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2010 ). Infection by B. sorokiniana in wheat and the black point disease can lower
the quality and market value of grains, cause seedling blight, and reduce seed ger-
mination and seedling emergence (Al-Sadi and Deadman 2010 ; Acharya et al.
2013 ).
Penetration into the seed is achieved through the ovary wall and seed coat. In
addition, the spores of B. sorokiniana can be carried on seed coat surfaces. B. soro-
kiniana is one of the long living seed-borne pathogens.

4.2 Common Root Rot of Wheat

Common root rot in wheat and barley, caused by B. sorokiniana, is an important
disease all over the world (Tunali et al. 2008 , Al-Sadi and Deadman 2010 ) and is
characterized by symptoms that appear on the roots, sub-crown internodes and
crowns. These symptoms include necrosis in the form of dark brown or black col-
ored lesions on the basal stem, crowns, sub-crown internodes and roots (Al-Sadi
and Deadman 2010 ) (Fig. 2 ). B. sorokiniana invades the roots and shoot base caus-
ing lignification and death of the epidermal cells. The necrotic symptoms on the
sub-crown internodes (Fig. 2 ) and roots (Fig. 3 ) are commonly used to evaluate the
resistance of different varieties (Liljeroth et al. 1996 ; Al-Sadi and Deadman 2010 ).

Table 1 Examples of diseases associated with wheat in dry areas of the world

Disease Causal organism

Estimated annual yield

lossesa References

Common root

rot

Bipolaris

sorokiniana and

Fusarium

5–40 % in Syria (Wiese ( 1987 ), Bailey et al.

( 1997 ), and Acharya et al.

2013 )

Leaf blight Alternaria spp. Variable yield loss;

important in India,

Middle East, Nigeria and

other countries

Wiese ( 1987 )

Loose smut Ustilago tritici Can reach 27 % in

different parts of the

world

Wiese ( 1987 )

Head blight Fusarium spp. Variable levels of loss Wiese ( 1987 ) and Wiersma

and Motteberg ( 2005 )

Spot blotch Bipolaris

sorokiniana

4–43 % in Bangladesh,

China, and South Asia

Acharya et al. ( 2013 ) and

Chowdhury et al. ( 2013 )

Stem rust Puccinia graminis

f.sp. tritici

5–7 million metric tons

worldwide

Pardey et al. ( 2013 )

Cyst

nematodes

Heterodera avenae 3–49 % in India,

15–20 % in Pakistan,

40–92 % in Saudi Arabia

Bhatti et al. ( 1981 ) and

Nicol et al. ( 2011 )

aThe losses are not constant, they depend on the species, cultivar, environment, and virulence of the
pathogen isolate (Al-Sadi 2016 )

A.M. Al-Sadi