8th INTERNATIONAL WHEAT CONFERENCE

effeCTIVe yeLLoW RuST ReSISTANCe geNeS IN WheAT
uNdeR moRoCCAN CoNdITIoNS
1 A Ramdani, 2 A Yahyaoui, 2 K Nazari, 3 S M Udupa
1 INRA – CRRA Meknès, Morocco, P.O.Box 578
2 ICARDA, Aleppo, Syria, P.O.Box 5466
3 ICARDA, Rabat Instituts, Rabat, Morocco, P.O.Box 6299
E-mail Address of presenting author: ramhamid@hotmail.com
In order to monitor yellow (stripe) rust (Puccinia striiformis) virulence changes in time
and space and to assess the effectiveness of yellow (stripe) rust resistance genes, a set
of wheat Triticum aestivum) differential cultivars comprising Avocet near isogenic lines
and varieties/lines having known resistance genes was grown under field conditions and
tested for rust resistance at five contrasting locations (Meknès, Douyet, Annoceur, Allal
Tazi and Marchouch) during four cropping seasons (from 2005-06 to 2008-09). Planting
date was towards the end of November in plots of two 0.5 m rows 30 cm apart. Yellow
rust disease was scored during grain filling using modified Cobb scale coupled with reaction
types to determine the coefficients of infection (CI). During the four years and at
all locations, the CI for yellow rust on susceptible lines/cultivars exceeded 80% except at
Annoceur and Meknes in 2007-08 where the CI did not exceed 60 and 30 respectively. In
2007-08 cropping season, yellow rust was almost absent at Allal Tazi except some pustules
on some lines and at Marchouch the most susceptible lines exhibited a CI of 15.
The coefficients of infection for yellow rust ranged from 0 to 100, 0 to 30, 0 to 90 and 0
to 100 at Meknes during 2008-09, 07-08, 06-07 and 05-06 cropping seasons respectively.
During 2007-08, the maximum value of CI at Douyet, Annoceur, Meknes, Marchouch
and Allal Tazi was 80, 60, 30, 15 and 0.5 respectively. Lines possessing Yr1, Yr5, Yr15 and
YrSP exhibited complete immunity towards yellow rust across years and locations. Line
possessing Yr10 was immune except in 2005-06 where the CI was 5 and reached 60 at
Marchouch and Douyet respectively. Line possessing Yr17 was also immune except at
Meknes in 2005-06 and 2008-09, at Annoceur in 2008-09 and at Marchouch in 2005-06
where the CI was 50, 10, 20 and 0.5 respectively. Line carrying Yr 27 exhibited a high variation
with regard to its reaction to yellow rust. Its CI ranged from 0 at Meknes in 2006-07
to 100 in 2008-09
Keywords: Wheat, yellow rust, Yr gene, Morocco
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