Resistance Evaluation of G, CG, or M Series Apple Rootstocks to Soil-borne Diseases (Phytophthora Root Rot, White Root Rot, and Southern Blight) and Woolly Apple Aphid

In this study, the resistance of the industry-standard M26 and M9 rootstocks and the promising eliteG or CG rootstocks was evaluated not only for soil-borne diseases, such as Phytophthora root rot(Phytophthora cactorum), white root rot (Rosellinia necatrix), and southern blight (Athelia rolfsii),but also for woolly apple aphid [Eriosoma lanigerum (Huasm.)]. On February 27, 2019, each unworkedrootstock plant was harvested from stool-beds, then planted in 2-L pots and grown in a greenhouse. For P. cactorum, M9 was the most resistant, and CG5087 and G935 were not. There was littledifference in susceptibility to R. necatrix among rootstocks, but G or CG rootstocks were generallyless susceptible than the M series. The susceptibility to A. rolfsii was higher (p < 0.05) in M seriesrootstocks than in G or CG series rootstocks, and the mortality reached 80% and 53% for M9 andM26, respectively, and 7% for G935. As a result, M9 and G11 showed resistance to P. cactorum,whereas G or CG rootstocks showed relative resistance to R. necatrix and A. rolfsii. For woollyapple aphid, G11, G202, G214, and CG5087 were immune, but G935, CG4814, M26, and M9 werenot. KCI Citation Count: 0