Plant-microbiome interactions under drought—insights from the molecular machinist’s toolbox

Plants face numerous challenges in novel and harsh environments, including altered precipitation regimes, salinity, extreme temperatures, increased atmospheric CO2, nutrient deficiency, heavy metals, and oxygen. Drought remains a major constraint to crop productivity and meeting food demand, with the frequency, intensity, and duration of drought expected to raise in the coming century. The “cry for help” hypothesis proposes that timely recruiting of the microbiome by plants may confer benefits in stress alleviation, plant growth, fitness, and health. The root-associated microbiome harbors 10–100 times more functional genes than the host, which can significantly stimulate the metabolic and genetic potential of plant–microbiome assembly. However, cross-talk among drought and the root-associated microbes, and among the root-associated microbiome and the host-plant, is less well understood. Understanding the molecular aspect of multiple mechanisms by which microbes associate with plants during drought stress is of fundamental importance in plant biology and agriculture. In this review, we examine the progress in research on the response of plant and its microbiome assemblages and interactions to drought stress, including the impact of drought and root exudates on host resilience. We delve into the potential of ‘omics’ technologies to unravel the signaling networks underlying these interactions and the multiway interactions that occur among the host and its associated microbiome. We then discuss the shortfalls, challenges, and future research directions in this field. Overall, we argue that harnessing/manipulating the crop microbiome presents a promising strategy for improving agricultural systems in the face of global climate change

Biodiversity of the public green spaces in the Urban District of Marrakesh (UDM) (Morocco)

En milieu urbain, l’espace vert public (EVP) constitue un enjeu majeur du développement durable, tant en matière d’environnement que de qualité de vie de leurs usagers. La présente étude présente une première recherche sur les EVP de la ville de Marrakech permettant de disposer d’une base de données scientifiques sur ces EVP qui va aider à la prise de décision et de planification environnementale de la ville. Elle vise (i) l’étude de la diversité de la flore ornementale (ii) et l’analyse de la structure et la répartition spatiale de ces EVP. La prospection a concerné 50 EVP urbains répartis sur les 5 arrondissements de la ville. Les résultats ont montré une diversité de la flore ornementale qui s’élève à 297 espèces asculaires, réparties en 212 genres et 88 familles et dont 77 % des espèces sont exotiques. Cette richesse spécifique est dominée par 12 familles qui détiennent 142 espèces réparties en 85 genres. La fréquence, l’origine et le type biologique des espèces sont très diversifiés. L’étude de la structure a fait ressortir 4 types d’EVP qui diffèrent par leur taille et leur fonction. L’analyse de l’affinité floristique des EVP-CUM a fait apparaître 13 groupes qui se distinguent par leurs compositions floristiques. En conséquence, les EVP de la ville contribuent vivement à la conservation et l’accroissement de la diversité floristique et à l’amélioration de la qualité esthétique de la ville de Marrakech

OPTIMISATION DE LA CROISSANCE ET DU DEVELOPPEMENT DU PALMIER DATTIER EN PEPINIERE PAR L’UTILISATION D’AMENDEMENTS BIOLOGIQUES, ORGANIQUES ET CHIMIQUES

This study shows the comparative effects of Bactériosol®, compost from green waste, developed by Mezy (1978) and other organic and chemical fertilizers to increase growth and development of cultivar of date palm ‘Bouffgouss‘ (Phoenix dactylifera L.) cultivated in greenhouses at the nursery of Marrakesh. We examined the effectiveness of Bactériosol ® compared with natural manure and chemical NPK fertilizer applied at different concentration. Four months after application of various amendments on the culture substrate of date palm aged 16 months, the effect on the biomass production occurred for treated plants by Bacteriosol® compared to other treatments with chemical fertilizers or natural fertilizers. The ionic contents of N, P, K and Na are significantly higher in plants treated by Bactériosol ® than other plants. The beneficial effect of Bactériosol ® on biomass and plant state is remarkable on young date palm

Impact of applying composted biosolids on wheat growth and yield parameters on a calcimagnesic soil in a semi-arid region

A field trial in a semi-arid climate was carried out on wheat (Triticum aestivum var. Marchouch) growing on a calcimagnesic soil using compost applied at 42 T/ha during the three years of study, but in different ways: C1, C2 and C3. Over this period, the level of total Kjeldhal nitrogen (TKN) increased in the soil amended by high doses (C2 and C3, by about 33 and 50%) compared with steady low amendment (C1) and to both controls NF (soil without fertilisation) and MF (soil receiving mineral fertilization). Adding compost also led to a positive influence on cation exchange capacity (CEC) by increasing humic substance levels (HS) which doubled in plots C2 and C3 compared with both controls. In NF soil, the TKN, total organic carbon (TOC) and the pH of soil showed a clear negative correlation with the agronomic parameters. In the MF soil, most physico-chemical parameters correlated well with the agronomic parameters: input of mineral elements balancing export through harvest. In amended soil, especially in C3 plots, HS and CEC showed significant correlations with most agronomic parameters (P1: 69.1%) due to enhanced CEC and sequestration of available carbon in the form of stable humic structures.Key words: Compost, wheat growth, calcimagnesic soil, semi-arid region

PLFAs of the microbial communities in composting mixtures of agro-industry sludge with different proportions of household waste

Phospholipid fatty acids (PLFAs) were analysed at different time periods during composting of two waste mixtures rich in fats, M1 (22%) and M2 (39%), with the aim of monitoring changes in microbial community structure. The two mixtures consisted of a sludge sample collected from a vegetable oil refinery effluent treatment plant combined with household wastes. The PLFA profiles of both mixtures revealed that, at the start of the process, fungi and Gram-negative bacteria (GÀ) were more abundant in M2 than in M1. During the thermophilic phase, branched PLFA (i15:0, a15:0, i16:0, and i17:0) markers of Gram-positive bacteria (Gþ), became more abundant in M1, while G- bacteria were predominant in M2. The PLFA profiles in M1 representing non-specific, Gþ and GÀ bacteria as well as fungi decreased during the cooling phase (maturation) while an increase was recorded in M2, which was richer in fats. The ShannoneWeaver diversity index (Ish) showed a greater increase during M1 composting (from 0.69 to 1.05), mainly for Gþ bacteria and GÀ bacteria, than in M2 composting (from 0.79 to 0.84). Principal components and cluster analyses revealed a succession of different communities during composting, which varied from fungi and GÀ bacteria to Gþ and thermophilic and thermotolerant GÀ bacteria. The end of composting was characterized by a reduction of all these microbial entities, especially for M1, except actinomycetes, which are associated with compost stability

Safe Cultivation of Medicago sativa in Metal-Polluted Soils from Semi-Arid Regions Assisted by Heatand Metallo-Resistant PGPR

Soil contamination with heavy metals is a constraint for plant establishment and development for which phytoremediation may be a solution, since rhizobacteria may alleviate plant stress under these conditions. A greenhouse experiment was conducted to elucidate the effect of toxic metals on growth, the activities of ROS (reactive oxygen species)-scavenging enzymes, and gene expression of Medicago sativa grown under different metal and/or inoculation treatments. The results showed that, besides reducing biomass, heavy metals negatively affected physiological parameters such as chlorophyll fluorescence and gas exchange, while increasing ROS-scavenging enzyme activities. Inoculation of M. sativa with a bacterial consortium of heat- and metallo-resistant bacteria alleviated metal stress, as deduced from the improvement of growth, lower levels of antioxidant enzymes, and increased physiological parameters. The bacteria were able to effectively colonize and form biofilms onto the roots of plants cultivated in the presence of metals, as observed by scanning electron microscopy. Results also evidenced the important role of glutathione reductase (GR), phytochelatin synthase (PCS), and metal transporter NRAMP1 genes as pathways for metal stress management, whereas the gene coding for cytochrome P450 (CP450) seemed to be regulated by the presence of the bacteria. These outcomes showed that the interaction of metal-resistant rhizobacteria/legumes can be used as an instrument to remediate metal-contaminated soils, while cultivation of inoculated legumes on these soils is still safe for animal grazing, since inoculation with bacteria diminished the concentrations of heavy metals accumulated in the aboveground parts of the plants to below toxic levelsMarruecos. Centre National pour la Recherche Scientifique et Technique (CNRST)-España, Ministerio de Economía y Competitividad (MINECO)-PPR2 /2016/42Unión Europea (FEDER)-CGL2016-75550-

Effects of Slag-Based Fertilizer to Mitigate Salinity Stress on Greenhouse Durum Wheat (Triticum Durum Desf.) Cultivars

For a modern agricultural, the search for sustainable practices to increase productivity is fundamental. Steel slag have been studied for their potential use in agriculture. These substances present a great possibility of agricultural applications since they are rich in nutrients, which enhance plant uptake. In this regard, the effect of steel slag based-fertilizer was investigated in the greenhouse durum wheat cultivation in pots under salt-stress conditions. Two slag doses: 10 g slag/ kg soil (D1) and 20 g slag/ kg soil (D2) were evaluated under no salt-stress (0 mM NaCl) and salt-stress conditions (100 mM NaCl) for salinity stress mitigation. Morpho-physiological and biochemical parameters of wheat were measured and compared to the different treatments. Wheat exposure to salinity decreased its biomass, stomatal conductance, efficiency of photosystem II, protein content and increased total soluble sugars, hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents. Amended plants with 10 g slag/ kg soil (D1), led to a significant improve in biomass with an increase of shoot and root dry weights (133% and 400% respectively), stomatal conductance (22 %), soluble sugars (14 %) and protein content (158%) under salinity conditions as compared to the control treatment 0 g slag/ kg soil (C), indicating a positive influence on durum wheat plants. However, soil enrichment with 20 g slag/ kg soil (D2) decreased plant growth parameters and presented the highest levels of H2O2 and MDA contents compared to the control and treatment D1 after three months of cultivation under salt-stress. This study supports the hypothesis of the application of slag at lower dose improve productivity of durum wheat and mitigate salinity stress

Use of Olive Mill Wastewaters as Bio-Insecticides for the Control of <em>Potosia Opaca</em> in Date Palm (<em>Phoenix dactylifera L.</em>)

The date palm is one of the most economically important perennial plants of the North Africa and in Morocco, where it is extensively cultivated for food and many other commercial purposes. Palm trees are threatened by many pests such as Potosia opaca newly identified in Morocco, especially in Marrakesh and Errachidia regions. In addition, olive mill wastewaters (OMW) are an environmental problem in olive oil producing countries such as Morocco. Generally, these effluents are drained into ecosystems without any pre-treatment. To reduce their negative impact and to get benefits in particular from their high phenolic content, OMW were used as bio-insecticides in crude form. The results showed that crude OMW were effective to control this pest causing a weight loss similar to Cordus insecticide (17% vs. 15%) and mortality almost similar to Kemaban insecticide. OMW’s biocide potential was related principally to their high phenolic content. Based on HPLC analysis, ten phenolic molecules were identified, including two which were revealed as the major monomeric phenolic compounds in OMW, 0.248 g/L of hydroxytyrosol and 0.201 g/L of tyrosol. In this chapter, the potential use of OMW as bio-insecticides for the control of P. opaca in date palm is discussed

Effects of Slag-Based Fertilizer to Mitigate Salinity Stress on Greenhouse Durum Wheat (Triticum Durum Desf.) Cultivars

For a modern agricultural, the search for sustainable practices to increase productivity is fundamental. Steel slag have been studied for their potential use in agriculture. These substances present a great possibility of agricultural applications since they are rich in nutrients, which enhance plant uptake. In this regard, the effect of steel slag based-fertilizer was investigated in the greenhouse durum wheat cultivation in pots under salt-stress conditions. Two slag doses: 10 g slag/ kg soil (D1) and 20 g slag/ kg soil (D2) were evaluated under no salt-stress (0 mM NaCl) and salt-stress conditions (100 mM NaCl) for salinity stress mitigation. Morpho-physiological and biochemical parameters of wheat were measured and compared to the different treatments. Wheat exposure to salinity decreased its biomass, stomatal conductance, efficiency of photosystem II, protein content and increased total soluble sugars, hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents. Amended plants with 10 g slag/ kg soil (D1), led to a significant improve in biomass with an increase of shoot and root dry weights (133% and 400% respectively), stomatal conductance (22 %), soluble sugars (14 %) and protein content (158%) under salinity conditions as compared to the control treatment 0 g slag/ kg soil (C), indicating a positive influence on durum wheat plants. However, soil enrichment with 20 g slag/ kg soil (D2) decreased plant growth parameters and presented the highest levels of H2O2&nbsp;and MDA contents compared to the control and treatment D1 after three months of cultivation under salt-stress. This study supports the hypothesis of the application of slag at lower dose improve productivity of durum wheat and mitigate salinity stress

Effects of Slag Applications and Salinity Stress on Greenhouse Durum Wheat (Triticum durum Desf.) Plants

The search for sustainable practices to increase productivity is a fundamental need in current agriculture. Steel slag has been studied for its potential use in agriculture. These substances present a great ability of agricultural applications since they are rich in nutrients. The effect of steel slag-based fertilizer was investigated on greenhouse durum wheat cultivar under salt-stress conditions. Two doses of slag: 10 g slag/ kg soil (D1) and 20 g slag/ kg soil (D2) were evaluated under no salt-stress (0 mM NaCl) and salt-stress conditions (100 mM NaCl) for salinity stress mitigation. Morpho-physiological and biochemical parameters of wheat were measured and compared to the different treatments. Exposure of wheat to salinity decreased its biomass, stomatal conductance, efficiency of photosystem II, and protein content, but it increased total soluble sugars, hydrogen peroxide (H2O2), and malondialdehyde (MDA) contents. Amended plants with 10 g slag/ kg soil (D1) led to a significant improvement in biomass with an increase of shoot and root dry weights (133% and 400% respectively), stomatal conductance (22 %), soluble sugars (14 %), and protein content (158%) under saline conditions compared to the control treatment with 0 g slag/ kg soil (C), thus indicating a positive influence on durum wheat plants. Soil enrichment with 20 g slag/kg soil (D2) decreased plant growth parameters and presented the highest levels of H2O2 and MDA contents compared to the control and treatment (D1) after three months of cultivation under salt stress. This study supports the hypothesis of the application of slag at lower dose, which improves productivity of durum wheat and mitigate salinity stress