Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/31/2005
Publication Date: 2/24/2006
Citation: Klindworth, D.L., Miller, J.D., Xu, S.S. 2006. Registration of rusty durum - a genetic stock that is near-universally susceptible to wheat stem rust. Crop Science 46:1012-1013. Interpretive Summary: To study the inheritance of genes that confer resistance to any plant disease, it is necessary to cross plants having resistance to the disease with plants susceptible to the disease. In the case of the wheat disease called stem rust, there are different races (or stains) of the disease. Generally, wheat plants are resistant to some races, but are susceptible to others. By finding a wheat line having susceptibility to all races, it will be easier to plan and conduct genetic studies. With the objective of finding such a wheat line within the class of wheats called durum, we examined the offspring of a mating where one of the parents was known to have only a single gene for resistance and which functions only when the plants are grown at temperatures of 21'C or higher. We first tested at temperatures that did not exceed 21'C with a race called Pgt-LBBL. This race was used because it has the characteristic that almost any gene in wheat that conditions resistance to stem rust is effective against this race. We found a selection of wheat, which we subsequently named Rusty, which has susceptibility to Pgt-LBBL at temperatures of less than 21'C. We also tested Rusty with 10 additional races of stem rust, and Rusty was found to be highly susceptible to all of these races. We have released Rusty because we think it will be useful to geneticists who are studying stem rust resistance in durum wheat.
Technical Abstract: Genetic studies of stem rust (Puccinia graminis Pers.:Pers. f.sp. tritici Eriks. & Henn.) resistance in durum wheat (Triticum turgidum L. var. durum) would be easier if a near-universally susceptible durum wheat were used in crosses to resistant durum wheats. With the objective of selecting a near-universally susceptible durum wheat, we screened the progeny of crosses having Marruecos 9623 (PI 192334) in their parentage. Marruecos 9623 is a tetraploid wheat known to carry only a single thermosensitive gene (SrM) that confers an intermediate infection type to avirulent pathotype, Pgt-LBBL at low temperature (19-21'C). The pathotype Pgt-LBBL is an important race for screening for new stem rust resistance genes since it has an avirulent reaction to most host resistance genes. We screened the progeny of 13 BC1F1 plants that had a susceptible reaction to pathotypes Pgt-JCMN and Pgt-LBBL. The BC1F2 progenies were tested for temperature-insensitive susceptibility to Pgt-LBBL under conditions where greenhouse temperatures did not exceed 20'C. A single BC1F3 plant from the cross Langdon 4D(4B)/2*Line 47-1 (Marruecos 9623 is in the parentage of Line 47-1) was selected for temperature-insensitive susceptibility to Pgt-LBBL,and the progeny of this plant were named Rusty. Rusty has also been tested and found to have a highly susceptible reaction to stem rust pathotypes Pgt-TPMK, -THTS, -TMLK, -TCMJ, -RTQQ, -MCCF, -QTHJ, -QCCJ, -HKHJ, and -JCMN. Phenotypically, Rusty closely resembles Langdon with the exception that Rusty has black chaff. Rusty will be useful to researchers studying genetics of stem rust resistance in tetraploid wheats or in crosses designed to select single gene lines from a parent containing multiple genes for stem rust resistance.