Many crosses between Pinus cembra and other white pines have been attempted but only Pinus cembra x Pinus wallichiana A. B. Jacks. and Pinus cembra x Pinus monticola Dougl. were successful. After 11 years of testing, the following important results were observed: (1) Significant genetic differences were found between hybrids and their parents for most traits; (2) Both hybrid crosses resulted in individuals that have some important traits outside the range of the parents; (3) Pinus cembra x Pinus wallichiana was intermediate between parents iin both blister rust resistance and growth traits; this hybrid incorporated blister rust resistance genes from the female parent and fast growth from the male parent; (4) Pinus cembra x Pinus monticola displayed heterosis in 6 of the 9 tested traits, including all growth traits; it inherited outstanding form and growth from the male parent; (5) Both hybrids represent a potentially important planting stock for middle to high altitude sites.
