Sr11

(Knott and Anderson, 1956) (Plate 3-14)

Synonym

Kc2 (Watson and Stewart, 1956). Knott and Anderson (1956) originally asssigned symbols Sr11 and Sr12 assuming that linked complementary genes were involved. It was later shown that abnormal gametic transmission rates were responsible for disturbed genetic ratios obtained in crosses involving Chinese Spring as the susceptible parent (Luig, 1960, 1968; Sears and Loegering, 1961) and Sr11 became the accepted symbol.

Chromosome Location

6B (Plessers, 1954; Sears, 1954; Knott, 1959); 6BL (Sears, 1966). Sr11 was mapped more than 60cM from the 6B centromere and from the awn inhibitor B2 which is near the centromere (Sears, 1966). Genetically, it shows close repulsion linkage with Lr9 derived from T. umbellulatum, but ER Sears (pers. comm. 1966) obtained a rare recombinant with both genes (available as Sydney University accession C66.10). Heyne and Johnston (1954) reported linkage of 23 cM between Sr11 and Lr3, but workers at The University of Sydney failed to obtain recombination between these genes (Luig, 1964). We do not know of any wheat accession that carries Sr11 and an Lr3 resistance allele.

Low Infection Type

; to 2-. Roelfs and McVey (1979) reported infection types of 2 to 2+3- with certain cultures.

Environmental Variability

Low.

Origin

T. turgidum var. durum cv. Gaza. It is assumed that all sources of Sr11 derive from Bobin W39*2/Gaza material originally produced in Australia, but subsequently widely distributed. Watson and Stewart (1956) concluded that Timstein was derived from this material rather than a T. timopheevii cross.

Pathogenic Variability

Variability occurs in all geographic areas. Virulence frequencies are extremely high in Australia (Zwer et al., 1992), South Africa (Le Roux and Rijkenberg, 1987a), Canada (Harder and Dunsmore, 1990) and the USA (Roelfs et al., 1991), but relatively low on the Indian subcontinent and Europe (Luig, 1983). These results were supported by Huerta-Espino (1992) who also reported low to moderate frequencies of virulence in certain regions of South America and North Africa and no virulence in China.

Reference Stocks

i: ISr11-Ra C.I.14171 (Loegering and Harmon, 1969); Lee/10*Marquis (Knott, 1965).

s: Chinese Spring*7/Kenya Farmer 6B (Loegering and Sears, 1966); Chinese Spring*9/Timstein 6B (Sears et al., 1957).

v: Charter W1371 (Luig and Watson, 1965); Gabo W1422 C.I.12795; Timstein C.I.12347 (Knott and Anderson, 1956; Sears et al., 1957); Yalta W1373 (Luig and Watson, 1965). Lee Sr9g Sr16 C.I.12488 (Knott and Anderson, 1956).

Source Stocks

Sr11 is present in a large number of Australian and Kenyan wheats (see McIntosh, 1988a) and CIMMYT cultivars (Roelfs and McVey, 1979).

China: Qing-Chung 5 Sr5 Sr6.

Europe: Flevina.

India: N.P.790 Sr5.

 

Seedling leaves of (L to R): Gabo, Lee, CS*7/Kenya Farmer 6B and Chinese Spring; infected with A. pt. 116-4, 5 [P11] and B. pt. 116-2, 3, 7 [p11]. Lower infection types (; to ;1-) may be obtained with some cultures.

 

Use in Agriculture

When first exploited in Australia in the mid 1940s Sr11 was widely effective but its widespread use was followed by increased virulence frequencies. This increase was so spectacular that the pathogen population became genetically fixed for the corresponding pathogen gene for virulence. The consequence is that Sr11 can be detected only with avirulent cultures held in the laboratory and its presence or absence is no longer of relevence to Australian wheat breeders. Charter has been used in India to differentiate pathotypes virulent for Sr11; that is, Charter carries a second gene which cannot be detected using Australian isolates (see Luig, 1983).