Ten clones of western white pine differed in their susceptibility to white pine needle blight. Two clones were significantly less infected than the average and two clones were significantly more infected than the average. This variability suggests a simple inheritance, maybe just one or two genes.
United States Department of Agriculture, Forest Service, "Genetic Variation in Susceptibility of Western White Pine to Needle Blight" (1978). Forestry. Paper 67.