Molecular analyses in wheat and Aegilops tauschii reveals a new orthologue of the leaf rust resistance gene Lr19 on 7DL chromosome of Ae. tauschii

Abstract

Leaf rust is one of the most devastating wheat diseases worldwide, to which many resistance genes have been ‎successfully introgressed ‎from wheat wild relatives. Though the Thinopyrum ‎ponticum-derived leaf rust resistance gene Lr19, is widely effective worldwide and previous studies ‎have shown its likely presence in Aegilops tauschii, no ‎thorough investigation has been conducted to confirm this. The present study aimed to ‎examine the presence of Lr19 in Ae. tauschii using a collection of molecular and bioinformatic analysis. Accordingly, the Thatcher line was used as susceptible, and a Thatcher+Lr19 (TcLr19) and Agatha were used as resistant lines. CDHLQ pathotyping coupled with DNA markers genotyping verified the presence of an Lr19 orthologue on Ae. tauschii 7DL (AtLr19). Sequencing of the GB marker products from Ae. tauschii and TcLr19 showed 99% homology in these fragments, confirming phenotyping and genotyping results. Both isolated segments were matched to a putative melatonin biosynthesis gene, namely O-methyltransferase-2 (OMT2) mapped to 7DL, with 100% identity. A hierarchical gene network was reconstructed using all identified putative genes within a genomic region containing 2.5 cM upstream and downstream of the OMT2 gene. Results indicated that several numbers of important biotic stress-responsive genes such as RPM1, RGA2, TRIUR3, BURP12, and myosin-11, were located downstream of melatonin as a master regulator molecule through the OMT2 node. To our knowledge, this is the first report of finding an orthologue for ‎Lr19 in Ae. tauschii, which provides insights into the possible regulatory route of LR19.

Transcriptome analysis of Lr19-virulent mutants provides clues for the AvrLr19 of Puccinia triticina

“…Among them, Lr9 , Lr19 , Lr24 , Lr34 , Lr37 , Lr38 , Lr46 , Lr47 , Lr51 , Lr53 , Lr68 and Lr42 are known to confer effective resistance to leaf rust according to the field survey in Sichuan province, China ( Gao et al, 2019 ). Lr19 was derived from the grass Agropyron elongatum and was transferred to the long arm of wheat chromosome 7D ( Pourkhorshid et al, 2022 ). Although resistance of Lr19 has been overcome by some virulent Pt races in Mexico ( Huerta and Singh, 1994 ), Russia ( Lind and Gultyaeva, 2007 ), Ukraine ( Elyasi-Gomari and Panteleev, 2006 ) and India ( Bhardwaj et al, 2005 ), it still showed high resistance to all the collected Pt races in China ( Zhang et al, 2020 ).…”