Inheritance and mapping of stem rust resistance of wheat line, PI 410966

Benjamin W Campbell, Purdue University

Abstract

Stem rust (Puccinia graminis f. sp tritici, abbreviated Pgt) of wheat (Triticum aestivum L.) is one of the most destructive cereal diseases globally. Concern about the disease has increased since 1999 with the discovery in Uganda, Africa of a new virulence genotype of Pgt, known as Ug99 (also TTKS). This new genotype is capable of attacking a majority of current wheat cultivars worldwide. The spring wheat line PI 410966, was identified as resistant to race Ug99 in international stem rust nurseries carried out by the USDA-ARS in 2005 and 2006. The objectives of this experiment were to characterize the resistance and to determine the chromosomal location of the stem rust resistance gene(s) in PI 410966. Two mapping populations were developed from a cross between PI 410966 and two susceptible wheat lines: LMPG-6 and OK3040. Since PI 410966 serves as the only source of resistance for these two populations, the phenotypic data from both populations can be combined and analyzed as one large population. Tests for resistance were carried out on the F2:3 families: one test with inoculations of P. graminis race 15B at Purdue University and one test with Ug99 at the USDA-ARS Cereal Disease Laboratory (CDL) at St. Paul, MN. F2:3 segregation ratios of 1:2:1 (resistant:segregating:susceptible) in both F2:3 tests indicated that resistance of PI 410966 to each Pgt race is conditioned by one gene. The CDL conducted a second inoculation test with Ug99 in the F6:7 generation, and at Purdue University a second inoculation test against race 15B was conducted in the F8:9 generation. A total of 264 wheat simple sequence repeat markers were used in the mapping process. CDL F6:7 data was used to genetically map the resistance gene effective against Ug99 to the centromeric region on 2BS. The location of the gene and marker data suggest that the Ug99 resistance gene in PI 410966 could be a new gene, an allele of either Sr36 or Sr40, or either Sr36 or Sr40. The pedigree of PI 410966, from the Germplasm Resource Information Network (GRIN), does not identify a source of Sr36 or Sr40. Phenotypic and genotypic data suggest that two stem rust resistance genes are present in PI 410966, each gene acting specifically against Pgt race 15B or Ug99.

Degree

M.S.

Advisors

Ohm, Purdue University.

Subject Area

Agronomy|Genetics|Plant Pathology

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