CHARACTERIZATION OF RUSSIAN WHEAT APHID RESISTANCE IN A HARD WHITE SPRING WHEAT

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is a recently introduced insect pest that is a serious threat to wheat (Triticum aestivum L.) production. While many hexaploid wheat lines have been identified as RWA-resistant, little is known about the mechanisms of resistance of these lines. This study was conducted to characterize the plant components (i.e., tolerance, antixenosis, and antibiosis) contributing to resistance of PI 140207, a hard white spring wheat, originally collected in Iran, that has a moderate level of resistance to the RWA. In greenhouse beds, PI 140207 exhibited fewer deleterious traits than other RWA-resistant lines, and thus was selected for further study. A series of tests designed to evaluate levels of tolerance, antixenosis (nonpreference), and antibiosis were conducted in the greenhouse in the spring of 1991. PI 140207 was compared with 'Pavon', a RWA-susceptible hard white spring wheat, in all tests. Tolerance of PI 140207 to RWA feeding, as measured by chlorosis damage rating, was moderate. Antibiosis of PI 140207, as measured by (i) population growth within an RWA colony, (ii) RWA life history analysis, and (iii) physical condition and weight of 7-d-old RWA progeny, was easily detected and differed significantly from Pavon. Antixenosis may also play a small role in the complex interaction of resistance components. PI 140207 is a valuable new source of resistance for germplasm enhancement efforts.