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Pathotype Tracker

Status Summary: Ug99 Lineage – May 2010

Ug99 is unique as it is the only known race of P. graminis f. sp. tritici with virulence to the stem rust resistance gene Sr31. It also possesses virulence to virtually all the resistance genes of wheat origin, plus others of alien origin. The pathogen is changing rapidly and seven known variants have been identified within the Ug99 lineage of wheat stem rust. All are considered to be single step mutations. Acquired virulence to additional important Sr genes, notably Sr24 and Sr36, is known from Kenya (Sr24, Sr36), Ethiopia (Sr24), South Africa (Sr24) and Tanzania (Sr24, Sr36). Race TTKST, carrying combined Sr31 + Sr24 virulence, caused epidemics in Kenya in 2007.

Ug99 Lineage: Proposed Evolutionary Summary

Summary Table – Ug99 lineage

Race a

 

Common Alias

Key Virulence (+) or Avirulence (-) *

Year of Identification

Confirmed Countries (year)

TTKSK

 

Ug99

+Sr31

1999

Uganda (1998/9), Kenya (2001), Ethiopia (2003), Sudan (2006), Yemen (2006), Iran (2007), Tanzania (2009)

TTKSF

 

 

-Sr31

2000

South Africa (2000), Zimbabwe (2009)

TTKST

 

Ug99 + Sr24

+Sr31, +Sr24

2006

Kenya (2006), Tanzania (2009)

TTTSK

 

Ug99 + Sr36

+Sr31, +Sr36

2007

Kenya (2007), Tanzania (2009)

TTKSP

 

 

-Sr31, +Sr24

2007

South Africa (2007)

PTKSK

 

 

+Sr31, -Sr21

2007

[Uganda (1998/9)?], Kenya (2009), Ethiopía (2007)

PTKST

 

 

+Sr31, +Sr24, -Sr21

2008

Ethiopia (2007), Kenya (2008), South Africa (2009)

 a Some uncertainty exists over the reaction of the Sr21 gene (this influences the initial code letter being “T” (+Sr21) or “P” (-Sr21). Current table presents most plausible races

* Only key Sr genes are indicated, not the complete virulence/avirulence profile

Overview
Summary status (April 2011) of known pathotypes in the Ug99 lineage. (Click for larger view)