Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

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Wheat rust surveillance
A. Yahyaoui
ICARDA, Aleppo, Syria
Monitoring of the trans-boundary air-borne rust diseases in field surveys using
biological trap nurseries, when complemented with epidemiological
investigations of pathogen movement through DNA fingerprinting and race
analysis in order to determine the origin of new pathotypes, will provide an
early warning system for farmers growing potentially susceptible cultivars.
Furthermore, the knowledge of effective resistance genes in the region though
testing them at rust hot-spots will enable breeders to incorporate and
accumulate these genes in wheat germplasm, thus contributing to the
development of resistant cultivars that sustain resistance for longer.
Monitoring the evolution and migration of Ug99 is a high priority because:
(1) several currently grown cultivars carry race-specific resistance genes that
have a short life span; (2) the same cultivars are being grown over large areas
in more than one country; and (3) the same genes conferring resistance to
several rusts are deployed in cultivars grown in different countries. Rust
populations share similar pathotypes in different regions, but novel virulence
when it occurs would rapidly build up a large inoculum load on the defeated
varieties, which often occupy large areas, and would move across a wider
region. The expected movement of Ug99 based on simulations of the pathway
of yellow rust in the 1990s could deviate, with the potential for devastating
impacts on wheat production. The imminent threat of Ug99 and the
development of more complicated races of both stem and yellow rust can be
avoided or reduced though a global monitoring system that would provide an
early warning system that would help avoid tremendous crop losses.