Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

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and genera into wheat (Knott and Dvorak, 1976; Sharma and Gill, 1983) and
exploited commercially.
Germplasm of various Triticum species has been screened for resistance to
stripe rust. Resistance sources have been identified in Triticum monococcum and
T. timopheevii (Mikhova, 1988), T. dicoccoides (The, Nevo and McIntosh, 1993)
and a number of Aegilops species (Damania and Pecetti, 1990).
In this study, diversity for stripe rust resistance in T. turgidum, Ae. speltoides
and derivatives of T. turgidum × Ae. speltoides crosses were evaluated for use in
future to manage stripe rust disease of wheat.
Material and methods
A set of 21 Ae. speltoides × durum lines, 5 durum parents and 32 Ae. speltoides
accessions, including 14 parents, were planted in 15-cm diameter pots under
glasshouse conditions at CDRP Murree substation. Four- to six-week-old
plants were inoculated with urediospore suspensions of bulk inoculum
suspended in mineral oil and petroleum ether (50:50). The bulk inoculum had
virulence for genes Yr1, Yr3, YrSD, Yr5, Yr4, Yr7, Yr6+, YrCV and YrSP.
Inoculated plants were placed in open air for two hours to evaporate the oil.
Plants were then transferred to a dew chamber set at 15–18°C in a growth
room with a 16 h light and 8 h dark period for 24 h. Plants were then
transferred to a greenhouse held at 10–15°C. Three weeks after inoculation the
infection types were recorded on the plants when the susceptible check was
showing maximum infection on a 0–9 scale (McNeal et al., 1971).
Results and discussion
Among five durum parents screened, four lines, namely CROC1,
CPI/GEDIZ/GOO/JO/CRA, D67.2/P66.270 and CETA, were resistant to the
stripe rust inoculum used, while Arlin 1 was susceptible. Three of the
Ae. speltoides accessions screened were immune, nine resistant and four
moderately resistant to the inoculums of stripe rust used (Table 1).
Among crosses, accessions #1 and #3 seem to have derived resistance from
their durum parent CPI/GEDIZ/GOO/JO/CRA, and accessions #8 and #9
inherit their resistance from CROC, as Ae. speltoides lines 124, 129, 134 and 137
lack resistance against the inoculum used (Table 2). Accessions #11 and #12
have inherited their resistance from Ae. speltoides (126) as one of their parents is
susceptible durum accession D67.2/P66.270. Resistance in accessions #19 and
#20 is inherited from resistant Ae. speltoides (144) and Ae. speltoides (146)
respectively, as Arlin 1 is susceptible. The source of resistance for accession #21
is not clear as Ae. speltoides (144) was not available for screening; resistance