Achieving Zero Net Land Degradation: Challenges and opportunities

Water shortage is a major environmental stress that causes the generation of reactive oxygen species (ROS). The increase in ROS production induces molecular responses, which are key factors in determining the level of plant tolerance to stresses, including drought. The aim of this study was to determine the expression levels of genes encoding MAPKs (MAPK3 and MAPK6), antioxidant enzymes (CAT, APX and GPX) and enzymes involved in proline biosynthesis (P5CS and P5CR) in Triticum aestivum L. seedlings in response to short-term drought conditions. A series of wheat intervarietal substitution lines (ISCSLs) obtained by the substitution of single chromosomes from a drought-sensitive cultivar into the genetic background of a drought-tolerant cultivar was used. This source material allowed the chromosomal localization of the genetic elements involved in the response to the analyzed stress factor (drought). The results indicated that the initial plant response to drought stress resulted notably in changes in the expression of MAPK6 and CAT and both the P5CS and P5CR genes. Our results showed that the substitution of chromosomes 3B, 5A, 7B and 7D had the greatest impact on the expression level of all tested genes, which indicates that they contain genetic elements that have a significant function in controlling tolerance to water deficits in the wheat genome.

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Analysis of wheat gene expression related to the oxidative stress response and signal transduction under short-term osmotic stress

The growth and persistence of rhizobacteria in soils are highly impacted by moisture stress. In this study, we report the first transcript analysis of four Pseudomonas strains (PS1, PS2, PS3, and PS4) isolated from the root-soil interface of rice and maize associated with different moisture levels during water deprivation. Filtered Pseudomonas sp. cells incubated at low (RH10%) and high (RH85%) relative humidity showed decreased survival of all Pseudomonas sp. at RH10% when compared with RH85%. RT-PCR showed differential expression of treS (trehalose synthase), rpoS (sigma factor), mucA (alginate regulatory gene), and fliM (flagellar motor switch protein gene) in response to exposure to RH10%. However, molecular fingerprinting and nutrient assimilation profile of Pseudomonas strains demonstrated genetic and physiological variation between the four strains irrespective of water regime and host. In vitro testing of these strains showed ACC deaminase activity and gibberellic acid, abscisic acid, indole acetic acid, and exopolysaccharide production. We determined that 50 μl of 1.2 × 103  CFU ml-1 of these Pseudomonas strains was enough to protect Arabidopsis plants against drought stress in a pot experiment. Inoculated plants increased their root colonization ability and biomass; however, PS2 showed higher survival (95%), relative water content (59%), chlorophyll (30%), glycine betaine (38%), proline (23%), and reduced MDA (43%) in shoots than irrigated control under induced water deprivation. It can be concluded that all Pseudomonas strains were effective in mitigating drought stress, however, PS2 appears to impart more resistance to drought than the other strains by upregulating key defense mechanisms.

Drought-tolerant Pseudomonas sp. showed differential expression of stress-responsive genes and induced drought tolerance in Arabidopsis thaliana.

In this study, two wheat cultivars XM13 and AK58 under different drought tolerance were compared by evaluating seed germination, seedling growth and microstructures in order to identify the drought resistance of two wheat cultivars. Results showed that the germination of wheat seeds could be inhibited by drought stress, the germination energy significantly decreased with the increase of drought degree, and the germination energy of AK58 was significantly stronger compared with XM13. Although the root length of wheat XM13 were little influenced by drought stress, AK58 can be promoted and appeared significant differences with the control except the stress of 25% PEG6000. Along with the increase of drought degree, the volume of cortex cell in root had a trend of decline, even shrank at the stress of 15%-25% PEG6000, but effect of drought stress on root growth of wheat XM13 was especially significant compared with wheat AK58. In addition, leaf area of wheat seedling decreased under drought stress, but the decreasing amplitude of wheat AK58 leaf area was greater than XM13. Further study identified that palisade tissue cell in leaf gradually became shorter and disorder, and the thickness of spongy tissue decreased, which was especially significant under the stress of 20%-25% PEG6000. Compared with wheat XM13, the atrophy of endodermis cell in leaf of wheat AK58 should be later. Therefore, the drought-resistant ability of two cultivars wheat was different, and wheat AK58 might be stronger and could better adapt to drought stress compared with wheat XM13. © 2017 Friends Science Publishers

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Effects of drought stress on growth and development of wheat seedlings.

A conceptual model of natural land degradation based on regressive pedogenesis in semiarid tropical environments

The evaluation of changes occurring in the dynamics of arid lands and desertification processes is carried out with regard for the influence of the climatic factor on land aridization. The total land area and area of arid lands by continent, including the territory of Dagestan and the southern regions of Russia, are characterized for the first time. It is shown that the problem of arid lands and desertification has both scientific and socioeconomic meanings. In different arid and subarid zones, the origins and dynamic properties depend on region-wide conditions: in warm-temperate and subarid conditions, the processes of desertification are manifested with the leading role of the anthropogenic factor; in tropical and subtropical zones, they occur under the influence of the climatic factor.

The Arid Regions of the World and Their Dynamics in Conditions of Modern Climatic Warming

The assessment of the situation of global desertification emphasizes the need for information characterizing the global progress of arid degradation and the damage caused by it. Amid the current climate warming, more regions will be affected by droughts, which compromise the sustainability of degrading lands. Concurrently, the drought frequency intensely increases in arid regions. The efforts of scientists and practical workers over the past 25 years, which is reflected in the journal Arid Ecosystems, made it possible to obtain final information about the degradation patterns of soils, vegetation, and animal life. Based on the scientific achievements in the field of anthropogenic dynamics of desertification processes and the formation of the resource-study potential of individual components of arid ecosystems, it is necessary to develop a sound approach to the strategy and to identify implementation methods for the presented concepts, programs, and projects. The generalizations of theoretical findings in the field of the soil-cover productivity and sustainability restoration made it possible to present a fundamental research concept for arid lands of the world in the form of an independent concept of a “green economy”. Its main distinctive feature is a differentiation of the effects caused by the human factor on the natural and medical–biological blocks. Assessment of the effects caused by the social situation of people living under the conditions of droughts, hot winds, and climate warming is an integral part of the second block.

Priorities in the Development of the Research Strategy for Arid Lands of the World

The theoretical foundations and principles of the use of fresh groundwater (FGW) and its role in combating desertification and the development of the biological potential of arid lands are presented. The advantages of FGW in comparison with surface irrigated water are revealed: protection from pollution, evaporation, and protection of natural reserves and their natural renewability. The areas of arid lands by continent, differences in the FGW depth, and the parameters of the recommended type of drip irrigation on the example of one of the arid regions of the Tersko–Kumskaya artesian lowland are given. The natural renewal and close occurrence on the FGW surface in the delta-alluvial plains of Eurasia is compared with the conditions of equatorial Africa.

The Use of Fresh Groundwater from Arid Regions of the World in the Fight against Land Desertification

Patterns of the formation of productive resources in soils of arid territories are revealed. The functioning of an independent category of soil production resources is justified, and the parameters of factors associated with the seasonal cycles of the soil hydrochemical properties are described. The production processes are shown to be specific by the soil types and their independence on the sizes of functioning soil areas. The technologies of the development of productive resources with the cultivation of plants with a short vegetative cycle have been experimentally studied based on the use of natural laws of salt and water accumulation.

Regularities of the Formation of Production Resources on Saline Soils of the Terek-Kuma Lowland

New approaches using mathematical methods have been developed for estimation of the effect of undrained plain heights in delta ecosystems on soil diversity. This makes it possible to consider the effect of positive elements in the delta plain located below the zero marks that favoring the formation of local drainage. Models have been developed from the height gradients of the Terek–Kuma Lowland by the least squares method. The proposed method has revealed the soil diversity and spatial parameters characteristic of alluvialdelta coastal plains common to different continents.

Z. G. Zalibekov

Papers

The Arid Regions of the World and Their Dynamics in Conditions of Modern Climatic Warming

Priorities in the Development of the Research Strategy for Arid Lands of the World

The Use of Fresh Groundwater from Arid Regions of the World in the Fight against Land Desertification

Regularities of the Formation of Production Resources on Saline Soils of the Terek-Kuma Lowland

Regional distribution patterns of soils in delta ecosystems and their potential use on different continents