Leaf rust of wheat (Triticum aestivum L.) caused by Puccinia recondita Roberge ex Desmaz. f. sp. tritici (Prt) has been controlled through incorporation of genetic resistance into host genotypes. Somaclonal variation may provide additional sources of resistance genes. This study was conducted to determine the gene source and inheritance of improved resistance to leaf rust found in somaclones of ‘Coker 916’. Two wheat somaclones, regenerated from immature embryo-derived calli of Coker 916, had increased field resistance to leaf rust and were screened with 36 Prt isolates to identify Lr genes. Screening results indicate Coker 916 contains Lr3, 10, and possibly Lrl4a, 15, 20, and either 27 or 31. The pedigree of Coker 916 includes known sources of Lrl, 3, 10, 11, 14a, and 27 seedling-resistance genes. The two somaclones, LTC 122 and LTC 140, contain Lr3, Lr10, and additional resistance genes not found in Coker 916, possibly Lr genes 1, 3ka, 9, 14a, 15, 18, 20, 23, 27, 30, 31, 32, and/or 33. Four Rl-derived R2 LTC 122 lines reacted identically to leaf rust isolates; thus the altered resistance may have been monogenic in the R0 plant. Crosses were made between Coker 916 and the somaclones. The F2 progeny of LTC 122 × Coker 916 contained both Lr3 and LR10 and segregated for two additional independent, dominant resistance genes in a 15 (low disease reaction): 1 (high disease reaction) ratio. Somaclonal variants should be useful sources of additional resistance to foliar pathogens.
Approved for publication by the Director of the Louisiana Agric. Exp. Stn. as Manuscript no. 91-09-5183.