Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

nurseries were irrigated with mist and flood irrigation to promote disease
development.
The percentage leaf area affected (severity) was scored using the modified
Cobb’s scale of Peterson, Campbell and Hannah (1948) at the end of the season
when leaves were alive and green. Reaction (infection type) of each line or
cultivar was evaluated at the same time (Roelfs, Singh and Saari, 1992).
The two scores were then converted to a coefficient of infection (CI). This CI
was obtained by multiplying the constant value for infection types (0=0; R=0.2;
MR=0.4; I=0.6; MS=0.8; and S=1) and the leaf area affected (severity). The
entries were classified according to their CI values.
119
Results and discussion
A heavy epidemic of the disease was established on the experimental materials
in all locations and susceptible cultivars were severely infected at each nursery.
The infection type and severity of susceptible check cv. Bolani was 100S in all
locations. The uniform disease development allowed successful evaluation of
the nurseries for resistance The results showed that 132 entries were resistant
to yellow rust in all locations (Tables 1, 2, 3 and 4). Only a few genotypes were
moderately resistant, moderately susceptible or susceptible.
The results of this research were sent to ICARDA for final analysis and as
input to breeding programmes of the WANA region.
References
Johnson, R. 1981. Durable disease resistance. pp. 55–63, in: J.F. Jenkyn and R.T. Plumb
(editors). Strategies for Control of Cereal Diseases. Blackwell, Oxford, UK.
McIntosh, R.A., Wellings, C.R. & Park, R.F. 1995. Wheat Rusts: An Atlas of Resistance
Genes. CSIRO Publications, Australia. 200 p.
Peterson, R.F., Campbell, A.B. & Hannah, A.E. 1948. A diagrammatic scale for
estimating rust intensity of leaves and stems on cereals. Canadian Journal of Research,
26c(5): 496–500.
Roelfs, A.P., Singh, R.P. & Saari, E.E. 1992. Rust Diseases of Wheat: Concepts and
Methods of Disease Management. CIMMYT, Mexico. 81 p.
Torabi, M., Mardoukhi, V., Nazari, K., Afshari, F., Forootan, A.R., Ramai, M.A.,
Golzar, H. & Kashani, A.S. 1995. Effectiveness of wheat yellow rust resistance
genes in different parts of Iran. Cereal Rusts and Powdery Mildews Bulletin, 23: 9–12.
Wellings, C.R. 1986. Host:Pathogen Studies of Wheat stripe rust in Australia. PhD
Thesis. University of Sydney, Australia. 237 p.
Zadoks, J.C. 1961. Yellow rust of wheat. Studies in epidemiology and physiologic
specialisation. Tijdschrift over plantezieken [Netherlands Journal of Plant Pathology],
67: 69–256.