Resistance of potato clones to the green peach aphid and potato leafroll virus

During 1980 and 1981 potato cultivars and breeding selections, including cultivated species and their hybrid derivatives, were evaluated for resistance to the green peach aphid (GPA),Myzus persicae (Sulzer), and to potato leafroll virus (PLRV). Criteria used were the number of aphids which colonized the clones in free choice field experiments and the number of plants derived from these experiments which showed symptoms of PLRV infection. Generally, greater resistance to GPA was found inSolarium tuberosum gp.andigena selections and hybrids than in gp.tuberosum cultivars. There were approximately fourfold differences in season-mean GPA levels among the clones tested each year. Forty-two families, representing a cross-section of the USDA breeding populations at the University of Idaho Research and Extension Center, Aberdeen, showed a similar range in colonization levels. Resistance to GPA colonization appeared to be more prevalent in gp.andigena, gp.phureja, and gp.stenotonum derivatives. There was a weak positive correlation (r² = .34, P = .01) between foliar total glycoalkaloids and season-mean GPA colonization levels for six clones representing the range of observed resistance to GPA. Resistance to GPA colonization was apparently not directly related to resistance to PLRV infection. Katahdin, for example, was relatively susceptible to GPA colonization but very resistant to PLRV infection whereas selection A69657-4 (gp.andigena) was among the most resistant to GPA colonization but among the more susceptible to PLRV infection. Breeding for resistance to GPA colonization therefore may not be as promising for PLRV control as developing PLRV resistant cultivars.