(McIntosh, 1988a) (Plate 3-20)
sr17 (McIntosh et al., 1967). Because this gene is recessive, it was originally designated with a lower case letter. However, adoption of the Rules of Genetic Nomenclature for Wheat (McIntosh, 1988a) required that all genes involved in disease response should be designated with upper case letters irrespective of dominance. This decision was taken in order to provide for less ambiguity in verbal communication of genetic information.
7B (Law and Wolfe, 1966); 7BL (McIntosh et al., 1967). Sr17 is genetically linked with Pm5 and Lr14a (see McIntosh, 1988a).
Low Infection Type
;, X, X+.
Temperature-sensitive (Roelfs and McVey, 1979). Sr17 is more effective at low temperatures, becoming ineffective above 25°C.
Assumed to be T. turgidum var. dicoccum cv. Yaroslav emmer used in the development of Hope and H-44 by McFadden (1930). Sr17 has not been detected in a tetraploid wheat by formal genetic studies. Indeed an accession of Yaroslav that possesses the relevant genes of Hope wheat, that is, Sr2, Sr17, Lr14a and Pm5, is not available.
P. graminis populations in North America and Australia are polymorphic (Roelfs and McVey, 1979; Luig, 1983). Huerta-Espino (1992) found low frequencies of avirulence in North Africa and Spain, Kenya and the Malagasy Republic, Turkey and South America.
s: Chinese Spring*6/Hope 7B (McIntosh et al., 1967).
v: Hope Sr2 Sr7b Sr9d (McIntosh et al., 1967; Knott, 1971); H-44 Sr2 Sr7b Sr9d (McIntosh et al., 1967; Knott, 1971). Spica Sr7b (McIntosh et al., 1967).
Sr17 is present in many USA and Mexican wheats (Roelfs and McVey, 1979), particularly those with Lr14a and Pm5 as all three genes are linked. European workers (Heun and Fischbeck, 1987a, 1987b; Hovmøller, 1989; Lutz et al., 1992) reported that the gene Mli for resistance to powdery mildew is identical to Pm5. It would be of interest to determine if wheats reported to possess Mli also carried Sr17 or Lr14a.
Africa: Giza 144 Sr11.
Australia: Glenwari; Hofed. Gala Sr2. Warigo Sr2 Sr7b. Lawrence Sr2 Sr7b Sr9d. Mendos Sr7a Sr11 Sr36. Hopps Sr9d
Canada: Selkirk Sr2 Sr6 Sr7b Sr9d Sr23.
CIMMYT: Nadadores Sr11.
Europe: Sava Sr5. Adam Sr5 Sr8a. Dunav-1 Sr9b.
New Zealand: Aotea.
USA: Auburn; Brule; Gage; Larned; Riley 67; Scoutland; Winalta. Scout Sr2. Newthatch Sr2 Sr5 Sr7b Sr12. Redman Sr2 Sr7b Sr9d; Renown Sr2 Sr7b Sr9d. Lancer Sr2 Sr9d. Era Sr5 Sr6 Sr8a. Centurk Sr5 Sr6 Sr8a Sr9a. Homestead Sr6. Colt Sr6 Sr8a Sr9a Sr24. Lancota Sr9b Sr10. Osage Sr24.
Use in Agriculture
From the time of their release in the 1920s, Hope and H-44 have displayed durable resistance to stem rust. A vast literature on these resistances indicates involvement of genes conferring both seedling and adult plant resistances. At various times, and using a limited range of pathogenic variability, researchers have obtained different results when determining the resistance genotype [see Hare and McIntosh (1979) for review]. Sr17 is a significant component of this resistance and can be found in a wide range of Australian, Mexican, USA, Canadian and Indian cultivars. However, the durability of resistance in Hope and H-44 and their derivatives is associated with Sr2.