Wheat Ym2 originated from Aegilops sharonensis and confers resistance to soil-borne Wheat yellow mosaic virus infection to the roots

Abstract

Wheat yellow mosaic virus (WYMV) is a pathogen transmitted into its host’s roots by the soil-borne vector Polymyxa graminis . Ym1 and Ym2 genes protect the host from the significant yield losses caused by the virus, but the mechanistic basis of these resistance genes remains poorly understood. Here, it has been shown that Ym1 and Ym2 act within the root either by hindering the initial movement of WYMV from the vector into the root and/or by suppressing viral multiplication. A mechanical inoculation experiment on the leaf revealed that the presence of Ym1 reduced viral infection incidence, rather than viral titer, while that of Ym2 was ineffective in the leaf. To understand the basis of the root specificity of the Ym2 product, the gene was isolated from bread wheat using a positional cloning approach. The candidate gene encodes a CC-NBS-LRR protein and it correlated allelic variation with respect to its sequence with the host’s disease response. Ym2 (B37500) and its paralog (B35800) are found in the near-relatives, respectively, Aegilops sharonensi s and Aegilops speltoides (a close relative of the donor of bread wheat’s B genome), while both sequences, in a concatenated state, are present in several accessions of the latter species . Structural diversity in Ym2 has been generated via translocation and recombination between the two genes and enhanced by the formation of a chimeric gene resulting from an intralocus recombination event. The analysis has revealed how the Ym2 region has evolved during the polyploidization events leading to the creation of cultivated wheat.

A papain-like cysteine protease-released small signal peptide confers wheat resistance to wheat yellow mosaic virus

“…Among these genes, YmYF (527.4–629.6 Mb), YmIb (582.5–728.6 Mb), Q.Ymym (582.5–629.6 Mb) and Qym1 (577.4–629.6 Mb) are located on chromosome 2DL and appear to be at the same locus based on the physical position of the linked markers 10 , indicating that this locus on chromosome 2D is important for wheat resistance to WYMV infection. Recently, a resistance gene Ym2 was isolated using positive cloning approach, which acts within the root either by hindering the initial movement of WYMV from the vector into the root and/or by suppressing viral multiplication 11 . However, the genetic and molecular mechanisms underlying wheat resistance to WYMV remain poorly understood.…”

Identification of Barley yellow mosaic virus Isolates Breaking rym3 Resistance in Japan

“…Photos of the field plant were taken using a Canon X7 camera (Canon, Tokyo, Japan). The BaYMV-induced mosaic symptom was observed using an Axio Zoom V16 microscope (Zeiss, Oberkochen, Germany) [ 40 ].…”

Back to the future for drought tolerance

“…Once a drought‐tolerant accession is identified, the subsequent challenge involves determining the most efficient methods to integrate the tolerance mechanism from the selected accession to the elite cultivar. The employment of wild relatives in modern breeding has been most successful in transferring traits controlled by one or a few major genes through backcrossing methods, such as disease resistance (Mammadov et al ., 2018; Mishina et al ., 2023). However, drought tolerance mechanisms are likely to be controlled by hundreds of genes.…”