The effects of host-plant genotype, hybridization, and environment on gall-aphid attack and survival in cottonwood: the importance of genetic studies and the utility of RFLPs

Using restriction fragment length polymorphisms, the authors show how host-plant genotype and hybridization in cottonwood affects the attack and survival of the gall-forming aphid, Pemphigus betae. Fremont cottonwoods Populus fremontii hybrid F1's and backcross 1's were highly resistant, while backcross 2's, 3's, and 4's and pure narrowleafs Populus angustifolia ranged from highly resistant to highly susceptible with only a few trees being highly resistant. -from Authors