The Eleventh Regional Wheat Workshop For Eastern ... - Cimmyt

HOST RANGE OF WHEAT STEM RUST IN ETHIOPIA
Zerihun Kassaye l and O.S. Abdalla 2
IPlant Protection Research Center, P.O. Box 37, Ambo, Ethiopia
2C1MMYTIICARDA, P.O. Box 5466, Aleppo, Syria
ABSTRACT
Surveys were conducted to identify the host ranges of stem rust of wheat on
non-Triticum grasses collected in Arsi, Bale, East and Western Shewa,
Ethiopia, during the main and off-seasons, 1997-1998. Seedlings of
susceptible wheat varieties were inoculated with urediospores collected from
weeds, and vice versa. Of 10 rust infected weed species, Lolium temulentum
and Setaria pumila were identified to be secondary hosts for wheat stem rust.
Leaves of Avena fatua, Snowdenia polystachya, Cynodon dactylon, Bromus
pectinatus and Euphorbia shiperiana turned yellow, but no sporulation
occurred. Wheat sown in the off-season sown and volunteer wheat in fallow
lands, along the edges of crop fields, roads, irrigation canals and under
orchards were found to be good sources ofstem rust infection.
INTRODUCTION
Wheat is one of the most important cereal crops in Ethiopia. The area under production in
Ethiopia is about 750,000 ha (Hailu, 1991). Average national wheat yields are low, ranging
from 1.1 t ha- 1 on the peasant farms to 2.0 t ha- 1 on state farms (Hailu et al., 1991).
Diseases are a major constraint to wheat production in the country. The importance of rust
diseases, was recognized in 1930 by Castellani, 1938; Sibilia, 1938. Wheat stem rust is the
widely distributed and can cause serious yield loss. Severity of stem rust epidemic is
determined by the virulence of the pathogen, resistance of the host, favorable environment,
and time available for disease development.
In some parts of the world, wild grasses or weeds play an important role in the epidemiology
of wheat rust (Puccinia spp). A number ofgrass species have been observed to be susceptible
to these pathogens (Roelfs et al., 1992). Endemicity of rust is possible only if there is either
annual continuity of hosts a resting period for the pathogen, or both. Continuity of hosts can
be provided by crop cultivars, alternate host(s) or accessory graminaceous hosts (Zadoks,
1980). For instance in Mediterranean countries, uredoinoculum has a graminicolous facies,
with inoculum accumulation occurring on wheat migrating to grasses situated in the Atlas
mountains (Zadoks, 1965) as crop harvest occurs.
In Ethiopia, attempts have been made to investigate the specialization of stem rust on wild
grasses. As a result it has been reported that Lotium spp. were considered as possible
secondary hosts of stem rust (SPL, 1978; Loban et al., 1988). However, there remains a
scarcity of information available on the host range of this pathogen in Ethiopia. This paper
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