Sr27

(McIntosh, 1988a) (Plate 3-28)

Chromosome Location

3A (3A.3R translocation) (Acosta, 1962).

Low Infection Type

0; to 12=.

Environmental Variability

Low (Roelfs and McVey, 1979).

Origin

S. cereale cv. Imperial.

Pathogenic Variability

Virulence for Sr27 is rare. Harder et al. (1972) isolated an east African culture virulent on a Pembina line with Sr27. Luig (1983) reviewed Australian work showing that cultures of P. graminis f. sp. secalis and certain hybrids of P. graminis f. sp. tritici and P. graminis f. sp. secalis were virulent. McIntosh et al. (1983) showed that isolates of P. graminis f. sp. tritici from triticale cv. Coorong were virulent on wheat seedlings with Sr27. A greenhouse mutant with virulence on Coorong was also virulent on seedlings with Sr27. The results were accepted as evidence that the resistance gene in Coorong and many other triticale lines developed in Mexico was Sr27. Virulence on triticale cultivars with Sr27 was found in South Africa in 1988 (Smith and Le Roux, 1992).

Reference Stocks

i: Chinese Spring WRT 238.5 (Acosta, 1962). Justin, Selkirk and Pembina derivatives of WRT 238.5 (Stewart et al., 1968). Sr27/9*LMPG (Knott, 1990).

ad: Chinese Spring + Imperial 3R (2n = 44) (ER Sears, pers. comm. 1969).

Source Stocks

Widespread in triticales, for example Coorong, Towan, Dua, Tyalla, Arabian, Bura S (McIntosh et al., 1983). Some sources of Setter carry Sr27.

Seedling leaves of (L to R): CS WRT 238.5, Coorong triticale, Satu triticale and Chinese Spring; infected with A. pt. 34-2 [P27] and B. pt. 34-2, 12 [p27]. The resistant response of wheat with Sr27 is lower than that of Coorong. Both CS WRT 238.5 and Coorong are susceptible with pt. 34-2, 12 which was originally collected from Coorong. Satu triticale appears to be more resistant with pt. 34-2, 12 but this effect is due to a significantly lower intensity of infection.

 

Use in Agriculture

Wheats with Sr27 have not been released in agriculture. Pathogen samples collected from Coorong triticale in eastern Australia were shown to be virulent for Sr27 (McIntosh et al., 1983). Coorong and many other triticale lines were extremely susceptible to this pathotype. McIntosh et al. (1983) further showed that Sr27 occurred at high frequency in lines present in nurseries distributed from CIMMYT and gave warning of genetic vulnerability in triticale. Cultivar Satu was recommended in Australia as a replacement for Coorong, but a further mutant of the ‘Coorong’ pathotype quickly developed. Genetic studies indicated that a single gene in Satu was allelic with the gene (Sr27) in Coorong.