Geographic origin of cottonwood from the southeast affects Melampsora infection in 3-year-old clonal trialsThis article is part of a larger document. View the larger document here.
Open-pollinated seeds were collected separately by mother tree from several trees in each of 64 natural stands of eastern cottonwood (Populus deltoides J. Bartram ex Marsh. var. deltoides) in the Southeastern United States. Rooted cuttings from the seedlings were grown at four sites (North Carolina, Florida, Alabama, and Missouri). Measurements were taken during September-October in each of the first 3 years after planting for Melampsora medusae Thuem. f.sp. deltoidae leaf rust infection. Average severity of infection over the 3 years varied with latitude and longitude of the stand where the seeds were collected, with subregion of origin, and with individual stand of origin within subregion. However, differences among riversystem groups or topographic positions (upland or bottomland) for stand origins within subregions were not significant. Some of the natural stands were comparable in resistance (less infection) to a set of 12 “check” clones in the trials that came from former tree improvement programs in the lower Mississippi River Valley and Texas.