EFFECT OF RUSSIAN WHEAT APHID ON WHEAT ROOT AND SHOOT DEVELOPMENT IN RESISTANT AND SUSCEPTIBLE GENOTYPES

Genetic resistance is an Important management component in the control of Russian wheat aphid (Diuraphis noxia Mordvilko) (RWA). The range o f leaf symptoms associated with several resistance sources indicate th at differences may occur in seedling development. This study was condu cted to determine differences in wheat (Triticum aestivum L.) seedling shoot and root development among resistant and susceptible wheat geno types infested with RWA. The effectiveness of one resistance source id entified in greenhouse seedlings was characterized in field-grown F-2 plants. Visual damage and leaf and root development were measured for 17 lines in the greenhouse. Dry weight, grain yield, and harvest index were studied in infested and noninfested, field-grown F-2 populations generated from 'Moro'/PI294994 and 'Hyak'/PI294994. PI48650 and PI294 994 had superior seedling shoot and nodal root system development when compared to susceptible genotypes. Visual evaluations were effective in separating susceptible genotypes from potential resistance sources; however, leaf symptoms were not effective in characterizing the most promising RWA resistance resources. Root measurements in conjunction w ith leaf symptoms identified seedling genotypes least affected by RWA. Russian wheat aphid resistant adult-plants produced significantly mor e dry weight and grain yield and a greater harvest index than suscepti ble plants in the two populations. Trends for these characteristics we re similar for resistant plants in the infested population and plants in the noninfested population.