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Crop Biotech Update

Resistance to Recombinant Stem Rust Race TPPKC in Wheat

June 3, 2011

Wheat stem rust has re-emerged as a serious threat to production since the discovery of Ug99 in 1950s. Thus, the gene (SrWld1) in wheat that confers resistance to all North American stem rust races is very important, especially in hard red spring (HRS) wheat cultivars. A sexually recombined race of stem rust with virulence to SrWld1 was discovered in 1980s. This led D. L. Klindworth, a scientist from USDA-ARS, and colleagues, to determine the genetics of resistance to the race.

The recombinant race was tested with the set of stem rust differentials and a set of wheat cultivars composed of 36 HRS and 6 durum. Through the use of aneuploid analysis, molecular markers, and allelism tests, the location of the chromosomes were identified. Differential tests labeled the race as TPPKC, which indicates that it is different from TPMKC by having virulence to genes Sr30 and SrWld1. Seven genes in wheat were found to be effective against TPPKC. Further tests indicated that five HRS and one durum cultivar were susceptible to TPPKC, all of which had SrWld1 as their major stem rust resistance gene.

The researchers concluded that TPPKC will not pose a great threat similar to TTKSK but may cause loss of some cultivars if TPPKC infests the fields.

Read the original paper at