Genetic variation in blister-rust resistance and growth traits in Pinus strobus x P.peuce hybrid at age 17: (Experiment 2)

The major objective of this paper was to provide basically information about genetic variation within a 17 years old P. strobus x P. peuce F-1 hybrid population. The progeny trial involved factorial mating among 5 female x 5 male parents. The 25 families and the 2 parent species controls were artificially inoculated at age 2, 3 and 4, by using leaves of Ribes nigrum L. heavily infected by the Cronartium ribicola. At age 6, the families were planted out at 3 m x 3 m spacing using a randomized complete block design with 10 trees row-plot in each of the three blocks. Eleven traits (blister-rust resistance and growth traits among them) were assessed at age 17 and the major results are presented here. (1). Highly significant (p below0.01; p below 0.001) differences among hybrid families for all but one trait were found; (2) The male, female and male x female effects were highly significant (p below 0.01; p below 0.001) for both blister-rust resistance and growth traits; (3) The high parent heterosis was negative whereas the mid-parent heterosis was positive for all but one trait; mid-parent heterosis accounted for 27.3% for blister-rust resistance and 27.7% for volume growth; (4) Tree survivors accounted for 86% for hybrid, 93%for Balkan pine and only 21% for eastern white pine; (5) Good general combiners, not only for growth, but for blister-rust resistance, too, were found among eastern white pine parents as four of 10 parents had positive significant gca effects for blister- rust resistance and six for volume growth; (6) Highly significant positive correlations were found among growth traits, but no significant correlations between any growth trait and blister-rust resistance; (7) A genetic gain of 11.5% in blister-rust resistance and 8.9% in volume growth could be expected.