4.9.5 Application of Nanotechnology to Increase Drought
Tolerance in Soybean
Nanotechnology is one of the promising approaches that has been extensively
studied as biotechnological tools where metal-based nanoparticles are being applied
in the crop system to study the effectiveness and targeted delivery of the molecular
product stimulating the regulation pathways (Tripathi et al. 2018). Nanoparticles
(nano-scale particles ¼ NSPs) are atomic or molecular aggregates with at least one
dimension between 1 and 100 nm (Roco 2003) and are used in low quantity as the
replacement of plant mineral nutrients. As compared to conventional fertilization the
amendment of nanoparticles improved the plant response to drought stress (Saxena
et al. 2016). The application of these micronutrient-based nanoparticles, such as
copper, iron, cobalt, manganese, magnesium, nickel, and zinc, helps to increase the
crop yield, even under environmental stress conditions (Ashraf et al. 2012).
ZnO nanoparticles (NP) application increased seed germination of soybean under
water stress (Sedghi et al. 2013). The use of extremely low concentrations of ZnO
NP, lower than 500 ppm, can guarantee the enhancement of the Zn content in the
seed without toxicity to plant cells (Hossain et al. 2016). The physiological traits,
viz. drought tolerance index, relative water content, and biomass reduction rate, were
significantly improved, especially in Fe NP-treated plants. Fe and Cu NP-treated
plants maintained relative water content (RWC) at 71%, which was significantly
higher than the RWC of control plants (64%) (Linh et al. 2020). Root architecture
plays an important role in resistance to drought. Iron oxide NPs at the concentration
of 50 to 2000 mgL
1 increased root growth by 6–40% in soybean (Alidoust and Isoda
2013). The efficacy of iron oxide NPs was higher due to higher solubility, higher
surface area, higher penetration through seed coat, and subsequently emerging roots
and better availability to root radicals (Denher et al. 2010). Quantitative PCR
analysis of drought-responsive genes showed a gene-, tissue-, and nanoparticledependent upregulation of gene expression. In addition to this the expression of
three drought-responsive genes promoted in leaves OD nanoparticle-treated plants.
The Fe NP triggered the expression of all tested genes in roots. The expression of the
selected drought tolerance marker genes, GmRD20A, GmDREB2, GmERD1,
GmFDL19, GmNAC11, GmWRKY27, GmMYB118, and GmMYB174, was
found to be upregulated in roots or shoots (or both) of NP-treated plants under
drought. This suggests that nanoparticle application can increase drought tolerance
of soybean by promoting the expression of genes associated with drought (Linh et al.
2020).
4.10 Conclusions and Future Perspectives
In just the past few years we have witnessed tremendous progress in soybean
genomics and an explosive expansion of new resources. We have seen the development of high-density soybean genetic maps, construction of physical and transcript
maps, EST sequencing and analysis, development of high-density cDNA and oligo
114
G. K. Satpute et al.
Tolerance in Soybean
Nanotechnology is one of the promising approaches that has been extensively
studied as biotechnological tools where metal-based nanoparticles are being applied
in the crop system to study the effectiveness and targeted delivery of the molecular
product stimulating the regulation pathways (Tripathi et al. 2018). Nanoparticles
(nano-scale particles ¼ NSPs) are atomic or molecular aggregates with at least one
dimension between 1 and 100 nm (Roco 2003) and are used in low quantity as the
replacement of plant mineral nutrients. As compared to conventional fertilization the
amendment of nanoparticles improved the plant response to drought stress (Saxena
et al. 2016). The application of these micronutrient-based nanoparticles, such as
copper, iron, cobalt, manganese, magnesium, nickel, and zinc, helps to increase the
crop yield, even under environmental stress conditions (Ashraf et al. 2012).
ZnO nanoparticles (NP) application increased seed germination of soybean under
water stress (Sedghi et al. 2013). The use of extremely low concentrations of ZnO
NP, lower than 500 ppm, can guarantee the enhancement of the Zn content in the
seed without toxicity to plant cells (Hossain et al. 2016). The physiological traits,
viz. drought tolerance index, relative water content, and biomass reduction rate, were
significantly improved, especially in Fe NP-treated plants. Fe and Cu NP-treated
plants maintained relative water content (RWC) at 71%, which was significantly
higher than the RWC of control plants (64%) (Linh et al. 2020). Root architecture
plays an important role in resistance to drought. Iron oxide NPs at the concentration
of 50 to 2000 mgL
1 increased root growth by 6–40% in soybean (Alidoust and Isoda
2013). The efficacy of iron oxide NPs was higher due to higher solubility, higher
surface area, higher penetration through seed coat, and subsequently emerging roots
and better availability to root radicals (Denher et al. 2010). Quantitative PCR
analysis of drought-responsive genes showed a gene-, tissue-, and nanoparticledependent upregulation of gene expression. In addition to this the expression of
three drought-responsive genes promoted in leaves OD nanoparticle-treated plants.
The Fe NP triggered the expression of all tested genes in roots. The expression of the
selected drought tolerance marker genes, GmRD20A, GmDREB2, GmERD1,
GmFDL19, GmNAC11, GmWRKY27, GmMYB118, and GmMYB174, was
found to be upregulated in roots or shoots (or both) of NP-treated plants under
drought. This suggests that nanoparticle application can increase drought tolerance
of soybean by promoting the expression of genes associated with drought (Linh et al.
2020).
4.10 Conclusions and Future Perspectives
In just the past few years we have witnessed tremendous progress in soybean
genomics and an explosive expansion of new resources. We have seen the development of high-density soybean genetic maps, construction of physical and transcript
maps, EST sequencing and analysis, development of high-density cDNA and oligo
114
G. K. Satpute et al.