Plant resistance components of two greenbug (Homoptera : Aphididae) resistant wheats

Several biotypes of the greenbug, Schizaphis graminum (Rondani), attack win ter wheat, Triticum aestivum L., on the Southern Plains every year. Two whe at germplasm sources of resistance ('Largo' and 'GRS 1201') have teen devel oped that provide protection against the three predominant greenbug biotype s (E, I, and K). Each source has agronomic and end-use quality advantages a nd disadvantages for the breeder to consider in choosing a greenbug-resista nt breeding line. We compared these two germplasms to determine their level s of resistance against biotype E. Components of resistance (i.e., antibios is, antixenosis, and tolerance) were measured oil seedlings of GRS 1201, La rge, and 'TAM W-101' (a susceptible control). Several aphid and plant measu rements (e.g., total number of aphids produced per plant, aphid selection p references, and plant damage ratings) were recorded for each plant entry.. Select data recorded for each resistance component were normalized and comb ined to derive a plant resistance index for each wheat entry. Results indic ated that GRS 1201 had a higher level of combined resistance components tha n did Largo, followed by TAM W-101, the susceptible control. These data pro vide additional information for the breeder to consider in selecting a gree nbug-resistant breeding line.