Plant Responses to Biotic and Abiotic Stresses: From Cellular to Morphological Changes

A special issue of Agronomy (ISSN 2073-4395). This special issue belongs to the section "Farming Sustainability".

Deadline for manuscript submissions: closed (20 January 2022) | Viewed by 12919

Special Issue Editor

Special Issue Information

Dear Colleagues,

In times of climate change, agricultural production systems are exposed to changing environmental conditions. With 7.27 billion inhabitants to date, the world population is projected to reach 9.1 billion people by 2050. Over the coming decades, global agriculture will face multiple challenges since the demand for food continues to grow rapidly with the same trend. In addition to an increase in food production, we need to significantly improve the resilience of food production to face detrimental environmental impacts, including biotic and abiotic stresses.  

During their lifecycle, plants have to cope with many abiotic and biotic stresses, each affecting their development or growth. Among these stresses, biotic stress (caused by bacteria, viruses, fungi, nematodes, insects …) and abiotic stress (such as flooding, cold, heat, salinity, or drought) can be distinguished. However, being sessile in nature, plants cannot escape from these stress, and instead adapt transcriptional, molecular, physiological, and morphological changes within their system to overcome the adverse conditions.

Therefore, understanding plant responses to these stresses implies a deep description of the mechanisms that operate at the physiological and molecular levels, which include complex transduction pathways, from signal perception to physiological responses. For this research topic, we welcome reviews, perspective, original research, opinions, and methods to underline the latest exciting progress on the understanding of systems biology and the molecular, physiological, and biochemical responses of plants to abiotic and biotic stresses. Some of the potential themes of this topic include but are not limited to:

  • Effect of climate change elements on plant fitness;
  • Crops performances under biotic and abiotic stress;
  • Biotic and abiotic stresses physiology and management;
  • Signaling transduction pathways and networks, from signal perception to physiological responses;
  • Plant acclimation mechanisms;
  • Plant defense activators and biostimulants to cope with biotic and abiotic stresses.

Prof. Dr. Essaid Ait Barka
Guest Editor

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Keywords

biotic stress; abiotic stress; plant acclimation; plant defense mechanisms

Published Papers (5 papers)

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Research

17 pages, 4341 KiB  
Article
The Evaluation of the Effects of Zn, and Amino Acid-Containing Foliar Fertilizers on the Physiological and Biochemical Responses of a Hungarian Fodder Corn Hybrid
Agronomy 2022, 12(7), 1523; https://doi.org/10.3390/agronomy12071523 - 25 Jun 2022
Cited by 3 | Viewed by 1680
Abstract
The benefit of applying foliar fertilizers is that crops can uptake them faster than soil fertilizers. The aim of this study was to test and valuate the effects of one zinc (Zn) and two amino acids-containing (AS) foliar fertilizers on a fodder corn [...] Read more.
The benefit of applying foliar fertilizers is that crops can uptake them faster than soil fertilizers. The aim of this study was to test and valuate the effects of one zinc (Zn) and two amino acids-containing (AS) foliar fertilizers on a fodder corn hybrid’s physiological and biochemical processes. The experiment was conducted in field conditions. The following parameters of a fodder maize hybrid were measured one, two, three, four, five, and six weeks after the treatments (WAT): physiological (relative chlorophyll content and the effectiveness of PSII); biochemical (activities of superoxide dismutase (SOD); ascorbate peroxidase (APX) and guaiacol peroxidase (POD); the concentration of malondialdehyde (MDA); and proline. The yield increased by 10%, 6%, and 10% at Zn, Zn+AS1, and Zn+AS2 treatments. The yield parameters, such as grain/cob and ear weight, were also significantly higher under the applied three treatments relative to the control. The relative chlorophyll content was significantly higher one, two, and four weeks after Zn-treatment, and some changes were also observed when Zn and amino acid-containing fertilizer were applied in combination. The latter sampling did not show any notable changes. In addition, the activity of SOD increased when Zn-containing fertilizer was applied, although the effect of AS-containing fertilizer did not show. There was a correlation between the SOD activity and some of the yield parameters. The increasing SOD activity indicated a higher yield (t/ha) and a higher cob weight. Full article
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12 pages, 817 KiB  
Article
Meloidogyne graminicola’s Effect on Growth Performance of Rice under Low Population Density
Agronomy 2022, 12(3), 587; https://doi.org/10.3390/agronomy12030587 - 26 Feb 2022
Cited by 4 | Viewed by 1665
Abstract
Meloidogyne graminicola is a destructive soil-borne pathogen that causes rice yield losses (Oryza sativa L.) in tropical and subtropical areas. This study investigated the effect of M. graminicola population densities on plant height, heading, and the photosynthetic parameters of rice in a [...] Read more.
Meloidogyne graminicola is a destructive soil-borne pathogen that causes rice yield losses (Oryza sativa L.) in tropical and subtropical areas. This study investigated the effect of M. graminicola population densities on plant height, heading, and the photosynthetic parameters of rice in a greenhouse. Two-week-old rice plants were inoculated with different M. graminicola densities (250, 500, 750, 1000, 1500, and 2000 J2s/plant) and observations were recorded at 30, 60, and 90 days after inoculation (DAI). Reductions in growth and photosynthetic parameters caused by M. graminicola densities were calculated in relation to a control (non-inoculated rice). Results revealed that M. graminicola infection with low population densities (0–500 J2s/plant) did not influence the rice plant height during 30–60 DAI, but significantly lowered the plant height, panicle growth rate, and panicle length of rice at 90 DAI. The chlorophyll content of rice inoculated with 500–2000 J2s was significantly lower than that of the control. Furthermore, M. graminicola infection with 500 J2s/plant significantly lowered the transpiration rate and net photosynthetic rate by 21.21% and 21.81%, respectively, compared with the control (p < 0.05). M. graminicola with a low population density significantly reduced the net photosynthetic rate of rice, which affected organic matter accumulation, resulting in growth retardation and lower yields (p < 0.05). Full article
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14 pages, 2231 KiB  
Article
Changes in Photosynthetic Pigments Content in Non-Transformed and AtCKX Transgenic Centaury (Centaurium erythraea Rafn) Shoots Grown under Salt Stress In Vitro
Agronomy 2021, 11(10), 2056; https://doi.org/10.3390/agronomy11102056 - 13 Oct 2021
Cited by 5 | Viewed by 1739
Abstract
The effects of graded sodium chloride (NaCl) concentrations (0-, 50-, 100-, 150-, and 200-mM) on photosynthetic pigment contents in in vitro grown shoots of important medicinal plant species (Centaurium erythraea Rafn) were investigated. Non-transformed, one AtCKX1 and two AtCKX2 transgenic centaury lines, [...] Read more.
The effects of graded sodium chloride (NaCl) concentrations (0-, 50-, 100-, 150-, and 200-mM) on photosynthetic pigment contents in in vitro grown shoots of important medicinal plant species (Centaurium erythraea Rafn) were investigated. Non-transformed, one AtCKX1 and two AtCKX2 transgenic centaury lines, with altered cytokinin profiles, were used in this study. The chlorophyll (Chl) and carotenoid contents differed in the non-transformed and transgenic lines. In general, salinity significantly reduced the Chl a and Chl b contents in comparison to the NaCl-free medium. The lowest Chl content was observed in AtCKX2 transgenic shoots grown on all the culture media. The total carotenoid content was increased in shoots of non-transformed and both AtCKX2 transgenic lines grown in 50-mM NaCl. On the other hand, in concentrations >50-mM NaCl, the total carotenoid content was decreased in all analysed centaury shoots. The Chl a/Chl b ratio in all the shoots increased progressively in the graded NaCl concentrations. Contrarily, the addition of NaCl in the culture medium reduced the Chl/carotenoid ratio in centaury shoots. Taken together, the results of this study partly explained the mode of centaury plant adaptations to salt stress in vitro. Thus, the results on centaury shoots confirmed that the determination of the photosynthetic pigment contents can be a very useful non-destructive screening method in order to discriminate susceptible and resistant plant species/lines to salt stress conditions. Full article
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18 pages, 1631 KiB  
Article
Utilization Efficiency of Growth Regulators in Wheat under Drought Stress and Sandy Soil Conditions
Agronomy 2021, 11(9), 1760; https://doi.org/10.3390/agronomy11091760 - 31 Aug 2021
Cited by 9 | Viewed by 2637
Abstract
Drought stress and nutrient status are highly important for plant growth and productivity. Two field experiments were conducted during two consecutive seasons (2017–2018 and 2018–2019) at El-Molak, Abo-Hammad, Sharkia, Egypt. This work was conducted under sandy soil conditions to evaluate the effects of [...] Read more.
Drought stress and nutrient status are highly important for plant growth and productivity. Two field experiments were conducted during two consecutive seasons (2017–2018 and 2018–2019) at El-Molak, Abo-Hammad, Sharkia, Egypt. This work was conducted under sandy soil conditions to evaluate the effects of foliar application with growth regulators (PGRs) such as cycocel (CCC), applied at 0, 500, or 1000 mg L−1, and/or salicylic acid (SA), applied at 0, 0.05, or 0.1 mM on the productivity as well as improving drought tolerance of three wheat cultivars, i.e., Gemmeiza 11, Misr 1, and Giza 171 under three irrigation intervals, i.e., 10, 15, and 20 days. Foliar spray was given at 35 and 50 days after planting (DAP). The obtained results showed that mean squares as a result of the main effect and first- and second-order interactions were significant (p ≤ 0.01) for all studied traits. The application of SA increased total chlorophyll content and flag leaf area (cm2) while the number of days to 50% heading was decreased; however, the number of spikes m−2, protein and proline contents were increased with the application of CCC. The cultivar Misr 1 outperformed the other cultivars in the most studied traits. Estimates of heritability in the broad sense (h2b) were, on average, higher in five physiological traits than other agronomic traits, and the highest estimate of h2b (95.1%) was shown by the number of days to 50% heading followed by protein content (91.90%). Among the interactions between irrigation and growth regulators, the I(10) × SA(0.1) recorded the highest flag leaf area (cm2), SPAD value, number of grains spike−1, 1000-grain weight (g), and grain yield (t ha−1). Among the interactions between irrigation and cultivars, the I(10) × Misr 1 recorded the highest flag leaf area (cm2), SPAD value, number of grains spike−1, and grain yield (t ha−1). Among the interactions among irrigation, growth regulators and cultivars, the I(10) × SA(0.1) × Misr 1 recorded the highest flag leaf area (cm2), number of grains spike−1, 1000-grain weight (g), and grain yield (t ha−1). Correlation coefficient between grain yield (t ha−1) and each of the number of days to 50% heading, flag leaf area, total chlorophyll content, number of spikes m−2, number of grains spike−1, and 1000-grain weight was positive and significant. Three main factors for the studied variables were created from the application of the factor analysis technique. Grain yield ha−1 (Y) can be predicted by the method of forwarding stepwise through applying the automatic linear regression analysis. Besides, the best prediction equation of grain yield ha−1 (Y) was formulated as: Ỷ = −14.36 + 0.11 number of grains spike−1 (NGS) + 0.09 1000-grain weight (THW) + 0.04 number of spike m−2 (NSm) + 0.03 days to 50% heading (DF) + 0.02 total chlorophyll content (TC) with adjusted-R2 (87.33%). Full article
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18 pages, 1958 KiB  
Article
Exploring Two Streptomyces Species to Control Rhizoctonia solani in Tomato
Agronomy 2021, 11(7), 1384; https://doi.org/10.3390/agronomy11071384 - 08 Jul 2021
Cited by 20 | Viewed by 4345
Abstract
Streptomyces species are effective biocontrol agents toward many plant pathogens. These microorganisms are well known for producing secondary metabolites, promoting plant growth and inducing plant defense mechanisms. In this study, the ability of tomato root-colonizing Streptomyces strains to trigger the resistance against Rhizoctonia [...] Read more.
Streptomyces species are effective biocontrol agents toward many plant pathogens. These microorganisms are well known for producing secondary metabolites, promoting plant growth and inducing plant defense mechanisms. In this study, the ability of tomato root-colonizing Streptomyces strains to trigger the resistance against Rhizoctonia solani (J.G. Kühn) AG4 was investigated. For this goal, we evaluated the pattern of LOXB and PAL1 genes expression changes upon pathogen inoculation in primed tomato plants. The results revealed that Streptomyces globisporous (Krasil’nikov) strain F8 and S. praecox (Millard and Burr) strain R7 were able to enhance the expression of lipoxygenase and phenylalanine ammonia lyase in tomato plants. This finding suggests that Streptomyces strains F8 and R7 may trigger jasmonic acid and phenyl propanoid signaling pathways in plants, therefore, resulting an induced defense status in tomatoes against R. solani. Biochemical characterization of these Streptomyces strains showed that they were strong producers of siderophores. S. praecox strain R7 produced siderophores of hyderoxamate and catechol types and S. globisporous strain F8 produced a phenolic siderophore. Moreover, they also produced protease while only the S. praecox strain R7 was able to produce amylase. Taken together, these results indicate that S. globisporous strain F8 and S. praecox strain R7 promote plant growth and reduces disease and hence are suitable for future in depth and field studies with the aim to attain appropriate biocontrol agents to protect tomatoes against R. solani. Full article
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