Seed production in the hybrids of Pinus sibirica and Pinus pumila in the north-eastern part of the hybrid zone

Abstract

Pinus sibirica and P. pumila hybrid zone have a vast territory. Previously, seed production was determined only in hybrids from the western part of the hybrid zone. The earlier established introgression of the species in the northeastern part of the hybrid zone gives more relevance to the study of the hybrid seed production in this area. The paper presents the results of the cone structure analysis in Siberian stone pine, Siberian dwarf pine and their hybrids, and also shows the dynamics of ovule development into a filled seed with a well-developed embryo. The final seed efficiency, i. e., the portion of sound seeds from the ovule number, was 65, 51, and 37 % for Siberian dwarf pine, hybrids, and Siberian stone pine, respectively. Low seed efficiency in P. sibirica was related with high portion of empty seeds in some individuals. The atypical seed efficiency in Siberian stone pine and hybrids could be explained by the lack of pure P sibirica, consequently, by the lack of F1 hybrids.