact of olive saplings and organic amendments on soil microbial communities and effects of mineral fertilization

Plant communities and fertilization may have an impact on soil microbiome. Most commercial olive trees are minerally fertilized, while this practice is being replaced by the use of organic amendments. Organic amendments can both fertilize and promote plant growth-promoting organisms. Our aims were (i) to describe the changes in soil bacterial and fungal communities induced by the presence of young olive trees and their interaction with organic amendments and (ii) to compare the effects of mineral and organic fertilization. We set up two parallel experiments in pots using a previously homogenized soil collected from a commercial olive orchard: in the first one, we grew olive saplings in unamended and organically amended soils with two distinct composts and compared these two soils incubated without a plant, while in the second experiment, we comparatively tested the effects of organic and mineral fertilization. OTUs and the relative abundances of bacterial and fungal genera and phyla were analyzed by 16S rRNA and ITS1 gene amplicon using high-throughput sequencing. Basal respiration and substrate-induced respiration were measured by MicroRespTM. The effects of the different treatments were analyzed in all phyla and in the 100 most abundant genera. The presence of olive saplings increased substrate-induced respiration and bacterial and fungal richness and diversity. Organic amendments greatly affected both bacterial and fungal phyla and increased bacterial richness while not affecting fungal richness. Mineral fertilization increased the relative abundance of the less metabolically active bacterial phyla (Actinobacteria and Firmicutes), while it reduced the most metabolically active phylum, Bacteroidetes. Mineral fertilization increased the relative abundance of three N2-fixing Actinobacteria genera, while organic fertilization only increased one genus of Proteobacteria. In organically and minerally fertilized soils, high basal respiration rates were associated with low fungal diversity. Basidiomycota and Chytridiomycota relative abundances positively correlated with basal respiration and substrate-induced respiration, while Ascomycota correlated negatively. Indeed, the Ascomycota phyla comprised most of the fungal genera decreased by organic amendments. The symbiotrophic phylum Glomeromycota did not correlate with any of the C sources. The relative abundance of this phylum was promoted by the presence of plants but decreased when amending soils with composts

Inducció de resistència sistèmica a les plantes per l'agent de control biològic "Trichoderma asperellum" soca T34 o substrats supressius

[cat] La utilització de composts com substrats de cultiu i/o l'ús d'agents de control biològic són una alternativa als mitjans de control de fitopatògens mitjançant fitosanitaris químics. Aquesta tesi consta de 4 capítols. En el Capítol I es va estudiar la capacitat de 5 composts procedents de residus municipals i agrícoles de suprimir la malaltia produïda pel patogen foliar Botrytis cinerea en plantes de cogombre. Els cinc composts van ser capaços de reduir la incidència i severitat de la malaltia en comparació amb els substrats de cultiu estàndard (2 torbes comercials). La reducció de la malaltia es va associar al subministrament de Ca, Mo i Si per part dels composts, a cert grau d'estrès salí produït en la planta, així com a l'alta activitat microbiològica dels composts. En el Capítol II es descriu el desenvolupament d'un mètode basat en la cromatografia líquida acoblada a detecció per espectrometria de masses en tàndem per a la quantificació simultània de les hormones àcid salicílic i àcid jasmònic en extractes vegetals. El mètode es va aplicar per a estudiar l'efecte de la colonització de l'arrel de plantes de cogombre per part de l'agent de control biològic Trichoderma asperellum T34 o la infecció per part del patogen Rhizoctonia solani . No es va observar cap efecte de T34 aplicat a l'arrel a 105 ufc/ml sobre els nivells d'aquestes hormones. R. Solani , va produir l'increment de les dues hormones, tant en arrel com en cotilèdon. En el Capítol III es va estudiar l'efecte de T34 aplicat a l'arrel de la planta de cogombre a 105, 106 i 107 ufc/ml sobre l'activitat peroxidasa, els nivells d'àcid salicílic i jasmònic i el proteoma dels cotilèdons en les primeres hores de la interacció. T34 activa l'activitat peroxidasa i eleva els nivells de les hormones estudiades de forma depenent a la concentració. A 105 no s'observen efectes. T34 aplicat a l'arrel a 107 ufc/ml és capaç de produir canvis el proteoma dels cotilèdons afectant l'expressió de proteïnes relacionades amb la defensa contra patògens. Aquest mateix tractament és capaç d'induir en la planta resistència sistèmica contra el patogen foliar Pseudomonas syringae pv. lachrymans . En el Capítol IV es va comprovar la capacitat de T34 aplicat a 105 ufc/ml per a induir resistència sistémica en Arabidopsis enfront dels patògens foliars Pseudomonas syringae pv. tomato , Hyaloperonospora parasitica i Plectosphaerella cucumerina . Aquesta resistència sistèmica és semblant a la induced systemic resistance (ISR) produïda per rizobacteris no patogènics. L'ús d'Arabidopsis mutants va permetre establir que la ISR induïda per T34 és independent d'àcid salicílic i depenent de NPR1 i MYB72. A més, la ISR induïda per T34 es basa en el priming ja que precondiciona a les plantes a expressar el gen LOX2 i el bloqueig d'espores de patògens mitjançant cal·losa de forma mes ràpida i intensa quan posteriorment responen a un atac.[eng] This thesis consists in 4 chapters. In Chapter I we checked the ability of 5 composts from municipal an agricultural wastes to suppress disease produced by the foliar pathogen Botrytis cinerea in cucumber plants. The 5 studied composts were able to reduce disease incidence and disease severity compared to standard growth media (2 commercial peats). The reduction in disease was related to the supply of Ca, Mo and Si to the plants, a certain degree of salt stress and the high microbial activity of the composts. In Chapter II we describe a method based in liquid chromatography coupled to mass spectrometry to simultaneously quantify salicylic and jasmonic acids in crude plant extracts. No effect on the hormones was found when the biological control agent Trichoderma asperellum T34 was applied to the roots at 105 cfu/ml. Rhizoctonia solani infection increased both hormones in both cotyledons and roots. In Chapter III we studied the effect of T34 applied to the roots at 105, 106 and 107 cfu/ml on peroxidase activity, salicylic and jasmonic acids levels and proteome of cucumber cotyledons during the early hours after the interaction. T34 affects peroxidase activity and hormone levels depending on the concentration. No effects at 105. T34 applied to the roots at 107 cfu/ml is able to produce changes to the proteome affecting the expression of defense related proteins. This treatment is also able to induce systemic resistance against the foliar pathogen Pseudomonas syringae pv. lachrymans. In Chapter IV we checked the ability of T34 applied at 105 cfu/ml to induce systemic resistance in Arabidopsis against the foliar pathogens Pseudomonas syringae pv. tomato, Hyaloperonospora parasitica and Plectosphaerella cucumerina. This systemic resistance is similar to induced systemic resistance (ISR) triggered by non pathogenic rhizobacteria. The use of Arabidopsis mutants allowed us to establish that ISR induced by T34 is salicylic acid independent but is dependent on NPR1 and MYB72. In addition ISR triggered by T34 is based on priming as it primes plants for enhanced LOX2 gene expression as well as callose deposition when plants face an stress

Activación del sistema inmunitario de las plantas: inducción de resistencia y reducción de enfermedades

Aquest article pretén fer una revisió breu de l’activació del sistema immunitari de les plantes, la qual ha estat molt estudiada en els últims cinquanta anys. Aquesta activació està induïda per patògens (microorganismes, nematodes i insectes) i també per organismes beneficiosos colonitzadors de la rizosfera i estímuls químics, i té un paper important en la reducció de diverses malalties i plagues. Hi estan implicades dues rutes de senyalització de la defensa: la dependent de l’àcid salicílic, o resistència sistèmica adquirida (RSA o SAR, de l’anglès systemic acquired resistance), i la independent de l’àcid salicílic, o resistència sistèmica induïda (RSI o ISR, de l’anglès induced systemic resistance). La primera està lligada a la resposta de les plantes davant l’atac de patògens mitjançant la síntesi de la fitohormona àcid salicílic i de proteïnes relacionades amb la patogènesi. La segona ruta comporta respostes de les plantes a organismes beneficiosos, i les hormones implicades són l’àcid jasmònic i l’etilè. Tanmateix, es presenten diversos resultats experimentals que avalen la implicació d’altres hormones en la modulació d’ambdues rutes.Bacteris i fongs rizosfèrics, com Trichoderma asperellum, soca T34, potencien les respostes sistèmiques, incrementant la capacitat defensiva de les plantes contra un ampli rang de patògens. Altres treballs mostren com les alteracions en el contingut dels exsudats radiculars de les plantes davant l’atac dels patògens les ajuden a mantenir poblacions d’organismes beneficiosos. Utilitzar compost de sansa com a substrat de cultiu activa respostes de defensa de les plantes via RSA, cosa que ocasiona un estrès positiu o eustrès sense cap efecte negatiu en el seu creixement i amb un efecte beneficiós en la defensa enfront de patògens.This paper makes a brief review of the activation of the plant immune system, which has been extensively studied over the last 50 years. The activation of the immune system of plants is induced not only by plant pathogens (microorganisms, nematodes and insects) but also by beneficial rhizosphere microorganisms and chemical stimuli, and it plays an important role in the reduction of a wide range of plant diseases and pests. Two main routes are involved: the salicylic-dependent or systemic acquired resistance (SAR) routeand the salicylic-independent or induced systemic resistance (ISR) route. The first route is linked to plants’ response to pathogens, with the involvement of the hormone salicylic acid and pathogenesis-related proteins. The second route is related to beneficial organisms, the involvement of jasmonic acid and ethylene hormones. Likewise, experimental results are presented that evidence the involvement of other plant hormones in the modulation of both routes. Rhizosphere-competent bacteria or fungus like Trichoderma asperellum, strain T34, bolster defence responses systemically and enhance the defensive capacity of plants against a wide range of pathogens. The alteration of root exudates by the attack of a pathogen has an effect on root microbial populations. Plants can maintain the populations of beneficial microorganisms close to their roots by exuding specific compounds. The use of olive mill compost as plant growth media stimulates plant defence response by SAR by producing a “eustress”, which is a kind of mild beneficial stress that is free of any detrimental effect on growth and exerts a favourable effect on plants’ defence capacity against pathogens.Este artículo pretende hacer una breve revisión de la activación del sistema inmunitario de las plantas, que ha sido muy estudiada en los últimos cincuenta años. Esta activación está inducida por patógenos (microorganismos, nematodos e insectos), y también por organismos beneficiosos colonizadores de la rizosfera y estímulos químicos, y tiene un papel importante en la reducción de diversas enfermedades y plagas. Se hallan implicadas dos rutas de señalización: la dependiente del ácido salicílico, o resistencia sistémica adquirida (RSA o SAR, del inglés systemic acquired resistance), y la independiente del ácido salicílico, o resistencia sistémica inducida (RSI o ISR, del inglés induced systemic resistance). La primera está vinculada a respuestas de las plantas frente a patógenos y la síntesis de la hormona ácido salicílico y proteínas relacionadas con la patogénesis. La segunda ruta comporta respuestas de las plantas a organismos beneficiosos; las hormonas implicadas son ácido jasmónico y etileno. Asimismo, se presentan diversos resultados experimentales que avalan la implicación de otras hormonas en la modulación de las dos rutas. Bacterias y hongos rizosféricos, como Trichoderma asperellum, cepa T34, potencian las respuestas sistémicas incrementando la capacidad defensiva de las plantas frente al ataque de patógenos. Las alteraciones en el contenido de exudados de las plantas consecuencia del ataque de patógenos ayudan a las plantas a mantener las poblaciones de organismos beneficiosos. La utilización de compost de alperujo como sustrato activa respuestas de defensa de las plantas vía RSA ocasionando un estrés suave o eustrés sin ningún efecto negativo sobre su crecimiento y con un efecto beneficioso frente a los patógenos

Effectiveness and versatility of the biological control of Phytophthora capsisi in pepper by Trichoderma asperellum T34

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 are discussed on the basis of the different modes of action of T34 and etridiazole. T34 is a useful biological alternative to chemicals for the control of P. capsici in pepper

Enhanced Botrytis cinerea resistance of Arabidopsis plants grown in compost may be explained by increased expression of defense-related genes, as revealed by microarray analysis

Composts are the products obtained after the aerobic degradation of different types of organic matter waste and can be used as substrates or substrate/soil amendments for plant cultivation. There is a small but increasing number of reports that suggest that foliar diseases may be reduced when using compost, rather than standard substrates, as growing medium. The purpose of this study was to examine the gene expression alteration produced by the compost to gain knowledge of the mechanisms involved in compost-induced systemic resistance. A compost from olive marc and olive tree leaves was able to induce resistance against Botrytis cinerea in Arabidopsis, unlike the standard substrate, perlite. Microarray analyses revealed that 178 genes were differently expressed, with a fold change cut-off of 1, of which 155 were up-regulated and 23 were down-regulated in compost-grown, as against perlite-grown plants. A functional enrichment study of up-regulated genes revealed that 38 Gene Ontology terms were significantly enriched. Response to stress, biotic stimulus, other organism, bacterium, fungus, chemical and abiotic stimulus, SA and ABA stimulus, oxidative stress, water, temperature and cold were significantly enriched, as were immune and defense responses, systemic acquired resistance, secondary metabolic process and oxireductase activity. Interestingly, PR1 expression, which was equally enhanced by growing the plants in compost and by B. cinerea inoculation, was further boosted in compost-grown pathogen-inoculated plants. Compost triggered a plant response that shares similarities with both systemic acquired resistance and ABA-dependent/independent abiotic stress responses

Effectiveness and versatility of the biological control of Phytophthora capsisi in pepper by Trichoderma asperellum T34

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 are discussed on the basis of the different modes of action of T34 and etridiazole. T34 is a useful biological alternative to chemicals for the control of P. capsici in pepper