Enhancement of plant growth, acclimatization, salt stress tolerance and verticillium wilt disease resistance using plant growth-promoting rhizobacteria (PGPR) associated with plum trees (Prunus domestica)

Plants interact with a great variety of microorganisms that inhabit the rhizosphere playing critical roles in several aspects of plant growth and protection against abiotic and biotic diseases. In this study, we performed a screening of bacteria associated with the rhizosphere of Prunus domestica trees to identify bacterial strains with plant growth-promoting activity. Ten strains isolated from the rhizosphere of P. domestica showed multiple in vitro plant growth promoting rhizobacteria (PGPR) activity such as the production of indole acetic acid, hydrogen cyanide, ammonia, solubilization of phosphates and antifungal activity against Verticillium dalhiae and Fusarium oxysporum f.sp. melonis. In planta, they significantly increased the growth (stem length, number of leaflets, leaf area and root weight) and biochemical (nitrate reductase activity, proline and chlorophyll content) parameters of tomato, as well as the rate of seed germination. Two selected strains (Pr7 and Pr8) with higher antagonistic activity against V. dalhiae and F. oxysporum f.sp. melonis protected tomato plants against Verticillium wilt and salt stress. In addition, they enhanced acclimatization of Vitis vinifera cv. Pinot noir and the peach root stock GF305 from in vitro to the greenhouse. 16S rRNA sequencing identified strains Pr7 and Pr8 as Pseudomonas stutzeri and Bacillus toyonensis, respectively. Since these two PGPR inoculants exhibited multiple traits beneficial to the examined host plants, they may be applied in the development of safe, and effective seed treatments as an alternative to chemical fungicides and fertilization but also for successful acclimatization of micropropagated plants.Mohamed Faize was supported by funding from the ‘Ministère de l'Enseignement Supérieur, de la Recherche Scientifique de la Formation des Cadres’ (MERSFC, Morocco) within the framework of ARIMNet2 Projec

Mise en évidence d'une relation entre les teneurs en acide abscissique des feuilles de vigne et des baies de raisin à l'époque de la véraison

L'acide abscissique (ABA) libre synthétisé par les feuilles pendant leur phase de croissance ne s'accumule pas dans ces organes sous forme libre mais sous forme de β-D-glucopyranose (ABA-GE). Les teneurs en ABA libre des feuilles des cépages étudiés sont inversement proportionnelles à leur surface et pourraient jouer un rôle dans le contrôle de leur croissance. Au cours de la véraison, l'ABA libre est exporté massivement vers les baies qui se comportent donc comme un pôle d'attraction très actif vis-à-vis de ce régulateur de croissance. L'accumulation de l'ABA sous ses deux formes se fait toujours dans un ordre bien déterminé: d'abord dans les pépins, puis dans les péricarpes et enfin dans les feuilles pour l'ABA libre et dans l'ordre inverse pour l'ABA-GE. Ce dernier interviendrait pour inactiver l'ABA libre, assurant ainsi un rôle régulateur. L'accumulation précoce de l'ABA libre dans les feuilles à la suite de différents traitements (suppression des grappes notamment) confirme que l'ABA des baies à la véraison provient des feuilles. Mais les expériences d'isolement de grappes, en présence ou en l'absence des feuilles opposées, montrent que dans ces conditions au moins les baies chlorophylliennes doivent aussi être capables de synthétiser de l'ABA

Relations entre la teneur en acide abscissique des bourgeons latents de vigne (<em>Vitis Vinifera</em> L. <em>var.</em> Merlot noir) et leur teneur en eau

Les variations de la teneur en cis-ABA des bourgeons latents, après la levée de dormance, apparaissent en étroite relation avec leur état hydrique. Toute diminution de la teneur en eau des bourgeons s'accompagne d'une augmentation de leur teneur en cis-ABA et, par suite, d'une diminution des possibilités de débourrement. En revanche, l'augmentation de la teneur en eau s'accompagne de la diminution de l'inhibition du débourrement des bourgeons par la réduction de leur teneur en cis-ABA

Effect of grapevine latent buds (<em>Vitis vinifera</em> L., cv. Merlot) chilling on their starch content: biochimical and cytological approachs

Biochimical analysis and photonic microscopy observations of starch were investigated in latent buds of Vitis vinifera L. (cv. Merlot) collected during their dormancy phase and during their cold storage at 2°C. Biochimical analysis showed that starch levels of grapevine latent buds was high (70 mg/g DW). Microscopical observations confirmed this result and showed a gradient of starch content in different regions of bud in which the foliars primordiums and scales were the starch richer. Buds conservation at 2°C reduced their starch content but this decrease begun only after 9 days of chilling corresponding to the time necessary for budbreak and for the beginning of increase the bud burst ability. The hydrolysis of starch seems begun at the first in apex and then propaged to the other regions of bud. In the scales, the most exposed region to cold, storage at 2°C during 56 days induced an increase of cellular tannins content and cell walls polysaccharides. These results were discuted in relation to the increase of bud burst ability and to their cold acclimatation

Endogenous levels of abscisic acid in various organs of <em>Vitis vinifera</em> L. (cv. Cabernet Sauvignon) between flower buds separated and grape closed stages

Free abscisic acid (ABA) and bound abscisic acid (ABA-GE: ABA glucose ester) contents and growth were investigated in leaves, internodes, flowers buds, flowers and berries of Vitis vinifera L. cv. Cabernet Sauvignon between flower buds separated and grape closed stages. The ABA levels in leaves and in internodes decrease when the growth was hight and increases when the growth become smaller or stopped. What is more, ABA was accumulated hightly in the flowers (at 50% of flowering) and then appears to be a good marker of flowering. ABA contents decreased at berry setting and till grape closed stage. In leaves, internodes, flowers buds and flowers, ABAGE and ABA show an inverse development and then suggests an interconversion phenomenon between theses two forms. Two most importants points were discuted in this paper: 1) The role of ABA in the controle of growth and development of the organs studied and (2) The translocation of abscisic acid between the organs studied and the role of ABA-GE in this transport

Relations entre la teneur en acide abscissique des bourgeons latents de vigne (<em>Vitis Vinifera</em> L. <em>var.</em> Merlot noir) et leur teneur en eau

Les variations de la teneur en cis-ABA des bourgeons latents, après la levée de dormance, apparaissent en étroite relation avec leur état hydrique. Toute diminution de la teneur en eau des bourgeons s'accompagne d'une augmentation de leur teneur en cis-ABA et, par suite, d'une diminution des possibilités de débourrement. En revanche, l'augmentation de la teneur en eau s'accompagne de la diminution de l'inhibition du débourrement des bourgeons par la réduction de leur teneur en cis-ABA

Possible relationship between aggressiveness of two <em>Eutypa lata</em> isolates and their polyamines and abscisic acid content

By HPLC analysis, we showed that myceliums of two Eutypa lata isolates cultivated in Enikson and Petersson medium culture synthesized polyamines (Putrescine, Spermidine and Spermine) and abscisic acid (ABA). ln this medium, myceliums of high virulent isolate (BXI-IO) produced fewer polyamines than less virulent isolate (BX 1-5) while inverse phenomenon was observed for ABA content. The two growth regulators were diffused in medium culture in which their levels increase with age of mycelium. In the end, variations of PA and ABA in myceliums show antagonist effect of the two growth regulators in Eutypa lata fungi

Mise en évidence de l'interconversion de l'acide abscissique et de l'abscissate de β-D-glucopyranose dans des feuilles de <em>Vitis vinifera</em> L. au cours de leur développement

L'évolution, dans les baies de raisin, de l'acide abscissique libre (ABA) et de sa forme conjuguée, l'abscissate de β-D-glucopyranose (ABA-GE), est maintenant bien connue (BROQUEDIS, 1987). On sait notamment qu'une forte accumulation de ce régulateur de croissance sous sa forme libre se produit à la véraison et que l'interconversion entre les deux formes d'ASA est possible. Comme il est généralement admis que l'ASA est essentiellement synthétisé par les feuilles, il était intéressant de savoir si, chez la vigne, de tels phénomènes d'interconversion étaient susceptibles de se produire également dans ces organes, contrairement à l'opinion actuellement admise à la suite de travaux réalisés sur d'autres plantes

Relationship between the levels of abscisic acid in latent buds, in leaves and in internodes of <em>Vitis vinifera</em> L. cv. Merlot during the dormancy phase

The levels of free and bound ABA (cis-ABA and cis-ABA-GE) were quantified weekly during the dormancy phase of three years in leaves, in latent buds and in internodes grapevine (Vitis vinifera L. cv. Merlot) by high pressure liquid chromatography (HPLC). An inverse variation between cis-ABA and cis-ABA-GE levels was observed in buds and in internodes during some phases of their development. This result seems suggest a possible interconversion phenomenon between these two ABA forms as described in others organs by some authors. The development of ABA in leaves, in buds and in internodes, showed three successive maximums of cis-ABA. The first maximum was observed in leaves during onset of dormancy, the second maximum in buds during dormancy and the last in internodes during the leaf fall. Maximums of cis-ABA in leaves and in buds are approximatively the some values (around of 150 µg/100 g Dry Weight) whereas in internodes is lower (60 µg/100 g Dry Weight). An inverse variation between cis-ABA of leaves and cis-ABA of buds was observed suggesting that the increase of cis-ABA in buds was caused by the cis-ABA translocation from leaves but also from roots. The removal of leaves on september 1997 during the dormancy phase, before leaf fall period, induced an increase of cis-ABA content in buds and internodes. These results seem suggest that before leaf fall period, ABA of buds and internodes were translocated to leaves. During this same period, the removal of leaves and buds induced a slightly soften of ABA content increase in internodes, that seems indicate that ABA was greatly translocated from roots. During the period of leaf fall, the leaf removal traitment induced a decrease of cis-ABA levels in buds and in internodes while the same traitment associated to buds removal stabilized the ABA levels in internodes. During this period, ABA seems exported from leaves to buds and internodes and the roots don't appear to operate significantly in the development of ABA in these two organs

Annual variations of alpha-amylase and invertases activities in buds and internodes of grapevines and their relation with carbohydrates and abscisic acid contents

The concentration of starch, soluble carbohydrates, free abscisic acid (ABA) and activities of α-amylases and invertases (the acid and the alkaline form) were investigated in buds and internodes of Vitis vinifera L. cv. Merlot during annual cycle. The levels of starch increased in the two organs from middle august to middle of November and the decreased until middle February. These variations seem to be controlled by α-amylase which activity was low during periods of starch accumulation and high when starch contents decreased. As the bud burst draws near (since the middle of February), starch accumulated in internodes and buds. However at the same time of the activity of α-amylase which activity also increased. Starch contents could be controlled by ABA which is known to reduce α-amylase activity. Indeed in internodes ABA content was high when α-amylase activity was low. This was also the case in the buds but after break dormancy phase. This difference of comportment of α-amylase towards ABA in the buds during the annual cycle could be in relation with the change of the physiological state of buds induced by the winter chilling. The invertases activities in buds and internodes changed inversely to the sucrose and raffinose contents during all the annual cycle suggesting that the levels of these sugars were controlled by invertases, highly by the acid form and slightly by the alkaline form. Nevertheless, in the buds, when alkaline activity of invertase was high, sucrose content was maximal. These invertases seem also implicated, with α-amylase, in the development of starch content particularly when starch was accumulated by glucose providing. In the case of buds, invertases activities appeared to change in the same sense of ABA content but not during all the cycle. This suggested that this growth regulator may not be crucial for the control of invertases activities