Rym11, a Critical Susceptibility Factor Whose Modification Confers Immunity to the Bymovirus Disease

Barley yellow mosaic virus (BaYMV) disease is a serious threat of winter barley production. Transmission of the virus occurs via the soil-borne plasmodiophorid Polymyxa graminis which prohibits plant protection by help of chemical treatment. Therefore, resistance breeding is the way to prevent yield losses. rym4/rym5 conferred by mutant alleles of the gene HvEIF4E has been the predominant source for resistance breeding so far, however, new isolates overcoming the resistance locus have been continually reported. Thus, there is a need for the use of novel resistance sources in barley breeding. The resistance gene rym11 located on 4HL (Nissan-Azzouz et al., 2005) confers immunity to all strains of BaMMV and BaYMV. After high-resolution mapping (Lüpken et al., submitted) the resistance gene rym11 was delimited to a 1.36 Mbp interval of the physical map containing 4 putative genes. A large deletion in one of these genes of the resistant parent pointed at the possibility that rym11 was conferred by loss-of-function of this. Natural and induced diversity for the gene was surveyed by re-sequencing or TILLING of the gene. F1 crosses of new resistance conferring variants and the originally identified partially deleted gene proved allelism between the variants confirming the identification of the gene rym11.