Editorial

3 pages, 195 KiB

Open AccessEditorial

Abiotic Stress Responses and Microbe-Mediated Mitigation in Plants

by Ying Ma

Agronomy 2023, 13(7), 1844; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy13071844 - 12 Jul 2023

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Agriculture bears the brunt of degraded ecosystems, as climate change, soil degradation, and biodiversity imbalances impede both productivity and quality [...] Full article

(This article belongs to the Special Issue Abiotic Stress Responses and Microbe-Mediated Mitigation in Plants)

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13 pages, 4993 KiB

Open AccessArticle

Endophytic Fusarium proliferatum Reprogrammed Phytohormone Production and Antioxidant System of Oryza sativa under Drought Stress

by Nighat Seema, Muhammad Hamayun, Anwar Hussain, Mohib Shah, Muhammad Irshad, Muhammad Qadir, Amjad Iqbal, Abdulwahed Fahad Alrefaei and Sajid Ali

Agronomy 2023, 13(3), 873; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy13030873 - 16 Mar 2023

Cited by 3 | Viewed by 1603

Abstract

The aim of the current study was to isolate endophytes from the roots of Rhazya stricta and assess their potential to improve the growth of drought-stressed sunflower seedlings. The potential role of the isolated endophytic fungus was initially screened by using two rice [...] Read more.

The aim of the current study was to isolate endophytes from the roots of Rhazya stricta and assess their potential to improve the growth of drought-stressed sunflower seedlings. The potential role of the isolated endophytic fungus was initially screened by using two rice varieties (mutant rice cultivar Waito-C: Gibberellins deficient; and Dongji byeo: Gibberellins-producing normal cultivar). A significant (p < 0.05) increase in various growth attributes of both rice varieties associated with one of the isolates i.e., N4 was noticed. Furthermore, the N4 isolate was tested for its role in improving the agronomic attributes of sunflowers under drought stress. The symbiotic association significantly (p < 0.05) improved the host growth and protection from PEG-induced drought stress. The drought mitigation in N4-associated sunflower seedlings can be linked with the regulation of phytohormones, stress-related metabolites, low-molecular-weight proteins and sugars, and scavenging of reactive oxygen species (ROS). Microscopic analysis revealed that the potent endophytic fungal strain consisted of thin and hyaline hyphae, forming dense olive-green mycelia (4–5 cm in dm) with black flask-shaped fruiting bodies. Based on the ITS sequence homology and phylogeny, the strain was identified as Fusarium proliferatum (MG251448). The results of this study concluded that this phytohormone-secreting endophyte can improve crop productivity in dry areas where drought stress is the main challenge faced by crops. Full article

(This article belongs to the Special Issue Abiotic Stress Responses and Microbe-Mediated Mitigation in Plants)

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16 pages, 1202 KiB

Open AccessArticle

Growth and Nutritional Responses of Juvenile Wild and Domesticated Cacao Genotypes to Soil Acidity

by César O. Arévalo-Hernández, Enrique Arévalo-Gardini, Abel Farfan, Martin Amaringo-Gomez, Andrew Daymond, Dapeng Zhang and Virupax C. Baligar

Agronomy 2022, 12(12), 3124; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy12123124 - 09 Dec 2022

Cited by 3 | Viewed by 1432

Abstract

Cacao is an important tropical crop and requires high-fertility soils for better growth and productivity; nevertheless, soils where this crop is grown are, in general, acidic and low in fertility. Therefore, germplasm with tolerance to soil acidity is desirable for cacao genetic improvement. [...] Read more.

Cacao is an important tropical crop and requires high-fertility soils for better growth and productivity; nevertheless, soils where this crop is grown are, in general, acidic and low in fertility. Therefore, germplasm with tolerance to soil acidity is desirable for cacao genetic improvement. The objective of this study was to evaluate cacao germplasm for early growth, nutrient concentration, and potential tolerance to soil acidity. A greenhouse experiment was conducted to evaluate 60 cacao genotypes with diverse geographic origins. Cacao seedlings were grown for six months in acid soil with and without lime. Growth parameters and the total concentration of N, P, K, Ca, Mg, Fe, Cu, Mn, and Zn were measured in shoots after harvest. Our results indicate that the best early growth predictors of acid soil tolerance are the number of leaves and root area. N, Ca, Mg, and K uptake may have a potential role in tolerance to soil acidity. Finally, the results revealed a large difference among cacao genotypes in terms of their responses to acid soil stress, which led to the selection of ten genotypes: CCN-51, PH-21, CCN-10, PAS-91, ICT-1087, ICS-95, UF-667, TSH-565, PH-144, ICT-1189 that are potentially tolerant to soil acidity and could be used for breeding acid soil-tolerant cacao varieties. Full article

(This article belongs to the Special Issue Abiotic Stress Responses and Microbe-Mediated Mitigation in Plants)

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22 pages, 2454 KiB

Open AccessArticle

Alleviation of Cr(VI) Toxicity and Improve Phytostabilization Potential of Vigna radiata Using a Novel Cr(VI) Reducing Multi-Stress-Tolerant Plant Growth Promoting Rhizobacterial Strain Bacillus flexus M2

by Manoj Srinivas Ravi, Chinnannan Karthik, Indra Arulselvi Padikasan and Ying Ma

Agronomy 2022, 12(12), 3079; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy12123079 - 05 Dec 2022

Cited by 3 | Viewed by 2196

Abstract

Chromium (Cr) is a toxic heavy metal discharged into the environment through various anthropogenic sources, which affects soil properties and fertility. Hence, an effective soil restoration strategy is the need of the hour. In this study, a potent Cr(VI)-reducing strain M2 was isolated [...] Read more.

Chromium (Cr) is a toxic heavy metal discharged into the environment through various anthropogenic sources, which affects soil properties and fertility. Hence, an effective soil restoration strategy is the need of the hour. In this study, a potent Cr(VI)-reducing strain M2 was isolated from the rhizosphere of Zea mays L. grown in leather industrial effluent contaminated sites and identified as Bacillus flexus through 16S rDNA sequencing. Strain M2 exhibited strong tolerance to multi-stresses such as temperature (up to 45 °C), pH (up to 9.0), Sodium chloride (NaCl) (up to 7%) and PEG 6000 (up to 50%) and showed strong Cr(VI) reduction with the presence of multi-stresses. The interaction of Cr(VI) with strain M2 was elucidated through various instrumentation analyses. Fourier Transform Infra-red (FTIR) Spectroscopy analysis confirmed that Cr(VI) exposures induce significant changes in the cell-surface functional groups. Raman spectrum and Transmission Electron Microscopy–Energy Dispersive X-ray spectroscopy (TEM-EDX) analysis confirmed the bio-reduction of Cr(VI) to Cr(III) and their intracellular localization as Cr(III). Further, strain M2 produced a significant quantity of Indole acetic acid (IAA), ammonia, and exopolysaccharide (EPS) and showed positive results for various plant-growth-promoting activities with the presence of Cr(VI). In greenhouse experiments, the strain M2 inoculation progressively increased the plant growth parameters and stabilized the antioxidant system of Vigna radiata under Cr stress. However, Cr(VI) exposure decreased the growth parameters and increased the level of proline content, Hydrogen peroxide (H₂O₂) accumulation_, and antioxidant enzymes expression in V. radiata. Interestingly, strain M2 inoculation significantly reduced the accumulation of Cr in root and shoot of V. radiata when compared to the uninoculated Cr(VI) treatment. Hence, this study confirms that rhizobacterial inoculation markedly reduced the negative impact of Cr toxicity and improved V. radiata growth even in harsh environments by stabilizing the mobility of Cr in the rhizosphere. Full article

(This article belongs to the Special Issue Abiotic Stress Responses and Microbe-Mediated Mitigation in Plants)

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15 pages, 2147 KiB

Open AccessArticle

Influence of Kosakonia sp. on the Growth of Arachis hypogaea L. on Arid Soil

by Mathiyazhagan Narayanan, Arivalagan Pugazhendhi, Selvaraj David, Nguyen Thuy Lan Chi, Omaima Nasif, Sulaiman Ali Alharbi and Ying Ma

Agronomy 2022, 12(8), 1801; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy12081801 - 29 Jul 2022

Cited by 1 | Viewed by 1565

Abstract

The current study focused on enumerating the potential plant growth-promoting rhizobacteria (PGPR) from the rhizosphere of Arachis hypogaea L. Among the several colonies grown on an Ashby plate, only seven isolates (Ah1 to Ah7) had nitrogen-fixing potential. The Ah4 isolate showed higher potential [...] Read more.

The current study focused on enumerating the potential plant growth-promoting rhizobacteria (PGPR) from the rhizosphere of Arachis hypogaea L. Among the several colonies grown on an Ashby plate, only seven isolates (Ah1 to Ah7) had nitrogen-fixing potential. The Ah4 isolate showed higher potential for plant growth-promoting (PGP) activities than the other isolates. This isolate was recognized as Kosakonia sp. MGR1 through 16S rRNA sequencing with 99.7% similarity to nitrogen-fixing Kosakonia genus and 61% match with K. cowanii in phylogenetic tree analysis. Kosakonia sp. MGR1 had the potential to produce an excellent quantity (26.17 µg·mL⁻¹) of indole-3-acetic acid (IAA) in 6% tryptophan-enriched media than the other concentrations (2%, 4%, 8%, and 10%). Additionally, it contained remarkable phosphate-solubilizing efficiency of tricalcium phosphate (29.3 µg·mL⁻¹) in 5 days of incubation. The growth conditions of Kosakonia sp. were optimized as 35 °C, pH 7.5, and 48 h of incubation with glucose. The isolate MGR1 produced 96.35 ± 3.45, 89.6 ± 5.61, and 99.21 ± 5.24 µg·mL⁻¹ of IAA, nitrogen, and soluble phosphate, respectively. Furthermore, Kosakonia sp. MGR1 had the potential to enhance the growth and biomolecule contents of A. hypogaea L. The results concluded that Kosakonia had admirable PGP activities; hence, it showed a significant impact on the active growth and biomolecules of A. hypogaea L. Full article

(This article belongs to the Special Issue Abiotic Stress Responses and Microbe-Mediated Mitigation in Plants)

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14 pages, 1378 KiB

Open AccessArticle

Hardening Blueberry Plants to Face Drought and Cold Events by the Application of Fungal Endophytes

by Ian S. Acuña-Rodríguez, Gabriel I. Ballesteros, Cristian Atala, Pedro E. Gundel and Marco A. Molina-Montenegro

Agronomy 2022, 12(5), 1000; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy12051000 - 21 Apr 2022

Cited by 11 | Viewed by 2647

Abstract

Harsh environmental conditions derived from current climate change trends are among the main challenges for agricultural production worldwide. In the Mediterranean climatic region of central Chile, sudden occurrence of spring cold temperatures in combination with water shortage for irrigation (drought) constitutes a major [...] Read more.

Harsh environmental conditions derived from current climate change trends are among the main challenges for agricultural production worldwide. In the Mediterranean climatic region of central Chile, sudden occurrence of spring cold temperatures in combination with water shortage for irrigation (drought) constitutes a major limitation to highbush blueberry (Vaccinium corymbosum) plantations, as flowering and fruiting stages are highly sensitive. Hardening crops may be achievable by boosting beneficial interactions of plants with microorganisms. Inoculation with symbiotic fungi isolated from plants adapted to extreme environments could be a good strategy, if they are able to maintain functional roles with non-original hosts. Here, we evaluated the effect of two Antarctic fungal endophytes (AFE), Penicillium rubens and P. bialowienzense, on the tolerance of V. corymbosum plants to cold events in combination with drought under controlled conditions. Inoculated and uninoculated plants were exposed for a month to one event of a cold temperature (2 °C/8 h) per week with or without drought and were evaluated in physiological, biochemical, and molecular variables. A complementary set of plants was kept under the same environmental conditions for two additional months to evaluate survival as well as fruit weight and size. There was an overall positive effect of AFE on plant performance in both environmental conditions. Endophyte-inoculated plants exhibited higher gene expression of the Late Embryogenesis Abundant protein (LEA1), higher photochemical efficiency (Fv/Fm), and low oxidative stress (TBARS) than uninoculated counterparts. On the other hand, plant survival was positively affected by the presence of fungal endophytes. Similarly, fruit diameter and fruit fresh weight were improved by fungal inoculation, being this difference higher under well-watered condition. Inoculating plants with fungal endophytes isolated from extreme environments represents a promising alternative for hardening crops. This is especially relevant nowadays since agriculture is confronting great environmental uncertainties and difficulties which could became worse in the near future due to climate change. Full article

(This article belongs to the Special Issue Abiotic Stress Responses and Microbe-Mediated Mitigation in Plants)

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18 pages, 1756 KiB

Open AccessArticle

Achromobacter xylosoxidans and Enteromorpha intestinalis Extract Improve Tomato Growth under Salt Stress

by Margarida Maria Santana, Ana Paula Rosa, Angel M. Zamarreño, José María García-Mina, Abdelwahab Rai and Cristina Cruz

Agronomy 2022, 12(4), 934; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy12040934 - 13 Apr 2022

Cited by 2 | Viewed by 1861

Abstract

The effect of seed coating salt-stressed tomato with the bacterium Achromobacter xylosoxidans BOA4 and/or irrigation with an extract of the marine algae Enteromorpha intestinalis (EI) is herein evaluated. The plant shoots and roots were harvested separately on day 50, following extensive saline stress. [...] Read more.

The effect of seed coating salt-stressed tomato with the bacterium Achromobacter xylosoxidans BOA4 and/or irrigation with an extract of the marine algae Enteromorpha intestinalis (EI) is herein evaluated. The plant shoots and roots were harvested separately on day 50, following extensive saline stress. The addition of BOA4 and/or EI extract resulted in an average increase of 33% in plant shoot DW, but an averaged decrease of 44% in the root to shoot biomass ratio. Anthocyanin content increased by over 34% and 44% with EI and BOA4 plus EI treatments, respectively. Since enhanced protein tyrosine nitration (PTN) is a known plant response to salt stress, the PTN level was inspected through 3-nitrotyrosine content determination. This was drastically increased by salt stress; however, BOA4, EI or both caused an averaged PTN decrease of 30% in stressed roots or shoots. This PTN response could be associated with tomato phenotypic characteristics and is postulated to be inversely correlated to cytokinin contents in stressed plants, namely cis-zeatin-type-cis-zeatin (cZ) plus cis-zeatin riboside (cZR), and isopentenyladenine (iP). The latter showed a drastic average increase by 3.6-fold following BOA4 and/or EI treatments of salinized tomato. This increment could be related to cytokinin biosynthesis induced by the applied bio-stimulants; IP and derivatives are the main cytokinins in seaweeds, and Achromobacter xylosoxidans BOA4 was shown to produce up to 17.5 pmol mL⁻¹ of isopentenyladenine. This work is the first report on the influence of bio-stimulants, used to improve salt stress tolerance, on plant PTN levels; BOA4 and/or EI treatments decreased PTN, while increasing cis-zeatin-type and iP cytokinins in tomato, the latter showed an enhanced tolerance to salt stress. Full article

(This article belongs to the Special Issue Abiotic Stress Responses and Microbe-Mediated Mitigation in Plants)

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11 pages, 1957 KiB

Open AccessArticle

Rhizobium Symbiosis Leads to Increased Drought Tolerance in Chinese Milk Vetch (Astragalus sinicus L.)

by Yajie Liu, Zhenfei Guo and Haifan Shi

Agronomy 2022, 12(3), 725; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy12030725 - 17 Mar 2022

Cited by 12 | Viewed by 2554

Abstract

Chinese milk vetch (Astragalus sinicus L.) is an important leguminous green manure that frequently suffers from seasonal drought. To improve its drought tolerance, the effects of rhizobia inoculation on drought tolerance and the underlying physiological mechanism were investigated. Drought tolerance in combination [...] Read more.

Chinese milk vetch (Astragalus sinicus L.) is an important leguminous green manure that frequently suffers from seasonal drought. To improve its drought tolerance, the effects of rhizobia inoculation on drought tolerance and the underlying physiological mechanism were investigated. Drought tolerance in combination with nitrogen assimilation, free amino acids, and polyamines was investigated in milk vetch with active nodules (AN), with inactive nodules (LN), or without nodules (NN). AN plants had increased drought tolerance compared to LN and NN plants. Glutamine synthetase (GS), glutamine 2-oxoglutarate amino transferase (GOGAT), and glutamate dehydrogenase (GDH) activities were decreased after drought, with higher levels in AN plants than in LN and NN plants under both control and drought stress conditions. Higher levels of proline (Pro), arginine (Ala), alanine (Ala), and glutamate (Glu) were observed in AN plants compared with LN and NN plants. Putrescine (Put), spermidine (Spd), and spermine (Spm) levels were increased in response to drought, and higher levels of Put and Spd were maintained in AN plants. It is suggested that active nodulation leads to increased drought tolerance in milk vetch, which is associated with improved nitrogen fixation and ammonium assimilation, which in turn lead to the promotion of free amino-acid and polyamine synthesis. Full article

(This article belongs to the Special Issue Abiotic Stress Responses and Microbe-Mediated Mitigation in Plants)

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