J. B. Rudolph

Biotypic diversity in Colorado Russian wheat aphid (Hemiptera: Aphididae) populations.

Abstract The biotypic diversity of the Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Hemiptera: Aphididae), was assessed in five isolates collected in Colorado. Three isolates, RWA 1, RWA 2, and an isolate from Montezuma County, CO, designated RWA 6, were originally collected from cultivated wheat, Triticum aestivum L., and obtained from established colonies at Colorado State University. The fourth isolate, designated RWA 7, was collected from Canada wildrye, Elymus canadensis L., in Baca County, CO. The fifth isolate, designated RWA 8, was collected from crested wheatgrass, Agropyron cristatum (L.) Gaertn., in Montezuma County, CO. The four isolates were characterized in a standard seedling assay, by using 24 plant differentials, 22 wheat lines and two barley, Hordeum vulgare L., lines. RWA 1 was the least virulent of the isolates, killing only the four susceptible entries. RWA 8 also killed only the four susceptible entries, but it expressed intermediate virulence on seven wheat lines. RWA 6, killing nine entries, and RWA 7, killing 11 entries, both expressed an intermediate level of virulence overall, but differed in their level of virulence to ‘CO03797′ (Dn1), ‘Yumar’ (Dn4), and ‘CO960293-2′. RWA 2 was the most virulent isolate, killing 14 entries, including Dn4- and Dny-containing wheat. Four wheat lines, ‘94M370′ (Dn7), ‘STARS 02RWA2414-11′, CO03797, and ‘CI2401′, were resistant to the five isolates. The results of this screening confirm the presence of five unique Russian wheat aphid biotypes in Colorado.

Above winter wheat

Above, a hard red winter wheat (Triticum aestivum L. em. Thell.), is adapted for dryland production in the west central Great Plains of the United States. It carries a nontransgenic source of tolerance to imidazolinone herbicides derived by mutation induction with sodium azide. Above was developed cooperatively by the Colorado and Texas Agricultural Experiment Stations and released to seed producers in September 2001. Key words: Triticum aestivum, wheat (winter), cultivar description, herbicide tolerance

Plant Responses to Seven Russian Wheat Aphid (Hemiptera: Aphididae) Biotypes Found in the United States

ABSTRACT The Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Hemiptera: Aphididae), is a serious wheat, Triticum aestivum L., and barley, Hordeum vulgare L., pest throughout the small grain-producing areas in the western United States. The virulency and classification of recently described Russian wheat aphid biotypes 1–7 (RWA1-7) were clarified using 24 plant differentials. These seven biotypes had been described previously using various methods and test environments; therefore, the purpose of this study was to test them all under uniform environmental conditions. RWA1 was the least virulent of the biotypes tested, with susceptible ratings observed in five plant differentials and intermediate ratings observed in four plant differentials. RWA4, RWA5, RWA6, and RWA7 had intermediate virulence. RWA4, RWA5, and RWA7 share similar responses, with susceptible responses in six plant differentials and intermediate responses in five plant differentials. Small differences within a few plant differentials separate RWA4, RWA5, and RWA7. RWA6 has susceptible responses with only four plant differentials, but 10 plant differentials had intermediate responses. RWA3 was highly virulent, with susceptible responses in 10 plant differentials and intermediate responses in five plant differentials. RWA2 was the most virulent strain tested with susceptible responses to 12 plant differentials and intermediate responses to five plant differentials. This study has demonstrated that RWA1-7 have different combinations of virulence to the plant differentials tested, thereby confirming previous Russian wheat aphid biotype designations.

AP502 CL winter wheat

AP502 CL, a hard red winter wheat (Triticum aestivum L. em. Thell.), is adapted for dryland production in the west central Great Plains of the United States. It carries a n ontransgenic source of tolerance to imidazolinone herbicides derived by mutation induction with sodium azide. AP502 CL was developed cooperatively by the Colorado and Texas Agricultural Experiment Stations and released to seed producers in September 2001. Key words: Triticum aestivum, wheat (winter), cultivar description, herbicide tolerance.