Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

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Table 5. Nile Valley and Red Sea Cereal Rust Trap Nursery (NVRS-CRTN): yellow
rust differentials and commercial cultivars
Ref. No Cultivar Yr-Gene Ref. No Commercial Cultivar
89 Avocet S 104 Triticale
90 Avocet R YrA 105 Cham 4
91 Yr1/ 6* Avocet S Yr1 106 Cham 6
92 Yr5/ 6* Avocet S Yr5 107 Ghurab 2
93 Yr6/ 6* Avocet S Yr6 108 Bohouth 6
94 Yr7/ 6* Avocet S Yr7 109 Memof 22
95 Yr8/ 6* Avocet S Yr8 110 Seri 82
96 Yr9/ 6* Avocet S Yr9 111 Gereck 79
97 Yr10/ 6* Avocet S Yr10 112 Bezostaya
98 Yr15/ 6* Avocet S Yr15 113 Yuna
99 Yr17/ 6* Avocet S Yr17 114 Mirbashir 128
100 Yr18/ 3* Avocet S Yr18 115 Gobustan
101 YrSK /3* Avocet S Yr27 116 Azametli 95
102 YrSP / 6* Avocet S YrSP 117 Local cultivar
103 Morocco Check 118–129 12 Local cultivars
130 Local cultivar
Results and discussion
Disease surveys provide useful information on the prevalence, incidence and
severity of diseases on a crop over space and time (Yahyaoui et al., 2004a;
Wellings et al., 2000). The information generated from the surveys was used to
describe the level of resistance found in the cultivars or landraces. The disease
surveys conducted over the past 5 years revealed that the primary diseases of
wheat were yellow, leaf and stem rusts, tan spot and Septoria leaf blotch.
Other less prevalent diseases on this crop were common bunt, scab and
powdery mildew. The average incidence of these diseases varied according to
the zone surveyed. A rapidly evolving disease on both durum and bread
wheat is tan spot disease (Pyrenophora tritici-repentis). Table 6 summarizes the
disease distributions and their relative importance in CWANA countries
surveyed. This paper reports on pathotype diversity and distribution as
revealed by the use of the rust trap nurseries, with emphasis on yellow rust
(Puccinia striiformis f.sp. tritici) since yellow rust continues to be the most
widespread disease in CWANA.
Widely cultivated bread wheat varieties are succumbing to this devastating
disease, particularly in Central Asia and the Caucasus. Known yellow rust
resistance genes (McIntosh, Wellings and Park, 1995) are becoming ineffective
against new evolving races that are rapidly spreading across the region.