Sr9e

(McIntosh and Luig, 1973a) (Plate 3-11)

Synonyms

Srv (Smith, 1957), Srd1v (Kenaschuk et al., 1959).

Low Infection Type

1- to 2+.

Environmental Variability

Low.

Origin

T. turgidum. Sr9e occurs in Vernal emmer selected as a P. graminis tritici differential by Stakman et al. (1962). It is also present in some North American durum wheats. McVey (1990) postulated the presence of Sr9e in 174 of 578 spelt wheat accessions.

Pathogenic Variability

Virulence occurs at a high frequency in North America and at relatively low frequencies in other geographic areas (Luig, 1983; Huerta-Espino, 1992).

Reference Stocks

i: Sr9e/7*LMPG (Knott, 1990).

v: Vernstein (Luig and Watson, 1967).

tv: Vernal emmer (Smith, 1957).

Source Stocks

Australia: Sunstar Sr8a Sr12. Combination III Sr36.

South Africa: SST 3R (Sharma and Gill, 1983); SST-16 (Sharma and Gill, 1983); SST 33 (Le Roux and Rijkenberg, 1987b); SST-66 (Le Roux and Rijkenberg, 1987b).

tv: C.I.7778 (Luig and Watson, 1967). Sr9e is present in a range of North American durums (RA McIntosh, unpublished 1973). The Mexican cultivar Yavaros 79 Sr12 and various durums with additional genes were shown to carry Sr9e (Singh et al., 1992).

 

Seedling leaves of (L to R): Vernal emmer, Sunstar, Vernstein and Chinese Spring; infected with A. pt. 126-5, 6, 7, 11 [P9e] B. pt. 98-1, 2, 3, 5, 6 [P9e] and C. a mutant of pt. 98-1, 2, 3, 5, 6 virulent for Sr9e [p9e]. Tests were performed at 20°C. Note the lower sporulation with pt. 126-5, 6, 7, 11, but the similar area of necrosis/chlorosis to pt. 98-1, 2, 3, 5, 6. The lower IT ;1 associated with Sunstar in A. and B. and IT 23 in C. is attributed to Sr12.

 

Use in Agriculture

The use of Sr9e as a source of resistance in South African bread wheats was followed by an increased pathogen virulence frequency. Although virulence for Sr9e was occasionally detected in Australian surveys, no isolate from wheat-growing areas was virulent on seedlings of Sunstar. Many North American durums appear to carry Sr9e as a component of their oligogenic resistances. However, Sr9e is not effective against race 15B which has been important since the 1950s.