The Wild Emmer Wheat Gene PmG16, Conferring Resistance to Powdery Mildew, is an Orthologue of Pm60 from Triticum Urartu

Abstract

Wild emmer wheat (WEW), the tetraploid progenitor of durum and bread wheat, is a valuable genetic resource for resistance to powdery mildew fungal disease caused by Blumeria graminis f. sp. tritici (Bgt). PmG16 gene, derived from WEW, confers high resistance to most tested Bgt isolates. We mapped PmG16 to a 1.4 cM interval between the flanking markers uhw386 and uhw390 on Chromosome 7AL. Based on gene annotation of WEW reference genome Zavitan_V1, 34 predicted genes were identified within the ~3.48 Mb target region. Six genes were annotated as associated with disease resistance, of which TRIDC7AG077150.1 was found to be highly similar to Pm60, previously cloned from Triticum urartu and residing in the same syntenic region. A functional molecular marker (FMM) for Pm60 (M-Pm60-S1) co-segregated with PmG16, suggesting that WEW PmG16 is probably an orthologue of Pm60 from Triticum urartu (designated here as TdPm60). Sequence alignment identified only eight SNPs that differentiate between TdPm60 and TuPm60. Furthermore, our results suggest that other WEW powdery mildew resistance genes MlIW172 and MlIW72, that also mapped to the same region of Chromosome 7AL, might be identical or allelic to TdPm60. Screening of 230 WEW accessions with Pm60 specific markers, 58 resistant accessions were identified from Southern Levant harboring the TdPm60 allele, while all the susceptible accessions showed no PCR amplifications. Deployment of TdPm60 is clearly more advantageous over TuPm60 since it can be rapidly introgressed by classical breeding approaches into bread wheat genetic background.