EVALUATION OF LEAF RUST RESISTANCE FROM WHEAT CHROMOSOMAL TRANSLOCATION LINES

The genetic pool of effective sources of rust resistance used in wheat (Triticum aestivum L.) breeding includes related species. As part of a search for new sources of resistance, a group of radiation-induced r ust-resistant wheat Agropyron intermedium [(Host) P.B.] derivatives or iginally developed by A. Wienhues were investigated. Resistance to lea f rust [Puccinia recondita Roberge ex Desmaz. f. sp. tritici (Eriks. & E. Henn) D.M. Henderson) was transferred to the spring wheat cultivar Thatcher. The inheritance of leaf-rust resistance was studied in F3 l ines developed from the fifth backcross to Thatcher. A number of backc ross lines with different types of resistance were selected and evalua ted for rust reaction in greenhouse and field tests. RL6097 had gene L r38 present in wheat A. intermedium T6DS.6DL-7Ai#2L chromosome translo cation (where a 4.19-mum segment of the long arm of A. intermedium chr omosome 7Ai#2 replaced a 1.45-mum segment of the long arm of wheat chr omosome 6D) derived from translocation line T7 as identified by C-band ing. The male transmission rate of this translocation was reduced. Alt hough this line was highly resistant to leaf rust, its grain yield was low. None of the other backcross lines had A. intermedium chromatin. RL6093 had an unidentified gene for leaf rust resistance from addition line T2. Two genes, Lr3bg (RL6094) and Lr16 (RL6096), were obtained f rom T6. Adult-plant resistance to leaf rust was also transferred from several of the translocation lines. This resistance may be different f rom that previously reported, and may have originated from the translo cation lines' donor parent 'Heine IV'. Of the genes found, Lr38 may no t be useful in wheat breeding because of the reduced yield of RL6097; however, the gene for seedling resistance in RL6093 and the adult-plan t resistance in RL6095 should be useful.