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Drought and heat are worldwide problems in drylands. What makes planning
against drought difficult is that the farmers and researchers don’t know when it is
going to hit the crop; another problem with drought tolerance is that it is a polygenic
trait with low heritability and high genotypic × environmental (G×E) interaction.
Supplying sufficient food for the increasing population is a huge challenge,
nonetheless global food security is threatened by climate change (Lal et al. 2005 ).
Climate change refers to changes in the distribution of weather across a period of
time that ranges from decades to millions of years. It can be a change in the average
weather or a change in the distribution of weather events around an average.
Maximum and minimum relative humidity levels have shown increasing trend, cli-
mate change is worsening the current situation through its effects on the world wide
agricultural systems (Battisti and Naylor 2009 ; Bloem et al. 2010 ). Due to climate
change, more severe scenarios such as drought in some areas and the increase in
frequency and severity of extreme droughts in other areas are expected (IPCC 2007 ;
Carnicer et al. 2010 ). Climate change is affecting agriculture both directly and indi-
rectly, worldwide; temperature (high and low), emission of greenhouse gases and
precipitation patterns directly affect the crops, pathogens, insects, and weeds.
Several new diseases, weeds, and insect-pests have started appearing with the
changing climate.
Several new diseases such as powdery mildew and foliar blight of wheat have
started appearing, and there is a risk of stem rust (black rust), caused by Ug99,
which started from Uganda and has now spread up to Iran and further. Likewise,
new insect pests such as black aphids and pink stem borer have started appearing on
wheat. Crops requiring chilling for flowering, will not be getting enough chilling
hours, which may reduce their production. New technologies must be developed to
accelerate breeding through improving genotyping and phenotyping methods and
by increasing the available genetic diversity in crop breeding programs (Dhillon
et al. 2013 ). Climatic changes in most of the crop growing areas are expected to
experience changes in drought, canopy temperature, salinity, etc., For example,
wheat is negatively affected by drought in more than 50 % of its cultivated area
(Rajaram 2001 ); its productivity is usually limited by shortage of moisture neces-
sary to maximize biomass and most importantly to complete grain filling (Aprile
et al. 2009 ). The largest producers of pulses (South Asian countries, China and
some African countries) having around 70 % of the global production are located in
areas that experience shortage of water (Gowda et al. 2009 ).
As the average temperature is predicted to rise, some regions will be expecting
more heat, the greater heat will complicate the situation by increasing agricultural
droughts with high evapotranspiration resulting in low soil moisture (Battisti and
Naylor 2009 ). The 1.8 °C rise in average global temperature predicted for 2050
(Meehl and Tebaldi 2004 ) will force farmers to grow genotypes which are more
tolerant, among other factors, to high temperatures (Farooq et al. 2011 ). Around 9
million hectares of wheat is grown in tropical and subtropical areas of the develop-
ing countries with temperatures as high as 17.8 °C in the coolest month of the grow-
ing season (Ortiz et al. 2007 ). Even in the developed countries heat stresses has
demonstrated the negative effect on yield. In areas where daily temperature may rise
up to 35° C during grain filling, heat stress not only negatively affects yield but also
Q. Sohail et al.