Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

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Material and methods
Wheat nurseries comprising isogenic lines along with conventional stripe rust
differentials were planted under field conditions in the stripe rust zones of
Pakistan, together with leading cultivars. Each line was planted in a single row
1 m long with rows spaced at 30 cm. The entire nursery was surrounded by
susceptible cv. Local White as spreader, and cv. Morocco was included as a
susceptible check. Stripe Rust was allowed to develop under natural
conditions. Disease severity and reaction on each entry was recorded using the
scale of McNeal et al. (1971).
Results and discussion
Data of the average disease response from locations at the Agricultural
University of Peshawar (AUP), the Nuclear Institute of Food and Agriculture
(NIFA), Peshawar, the Cereal Crop Research Institute (CCRI), Pirsabak, and
the National Agricultural Research Centre (NARC), Islamabad, represent the
virulence spectrum of the area for the cropping seasons 1998/99, 1999/2000
and 2002/03, while data from Sialkot represented virulence patterns of the
northern Punjab for 1999/00. Data for 2000/01 and 2001/02 were not available
due to the prevalence of dry conditions unfavourable for pathogen
development. The patterns of infection on the differential hosts, near-isogenic
lines and commercial cultivars carrying postulated genes of resistance against
P. striiformis was found to be similar during the period of study.
Cvs Kalyansona (Yr2), Lee (Yr7), Seri (Yr9) and Federation (Yr9+) showed
moderately susceptible to susceptible reactions at different locations in NWFP
(AUP, NIFA Peshawar and CCRI Pirsabak). Rust development for these genes
at locations in NWFP seems to be more than in Islamabad. Kalyansona (Yr2),
which was 0 at NARC during the 1998/99 cropping season showed MR-MS
type of reaction in 1999/00 and 90S reaction in 2002/03, indicating progressive
development of virulence against Yr2 at NARC. Line WL 711, carrying Yr2,
was susceptible at NARC in 1998/99 and 1999/00, and at CCRI Pirsabak in
1999/00. Similarly, Mexipak was susceptible during 1999/00 and 2002/03.
Vilmorin (Yr3), which showed MR-MS reaction at NIFA Peshawar in 1998/99
was susceptible here in 1999/00. Kirmani et al. (1989) reported absence of
virulence against this gene. Susceptible reaction for YrA in 2002/03 could be
anticipated at NARC as virulence for this gene prevailed in CCRI Pirsabak in
1998/99 and in NIFA Peshawar in 1999/00. Virulence for this gene was
reported from the stripe rust zones of NWFP and Punjab in the past (Kirmani
et al., 1989). Cv. Heines Kolben (Yr6) showed MS-S reaction at NARC in
1998/99 and susceptible reaction at CCRI Pirsabak and Sialkot in 1999/00.
Virulence for these genes was also reported in the past by Kirmani et al. (1989).
Yr6 is one of the most frequent genes in our commercial wheat cultivars, either