Diversity and similarity of wheat powdery mildew resistance among three allelic functional genes at the Pm60 locus

• Published in: The Plant journal : for cell and molecular biology 2022-06, Vol.110 (6), p.1781-1790
• Main Authors: Zou, Shenghao, Shi, Wenqi, Ji, Jiahao, Wang, Huanming, Tang, Yansheng, Yu, Dazhao, Tang, Dingzhong
• Format: Article
• Language: English
• Subjects: Airborne microorganisms; Alleles; Blumeria graminis f. sp. tritici; Cloning; Cultivation; Disease resistance; Gene silencing; Genes; Genetic transformation; Grain cultivation; High resistance; Insertion; Leucine; Plant breeding; Pm60a; Pm60b; Powdery mildew; Similarity; Triticum aestivum; Triticum urartu; Viruses; Wheat
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/tpj.15771

SUMMARY Cultivated wheat is continually exposed to various pathogens. Blumeria graminis f. sp. tritici (Bgt) causes powdery mildew disease and significant yield loss. Pm60 was cloned from Triticum urartu and confers race‐specific powdery mildew resistance in wheat. Pm60a and Pm60b are allelic variants of Pm60 and have two leucine‐rich repeat motifs deletions and insertions, respectively, which were detected in other T. urartu accessions. Through map‐based cloning, virus‐induced gene silencing, and stable transformation assays, we demonstrated that Pm60a and Pm60b conferred Bgt E09 resistance resembling that provided by Pm60. However, the homozygous Pm60a (but not Pm60 or Pm60b) transformants driven by the native promoters lacked race‐specific resistance when they were inoculated with Bgt E18. As all three T. urartu accessions contained the three foregoing alleles, they had high resistance to Bgt E18. Pyramiding Pm60a with either of the allelic genes in F1 plants did not cause mutual allele suppression or interference with Bgt E18 resistance. Deletion (but not insertion) of the two leucine‐rich repeat motifs in Pm60a substantially narrowed the resistance spectrum. In T. urartu accession PI428210, we identified another locus adjacent to Pm60a and resistant to Bgt E18. Characterization of the alleles at the Pm60 locus revealed their diversity and similarity and may facilitate wheat breeding for resistance to powdery mildew disease caused by B. graminis f. sp. tritici. Significance Statement In the present study, we identified Pm60a and Pm60b, which are allelic variants at the Pm60 locus. The three foregoing alleles confer resistance to Bgt E09, which causes powdery mildew disease in wheat. Bgt E18 resistance was only absent in Pm60a transgenic plants as this allele has two leucine‐rich repeat (LRR) motif deletions. Pyramiding Pm60a with Pm60 or Pm60b did not hinder Bgt E18 resistance in wheat. Assays involving 54 Bgt isolates confirmed that deletion of the two LRR motifs in Pm60a markedly narrows the Bgt resistance spectrum. In contrast, the insertion of additional LRR motifs in Pm60b did not enhance Bgt resistance. The foregoing findings demonstrated diversity and similarity among alleles at the Pm60 locus and may support wheat breeding for powdery mildew disease resistance.