• Novel Chromosome Engineering Materials Provide Resistance to Ug99 for Wheat Breeders

    TIME: 14 Jun 2022
    Dr. HAN Fangpu's group from the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences reports the establishment of new wheat-rye addition lines that conferred resistance to Ug99 in an article published online in Theoretical and Applied Genetics (DOI:10.1007/s00122-022-04127-7).
    Ug99, a new strain of Puccinia graminis f. sp. Tritici (Pgt), is virulent to several wheat cultivars worldwide and a significant threat to global food security. Consequently, it is of great significance and urgency to mine new resistance gene sources and transfer them into wheat. Rye (Secale cereal L., 2n=2x=14, RR), a close relative of wheat, is resistant to leaf rust, stripe rust, stem rust and powdery mildew. Rye has become a valuable resource of several broad-spectrum disease resistance genes for improvements in wheat genetics.
    In this study, the researchers developed two completely new sets wheat-rye disomic addition lines by molecular cytogenetic methos. Subsequently, a new set of telosomic addition lines were obtained from the progenies of wheat-rye monosomic addition lines. The researchers discovered that the wheat-rye 3RL telosomic addition line carried a novel resistance gene to Ug99 through assessments of disease resistance, cytological analysis, and molecular markers. Therefore, the new Ug99 resistance gene can be used for wheat breeding in the future.
    In addition, various chromosomal and centromeric variations are induced by wheat-rye distant hybridization. This process resulted in ring chromosomes, minichromosomes, dicentric chromosomes, and tricentric chromosomes from the progenies of wheat-rye hybrids. These materials are valuable genetic resources that could be applied towards the exploration of the centromere structure, activation/inactivation, and functions. These resources will provide important genetic diversity towards future wheat-rye hybrid offsprings, and may lead to discovery of other Ug99 resistance gene to be introduced into wheat in the future.
    This work was supported by the National Science Foundation of China and the Ministry of Science and Technology of China.
    The karyotype of wheat-rye addition lines and assessment of resistance to Ug99 (Image by IGDB). (a) Wheat-rye1R-7R addition lines; (b) wheat-rye 1RS-7RL telosomic addition lines; (c) phenotype of leaves inoculated with wheat stem rust race Ug99; 1-2: rye PI 613196 and PI 428373, 3-4: octoploid triticales 843-61 and 843-42, 5: wheat-rye 3R addition line, 6: wheat-rye 3RL addition line, 7: wheat-rye 3RS addition line, 8: wheat line 843, 9: Federation*4/Kavkaz, 10: line 37.
    Dr. HAN Fangpu
    Institute of Genetics and Developmental Biology, Chinese Academy of Sciences