Sr24

(McIntosh et al., 1976) (Plate 3-25)

Chromosome Location

3D (McIntosh et al., 1976; Smith et al., 1968; Sears, 1973); 3DL (Hart et al., 1976); 3Ag (Sears, 1977). Two other translocation lines produced by Sears involve chromosome 3BL (Sears, 1977). A further translocation is present in cultivar Amigo (see Lr24). Sr24 is completely associated with Lr24 (McIntosh et al., 1976).

Low Infection Type

l- to 22+.

Environmental Variability

Low (Roelfs and McVey, 1979).

Origin

Th. ponticum.

Pathogenic Variability

Virulence for Sr24 has been reported in South Africa (Le Roux and Rijkenberg, 1987b) and India (Bhardwaj et al., 1990). Sydney University culture 57096 [pt. 34-(4), 7] produces IT 3 on seedlings with Sr24. This Australian culture is assumed to have arisen from somatic hybridisation between P. graminis f. sp. tritici and P. graminis f. sp. secalis (Luig, 1983). Huerta-Espino (1992) did not find virulence for Sr24 among a wide range of international collections.

Reference Stocks

i: Sr24/9*LMPG (Knott, 1990); various 3D/Ag translocation lines produced by Sears (1972b, 1973, 1977) can be considered near-isogenic to Chinese Spring.

s: Chinese Spring 3Ag(3D) (Sears, 1973).

v: Agent (McIntosh et al., 1976).

Source Stocks

Australia: Janz Sr5; Torres Sr5 (Brennan et al., 1983); Vasco Sr5. Sunco Sr5 Sr6 Sr8a Sr36. Sunbird Sr5 Sr8a. Sunelg Sr26.

North America: Abilene; Amigo (The et al., 1992); Arapahoe; Arkan; Blueboy II (McIntosh et al., 1976); Centura; Century; Cimmaron; Cloud; Cody; Coker 9733; Collin; Fox; Mesa; Norkan; Parker 76; Payne; Rio Blanco; TAM200; Terral 101; Thunderbird; Timpaw; Trailblazer; Twain; Wanken. Karl Sr2 Sr9d. Siouxland Sr5 Sr31 (Schmidt et al., 1985). Butte 86 Sr6 (Modawi et al., 1985). Colt Sr6 Sr8a Sr9a Sr17. Osage Sr17; Sage Sr17 (Livers, 1978). Jasper Sr31; Longhorn Sr31.

South Africa: Gamka; Karee; Kinko; Palmiet; SST25; SST44 = T4R; SST102; Wilge (Le Roux and Rijkenberg, 1987b); SST23 (Sharma and Gill, 1983).

Use in Agriculture

Derivatives of Agent were widely used in the USA and South Africa as a source of leaf rust resistance. P. graminis pathotypes with virulence for Sr24 were found in South Africa in 1984 (Le Roux, 1985) and in India in 1989 (Bhardwaj et al., 1990). All backcross derivatives with Lr24/Sr24 from Agent added to white-seeded Australian wheats were found to be red seeded (RA McIntosh, unpublished 1973). Several of Sears’s 3D/Ag translocation stocks were then used, and of these, transfers #3 and #14 gave white-seeded derivatives. These lines were used to develop Australian cultivars, the first of which, Torres, was released in 1983. Australian lines were subsequently used in Indian backcrossing programs but virulence for Sr24 was detected before cultivars could be commercialised.

The et al. (1992) found that Amigo carried Sr24/Lr24. Amigo carries an independent translocation with stem rust resistance from rye and, although the chromosome location of Sr24 in this red-seeded stock was unknown, white-seeded derivatives were easily selected in Australian backcrossing programs.