Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

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Epidemiology of wheat yellow
rust (Puccinia striiformis f.sp.
tritici) in Iran
M. Torabi
Seed and Plant Improvement Institute (SPII), Karaj, Islamic Republic of Iran
Introduction
Wheat yellow (stripe) rust is the major disease of wheat in Iran. Several
epidemics of this disease have occurred during last 30 years, the most recent
being in 1993 and 1995 (Torabi, 1980; Torabi et al., 1995). The yield losses
caused by the disease were estimated to have been about 1.5 and 1 million
tonne in 1993 and 1995, respectively (Torabi et al., 1995). Several high yielding
wheat cultivars, such as Azadi, Quds and Falat, released in Iran before 1993,
became susceptible to yellow rust. Cultivation of cultivar Falat (Yr9 resistance)
and the emergence of pathotypes of yellow rust with virulence for the Yr9 gene
were the most important factors for epidemics of yellow rust during 1991–1995
in many parts of the wheat growing areas of Iran (Torabi et al., 1995).
In many wheat growing areas of Iran, summer conditions are typically dry
and hot, so survival of yellow rust during the summer period is important for
the epidemiology of the disease. At the same time, in climatically moderate
and cold regions, where temperature is mild during summer, yellow rust can
survive on volunteer wheat and wild grasses in the absence of a wheat crop in
fields. The survival of the fungus during winter in these regions needed
investigation. The present study was carried out to investigate different factors
affecting the epidemics of yellow rust in different parts of Iran.
Materials and methods
The study covered 11 provinces—Ardebil, Moghan, Fars, Golestan, Hamedan,
Khuzestan, West Azarbaijan, Mazandaran, Kermanshah, Sistan and
Baluchistan—for four years (1995–98).
Study on disease progress
Five fields in five different locations in each province were chosen for studying
the effects of different climatic factors, including temperature, relative
humidity and rainfall, on disease incidence and epidemiology.