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Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

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260<br />

ACI values for AUDPC were used to characterize a large number <strong>of</strong><br />

cultivars and elite l<strong>in</strong>es under artificial <strong>in</strong>oculation <strong>in</strong> screen<strong>in</strong>g for yellow,<br />

stem and leaf rusts. Selected l<strong>in</strong>es will be fur<strong>the</strong>r tested under natural <strong>in</strong>fection<br />

challenge at hot-spots for yellow rust (Azerbaijan, Ethiopia, Lebanon, Iran,<br />

Tajikistan and Yemen), leaf rust (Ethiopia, Lebanon, Kazakhstan and Morocco)<br />

and stem rust (Egypt, Ethiopia, Kenya, Morocco and Tunisia).<br />

Among 200 bread wheats tested, three accessions showed complete<br />

resistance and 28 showed adequate adult plant resistance to <strong>the</strong> three rusts.<br />

About 71 accessions showed comb<strong>in</strong>ed resistance to two rusts (Figure 5). Over<br />

70 accessions show<strong>in</strong>g resistance to a s<strong>in</strong>gle rust disease (Table 2) or<br />

comb<strong>in</strong>ations <strong>of</strong> <strong>the</strong> rusts will be fur<strong>the</strong>r evaluated for resistance to stem rust at<br />

hot-spots <strong>in</strong> East Africa.<br />

Table 2. Distribution <strong>of</strong> 200 wheat l<strong>in</strong>es accord<strong>in</strong>g to <strong>the</strong>ir levels <strong>of</strong> reaction to rust<br />

diseases under artificial <strong>in</strong>oculation at Tel Hadya, Aleppo<br />

Resistance level<br />

Complete resistances<br />

(R-type)<br />

3<br />

<strong>Rust</strong>s<br />

YR-<br />

LR<br />

YR-<br />

SR<br />

LR-<br />

SR<br />

YR SR LR<br />

3 0 14 9 33 18 0<br />

Adult plant resistance 28 7 40 5 20 1 1<br />

Susceptible<br />

to 3 rusts<br />

Total number <strong>of</strong> l<strong>in</strong>es 31 7 54 14 53 19 1 21<br />

NOTES: <strong>Rust</strong> diseases: YR = yellow rust; LR = leaf rust; SR = stem rust. Adult plant resistance is measured<br />

as discussed for known resistance genes<br />

Frequency distribution <strong>of</strong> resistance levels for three wheat<br />

rusts <strong>in</strong> 200 Triticum aestivum breed<strong>in</strong>g l<strong>in</strong>es<br />

30<br />

Res APR TOT<br />

Frequency distribution (%)<br />

25<br />

20<br />

15<br />

10<br />

5<br />

0<br />

3<strong>Rust</strong>s YR-LR YR-SR LR-SR YR SR LR SUSC<br />

<strong>Rust</strong> diseases<br />

Figure 5. Frequency distribution <strong>of</strong> resistance levels among a collection <strong>of</strong> bread<br />

wheat breed<strong>in</strong>g l<strong>in</strong>es and varieties

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