QTLs for HT related traits have been discovered for example cellular membrane
stability, pollen germination, and pollen tube growth in maize (Ottaviano et al. 1991;
Frova and Sari-Gorla 1994). Which identified for different traits involved in heat
stress tolerance like grain filling duration (Yang et al. 2002; Mason et al. 2010;
Barakat et al. 2012; Paliwal et al. 2012), grain number (Pinto et al. 2010), leaf
senescence (Mason et al. 2010; Vijayalakshmi et al. 2010), reproductive stage
(Farooq et al. 2011), tillering, stay green character (Kumar et al. 2010; Li et al.
2010) and canopy temperature (Paliwal et al. 2012) have been identified in wheat.
Mason et al. (2010) also identified many QTLs associated with yield and yield
attribute traits. Some QTLs have a small effect on the phenotype, to overcome this
marker-assisted recurrent selection (MARS) or genomic selection (GS) approach is
used to pyramiding several QTLs using large populations (Tester and Langridge
2010). The identification of QTLs and their significant use in MAS, MARS, and
marker-assisted backcross breeding is helping to improve heat tolerance in different
crops (Zheng et al. 2012). Incorporation of genes of interested traits into the desired
plants to improve tolerance against HS utilized through genetic engineering and
transgenic approaches can be followed (Chapman et al. 2012).
Transgenic approaches involve the incorporation of superior genes to elite
cultivars and thus helps to avoid the issue of linkage drag, to develop plant tolerance
to HS (Zheng et al. 2012). In maize, gene phosphoenolpyruvate carboxylase
(ZmPEPC) overexpressed improved heat tolerance in wheat by enhancing activities
of the photochemical enzyme, delayed chlorophyll degradation, upregulated expression of genes related to photosynthesis, adjusted contents of proline (Qi et al. 2017).
In the wheat transfer of maize elongation factor (EFTu) EFTu1gene overexpressed
and improved tolerance to HT stress. Fu et al. (2008) reported in wheat, the increase
in the protein synthesis EFTu in the chloroplast. The constitutive expression of EFTu
in transgenic wheat protects leaf protein from denaturation, lowering thylakoid
membranes disruption, and enhanced photosynthetic capability. According to Ristic
et al. (2008), transgenic wheat accruing more EFTu has exceptional tolerance to HS
than those exposed to less EFTu transgene of certain heat shock protein also
improved tolerance against HS. In maize transgenic overexpression of certain heat
shock factors (HSF) and HSF-fusion proteins transfer from A. thaliana results in an
expression of Hsp101 results increase in thermotolerance (Iba 2002; Queitsch et al.
2000).
In addition to conventional, molecular breeding, transgenic approach, and agronomic management practices like soil moisture management, application of fertilizer, sowing methods, maintaining proper time and use of exogenous protectants can
also attenuate the effect of HS (Ortiz et al. 2008; Singh et al. 2011). Applications of
organic mulches conserve soil moisture and increase nitrogen use efficiency in wheat
(Chakraborty et al. 2008; Singh et al. 2011). The CaCl 2 application increase
antioxidants like SOD, guaiacol peroxidase, and CAT (Dias et al. 2009). In maize
and wheat, early sowing prevents HS at the flowering stage (Perego et al. 2014; Kajla
et al. 2015). Use of Bacillus amyloliquefaciens (UCMB5113) and Azospirillum
brasilense (NO40) strains for seed treatment reduces ROS generation provides
3 Plant Morphological, Physiological Traits Associated with Adaptation Against. . .
67
stability, pollen germination, and pollen tube growth in maize (Ottaviano et al. 1991;
Frova and Sari-Gorla 1994). Which identified for different traits involved in heat
stress tolerance like grain filling duration (Yang et al. 2002; Mason et al. 2010;
Barakat et al. 2012; Paliwal et al. 2012), grain number (Pinto et al. 2010), leaf
senescence (Mason et al. 2010; Vijayalakshmi et al. 2010), reproductive stage
(Farooq et al. 2011), tillering, stay green character (Kumar et al. 2010; Li et al.
2010) and canopy temperature (Paliwal et al. 2012) have been identified in wheat.
Mason et al. (2010) also identified many QTLs associated with yield and yield
attribute traits. Some QTLs have a small effect on the phenotype, to overcome this
marker-assisted recurrent selection (MARS) or genomic selection (GS) approach is
used to pyramiding several QTLs using large populations (Tester and Langridge
2010). The identification of QTLs and their significant use in MAS, MARS, and
marker-assisted backcross breeding is helping to improve heat tolerance in different
crops (Zheng et al. 2012). Incorporation of genes of interested traits into the desired
plants to improve tolerance against HS utilized through genetic engineering and
transgenic approaches can be followed (Chapman et al. 2012).
Transgenic approaches involve the incorporation of superior genes to elite
cultivars and thus helps to avoid the issue of linkage drag, to develop plant tolerance
to HS (Zheng et al. 2012). In maize, gene phosphoenolpyruvate carboxylase
(ZmPEPC) overexpressed improved heat tolerance in wheat by enhancing activities
of the photochemical enzyme, delayed chlorophyll degradation, upregulated expression of genes related to photosynthesis, adjusted contents of proline (Qi et al. 2017).
In the wheat transfer of maize elongation factor (EFTu) EFTu1gene overexpressed
and improved tolerance to HT stress. Fu et al. (2008) reported in wheat, the increase
in the protein synthesis EFTu in the chloroplast. The constitutive expression of EFTu
in transgenic wheat protects leaf protein from denaturation, lowering thylakoid
membranes disruption, and enhanced photosynthetic capability. According to Ristic
et al. (2008), transgenic wheat accruing more EFTu has exceptional tolerance to HS
than those exposed to less EFTu transgene of certain heat shock protein also
improved tolerance against HS. In maize transgenic overexpression of certain heat
shock factors (HSF) and HSF-fusion proteins transfer from A. thaliana results in an
expression of Hsp101 results increase in thermotolerance (Iba 2002; Queitsch et al.
2000).
In addition to conventional, molecular breeding, transgenic approach, and agronomic management practices like soil moisture management, application of fertilizer, sowing methods, maintaining proper time and use of exogenous protectants can
also attenuate the effect of HS (Ortiz et al. 2008; Singh et al. 2011). Applications of
organic mulches conserve soil moisture and increase nitrogen use efficiency in wheat
(Chakraborty et al. 2008; Singh et al. 2011). The CaCl 2 application increase
antioxidants like SOD, guaiacol peroxidase, and CAT (Dias et al. 2009). In maize
and wheat, early sowing prevents HS at the flowering stage (Perego et al. 2014; Kajla
et al. 2015). Use of Bacillus amyloliquefaciens (UCMB5113) and Azospirillum
brasilense (NO40) strains for seed treatment reduces ROS generation provides
3 Plant Morphological, Physiological Traits Associated with Adaptation Against. . .
67