A High‐Density Map and PCR Markers for Russian Wheat Aphid Resistance Gene Dn7 on Chromosome 1RS/1BL

Abstract

The Russian wheat aphid (RWA) [Diuraphis noxia (Kurdjumov)] is an economically significant insect pest of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) in the USA. Since 1986, only one biotype existed in the USA. In 2003, a new biotype appeared which was virulent to all known resistance genes in wheat, with the exception of Dn7. Dn7 is a rye gene transferred into a wheat background via 1RS/1BL translocation. It was previously mapped; however, no PCR‐based markers were developed for marker‐assisted selection (MAS) and the map was sparse. This study presents a higher density map of Dn7 containing 19 markers. The markers spanning Dn7 are XHor2 and Xscb241 at distances of 1.4 and 1 cM, respectively, from Dn7 PCR markers were developed and tested on 19 wheat cultivars. Two markers which amplified rye‐specific fragments proved to be useful for MAS. Xrems1303 amplified a 320‐bp band only in cultivars with high‐level resistance to biotype 2 and is effective for MAS of Dn7. Xib267 is linked to the susceptible locus and amplified a fragment specific for rye Petkus 1RS and would be a good marker for selecting against the susceptible locus. The value of Dn7 as a source of resistance has increased because of the broad spectrum resistance it provides against several biotypes. The markers developed in this study will be useful for facilitating the transfer of Dn7 into wheat cultivars with or without translocation chromosomes containing 1RS.

Genetic mapping of resistance to Diuraphis noxia (Kurdjumov) biotype 2 in wheat (Triticum aestivum L.) accession CI2401

“…Synthetic hexaploids from CIMMYT with resistance to RWA2 have also been reported (Sotelo et al 2009). However, only two other genes with resistance to RWA2, Dn7 and Dn626580, were genetically characterized and mapped prior to this study (Anderson et al 2003;Lapitan et al 2007;Valdez et al 2012). The markers developed in our study will be useful for MAS of Dn2401 in wheat breeding programs.…”

Cytogenetic identification of wheat-Psathyrostachys huashanica amphiploid × triticale progenies for English grain aphid resistance

“…Two greenbug resistance genes, Gb2 and Gb6, and one Russian wheat aphid resistance gene Dn7 are located on 1RS, and four greenbug resistance genes Dnx (Dnr1, Dnr2, Dnr3, and Dnr4) located on 1RL, 3RS, 4R and 7R, respectively (Fritz et al, 1999; Lapitan et al, 2007;Marais et al, 1994;Nkongolo et al, 1996;Tyrka and Chelkowski, 2004). Numerous translocations, additions and synthetic triticale have been developed for transfer of these genes to wheat (Hesler, 2005;Marais et al, 1994;Nkongolo et al, 2009Nkongolo et al, , 2011, and a number of molecular maps are available (Anderson et al, 2003;Fritz et al, 1999;Lapitan et al, 2007;Tyrka and Chelkowski, 2004). However, few studies have focused on EGA in spite of its tremendous damage in wheat worldwide.…”

Genetic diversity of wheat–rye 1BL.1RS translocation lines derived from different wheat and rye sources

“…Wheat cultivar Amigo with 1AL.1RS translocation carries Pm17, stem rust and greenbug (Gb6) resistances from Insave rye (Friebe et al 1995;Hsam and Zeller 1997). A gene (Dn7) for resistance to Russian wheat aphid was transferred to the 1BL.1RS chromosome of the Veery selection Gamtoos from a line carrying a 1RS telosome from rye cultivar Turkey 77 (Marais et al 1994;Lapitan et al 2007). Significant differences among the 1BL.1RS translocation lines, originating from different and identical rye varieties, were also observed in the current experiment on reactions to stripe rust and powdery mildew.…”