BGS 731, Required for Puccinia graminis resistance 2, rpr2

ɣ08-118; R43-22#1 (4).

Monofactorial recessive (2, 3, 4).
Location in chromosome 6H (3); mapped to a 0.6 cM interval in 6H between markers Locus_6H_331 and GMS006 (2, 3).

The rpr2.b mutant induced a moderate susceptible reaction to Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. E. Henn (Pgt) race MCCF in the cultivar, Morex, which has the Rpg1.a gene (see BGS 511) for resistance to P. graminis (wheat stem rust). The rpr2.b mutant has been partially characterized (2, 3) with an infection type (IT) range of 2.1; to 3; with amode 3.2 (rated by 1), or IT of 3-2 to 3 (rated by 2, 3), or IT of 2.3- to 3.3- (rated by 6). The rpr2.b mutant is not allelic to rpr1.a, rpr3.c, rpr4.d; rpr5.e, or rpr6.f (2, 3). Barley often exhibits mesothetic reactions with two or more ITs on a single leaf; therefore, ITs observed are recorded in order of their prevalence (5). Overall the rpr2.b mutant stock is moderately susceptible as opposed to the parent line Morex, which is typically rated as moderately resistant. (4, 5). The RPG1 protein is present in the rpr2.b line and apparently functional as indicated by the observations that the RPG1 protein was phosphorylated within 15 min of inoculation with Pgt race MCCF urediniospores and degraded within 24 hrs of infection as expected for a functional RPG1 protein (2, 3, 4).
[Infection type (IT) for wheat stem rust (Puccinia graminis f. sp. tritici) seedling reaction is based on a 0-4 scale, defined by Stackman et al. (5), where 0 is highly resistant and 4 is highly susceptible with the in between numbers representing intermediate reactions which are further modified by + or – and a fleck symbol = ;), which indicates a small necrotic area. IT1 indicates minute uredinia; IT2 small uredinia with chlorosis; IT3 medium uredinia often with chlorosis; and IT4 indicates large uredinia with chlorosis (5)].

A gamma-ray induced mutant in Morex (CIho 15773) (3, 4).

rpr2.b (ɣ08-118; R43-22#1, GSHO 3693) in Morex (CIho 15773) (3, 4).

rpr2.b (ɣ08-118; R43-22#1, GSHO 3693) in Morex; rpr2.b in F2 seed lots GSHO 3694 and GSHO 3695 (4).

1. Brueggeman, R.S. (Unpublished).

2. Gill, U.S. 2012. Understanding and characterizing the genes associated with Rpg1 mediated resistance pathway against stem rust. Ph.D. Thesis. Washington State University, Pullman.

3. Gill, U., R. Brueggeman, J. Nirmala, Y. Chai, B. Steffenson, and A. Kleinhofs. 2016. Molecular and genetic characterization of barley mutants and genetic mapping of mutant rpr2 required for Rpg1-mediated resistance against stem rust. Theor. Appl. Genet. 129 (8):1519-1529.

4. Kleinhofs, A. (Unpublished).

5. Stakman, E.C., D.M. Steward, and W.Q. Loegering. 1962. Identification of physiologic races of Puccinia graminis var. tritici. U.S. Dep. Agric. ARS E-617.

6. Steffenson, B.J. (Unpublished).

A. Kleinhofs. 2015. Barley Genet. Newsl. 45:243.

A. Kleinhofs. 2016. Barley Genet. Newsl. 46:139-140.