Host‐induced gene silencing of an important pathogenicity factor P s CPK 1 in Puccinia striiformis f. sp. tritici enhances resistance of wheat to stripe rust

Summary Rust fungi are devastating plant pathogens and cause a large economic impact on wheat production worldwide. To overcome this rapid loss of resistance in varieties, we generated stable transgenic wheat plants expressing short interfering RNA s (si RNA s) targeting potentially vital genes of Puccinia striiformis f. sp. tritici ( Pst ). Protein kinase A ( PKA ) has been proved to play important roles in regulating the virulence of phytopathogenic fungi. Ps CPK 1 , a PKA catalytic subunit gene from Pst , is highly induced at the early infection stage of Pst . The instantaneous silencing of Ps CPK 1 by barley stripe mosaic virus ( BSMV )‐mediated host‐induced gene silencing ( HIGS ) results in a significant reduction in the length of infection hyphae and disease phenotype. These results indicate that Ps CPK 1 is an important pathogenicity factor by regulating Pst growth and development. Two transgenic lines expressing the RNA interference ( RNA i) construct in a normally susceptible wheat cultivar displayed high levels of stable and consistent resistance to Pst throughout the T 3 to T 4 generations. The presence of the interfering RNA s in transgenic wheat plants was confirmed by northern blotting, and these RNA s were found to efficiently down‐regulate Ps CPK 1 expression in wheat. This study addresses important aspects for the development of fungal‐derived resistance through the expression of silencing constructs in host plants as a powerful strategy to control cereal rust diseases.