Seed efficiency of Pinus sibirica and Pinus pumila hybrids on Lake Baikal shore

Abstract

Two 5-needle pine species, Pinus sibirica and P. pumila, have vast geographic distribution and form wide hybrid zone in the Eastern Siberia. In the interspecies hybridization studies, seed production of hybrids has primary significance for further evolution of the cross-pollinated species. Seed efficiency of the hybrids and their parental species found on the eastern shore of Lake Baikal was studied. It was shown that mature cones of the hybrids were smaller than that in P sibirica but bigger than that in P. pumila. Seed efficiency, i. e., portion of ovules which give rise filled seeds with well-developed embryo, of the hybrids was 34.0 % and was almost 2-fold less than that in P. pumila (66.2 %) and quite comparable with that in P. sibirica (36.8 %). Low seed efficiency in P. sibirica was due to low seed formation frequency and high portion of empty seeds. Main reproductive losses in the hybrids occurred at all stages from the seed development beginning, portions of the aborted and empty seeds were especially high. Thus, seed efficiency of the hybrids appears high enough for further renewal, but, as a rule, only F1 hybrids are found on Lake Baikal shore.