Submitted to: Journal of Agricultural and Urban Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 25, 1996
Publication Date: N/A
Interpretive Summary: The Russian wheat aphid is one of the most serious pests of barley in North America. It was first detected in the United States in 1986 and since then has inflicted serious losses to the barley industry. The ideal way of managing small-grain pests is through the use of resistant varieties. Recently, scientists released a selection from PI 366450 (STARS-9301B) as Russian wheat aphid-resistant germplasm. Previous studies reported on the mechanisms of resistance of first-leaf seedlings of PI 366450, but information on later plant growth stages was not available. This information is of value to barley breeders in plant resistance programs and to pest management specialists who study aphid population dynamics. Antixenosis (preference/nonpreference) tests and antibiosis (effects of the resistant plant on the biology of the aphid) tests were conducted in the laboratory on older plants of the resistant PI (Plant Introduction) and 'Morex,' a Russian wheat aphid-susceptible cultivar. The most important finding was that aphid reactions on older plants were similar to those found earlier on first-leaf plants. Antixenosis does not seem to be an important resistance mechanism, but antibiosis continues to contribute to resistance in older barley plants and could help in reducing aphid populations in the field. Earlier tests showed that tolerance to the Russian wheat aphid appears to be the most important mechanism of resistance in first-leaf plants of PI 366450. This may also be true in older plants, but tests have not yet been devised to confirm this.
Technical Abstract: The Russian wheat aphid, Diuraphis noxia (Mordvilko), is a serious pest of barley in western North America. Because plant resistance is the ideal way of managing this new pest, researchers have recently released a selection from PI 366450 (STARS-9301B) as Russian wheat aphid-resistant germplasm. Information about the antixenosis and antibiosis mechanisms of resistance of PI 366450 in the 1st-leaf stage was previously reported, but informatio about these mechanisms of resistance in later plant growth stages has not been available. These data are desirable for barley breeders in plant resistance programs and for pest management researchers studying aphid population dynamics. This study reports on antixenosis and antibiosis tests conducted in the laboratory and growth chamber on three plant growth stages of PI 366450 and 'Morex,' a Russian wheat aphid-susceptible cultivar. In general, aphid reactions in the later plant growth stages were similar to those on 1st-leaf plants. Antixenosis does not appear to be an important resistance mechanism, while antibiosis continues to contribute to resistance in more mature plants. Previous work showed that tolerance is the most important resistance mechanism of PI 366450 seedlings. Tolerance data for older plants is not available because a practical uniform test to determine tolerance levels at these plant growth stages has not been developed.