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Infestations of Russian wheat aphid (RWA), Diruaphis noxia (Mordvilko), reduce grain yield and quality of barley, and have induced producers in some areas to cease growing barley (Hordeum vulgate L.). No RWA-resistant barley cultivars that are adapted to North America exist. Resistance from the germplasm line STARS 9301B was transferred into adapted germplasm via backcrossing. Our objective was to determine the potential utility of this resistance for the protection of yield and malting quality in adapted germplasm. We studied the effect of RWA infestations on grain yield and malting quality of STARS 9301B, the susceptible adapted parents 88Y315 and 'Garnet', and five backcross-derived progeny. Four of the backcross-derived lines were rated as highly resistant and one as moderately resistant, and were superior to STARS 9301B and similar to their recurrent parents with respect to agronomic performances and, to a lesser extent, malting qualities. When infested at the boot to heading stage, STARS 9301B, and the highly resistant progeny lines had negligible reductions in agronomic performances and malting qualities; slightly greater reductions were observed for the susceptible parents and the moderately resistant progeny line. When infested at the three-to six-leaf stage, STARS 9301B and the resistant backcross-derived lines showed relatively small reductions in their agronomic performances and malting qualities. In sharp contrast, however, the susceptible parents, and to a lesser extent the moderately resistant progeny line, showed moderate to severe leaf streaking and rolling, head trapping, and reductions in their agronomic performances and malting qualities. STARS 9301B should provide a valuable source of resistance to RWA damage., THE RUSSIAN WHEAT APHID has caused over $1 billion in losses in the western USA since it was first identified in Texas in 1986. No biotypic variation has been discovered [...]

Most biotypes of the greenbug [Schizaphis graminum (Rondani)] are extremely damaging to barley (Hordeum vulgate L.). However, greenbug biotype G has been reported to be unable to successfully feed on barley, and is described as the first greenbug avirulent to 'Wintermalt' barley (which is susceptible to all other greenbug biotypes). The objective of this study was to determine the pest status of greenbug biotype G in barley by characterizing the response of select barley cultivars and germplasm to greenbug biotype G feeding. Eight barley and four wheat (Triticum aestivum L.) cultivars and germplasm were challenged with biotype G and damage ratings recorded after 22 d of infestation. Barley is indeed a host of biotype G and genetic diversity exists within barley for reaction to attack by greenbug biotype G. Three barley cultivars were killed by biotype G, while five were resistant to feeding damage. These new sources of resistance to greenbug biotype G in barley should prove useful in the development of new greenbug-resistant barley cultivars., THE GREENBUG IS AN economically important pest of barley in the USA (Starks and Webster, 1985). A 1942 greenbug outbreak that caused an estimated $38 million yield loss in small [...]

The genetic sources for host-plant resistance to the greenbug (Schizaphis graminum Rondani) in barley (Hordeum vulgare ssp. spontaneum) are limited in that only two single dominant genes Rsg1 and Rsg2 are available for the complex of greenbug biotypes. We evaluated four new barley lines from the Wild Barley Diversity Collection (WBDC) that previously showed potential for greenbug resistance. Three of those entries, WBDC 53, WBDC 117, WBDC 336, exhibited very dominant sources of resistance to older known biotypes B, C, E, F, H, I, and TX1, which also add to the host-plant differentials used to separate these greenbug biotypes. We also re-evaluated the earlier known set of greenbug biotypes that have been in culture for several years against the known host-plant differentials, and included seven newer greenbug isolates collected from Wyoming to the full complement of small grain differentials. This resulted in the discovery of five new greenbug biotypes, WY10 MC, WY81, WY10 B, WY12 MC, and WY86. Wyoming isolates WY4 A and WY4 B were identical in their phenotypic profile, and should be combined as a single unique greenbug biotype. These barley trials resulted in finding new sources of host-plant resistance, although more research needs to be conducted on what type of resistance was found, and how it can be used. We also document that the Wheatland, Wyoming area serves as a very conducive environment for the development of new greenbug biotypes. [ABSTRACT FROM AUTHOR]