GENETIC DIVERSITY IN PURE AND HYBRID POPULATIONS OF SCOTS PINE (Pinus sylvestris L.) AND JAPANESE RED PINE (P. densiflora SIEB. ET ZUCC.) IN THE RUSSIAN FAR EAST

Potenko, Vladimir V.

Gomel State Medical University, Republic of Belarus vpotenko@tut.by

Two members of the subgenus Diploxylon, Scots pine Pinus sylvestris L. and Japanese red pine P. densiflora Sieb et. Zucc. occur in the Russian Far East. In 1901 Komarov described P. funebris as a novel species found in the southern part of the Ussury River basin and in the northern half of the Korean peninsula. The species differed from both Scots and Japanese red pines. Since this species grew throughout cemeteries in northern Korea, Komarov suggested naming it "funeral pine". However, in the book Flora of the USSR Komarov (1934) speculated that P. funebris was close to P. densiflora and funeral pine being mentioned as a northern geographic variety of Japanese red pine. Based on the analysis of the formation of generative organs of funeral pine Urusov (1974) showed that P. funebris arose as a result of introgressive hybridization between Scots and Japanese red pines.

Based on the allozyme and chloroplast DNA analyses Szmidt & Wang (1993) inferred that var. sylvestriformis (Takenouchi) occurring in China might be regarded as a form of P. densiflora arisen from introgressive hybridization between Scots and Japanese red pines. More recently, Potenko (2003) and Potenko & Popkov (2003) revealed hybrid origin of P. funebris in the Russian Far East and supposed that var. sylvestriformis and P. funebris are the same taxon distributed in China, northern Korea and Russia.

The objectives of the current study were to estimate the level of genetic variation in pure and hybrid populations of P. sylvestris and P. densiflora. Seed material for the study was collected from 358 individual trees from six Scots pine natural populations, six funeral pine populations and two Japanese red pine populations. At least six megagametophytes per tree were subjected to horizontal starch gel electrophoresis to ascertain the parent tree’s genotype. Each megagametophyte was analyzed for 24 allozyme loci.

Table presents the average values of genetic variation in populations of P. sylvestris, P. funebris, and P. densiflora:

Taxon	А	P95	P	He	Ho	F
P. sylvestris	2.18	62.5	72.9	0.258	0.239	0.022
Hybrid populations (= P. funebris)	2.15	59.0	72.2	0.233	0.227	0.006
P. densiflora	1.98	45.9	62.5	0.201	0.196	0.020

Notes: А – mean number of alleles per locus, Р and P₉₅ – percentage of polymorphic loci, Н_е – expected heterozygosity,

Н_о – observed heterozygosity, F– Wright's fixation index.

Overall, the intrapopulation genetic variation values exhibited by marginal populations of P. sylvestris and P. densiflora were lower than those exhibited by the populations from the central segments of the pines’ distribution areas. The level of genetic variation exhibited only by the two northern hybrid populations located in close proximity to the P. sylvestris’ range appeared to be in general higher than those exhibited by the both parent species. Lower levels of intrapopulation variation in the southern hybrid populations in comparison with those in the northern ones may be explained by gene drift due to small sizes and scattered distributions of the hybrid populations assayed, and/or different degree of а past introgressive hybridization between Scots and Japanese red pines as followed from Bayesian analysis of genetic structure in the pure and hybrid populations.