Arbuscular mycorrhizae: natural modulators of plant–nutrient relation and growth in stressful environments

Moisture content and mycorrhizal fungi in maternal environment influence performance and composition of Lallemantia species offspring

The availability of soil water content and nutrition in the maternal plant environment plays pivotal roles in shaping the performance, physio-biochemical properties, and chemical composition of the produced seed. This study aimed to investigate the effects of water and arbuscular mycorrhizal fungi (AMF) of maternal plant environment on performance, physio-biochemical properties, and chemical compositions of Lallemantia species offspring. A split-factorial experiment was performed using a randomized complete block design (RCBD) with three replications. The main plot consisted of three drought stress (30 %, 60 % and 90 % of soil available water depletion). The subplots were the factorial combination of arbuscular mycorrhizal fungi (AMF- and AMF+) and Lallemantia species (L. iberica and L. royleana). The offspring of both Lallemantia species experienced a decrease in seed performance, superoxide dismutase, catalase, ascorbate peroxidase enzyme activities, proline, and chemical composition as well as a rise in hydrogen peroxide and lipid peroxidation due to the limited availability of water in the maternal plant environment. On the other hand, providing adequate nutrition in the maternal plant environment resulted in improved germination index, increased starch, and oil content, as well as higher levels of nitrogen and phosphorus in the offspring of both Lallemantia species. Compared to the offspring of L. royleana, the offspring of L. iberica had a higher number of achenes, seeds, seed weight, larger seed size, greater germination index, and higher levels of starch, oil, nitrogen, phosphorus, potassium, and calcium. In contrast, the offspring of L. royleana exhibited higher longevity, enhanced germination under osmotic and salinity stress, increased proline levels, and higher activities of antioxidant enzymes such as superoxide dismutase, catalase, and ascorbic peroxidase as well as sucrose and total soluble sugar. The study concludes that the best seed performance, antioxidant enzyme activities, and carbohydrate levels were observed in the offspring of both Lallemantia species produced under 60 % soil available water depletion with AMF inoculation in the maternal plant environment. These findings highlight the significant impact of the soil available water depletion and AMF inoculation on the seed performance, physio-biochemical properties, and chemical composition of the offspring, providing valuable insights for optimizing seed production and performance.

Biological roles of soil microbial consortium on promoting safe crop production in heavy metal(loid) contaminated soil: A systematic review

Heavy metal(loid) (HM) pollution of agricultural soils is a growing global environmental concern that affects planetary health. Numerous studies have shown that soil microbial consortia can inhibit the accumulation of HMs in crops. However, our current understanding of the effects and mechanisms of inhibition is fragmented. In this review, we summarise extant studies and knowledge to provide a comprehensive view of HM toxicity on crop growth and development at the biological, cellular and the molecular levels. In a meta-analysis, we find that microbial consortia can improve crop resistance and reduce HM uptake, which in turn promotes healthy crop growth, demonstrating that microbial consortia are more effective than single microorganisms. We then review three main mechanisms by which microbial consortia reduce the toxicity of HMs to crops and inhibit HMs accumulation in crops: 1) reducing the bioavailability of HMs in soil (e.g. biosorption, bioaccumulation and biotransformation); 2) improving crop resistance to HMs (e.g. facilitating the absorption of nutrients); and 3) synergistic effects between microorganisms. Finally, we discuss the prospects of microbial consortium applications in simultaneous crop safety production and soil remediation, indicating that they play a key role in sustainable agricultural development, and conclude by identifying research challenges and future directions for the microbial consortium to promote safe crop production.

Harnessing root exudates for plant microbiome engineering and stress resistance in plants

A wide range of abiotic and biotic stresses adversely affect plant's growth and production. Under stress, one of the main responses of plants is the modulation of exudates excreted in the rhizosphere, which consequently leads to alterations in the resident microbiota. Thus, the exudates discharged into the rhizospheric environment play a preponderant role in the association and formation of plant-microbe interactions. In this review, we aimed to provide a synthesis of the latest and most pertinent literature on the diverse biochemical and structural compositions of plant root exudates. Also, this work investigates into their multifaceted role in microbial nutrition and intricate signaling processes within the rhizosphere, which includes quorum-sensing molecules. Specifically, it explores the contributions of low molecular weight compounds, such as carbohydrates, phenolics, organic acids, amino acids, and secondary metabolites, as well as the significance of high molecular weight compounds, including proteins and polysaccharides. It also discusses the state-of-the-art omics strategies that unveil the vital role of root exudates in plant-microbiome interactions, including defense against pathogens like nematodes and fungi. We propose multiple challenges and perspectives, including exploiting plant root exudates for host-mediated microbiome engineering. In this discourse, root exudates and their derived interactions with the rhizospheric microbiota should receive greater attention due to their positive influence on plant health and stress mitigation.

Dark septate endophyte inoculation enhances antioxidant activity in Astragalus membranaceus var. mongholicus under heat stress

The influence of dark septate endophytic (DSE) on the antioxidant activity of Astragalus membranaceus var. mongholicus under heat stress was investigated. A. membranaceus plants, with or without DSE inoculation, were grown at 28°C for 8 weeks in a greenhouse and subsequently subjected to heat stress conditions (42°C) in an artificial climate chamber. DSE inoculation significantly decreased the malondialdehyde (MDA) content during the initial three days of heat stress. The activities of superoxide dismutase (SOD) and peroxidase (POD) of A. membranaceus leaves were significantly enhanced by DSE inoculation under heat stress, with SOD activities being 63-81% higher than in other treatments. The glutathione (GSH) and putrescine (Put) contents accumulated significantly on the third day under heat stress with DSE inoculation. Additionally, the contents of soluble sugars and proline (Pro) exhibited significant increases on the seventh day of heat stress and were 33-55% and 81-83% higher than in other treatments, respectively. Three-way ANOVA shows that DSE inoculation under heat stress exerted a significant impact on MDA. Multivariate linear regression and structural equality modelling (SEM) further show that the interaction among these antioxidants significantly decreased MDA content and maintained the normal function of cell membranes. In conclusion, DSE inoculation enhanced the heat tolerance of A. membranaceus by boosting its antioxidant capacity and reducing MDA production. This study highlights the potential of utilizing DSE as a strategy to enhance plant heat tolerance.

Symbiosis of Plants with Mycorrhizal and Endophytic Fungi

It has long been known that plants and microorganisms coexist [...].

Integrated strength of osmotic potential and phosphorus to achieve grain yield of rice under water deficit by arbuscular mycorrhiza fungi

Arbuscular mycorrhizal ecosystem provides sustainability to plant integrity under drought situations. However, host plants that survive in drought frequently lose yield. The potential of Funneliformis mosseae (F), Claroideoglomus etunicatum (C), and Acaulospora fovaeta (A) was assessed to evaluate in indica rice cv. Leum Pua during booting stage under 21-day water withholding. The effects of three inoculation types; (i) F, (ii) F + C (FC), and (iii) F + C + A (FCA), on physiological, biochemical, and yield traits were investigated. The three types showed an induced total chlorophyll content in the host as compared to uninoculated plants. Total soluble sugars and free proline were less regulated by FC and FCA inoculated plants than by F inoculated plants under water deficit conditions. However, the FC and FCA inoculations increased phosphorus content, particularly in the shoots of water-stressed plants. In the three inoculations, the FCA dramatically improved plant osmotic potential adaptability under water deficit stress. Furthermore, even when exposed to the water deficit condition, panicle weight, grain number, and grain maturity were maintained in FCA inoculated plants. According to the findings, the increased osmotic potential and phosphorus content of the FCA-inoculated rice plant provide a protection sign against drought stress and will benefit food security in the future.

Beneficial effects of arbuscular mycorrhizae on Cu detoxification in Mimosa pudica L. grown in Cu-polluted soils

Arbuscular mycorrhizal (AM) fungi are known to have beneficial effects on host plants growing on contaminated soils. The present study aimed at investigating the influence of two different AM fungi (Rhizophagus intraradices and Funneliformis mosseae) on the growth of plants and Cu uptake by Mimosa pudica L. grown in polluted soils containing various levels of Cu (Control, 400, 500, or 600 mg kg^-l soil) in pot experiments. Mycorrhizal colonisation rates by the two AM fungi decreased markedly with the increasing Cu levels in soils. This inhibition was more pronounced to F. mosseae than R. intraradices, indicating that R. intraradices was more tolerant to Cu than F. mosseae. Compared with non-mycorrhizal plants, R. intraradices inoculation increased plant growth (including shoot height, numbers of compound leaves and leaflets, and dry biomass) and P concentrations in the shoots and roots of M. pudica at all levels of Cu. Meanwhile, F. mosseae displayed a capability of growth promotion to M. pudica much later and lower than R. intraradices. F. mosseae and R. intraradices markedly decreased Cu concentration in shoots at 400-600 mg kg^-1 Cu levels. However, R. intraradices was more efficient than F. mosseae in decreasing the shoot Cu concentrations. As for the increasing Cu tolerance by R. intraradices, possibly it was reached though the improvement of phosphorus nutrition and the decline of Cu transport from roots to shoots of M. pudica. R. intraradices showed a good potential for improving medicinal plants growth and declining toxic effects in Cu-contaminated soils.

The status and natural impact of floriculture production in Ethiopia: a systematic review

Ethiopia's floriculture industry is exceedingly emerging, and, currently, it ranks as the sixth largest exporter of roses worldwide and second largest in Africa. Currently, many flowers, such as rose, gypsophila, carnations, and chrysanthemum, are growing. However, floriculture farms are contributing a high level of health risks and environmental problems in Ethiopia. Thus, the purpose of this paper is to scrutinize the status and impacts of floriculture industries in Ethiopia. The floriculture division is an emerging sector in Ethiopia, and the number of farms, income, job opportunities, and diversity of flowers are increasing. However, the health risks and environmental fates of the sector are also increasing. Ethiopian floriculture farms lack waste disposal technologies and workers' protective equipment and safety, and the chemicals, plastics, and corrugated irons used in the farms are carelessly disposed everywhere. Pesticides, plastics, and fertilizers are also freely discharged into water bodies and terrestrial land, which is causing the development of health risks; aquatic life hazards; and soil, water, and air pollution. However, Ethiopia has no strong and functional system or structure to control the impacts of floriculture farms. The government and the farm owners are not thoughtful about the environmental issues, health concerns, and socioeconomic impacts of the wastes. The government lacks regular control and assessment of farms, and the farms are engaging for their profit. Nevertheless, developed countries are currently using both natural and modern technologies to manage floricultural wastes. Ethiopia should therefore suggest manageable possible approaches and sound management strategies based on the findings of the analyses.

Arbuscular Mycorrhizal Fungi Induce Tolerance to Salinity Stress in Taro Plantlets (Colocasia esculenta L. Schott) during Acclimatization

Soil salinity is a problem that affects soil fertility and threatens agri-food crop production worldwide. Biotechnology, through plant micropropagation and the use of biofertilizers such as arbuscular mycorrhizal fungi (AMF), is an alternative to increase productivity and induce tolerance to salinity stress in different crops. This study aimed to evaluate the effect of different doses of the fungus Glomus intraradices on the ex vitro development of taro (Colocasia esculenta L. Schott cv. Criolla) plantlets under salinity stress during the acclimatization stage. In vitro-obtained C. esculenta plantlets were inoculated at different doses (0, 100, and 200 spores per plantlet) of G. intraradices during acclimatization. At 60 d of acclimatization in the greenhouse, plantlets were exposed to 100 mM NaCl salinity stress for 10 d. After the stress period, plantlet development, colonization percentage, and biomass were evaluated. In addition, the content of chlorophyll, carotenoids, proteins, proline, glycine-betaine, soluble phenols, and antioxidant capacity were quantified. The results showed differences in the developmental, physiological, and biochemical variables evaluated; however, no changes in total protein content were observed. Spore colonization showed that the symbiotic association has positive effects on the development of plantlets with or without salinity stress. This symbiotic interaction contributes to salinity stress tolerance in C. esculenta plantlets. The early application of AMF in in vitro-obtained taro plantlets is an alternative to increase or maintain the productivity of this crop in saline soils.

Crop Rotation and Minimal Tillage Selectively Affect Maize Growth Promotion under Late Wilt Disease Stress

In recent years, worldwide scientific efforts towards controlling maize late wilt disease (LWD) have focused on eco-friendly approaches that minimize the environmental impact and health risks. This disease is considered to be the most severe threat to maize fields in Israel and Egypt, and a major growth restraint in India, Spain, and Portugal. Today’s most commonly used method for LWD control involving resistant maize genotypes is under constant risk from aggressive pathogen lines. Thus, this study’s objectives were to evaluate the effect of crop rotation and avoiding tillage on restraining the disease. Such an agrotechnical approach will support the continuity of soil mycorrhiza networks, which antagonize the disease’s causal agent, Magnaporthiopsis maydis. The method gained positive results in previous studies, but many knowledge gaps still need to be addressed. To this end, a dual-season study was conducted using the LWD hyper-susceptible maize hybrid, Megaton cv. The trials were performed in a greenhouse and in the field over full dual-growth seasons (wheat or clover as the winter crop followed by maize as the summer crop). In the greenhouse under LWD stress, the results clearly demonstrate the beneficial effect of maize crop rotation with clover and wheat on plant weight (1.4-fold), height (1.1–1.2-fold) and cob yield (1.8–2.4-fold), especially in the no-till soil. The clover-maize growth sequence excels in reducing disease impact (1.7-fold) and pathogen spread in the host tissues (3-fold). Even though the wheat-maize crop cycle was less effective, it still had better results than the commercial mycorrhizal preparation treatment and the uncultivated non-infected soil. The results were slightly different in the field. The clover-maize rotation also achieved the best growth promotion and disease restraint results (2.6-fold increase in healthy plants), but the maize rotation with wheat showed only minor efficiency. Interestingly, pre-cultivating the soil with clover had better results in no-till soil in both experiments. In contrast, the same procedure with wheat had a better impact when tillage was applied. It may be concluded that crop rotation and soil cultivation can be essential in reducing LWD, but other factors may affect this approach’s benefits in commercial field growth.