ARS | Publication request: Resistance to recombinant stem rust race TPPKC in hard red spring wheat

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 26, 2011
Publication Date: August 1, 2011
Citation: Klindworth, D.L., Miller, J.D., William, N.D., Xu, S.S. 2011. Resistance to recombinant stem rust race TPPKC in hard red spring wheat. Theoretical and Applied Genetics. 123:603-613.

Interpretive Summary: Stem rust is a devastating disease of wheat. One of the most important genes for resistance to stem rust in North America is SrWld1, which originally conditioned resistance to all North American stem rust races. However, in the 1980s, James Miller found a wheat stem rust race having virulence on SrWld1. Our objective was to characterize the race and to determine the genetics of resistance to the race. To characterize the race, we tested it with a group of 20 wheats having known genes for stem rust resistance. Genes effective against the race were Sr6, Sr9a, Sr9b, Sr13, Sr24, Sr31, and Sr38. Based on this characterization, the race was coded as TPPKC. We determined the chromosomal locations of genes conditioning resistance to TPPKC in the varieties Len, Coteau, and Stoa. Those studies indicated that all three varieties carried Sr9b, Coteau and Stoa carried Sr6, and Stoa carried Sr24. TPPKC was tested against a set of 36 common wheat and 6 durum varieties. Five common wheat varieties and one durum variety were susceptible to TPPKC. Susceptible common wheat varieties were postulated to have SrWld1 as their major stem rust resistance gene. Divide, the susceptible durum variety, was postulated to lack Sr13. We concluded that although TPPKC does not constitute a threat similar to the new African races of stem rust (Ug99), some varieties would be lost from production if TPPKC could become established in the field.

Technical Abstract: The wheat (Triticum aestivum L.) stem rust (Puccinia graminis Pers.:Pers. f.sp. tritici Eriks. and Henn.) resistance gene SrWld1 conditions resistance to all North American stem rust races and is an important gene in hard red spring (HRS) wheat cultivars. A recombinant wheat stem rust race having virulence on SrWld1 was isolated in the 1980s. Our objective was to determine the genetics of resistance to the race. The recombinant race was tested with the set of stem rust differentials and with a set of 36 HRS and 6 durum cultivars. Chromosomal location studies in the cultivars Len, Coteau, and Stoa were completed using aneuploid analysis, molecular markers, and allelism tests. Stem rust differential tests coded the race as TPPKC, indicating it differed from TPMKC by having added virulence on Sr30 as well as SrWld1. Genes effective against TPPKC were Sr6, Sr9a, Sr9b, Sr13, Sr24, Sr31, and Sr38. Genetic studies of resistance to TPPKC indicated that Len, Coteau, and Stoa each carried Sr9b, that Coteau and Stoa carried Sr6, and Stoa carried Sr24. Results of the testing of HRS and durum cultivars indicated that five HRS and one durum cultivar were susceptible to TPPKC. Susceptible HRS cultivars were postulated to have SrWld1 as their major stem rust resistance gene. Divide, the susceptible durum cultivar, was postulated to lack Sr13. We concluded that although TPPKC does not constitute a threat similar to TTKSK and its variants, some cultivars would be lost from production if TPPKC could become established in the field.