Sr9g

(McIntosh and Luig, 1973*) (Plate 3-12)

Low Infection Type

2= to 3.

Environmental Variability

Low.

Origin

T. turgidum var. durum, including the Stakman et al. (1962) differentials Acme and Kubanka. Sr9g was transferred from durum cv. Iumillo to Marquillo and Thatcher from which it was introduced into other common wheats.

Pathogenic Variability

Virulence is common. Apart from southern Africa and Australia, avirulence for Sr9g is uncommon (Luig, 1983; Huerta-Espino, 1992).

Reference Stocks

s: Chinese Spring*7/Marquis 2B Sr16 (McIntosh et al., 1981); Chinese Spring*4/Thatcher 2B Sr16 (McIntosh et al., 1981). The ‘Marquis’ accession used by Sheen and Snyder (1964) was probably Thatcher or a closely related line.

v: Thatcher Sr5 Sr12 Sr16 (McIntosh et al., 1981).

tv: Acme (McIntosh et al., 1981); Kubanka (McIntosh et al., 1981). Both Acme and Kubanka have resistance genes additional to Sr9g.

Source Stocks

Australia: Hartog Sr2 Sr8a Sr30. Corella Sr5 (heterogeneous) Sr8a Sr12. Celebration Sr12 Sr16. Eagle Sr26 (Luig, 1983).

Europe: Hochzücht Sr5 Sr12.

North America: Lee Sr11 Sr16. Many Thatcher derivatives carry Sr9g (McIntosh et al., 1981).

tv: Iumillo which possesses additional genes including, presumably, Sr12 (McIntosh et al., 1981).

 

Seedling leaves of (L to R): Acme durum, Kubanka durum, Celebration, Lee, CS/Marquis 2B and Chinese Spring; infected with A. pt. 222-1, 2, 3, 5, 6 [P9g], B. pt. 34-1, 2, 3, 4, 5, 6, 7 [p9g] and C. pt. 126-5, 6, 7, 11 [p9g] and incubated at 21°C. The first five wheats carry Sr9g which is usually slightly more effective in durums. Each of these wheats express a different gene, or interactions, when infected with pt. 126-5, 6, 7, 11. Note how Acme (IT 3CN) and Kubanka (IT 11+) are distinguished with the last culture. Also with the third culture, Celebration shows evidence of interaction of Sr12 and Sr9g, Lee possesses Sr11 and the slightly retarded growth on CS/Marquis 2B relative to Chinese Spring is probably caused by Sr16.

 

Use in Agriculture

Sr9g is one of the genes transferred to Marquillo, and subsequently Thatcher, from the durum cv. Iumillo. Although not commonly effective in North America, avirulence for Sr9g is relatively frequent in Australia, southern Africa and India. Because resistance to avirulent cultures is effective, Sr9g is a useful resistance gene in these areas when used in combinations to ensure protection against a wide range of pathotypes. Because Sr9g is closely linked with Yr7 its presence in some instances may have resulted from selection for resistance to stripe rust.