Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

Disease severity (percentage of rust infection on the plant) and plant
response (infection type) were recorded following McIntosh, Wellings and
Park (1995). Five infection types are described, as follows:
0 – immune (no uredia or other symptoms of disease infection);
R – resistant (uredia minute, supported by distinct necrotic areas);
MR – moderately resistant (uredia small to medium, in green islands
surrounded by chlorotic or necrotic tissue);
MS – moderately susceptible (uredia medium in size, no necrosis but
chlorotic areas may be present); and
S – susceptible (uredia large, no necrosis, but chlorosis may be evident).
Cultivar Morocco and local cultivar Steklovidnaya 24 were used as
susceptible checks for multiplication of the pathogen in the greenhouse and as
the spreaders in the field tests. Inocula used in field tests were a mixture of
identified isolates maintained on susceptible varieties. Thus the wheat
genotypes were screened against stripe rust races predominant in the region.
Genetic analysis based on the reaction data of F 1 and F 2 plants and F 3
families to infection was used for identifying the genes for resistance. The
selected wheat cultivars have been crossed with susceptible cultivars to
determine the number of resistance genes, and other test cultivars to determine
allelism of genes and their identity. The seedlings and adult plants of the
parents and F 1 and F 2 progeny have been tested for resistance to the population
of races prevailing in Kazakhstan.
The aim of our research is to study inheritance of yellow rust resistance in
commercial varieties and advanced winter wheat lines grown in the region.
The field tests have shown that in south and south-east Kazakhstan
cv. Almaly demonstrated the highest resistance to yellow rust (0-R). In the high
to moderate resistance (R-MR) category were cvs Adir, Naz, Yuzhnaya 12,
Arap, Sultan and advanced lines from ICARDA and CIMMYT – BWKLDN-95,
BWKLDN-9 and MK-3744 (Table 1).
The data from testing international differentials and isogenic lines has
shown that Yr2+(Heines VII), Yr4+(Hybrid 46), Yr10/6*Avocet S,
Yr15/6*Avocet S, Yr18/6*Avocet S, Yr24/6*Avocet S and Yr26/6*Avocet S are
effective in our region (Kokhmetova et al., 2003). Therefore we suggest that
resistant genotypes present the abovementioned effective genes. Virulence for
genes Yr1, Yr6, Yr7, Yr9, Yr11 and Yr12 occurred in Kazakhstan.
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