Comparison of Diuraphis noxia resistance in wheat isolines and plant introduction lines

The Russian wheat aphid, Diuraphis noxia (Mordvilko), is one of the most im portant aphid pests of wheat, Triticum aestivum L., worldwide. Among the va rious pest management options, plant resistance is an economical management tactic to control D. noxia in cereal crops such as wheat. Researchers have identified D. noxia resistant germplasm and it has been incorporated into wheat. This study compared D. noxia resistance between the 'Betta' wheat is olines Betta-Dn1, Betta-Dn2, and Betta-Dn5 and their corresponding donor ge ne plant introduction (PI) lines PI 137739 (Dn1), PI 262660 (Dn2), and PI 2 94994 (Dn5). Although the Betta isolines and PI lines showed D. noxia resis tance when compared with Betta wheat, the degree of resistance in the isoli nes to D. noxia was different from their corresponding PI donors. Aphid num ber, aphid fecundity, and biomass per aphid were not different between Bett a-Dn1 and PI 137739 or Betta-Dn2 and PI 262660; however, the same parameter s were significantly lower on PI 294994 compared with Betta-Dn5. This indic ated that aphid resistance in PI 137739 and PI 262660 was probably governed by a single dominant gene, while the resistance in PI 294994 was controlle d by more than one gene. Additionally, plant biomass reduction was aphid de nsity dependent, which suggested that use of appropriate aphid infestation level is important when using plant biomass reduction as an indicator of re sistance. Plant resistance categorization showed that there was no detectab le difference in antixenosis among the seven lines evaluated. However, the higher aphid fecundity observed on PI 262660 compared with PI 137739 and PI 294994, in addition to no significant differences among the three PIs in p lant biomass reduction, suggested PI 262660 was a tolerant line, while PI 1 37739 and PI 294994 were antibiotic lines. Plant tolerance could not be elu cidated among the three Betta isolines using aphid fecundity and plant biom ass reduction as indicators.