No abstract

A possibility of selection of clones of the species Populus nigra L. with higher resistance to the rust Melampsora larici-populina Kleb. was tested in a set of 29 clones of P. nigra originating from individuals selected in various localities of the CR. Clones were tested in three localities for four years. Rust infection was evaluated according to a five-point scale. The two most resistant (R 1 ; R 2 ) and two most sensitive (S 1 ; S 2 ) clones were tested in laboratory conditions. The results of this test confirmed to be consistent with those obtained under field conditions. Significant differences between the progenies of resistant (R 1 × R 2 ) and sensitive (S 1 × S 2 ) parents proved the genetic control of resistance. Intermediate inheritance of resistance was found in the progenies S 1 × R 2 and R 1 × S 2 . Genetic effect of the paternal component was also expressed. A possibility of selection for resistance to M. larici-populina rust in P. nigra was proved.

Controlled pollination was carried out in the species Populus nigra L. in a greenhouse on isolated branches between sisters and a brother - inbreeding (S x B). Female trees (sisters) were also exposed to open pollination (OP) in the neighbourhood of a male tree (brother) and other Populus nigra trees in the vicinity. The analysis of 11 microsatellites was done in the offspring from the inbreeding (S x B) and from the OP. In OP offspring was found 20-76% of viable individuals that were coming from pollination with brother’s pollen (spontaneous inbreeding). These individuals were separated from the offspring. In a randomised field trial the offspring were evaluated for two years. Fitness decreased in S x B offspring, traits of plant height, trunk diameter, height increment and resistance to Melampsora larici-populina Kleb. were lower in comparison with those of OP offspring. A coefficient of inbreeding depression (δ) ranged from 0.373 to 0.034. The significance of differences between the offspring from S x B and OP of the particular sisters was proved. About 30% of homozygous microsatellite loci were identified in inbred S x B offspring, which was more than in OP offspring. This difference was significant in the offspring of three sisters; it was not significant in the offspring of one sister. This trend corresponded to the results of growth traits.