**5.2. Sustainable management practices and perspectives for wheat cropping under salinised conditions**

Some of the widely used and most promising perspectives and strategies against soil salinity are listed in **Table 1**, and some of them are explained in the next section in more detail. Beside excessive ECe in saline soils, it is of great importance and interrelated concentrations of particular ions (notably portion of exchangeable Na+ ; ESP) as well as soil pH reaction. According to some of chemical parameters, salt-affected soils generally can be categorised as: saline (ECe > 4 dS/m, ESP < 15 and pH <8.5), saline-sodic (ECe > 4 dS/m, ESP > 15 and pH <8.5) and sodic/alkaline (ECe >4 dS/m, ESP >15 and pH >8.5), and usually require specific strategy for reclamation often with low benefit/cost ratio for crops (Ondrasek et al. [85] and references therein). Sustainable agricultural management in saline/sodic conditions usually is combination of certain preventive actions (aiming to control salinity/alkalinity level) and/or remediate of saline/alkaline areas. For instance, saline soils might be easier for reclamation than sodic soils because the former often requires only salt leaching while the latter requires addition and certain Ca-/Mg-based soil amendments (e.g. gypsum) to replace excess ESP in addition to leaching (e.g. [91]).


**Table 1.** Some perspectives for improving wheat cropping in salt-affected agroecosystems.

Application of (in)organic soil amendments, such as mineral/organic fertilisers, lime, gypsum phospho-gypsum, and so on to salt-affected pedosphere has multi-beneficial impact [75]. Introduction of Ca-/Mg-enriched amendments enhances to maintain soil micro-aggregate structure in the soil profile, and consequently improves physical pedovariables such as improved flocculation, reduced spontaneous dispersion (air-dry aggregates) and dispersion of remoulded aggregates, increased hydraulic conductivity and soil aeration [92]. Furthermore, it was confirmed that soil salinity/alkalinity is frequently associated with microelement Zn deficiency, and that under such conditions, application of certain inorganic Zn-based fertilisers is able to improve salt tolerance but also and nutritional value of wheat. Namely, ~40% of the soils used for wheat production in Iran are Zn-deficient [93] and comparing to some other widely cropped cereals, wheat genotypes are especially very sensitive to Zn deficiency which markedly reduce wheat grain yield [94]. However, one of the biggest issues with soil amendments (Ca-/Mg-/Zn-based) application and their beneficial impact to crops in saline conditions is often lacking of their dissolution (i.e. phytoavailability of specific element/substance) due to (semi)arid conditions and/or not implemented irrigation practice.

durum *vs*. bread wheat genotypes could be more effective, not only in Cd root extraction, but also in Cd root to shoot (leaf/grain) translocation and deposition under excessive Cl salinity. Such genotypic differences should be considered also in wheat breeding programs related to

Some of the widely used and most promising perspectives and strategies against soil salinity are listed in **Table 1**, and some of them are explained in the next section in more detail. Beside excessive ECe in saline soils, it is of great importance and interrelated concentrations of particular

of chemical parameters, salt-affected soils generally can be categorised as: saline (ECe > 4 dS/m, ESP < 15 and pH <8.5), saline-sodic (ECe > 4 dS/m, ESP > 15 and pH <8.5) and sodic/alkaline (ECe >4 dS/m, ESP >15 and pH >8.5), and usually require specific strategy for reclamation often with low benefit/cost ratio for crops (Ondrasek et al. [85] and references therein). Sustainable agricultural management in saline/sodic conditions usually is combination of certain preventive actions (aiming to control salinity/alkalinity level) and/or remediate of saline/alkaline areas. For instance, saline soils might be easier for reclamation than sodic soils because the former often requires only salt leaching while the latter requires addition and certain Ca-/Mg-based soil

amendments (e.g. gypsum) to replace excess ESP in addition to leaching (e.g. [91]).

Species/varieties selection Cropping of more salt resistant wheat varieties (genotypes), although genotypic

elements) should be considered (explained above)

differences related to efficiency of mineral uptake and accumulation (e.g. trace

Implementation of subsurface drainage system may be useful approach for: (i) prevention of salt accumulation in sub/surface horizons as a consequence of seasonal sea water intrusion and/or capillary rising and/or (ii) salt leaching from the surface soil layers (e.g. [109]). Implementation of irrigation can decline vegetative growth of wheat

cropped on salt-affected soils but without evident yield reductions (e.g. [75])

It was shown that exploitation of certain microbial populations can be a promising alternative to alleviate crops stress under excessive root zone salinity [96]. Thus for instance, inoculation of wheat seeds prior sowing by salt-tolerant microbe colonies might be beneficial strategy for wheat cropping in salt-affected environment (e.g. [97])

Addition of natural or synthetic Ca-/Mg-/Zn based sources can ameliorate soil salinity/ sodicity [110] and related pedosphere constrains (e.g. Zn-deficiency; see above)

Over conservation land management (e.g. reduced/minimal/no tillage) is possible to preserve and/or enhance soil–plant water relations, soil organic matter content and

and/or Cl<sup>−</sup>

exclusion by crossing cultivars

rhizosphere biodiversity across the saline paddocks (e.g. [85])

of *Triticum aestivum* L. with genetically related (non)halophytes (e.g. [80])

Genetic improvement Genetic improvement of wheat genomes for salt-tolerance has a great potential of acquiring some halophytic traits such as Na+

**Table 1.** Some perspectives for improving wheat cropping in salt-affected agroecosystems.

; ESP) as well as soil pH reaction. According to some

**5.2. Sustainable management practices and perspectives for wheat cropping under** 

salt resistance (next section).

ions (notably portion of exchangeable Na+

**Perspective Description**

Amelioration of soil water

Soil amelioration by

Application of inorganic

management

microbes

amendments

matter

Conservation and increasing of soil organic

**salinised conditions**

38 Global Wheat Production

Another promising strategy to enhance wheat salt tolerance might be introduction of salt more tolerant root-associated microbes that enhance plant growth under excessive salinity. Namely, it was widely discussed how spatial rhizosphere adaptation of plants is also driven by genetic differentiation in closely associated microbe populations such as: (i) arbuscular mycorrhizal fungi (whose hyphal networks ramify throughout the soil and within the plant cells) then (ii) ectomycorrhizal fungi (over a fungal layer around the root system and root intercellular spaces) and (iii) root-associated plant growth-promoting rhizobacteria (see reviews by Rodriguez and Redman [95]; Dodd and Perez-Alfocea [96]). Alleviation of salt stress on yield and mineral nutrition (e.g. increased K/Na ratio) exploiting the arbuscular mycorrhizal fungi was confirmed in certain wheat varieties under field saline conditions [97]. For instance, the mycorrhizal colonisation enhanced grain wheat yield up to >31% in Kavir (spring cultivar), up to >32% in Roshan (spring and semi-early maturing cultivar) and even up to >38% in Tabasi (mutated salt tolerant line) [97]. Furthermore, Sadeghi et al. [76] applying the isolate of *Streptomyces* in cultivated soil with wheat (cul. Chamran) observed: (i) increased the growth/ development and shoot concentration of N, P, Fe and Mn in both saline and non-saline conditions and (ii) significant increases in germination rate, percentage and uniformity, shoot length and dry weight of salt-exposed plant (*vs*. non saline control). Also, studying the effect of inoculation of the five halotolerant bacterial strains in alleviation of NaCl-induced stress (80–320 mM) in wheat (var. HD 2733) Ramadoss et al. [98] observed an increase in root elongation (by >90%) and root dry weight (by >17%) in comparison with control (uninoculated) plants. Such beneficial effects of salt-tolerant microbes to (wheat) crops exposed to salinity are explained by improved plant water relations (e.g. due to enhanced accumulation of specific osmolytes), then regulating plant homeostasis and improved phytonutrients (e.g. N, P, K, Zn, Cu, Mn, Fe) uptake as well by enhanced germination rate [96, 97, 99].

Breeding programs to salt tolerance (as relatively long-term approach) are expecting that might have crucial role in (wheat) cropping under saline conditions in the near future (see down). Relatively little work has been done on breeding programs of wheat cultivars for saline conditions [80] given on polygenic character of salt tolerance, but continuous progress is evident. Namely, hexaploid bread wheat (*Triticum aestivum* L.) has one of the most complex (ABD) genomes (e.g. six copies of each chromosome, numerous of near-identical sequences scattered throughout, overall haploid size of >15 billion bases) [100], thus making wheat highly challenging for genome sequencing and detection of salt-tolerant genes and quantitative trait loci. Also, the huge amount of repetitive sequences poses a big challenge for sequencing the wheat genome [101]. For instance, first assembly of the wheat genome from 2012 was represented by only ~33% (5.42 billion bases) [102], another assembly from 2014 by ~66% (10.2 billion bases) [103] whereas assemblies from 2017 were extended to 78% (12.7 billion bases) [104] and recent assembly was almost completed with >15.3 billion bases [100]. Hence, the genomic complexity and its uncomplete assembly makes the wheat crop additionally extremely difficult for improvement to salt tolerance over conventional (e.g. traditional breeding) and/or modern genetic (e.g. molecular and transgenic breeding) approaches.

**Acknowledgements**

**Conflict of interest**

**Author details**

Veres Szilvia1

Croatia

**References**

10.1098/rstb.2010.0149

10.1080/07352680390243512

We have no conflict of interest declare.

\*, Ondrasek Gabrijel2

University of Debrecen, Debrecen, Hungary

\*Address all correspondence to: szveres@agr.unideb.hu

Nyíregyháza, University of Debrecen, Nyíregyháza, Hungary

Energy Security. 2015;**4**(3):178-202. DOI: 10.1002/fes3.64

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Thank you for the support of 'Kiváló malomipari paraméterekkel rendelkező adaptív őszi búza vonalak előállítása' (AGR\_PIAC\_13-1-2013-0002) grant and the EFOP-3.6.3- VEKOP-16- 2017-00008 project. The project is co-financed by the European Union and the European Social

Wheat Sensitivity to Nitrogen Supply under Different Climatic Conditions

http://dx.doi.org/10.5772/intechopen.76154

41

and Zsombik László3

1 Faculty of Agricultural and Food Sciences and Environmental Management, Department of Agriculture Botany, Crop Physiology and Biotechnology, Institute of Crop Sciences,

2 Faculty of Agriculture, Department of Soil Amelioration, University of Zagreb, Zagreb,

[1] Kearney J. Food consumption trends and drivers. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 2010;**365**(1554):2793-2807. DOI:

[2] Shewry PR, Hey SJ. The contribution of wheat to human diet and health. Food and

[3] Glass ADM. Nitrogen use efficiency of crop plants, physiological constraints upon nitrogen absorption. Critical Reviews in Plant Sciences. 2003;**22**:453-470. DOI:

[4] Good AG, Shrawat AK, Muench DG. Can less yield more? Is reducing nutrient input into the environment compatible with maintaining crop production? Trends in Plant

3 Institutes for Agricultural Research and Educational Farm, Research Institute of

Genetic improvement of wheat for salt-tolerance has also a great potential of acquiring some halophytic traits (genes) such as Na+ /Cl<sup>−</sup> exclusion and/or compartmentation by crossing wheat genotypes with genetically related halophytic plant species (e.g. *Lophopyrum elongatum*) [105]. In wheat salt resistance is associated with low rates of the root-to-shoot transport of Na+ with high selectivity for K+ over Na+ [106]. Bread wheat genotypes have a low rate of Na+ accumulation and enhanced K+ /Na+ discrimination which is controlled by a locus (Kna1) on chromosome 4D [107]. Contrary, durum wheat (tetraploid, AB genomes) have higher rates of Na+ accumulation and weaker K+/Na + discrimination [80] and is consequently less salt resistant *vs*. bread wheat (**Figure 2**). It was confirmed that salt−/draught-tolerant genes and quantitative trait loci identified in *T. dicoccoides* and *H. spontaneum* have great potential in wheat improvement also [108]. Finally, improvement in salt resistance of modern wheat genotypes will be generated from introducing new gene(s) by (i) crossing with new donor germplasm or (ii) transformation with single genes, and after the progeny has to be back-crossed into adapted cultivars before the donor genes are ready for cultivation [80].
