Resource competitive interactions as mechanism of date palm Bayoud disease suppression

In Morocco, soils that are naturally suppressive to date palm Bayoud disease have long been discovered. Although suppressiveness was attributed to biological activities of indigenous microbes, our knowledge on the specific mechanisms underpinning this property remains limited. In this study, we investigated nutrient competition between Fusarium oxysporum f. sp. albedinis, the causal agent of Bayoud disease, and saprophytic Fusarium as a factor of disease suppressiveness/conduciveness in suppressive and conducive soils. Growth of pathogenic and saprophytic Fusarium isolates from one suppressive and one conducive soils on 95 carbon sources was assessed. Fusarium isolates exhibited distinct nutrient use profiles and varied significantly with soil in carbon utilization. Isolates from the suppressive soil had significantly the greatest resource use efficiency, followed by the pathogenic isolates that grew significantly faster than the isolates from the conducive soil. Data on nutrient niche overlap showed that the pathogen is outcompeted by saprophytic Fusarium populations in the suppressive soil and outcompetes those in the conducive soil. Taken together, our results provide insight into the role of competition for carbon resources among pathogenic and saprophytic Fusarium communities as a driving factor in soil suppressiveness/conduciveness. This finding may also open novel research paths and offer opportunities for the development of biocontrol techniques against Bayoud disease in Moroccan date palm groves. Keywords: Date palm, Bayoud disease, nutrient competition, disease suppressio

Plant-driven selection of microbes in the rhizosphere and plant-microbe feedbacks

  L’effet des plantes sur les microorganismes du sol et les rétroactions entre les microbes et les plantes sont devenus le focus de beaucoup de recherche. Les dernières avancées dans le domaine des interactions plantes-microbes montrent que les plantes sont capables de façonner le microbiome de leur rhizosphère via des mécanismes divers. Dans cette revue, nous rassemblons des résultats de multiples études sur le rôle des plantes dans l’altération de la structure et des fonctions des microorganismes au niveau de la rhizosphère. En outre, nous discutons les rôles de différentes substances phytochimiques dans la médiation de ces effets. Finalement, nous soulignons que l’enrichissement sélectif de microorganismes spécifiques a aussi bien des rétroactions négatives, avec l’accumulation de pathogènes dans la rhizosphère, que positives, suite au recrutement de microflore bénéfique. Une meilleure compréhension des mécanismes qui régissent la sélection de microorganismes ayant des rétroactions positives ouvrira de nouvelles possibilités pour l’amélioration de la production agricole. Mots-clés: Plantes, microorganismes, rhizosphère, rétroactions.Plant impacts on soil microbial communities and plant-microbe feedbacks have become the focus of much research. Recent advances in plant-microbe interactions investigations show that plants are able to shape their rhizosphere microbiome through diverse mechanisms. In this review, we gather findings from across multiple studies on the role of plants in altering the structure and functions of microbes in the rhizosphere. In addition, we discuss the roles of diverse phytochemicals in mediating these effects. Finally, we highlight that selective enrichment of specific microorganisms in the rhizosphere has either negative feedbacks, with pathogen accumulation in the rhizosphere; or, perhaps most importantly, positive feedbacks as a result of the recruitment of a beneficial microflora. Insights into the mechanisms that underpin plant selection of microbial communities with positive feedbacks will provide new opportunities to increase crop production. Keywords: Plants, microbes, rhizosphere, feedbacks

Plant-driven selection of microbes in the rhizosphere and plant-microbe feedbacks

  L’effet des plantes sur les microorganismes du sol et les rétroactions entre les microbes et les plantes sont devenus le focus de beaucoup de recherche. Les dernières avancées dans le domaine des interactions plantes-microbes montrent que les plantes sont capables de façonner le microbiome de leur rhizosphère via des mécanismes divers. Dans cette revue, nous rassemblons des résultats de multiples études sur le rôle des plantes dans l’altération de la structure et des fonctions des microorganismes au niveau de la rhizosphère. En outre, nous discutons les rôles de différentes substances phytochimiques dans la médiation de ces effets. Finalement, nous soulignons que l’enrichissement sélectif de microorganismes spécifiques a aussi bien des rétroactions négatives, avec l’accumulation de pathogènes dans la rhizosphère, que positives, suite au recrutement de microflore bénéfique. Une meilleure compréhension des mécanismes qui régissent la sélection de microorganismes ayant des rétroactions positives ouvrira de nouvelles possibilités pour l’amélioration de la production agricole. Mots-clés: Plantes, microorganismes, rhizosphère, rétroactions.Plant impacts on soil microbial communities and plant-microbe feedbacks have become the focus of much research. Recent advances in plant-microbe interactions investigations show that plants are able to shape their rhizosphere microbiome through diverse mechanisms. In this review, we gather findings from across multiple studies on the role of plants in altering the structure and functions of microbes in the rhizosphere. In addition, we discuss the roles of diverse phytochemicals in mediating these effects. Finally, we highlight that selective enrichment of specific microorganisms in the rhizosphere has either negative feedbacks, with pathogen accumulation in the rhizosphere; or, perhaps most importantly, positive feedbacks as a result of the recruitment of a beneficial microflora. Insights into the mechanisms that underpin plant selection of microbial communities with positive feedbacks will provide new opportunities to increase crop production. Keywords: Plants, microbes, rhizosphere, feedbacks

Management of date palm Bayoud disease in Moroccan oases

«Bayoud», a vascular wilt disease, has become for more than a century a serious threat to date palm in Moroccan oases. The strategic importance of date palm cultivation to oasis agriculture drives the intensification of date production through the creation of new investment projects on soils that are potentially healthy, but very close to infested areas. The success of these investments requires drastic prophylactic and pathogen exclusion measures. In this work, we summarize the main research results to underpin this effort, we analyze the epidemiological situation of Bayoud disease in Morocco, and we bring insight to integrated management based on early detection, cartography, and genetic resistance to wall-off the disease and secure the investments in the new date palm growing areas

Evaluation of In Vitro Shoot Elongation and Rooting of Date Palm, and Determination of Physiological Characteristics of Regenerated Plantlets

The effects of various culture conditions on shoot elongation, rooting and plantlet acclimatization were tested. Adventitious shoots obtained through direct organogenesis of date palm (Phoenix dactylifera L.) cv. ‘Mejhoul’ were used as explants. The effects of culture medium texture, plant growth regulators, polyvinylpyrrolidone, adenine, myo-inositol, L-glutamine, and carbon source on in vitro plantlet quality and subsequent acclimatization were evaluated. The most effective culture medium was the semi-solid and half-strength Murashige and Skoog medium without plant growth regulators, supplemented with 30 g L-1 sucrose. After 3 months of culture on this medium, the average shoot length was 13.6 cm, the average number of adventitious roots per shoot was 3.6, and the average root length was 3.85 cm. The survival rate of these plantlets in acclimatization was 90%. On the other hand, liquid medium, plant growth regulators, polyvinylpyrrolidone, adenine, myo-inositol and L-glutamine did not increase the survival rate during acclimatization. Along with these experiments, some physiological characteristics of the plantlets obtained in vitro were also determined. Chlorophyll content and fluorescence, foliar surface and stomatal conductance were measured after 3 months of culture in each medium. The ranges were as follows: Chlorophyll content, 11.7-31.8 CCI; chlorophyll fluorescence, 0.633-0.795; foliar surface, 7.35-13.29 cm2; and stomatal conductance, 10.3-36.0 mmol m-2 s-1. Interestingly, positive correlations between the physiological characteristics of the plantlets and their survival percentage in the glasshouse were revealed. The findings of this investigation will be valuable for large-scale and cost-saving production of date palm cv. ‘Mejhoul’ plants

Management of date palm Bayoud disease in Moroccan oases

Le «Bayoud», fusariose vasculaire du palmier dattier, est une maladie séculaire sévissant dans les oasis marocaines. L’importance stratégique de la phoeniciculture dans l’agriculture oasienne amorce son intensification par la création de nouveaux projets d’investissement sur des terrains potentiellement indemnes du Bayoud, mais proches de zones contaminées. La réussite de ces investissements requiert des mesures drastiques de prophylaxie et d’exclusion de l’agent pathogène. Dans ce travail, nous résumons les principaux acquis de recherche pouvant étayer cet effort. Nous faisons une analyse de la situation épidémiologique du Bayoud au Maroc et nous apportons une vision de gestion intégrée basée sur la détection précoce, la cartographie, et la résistance génétique pour limiter l’expansion de la maladie et sécuriser les investissements dans les nouvelles aires d’extension de culture du palmier dattier. Mots clés: Palmier dattier, Bayoud, détection précoce, cartographie, résistance génétique«Bayoud», a vascular wilt disease, has become for more than a century a serious threat to date palm in Moroccan oases. The strategic importance of date palm cultivation to oasis agriculture drives the intensification of date production through new investment projects on soils that are potentially healthy, but very close to infested areas. The success of these investments requires drastic prophylactic and pathogen exclusion measures. In this work, we summarize the main research results to underpin this effort. We analyze the epidemiological situation of Bayoud disease in Morocco and we bring insight to integrated management based on early detection, cartography, and genetic resistance to wall-off the disease and secure the investments in the new date palm growing areas. Key words: Date palm, Bayoud, early detection, cartography, genetic resistanceLe «Bayoud», fusariose vasculaire du palmier dattier, est une maladie séculaire sévissant dans les oasis marocaines. L’importance stratégique de la phoeniciculture dans l’agriculture oasienne booste son intensification par la création de nouveaux projets d’investissement sur des terrains potentiellement indemnes du Bayoud, mais proches de zones contaminées. La réussite de ces investissements requiert des mesures drastiques de prophylaxie et d’exclusion de l’agent pathogène. Dans ce travail, nous résumons les principaux acquis de recherche pouvant étayer cet effort, nous faisons une analyse de la situation épidémiologique du Bayoud au Maroc, et nous apportons une vision de gestion intégrée basée sur la détection précoce, la cartographie, et la résistance génétique pour limiter l’expansion de la maladie et sécuriser les investissements dans les nouvelles aires d’extension de culture du palmier dattier. Mots clés: Palmier dattier, Bayoud, détection précoce, cartographie, résistance génétiqu

Maturation and Germination of Date Palm (Phoenix dactylifera L.) Somatic Embryos

Maturation and germination of somatic embryos are two crucial steps in the somatic embryogenesis process. Herein, we evaluated the effects of several factors on the maturation and germination of date palm somatic embryos. Globular somatic embryos of cv. ‘Najda’ were cultured on Murashige and Skoog medium at full strength (MS), half strength (1/2MS), and one-third strength (1/3MS), with or without agar, and supplemented with various concentrations of mannitol, sorbitol, polyethylene glycol (PEG, MW 8000) and abscisic acid (ABA). Our results showed that culture medium strength and texture (liquid or semi-solid), osmotic agents, and the concentration and time of exposure to ABA influence somatic embryo maturation. The highest mean number of mature somatic embryos (106.4 per 100 mg fresh weight callus) was obtained after 3 weeks of culture on full-strength liquid MS medium supplemented with 30 g L-1 PEG and 40 µM ABA, followed by 9 weeks of culture on the same medium but without ABA. Somatic embryo germination was achieved by transferring mature embryos to MS medium containing various combinations of 1-naphthalene acetic acid (NAA), 6-benzylaminopurine (BAP) and gibberellic acid (GA3). The highest germination rate (68%) of somatic embryos occurred in the presence of 0.5 mg L-1 NAA. However, there was no significant difference with the other germination media (54-66%). Plantlet acclimatization was successfully accomplished, and the survival rate was 80% after 6 months in the glasshouse. The findings of the present study open new prospects for massive propagation of this bayoud-resistant date palm cultivar

Antifungal Potential of Phytochemicals against Mauginiella scaettae, the Plant Pathogen Causing Inflorescence Rot of Date Palm

Date palm (Phoenix dactylifera L.) inflorescence rot caused by Mauginiella scaettae poses a serious threat to date palm in Morocco. The present study aims to determine the antifungal activity of five plant extracts against M. scaettae, including Acacia cyanophylla, Cupressus atlantica, Eucalyptus torquata, Nerium oleander, and Schinus molle and link this effect to their content in phenolics and flavonoids, as well as their antioxidant properties. Plant extracts exhibited significant discrepancies regarding their antifungal activity (p<0.05). The extracts of E. torquata and C. atlantica had the strongest and dose-dependent manner inhibitory effect against mycelial growth and spore germination. E. torquata and S. molle caused the greatest sporulation reductions of about 88.05% and 36.11%, respectively. In addition, there were significant differences among the examined plant extracts with respect to their total polyphenols (14.52–76.68 mg GAE/g DW), flavonoids (8.75–57.78 g RE/100 g DW), and antioxidant properties as measured by TEAC (74.77–391.23 mmol TE/g DW) and FRAP assays (87.18–474.04 mmol TE/g DW). Strong correlations were found between phenolic compounds and antioxidant activity suggesting that polyphenols play a key role in the observed antioxidant and antifungal activities

In Vitro Root Induction from Argan (Argania spinosa (L.) Skeels) Adventitious Shoots: Influence of Ammonium Nitrate, Auxins, Silver Nitrate and Putrescine, and Evaluation of Plantlet Acclimatization

Argania spinosa (L.) Skeels is an endangered plant species endemic to Morocco. In recent years, attempts to develop in vitro regeneration systems for this species were made. However, rooting and acclimatization of in vitro plants have been a bottleneck for successful propagation. In the present study, the effects of different concentrations of auxins, putrescine, silver nitrate (AgNO3) and ammonium nitrate on the in vitro rooting of adventitious shoots of two argan genotypes “Mejji” and “R’zwa”, were evaluated. The highest rooting percentages (86.6% in “Mejji” and 84.4% in “R’zwa”) were observed on Murashige and Skoog (MS) medium modified by reducing the ammonium nitrate concentration and supplemented with 1.5 mg L−1 indole-3-butyric acid (IBA), 0.5 mg L−1 1-naphthalene acetic acid (NAA), 2 mg L−1 AgNO3 and 160 mg L−1 putrescine. This medium resulted in the development of a good root system after only 10 days of culture. Plantlet acclimatization was carried out using different substrate mixtures, and high survival rates (100%) were observed when the substrate contained either peat alone or a sand–peat mixture (1:1, w/w). The high percentages of rooting and acclimatization reported in the present study are of high importance for rapid and large-scale propagation of this endangered species

First Study on the Electronic and Donor Atom Properties of the Ultra-Thin Nanoflakes Quantum Dots

Nanoflakes ultra-thin quantum dots are theoretically studied as innovative nanomaterials delivering outstanding results in various high fields. In this work, we investigated the surface properties of an electron confined in spherical ultra-thin quantum dots in the presence of an on-center or off-center donor impurity. Thus, we have developed a novel model that leads us to investigate the different nanoflake geometries by changing the spherical nanoflake coordinates (R, &alpha;, &#981;). Under the infinite confinement potential model, the study of these nanostructures is performed within the effective mass and parabolic band approximations. The resolution of the Schr&ouml;dinger equation is accomplished by the finite difference method, which allows obtaining the eigenvalues and wave functions for an electron confined in the nanoflakes surface. Through the donor and electron energies, the transport, optoelectronic, and surface properties of the nanostructures were fully discussed according to their practical significance. Our findings demonstrated that these energies are more significant in the small nanoflakes area by altering the radius and the polar and azimuthal angles. The important finding shows that the ground state binding energy depends strongly on the geometry of the nanoflakes, despite having the same surface. Another interesting result is that the presence of the off-center shallow donor impurity permits controlling the binding energy, which leads to adjusting the immense behavior of the curved surface nanostructures