Screening Jack Pine Seedlings for Resistance to Endocronartium harknessii. T. A. Burnes, Department of Plant Pathology, University of Minnesota, St. Paul 55108. R. A. Blanchette, C.-G. Wang, and D. W. French. Department of Plant Pathology, University of Minnesota, St. Paul 55108. Plant Dis. 72:614-616. Accepted for publication 17 February 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0614.

Concentrated suspensions of Endocronartium harknessii aeciospores in water or oil were sprayed onto 8-wk-old Pinus banksiana seedlings in the greenhouse. Spores, concentrated in oil, dispersed more readily and resulted in a higher incidence of infection than aeciospores in water. Red stem and needle lesions were visible 2–3 wk after inoculation, and galls developed 8 wk later. Seedlings from eight P. banksiana seed lots were inoculated and evaluated for resistance 12, 24, and 48 wk after inoculation. Several seed lots derived from P. banksiana, previously selected in the field for possible resistance to gall rusts, had significantly fewer galls 24 wk after inoculation than other seed sources tested.