Impact of Paraburkholderia phytofirmans PsJN on Grapevine Phenolic Metabolism

Phenolic compounds are implied in plant-microorganisms interaction and may be induced in response to plant growth-promoting rhizobacteria (PGPRs). Among PGPR, the beneficial bacterium Paraburkholderia phytofirmans PsJN was previously described to stimulate the growth of plants and to induce a better adaptation to both abiotic and biotic stresses. This study aimed to investigate the impact of PsJN on grapevine secondary metabolism. For this purpose, gene expression (qRT-PCR) and profiling of plant secondary metabolites (UHPLC-UV/DAD-MS QTOF) from both grapevine root and leaves were compared between non-bacterized and PsJN-bacterized grapevine plantlets. Our results showed that PsJN induced locally (roots) and systemically (leaves) an overexpression of PAL and STS and specifically in leaves the overexpression of all the genes implied in phenylpropanoid and flavonoid pathways. Moreover, the metabolomic approach revealed that relative amounts of 32 and 17 compounds in roots and leaves, respectively, were significantly modified by PsJN. Once identified to be accumulated in response to PsJN by the metabolomic approach, antifungal properties of purified molecules were validated in vitro for their antifungal effect on Botrytis cinerea spore germination. Taking together, our findings on the impact of PsJN on phenolic metabolism allowed us to identify a supplementary biocontrol mechanism developed by this PGPR to induce plant resistance against pathogens

Uso do etefon e épocas de aplicação do ácido abscísico para melhorar a cor da uva de mesa 'Rubi'

The objective of this work was to evaluate the effect of ethephon and of abscisic acid (ABA) application timing on the color of 'Rubi' Table grape. Eight treatments were evaluated: control, without application; ethephon 500 mg L-1 applied seven days after veraison (7 DAV); and two concentrations of ABA (200 and 400 mg L-1) arranged with three application timings at 7 DAV, at 15 days before harvest (DBH), and at 7 DAV + 15 DBH. ABA does not modify physical‑chemical characteristics of the cluster and improves the color of grapes, especially when applied twice (7 DAV + 15 DBH) at the concentration of 400 mg L-1.O objetivo deste trabalho foi avaliar o efeito do etefon e de épocas de aplicação do ácido abscísico (ABA) na cor da uva de mesa 'Rubi'. Oito tratamentos foram avaliados: controle, sem aplicação; etefon 500 mg L-1, aplicado sete dias após o início da maturação (7 DAIM); e duas concentrações de ABA (200 e 400 mg L-1) arranjadas em três épocas de aplicação, aos 7 DAIM, aos 15 dias antes da colheita (DAC) e aos 7 DAIM + 15 DAC. O ABA não altera as características físico‑químicas dos cachos e melhora a cor das uvas, especialmente quando aplicado duas vezes (7 DAIM + 15 DAC), à concentração de 400 mg L-1

Characterization of mechanisms involved in the resistance induced by Paraburkholderia phytofirmans PsJN against Botrytis cinerea in Vitis vinifera L.

Paraburkholderia phytofirmans souche PsJN est une bactérie endophyte capable d’induire une promotion de croissance de la vigne et de lui conférer une tolérance vis-à-vis des basses températures. Puisque la bactérie PsJN induit également une tolérance de la vigne contre la pourriture grise causée par le champignon Botrytis cinerea, l’objectif de ce travail était de caractériser les mécanismes de la résistance induite par P. phytofirmans suite à une infection par B. cinerea chez la vigne.Nos résultats indiquent que l’inoculation des racines de vitroplants par la bactérie PsJN entraîne des modifications du métabolisme phénolique au niveau des plantules bactérisées. En effet, des tanins d’origine gallique et ellagique sont accumulés au niveau des racines en réponse à PsJN alors qu’une accumulation de lignine a été observée dans la tige et d’anthocyanes dans les feuilles. De même, PsJN induit une résistance contre B. cinerea en potentialisant l'expression de gènes de défense dépendants de l’acide salicylique et de l’acide jasmonique dans les feuilles de vigne. Parallèlement, une accumulation de callose et d’H2O2 a été observée ainsi qu’une meilleure mobilisation des glucides dans les plantules bactérisées, corrélée à une réduction des dommages de l’activité photosynthétique.Suite aux résultats obtenus avec le modèle vitroplant, nous avons optimisé la bactérisation des boutures fructifère et évaluer l’impact de cette bactérie sur la résistance des inflorescences contre B. cinerea. Les résultats présentés dans ce travail permettent d’envisager l’utilisation de la bactérie PsJN comme agent de lutte biologique.Paraburkholderia phytofirmans strain PsJN is an endophytic beneficial bacterium able to promote the growth of grapevine and to induce the plant resistance to biotic and abiotic stresses. Indeed, the interaction between PsJN and grapevine confers to the grapevine a protection towards cold stress (4 °C), by reducing damages on the photosynthetic system and modulating the carbon metabolism. The PsJN strain also induces a protection against gray mold caused by Botrytis cinerea. In this context, the aim of this work was to better characterize this P. phytofirmans strain PsJN-induced resistance in grapevine against B. cinerea.Our results indicate that the inoculation of in vitro-plantlets roots with PsJN altered the phenolic metabolism in bacterized-plantlets. Gallic and ellagic derived tannins are clearly accumulated in roots of bacterized-plantlets whereas an accumulation of lignin in stems and anthocyanins in leaves was observed. We also showed that PsJN induces a protection against B. cinerea by priming the expression of genes involved in salicylic acid and jasmonic acid pathways. In parallel, an accumulation of callose and H2O2, as well as a better mobilization of carbohydrates in bacterized plantlets were observed. In addition to the defense mechanisms setting up by plants, we demonstrated that PsJN reduces in vitro and in vivo development of B. cinerea, in a dose-dependent manner.Following results obtained with the in vitro-plantlets model, we optimized the protocol of bacterization of grapevine fruiting cuttings by the PsJN strain, and evaluate the impact of the bacteria on to induce the resistance of inflorescences to B. cinerea. Our results provide new insights for the use of PsJN and suggest its commercial use as a biological control agent

Burkholderia phytofirmans PsJN confers grapevine resistance against Botrytis cinerea via a direct antimicrobial effect combined with a better resource mobilization

Plant innate immunity serves as a surveillance system by providing the first line of powerful weapons to fight against pathogen attacks. Beneficial microorganisms and Microbial-Associated Molecular Patterns might act as signals to trigger this immunity. Burkholderia phytofirmans PsJN, a highly efficient plant beneficial endophytic bacterium, promotes growth in a wide variety of plants including grapevine. Further, the bacterium induces plant resistance against abiotic and biotic stresses. However, no study has deciphered triggered-mechanisms during the tripartite interaction between grapevine, B. phytofirmans PsJN and Botrytis cinerea. Herein, we showed that in contrast with classical rhizobacteria, which are restricted in the root system and act through ISR, B. phytofirmans PsJN is able to migrate until aerial part and forms at leaves surface a biofilm around B. cinerea mycelium to restrict the pathogen. Nevertheless, considering the endophytic level of PsJN in leaves, the plant protection efficacy of B. phytofirmans PsJN could not be explained solely by its direct antifungal effect. Deeper investigations showed a callose deposition, H2O2 production and primed expression of PR1, PR2, PR5 and JAZ only in bacterized-plantlets after pathogen challenge. The presence of PsJN modulated changes in leaf carbohydrate metabolism including gene expression, sugar levels and chlorophyll fluorescence imaging after Botrytis challenge. Our findings indicated that protection induced by B. phytofirmans PsJN was multifaceted and relied on a direct antifungal effect, priming of defense mechanisms as well as the mobilization of carbon sources in grapevine leaf tissues

Ethephon use and application timing of abscisic acid for improving color of 'Rubi' table grape

The objective of this work was to evaluate the effect of ethephon and of abscisic acid (ABA) application timing on the color of 'Rubi' Table grape. Eight treatments were evaluated: control, without application; ethephon 500 mg L‑1 applied seven days after veraison (7 DAV); and two concentrations of ABA (200 and 400 mg L‑1) arranged with three application timings at 7 DAV, at 15 days before harvest (DBH), and at 7 DAV + 15 DBH. ABA does not modify physical‑chemical characteristics of the cluster and improves the color of grapes, especially when applied twice (7 DAV + 15 DBH) at the concentration of 400 mg L‑1

Agronomic evaluation of 'Bordô' grapevine (Ives) clones

'Bordô' grapevines (Vitis labrusca) have great relevance to viticulture due to the quality they can impart to wines and juices. However, this cultivar has high variation in yield, ranging from 6 to 11 t ha-1. The use of clones with superior genetic potential related to scions currently marketed may increase crop profitability and revitalize its cultivation. The aim of this study was to evaluate the agronomical responses of twelve clones of the Bordô cultivar selected over a period of 15 years according to yield and quality. The vineyard was planted in 2008. Grape plants were grafted onto '1103 Paulsen' rootstock and trained on vertical shoot positioning. The agronomical evaluations, performed in the 2011, 2012 and 2013 seasons, covered the duration of their phenological cycles, shoot growth, yield per plant, estimated total yield and physicochemical characteristics. Differences were found between clones in terms of phenology, yield components, and berry composition. Clone 6 had the lowest yield, averaging 5.0 t ha-1 whereas clone 13 was the most productive with 14.9 t ha-1. Based on the most productive vineyards in the region (10.8 t ha-1), the adoption of more productive clones can generate an increase in yield of around 38 %

Agronomic evaluation of 'Bordô' grapevine (Ives) clones

'Bordô' grapevines (Vitis labrusca) have great relevance to viticulture due to the quality they can impart to wines and juices. However, this cultivar has high variation in yield, ranging from 6 to 11 t ha-1. The use of clones with superior genetic potential related to scions currently marketed may increase crop profitability and revitalize its cultivation. The aim of this study was to evaluate the agronomical responses of twelve clones of the Bordô cultivar selected over a period of 15 years according to yield and quality. The vineyard was planted in 2008. Grape plants were grafted onto '1103 Paulsen' rootstock and trained on vertical shoot positioning. The agronomical evaluations, performed in the 2011, 2012 and 2013 seasons, covered the duration of their phenological cycles, shoot growth, yield per plant, estimated total yield and physicochemical characteristics. Differences were found between clones in terms of phenology, yield components, and berry composition. Clone 6 had the lowest yield, averaging 5.0 t ha-1 whereas clone 13 was the most productive with 14.9 t ha-1. Based on the most productive vineyards in the region (10.8 t ha-1), the adoption of more productive clones can generate an increase in yield of around 38 %