Evaluation and Reselection of Wheat Resistance to Russian Wheat Aphid Biotype 2

Abstract

Russian wheat aphid (RWA, Diuraphis noxia, Mordvilko) biotype 2 (RWA2) is virulent to most known RWA resistance genes and severely threatens wheat (Triticum aestivum L.) production in the hard winter wheat area of the U.S. western Great Plains. We determined RWA2 reactions of 386 cultivars from China, 227 advanced breeding lines and recently released cultivars from the United States, 505 landraces from countries where RWA is endemic, and 31 genetic stocks developed in the United States, Australia, Canada, and Russia. The majority of wheat accessions from China and the United States were highly susceptible to RWA2. Only nine landrace accessions produced a homogeneous resistant reaction. In addition, highly resistant plants were identified in 28 heterogeneous landraces. Thus, reselection was conducted to purify some potential resistance sources, and the single‐plant progenies of 220 selected plants were evaluated. Homogeneous resistant or highly resistant lines were identified from seven previously heterogeneous landraces. Reselection line PI 626759‐20‐32 offered a high level of resistance similar to lines carrying Dn7, the rye (Secale cereale L.)‐derived resistance gene associated with undesirable bread‐making quality. PI 626759‐20‐32 has the potential to supplement or replace Dn7 as a new RWA2 resistance source in wheat breeding.

Dn10, a New Gene Conferring Resistance to Russian Wheat Aphid Biotype 2 in Iranian Wheat Landrace PI 682675

“…RWA2 is virulent to Dn1 through Dn6 plus Dn8 , Dn9 , and Dny , whereas Dn7 , Dn2401 , Dn626580 , and Dn10 confer resistance to RWA2. As mentioned above, linkage drag associated with Dn7 makes it less attractive for use in wheat breeding (Xu et al, 2015). On the contrary, Dn2401 , Dn626580 , and Dn10 can be preferentially used to improve resistance to RWA2.…”

“…Wheat accessions resistant to RWA1 and RWA2 have been identified (Collins et al, 2005; Xu et al, 2015), but most of them have not been characterized. Genetic analysis of these RWA resistance sources will greatly facilitate their utilization in wheat breeding.…”

“…The susceptible check, ‘Yuma’, was grown in two cells, and a resistant check, ‘Yumar’ with Dn7 , in one cell in each tray. Aphids were increased on barley (Xu et al, 2015), and tested seedlings were infested 7 d after planting by placing heavily infested barley leaves close to each row of test plants. Test plants were evaluated at 3 wk after infestation using a 1‐to 6 scale representing highly resistant, resistant, moderately resistant, moderately susceptible, susceptible, and highly susceptible responses, respectively (Xu et al, 2015).…”

“…PI 682675 (formerly PI 624151-1-2) is a single-plant selection from Iranian wheat landrace PI 624151 (Xu et al, 2015). A total of 224 F 2 plants derived from cross PI 682675 ´ Zhengyou 6 were used in this study.…”

“…More recently, Xu et al (2015) screened 1149 wheat accessions for resistance to RWA2, and PI 682675 (formerly PI 624151‐1‐2), a selection from an Iranian landrace, exhibited high resistance. Phenotypic discrepancy between PI 682675 and another three RWA2 resistance sources—Yumar (with Dn7 ), CI 2401, and PI 626580—was observed (Puterka, unpublished data, 2017), suggesting that PI 682675 may carry a new RWA2 resistance gene.…”