CHARACTERISATION OF RESISTANCE TO LEAF RUST IN AN INTERNATIONAL BREAD WHEAT NURSERY

Abstract

Greenhouse seedling rust tests of the 35th International Bread Wheat Screening Nursery (IBWSN), distributed by the International Wheat and Maize Improvement Centre in 2002, demonstrated that 290 (58%) of the 500 entries likely carried the 1RS.1BL translocation, and therefore the rust resistance genes Lr26, Yr9 and Sr31. A selection of 109 lines identified as carrying this translocation was postulated to carry the major seedling resistance genes Lr3a, Lr13, Lr16, Lr19, Lr23, Lr24 and Lr27+Lr31 in addition to Lr26. The leaf rust seedling genes Lr13, Lr16 and Lr27+Lr31, were the most common seedling resistance genes in a selection of 100 lines lacking the 1RS.1BL translocation. While no new sources of seedling resistance to leaf rust were found in this study, and virulence is known for all of the seedling genes identified, 46 lines were identified that dispayed moderately high to very high levels of adult plant resistence (APR) to leaf rust in the field over 2 years that could be very useful in developing new wheat cultivars with resistance to Puccinia triticina. Of these, 24 were shown to carry Lr34, and based on pedigree analysis, it is expected that the APR gene Lr46 is also present in at least some lines. Genetic studies are needed to characterize the APR in these lines to assess their full value as sources of new leaf rust resistance.