Abstract
Powdery mildew is one of the most destructive diseases in the world, causing substantial grain yield losses and quality reduction in cereal crops. At present 23 powdery mildew resistance genes have been identified in rye, of which the majority are in wheat-rye translocation lines developed for wheat improvement. Here, we investigated the genetics underlying powdery mildew resistance in the Gülzow-type elite hybrid rye (Secale cereale L.) breeding germplasm. In total, 180 inbred breeding lines were genotyped using the state-of-the-art 600 K SNP array and phenotyped for infection type against three distinct field populations of B. graminis f. sp. secalis from Northern Germany (2013 and 2018) and Denmark (2020). We observed a moderate level of powdery mildew resistance in the non-restorer germplasm population, and by performing a genome-wide association study using 261,406 informative SNP markers, we identified a powdery mildew resistance locus, provisionally denoted PmNOS1, on the distal tip of chromosome arm 7RL. Using recent advances in rye genomic resources, we investigated whether nucleotide-binding leucine-rich repeat genes residing in the identified 17 Mbp block associated with PmNOS1 on recent reference genomes resembled known Pm genes.
Highlights
Powdery mildew (PM) is one of the most devasting diseases g lobally[4]
Our objective was to I) characterize PM resistance in the assayed germplasm, II) identify PM resistanceassociated single nucleotide polymorphism (SNP) markers to be implemented by marker-assisted selection for breeding novel resistant hybrid rye cultivars, III) investigate whether nucleotide-binding leucine-rich repeat (NLR) genes residing in PM resistance-associated blocks on the ‘Lo7’ and ‘Weining’ reference genomes resemble known Pm genes, and IV) develop a marker map for the 600 K highdensity SNP array and validate its performance in the assayed germplasm
To investigate the genetics underlying powdery mildew (PM) resistance, the assayed hybrid rye breeding germplasm was genotyped on the rye 600 K SNP array
Summary
Powdery mildew (PM) is one of the most devasting diseases g lobally[4]. In cereals, the causative agent of PM is the ascomycete fungus Blumeria graminis (DC.) speer (Bg), which is capable of inflicting severe grain yield loss (≥ 20%) and quality reduction in c ereals[5,6,7,8]. Evidence suggests that local use of host resistance and fungicides are the primary factors influencing the European B. graminis f. These findings underline the seriousness of long-distance dispersal of B. graminis spores, which allows novel and aggressive pathotypes to evolve through the recombination of distinct pathotypes and rapidly s pread[18]. 23 major PM resistance (R) genes have been identified in rye (Table 1). The majority of characterized Pm genes encode intracellular nucleotide-binding leucine-rich repeat (NLR) proteins that recognize pathogen effector molecules, leading to an effector-triggered immunity resistance response[43,44,45]. 770 canonical NLR genes have been identified in the ‘Lo7’ reference genome[50]. Several of the top-yielding hybrid rye cultivars examined in official Danish trials are susceptible to PM disease (Supplementary Table S1)[53]
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