Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

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Field assessment
The results of adult plant evaluation indicated that lines C-86-1, C-86-2, C-87-1,
C-87-2, C-87-3 and C-87-18 had the highest CI and rAUDPC. The rest of the
lines showed resistant reaction at this stage. The lines with low rAUDPC at the
adult plant stage and susceptible reaction at seedling stage could have durable
resistance, and lines with resistance reaction at both stages may carry racespecific
resistance (Sandoval-Islas et al., 1998). Durable resistance persists, even
if the pathogen changes its genotype. Such slow-rusting and high-temperature,
adult-plant (HTAP) resistance is controlled by more than one gene, at least 2 or
3 (Dehghani and Moghadam, 2004).
Researchers should select for durable resistance because although the rust
pathogen can easily change its genotype by mutation in the face of selection
pressure based on single-gene resistance it changes much more slowly when
faced with multiple-gene resistance (Hovmøller, 2001; Ben Yehuda et al., 2004).
Genetic diversity is often low at both field and regional scales in
populations of P. striiformis f.sp. tritici, but the potential diversity is higher
when taking into account the changes that may occur over time (years) and
samples representing large geographical areas (Hovmoller and Justesen, 2006).
Spores of the yellow rust fungus potentially may move across very large
distances within a relatively short time, a factor highlighting the need for
multinational disease and pathogen surveys.
Screening for slow-rusting using various disease-tolerant sources and the
use of appropriate cultural practices would enhance sustained use of high
yielding cultivars for a longer time (Resgui et al., 2006).
Based on slow-rusting traits, the lines tested may probably have genes for
varying degrees of slow yellow rusting and can be used for future
manipulation in wheat improvement programmes after confirmatory studies.
References
Ben Yehuda, P., Eilam, T., Manisterski, J., Shimoni, A. & Akster, Y. 2004. Leaf rust on
Aegilops speltoides caused by a new forma specialis of Puccinia triticina. Phytopathology,
94: 94–101.
Broers, L.H.M., Cuesta-Subias, X. & Lopez-Atilano, R.M. 1996. Field assessment of
quantitative resistance to yellow rust in ten spring bread wheat cultivars. Euphytica,
90: 9–16.
Chen, X. & Line, R.F. 2002. Identification of genes for resistance to Puccinia striiformis
f.sp. hordei in 18 barley genotypes. Euphytica, 129: 127–145.
Dehghani, H. & Moghaddam, M. 2004. Genetic analysis of latent period of stripe rust
in wheat seedlings. Journal of Phytopathology, 122: 325–330.