Sr18

(Baker et al., 1970) (Plate 3-21)

Synonyms

SrG2 (Luig and Watson, 1965); Srrl1 (Rondon et al., 1966); Srmq1 (Berg et al., 1963); SrPs1 and SrMn1 (Sanghi and Baker, 1972); R1 (Loegering and Powers, 1962).

Chromosome Location

1D (Sears et al., 1957; Baker et al., 1970; Anderson et al., 1971); 1DL (Williams and Maan, 1973).

Low Infection Type

; to ;2=.

Environmental Variability

Low.

Origin

Sr18 is present in a very high proportion of common wheat lines (Baker et al., 1970).

Pathogenic Variability

Avirulence in P. graminis f. sp. tritici is rare (Roelfs and McVey, 1979; Luig, 1983). However, avirulence for this gene is widespread in collections of P. graminis f. sp. secalis and in hybrids between P. g. tritici and P. g. secalis (Luig and Watson, 1972).

Reference Stocks

i: I Hope 1D-Ra (Loegering and Harmon, 1969); Sr18/8*LMPG (Knott, 1990); Mq-A and R1-A (Anderson et al., 1971).

s: Chinese Spring*6/Hope 1D (Sears et al., 1957).

v: Mona (Sanghi and Baker, 1972); Pusa (Sanghi and Baker, 1972). Hope Sr2 Sr7b Sr9d Sr17 (Luig, 1983). Reliance Sr5 Sr16 Sr20 (Anderson et al., 1971). Marquis Sr7b Sr19 Sr20 (Anderson et al., 1971). Gabo Sr11 (Luig and Watson, 1965).

Source Stocks

This gene is very difficult to identify with certainty because pathogen isolates avirulent for Sr18 usually possess additional genes for avirulence which render them unable to attack most wheat cultivars. Nevertheless, workers at The University of Sydney demonstrated its presence in most wheats (Baker et al., 1970). Indeed McIntosh (1988a) considered it more convenient to list wheats not possessing Sr18. These included Chinese Spring (Loegering and Harmon, 1969); Eureka (Baker et al., 1970); Federation (Baker et al., 1970); Little Club (Loegering and Harmon, 1969); Morocco (Baker et al., 1970); Prelude (Loegering and Harmon, 1969) and Yalta (Baker et al., 1970) as well as W2691 and Line E, both of which were especially bred at The University of Sydney for susceptibility to pathogen cultures with unusual genes for avirulence, including P18. The presence of p18 in P. graminis f. sp. tritici would be essential because Sr18 occurs in most common wheats. In contrast, P18 is unnecessary in P. graminis f. sp. secalis due to the absence of Sr18 in cereal rye. In this way genes such as Sr18 play a role in host specialisation.

 

Seedling leaves of (L to R): IHope 1D-Ra, W2691 /Purple Straw Selection, and tine AD = W2691*5/Kota; infected with University of Missouri culture 111 x 36.#97. The first two wheats show the reaction typical of plants with Sr18 whereas the high resistance of the third plant is conferred by Sr28.

 

Use in Agriculture

None.