Exchange, evaluation, and joint testing of genetic stock

During the past three years there have been important exchanges of ideas and Populus germplasm as well as new evaluations of the pathogens that challenge our energy plantations. Meetings and field tours were held at Enniskillen, Northern Ireland (1992), Casale Monferrato, Italy (1993), and Biri, Norway (1994). Important Populus germplasms were exchanged between the United States and Italy in support of research and breeding programs in the two countries and continents. The Serchio River in Italy has provided the most promising pollen parents so far. In co-operation with several individuals and groups, new plantings of a common set of poplar clones were established at several locations in North America to test for the presence of different species and strains of Melampsora leaf rust. In the results to date, only M. medusae has been found in samples from the mid-continental sites. Only M. medusae f. sp. deltoidae has been seen in the west coast planting. However, in another, related study, M. medusae, M. occidentalis, and M. abietis-canadensis were all found in central Iowa. The most abundant rust species, M. medusae, had a population structure indicating two races or biotypes.