Somatic Embryogenesis in Eastern White Pine (Pinus Strobus L.)

Abstract

Pinus strobus L. (eastern white pine or weymouth pine) is an important timber species of North America. It is one of the about one hundred species of the genus Pinus of the family Pinaceae of the order Coniferae (Mirov, 1967). Like all other species of Pinus, the haploid genome of Pinus strobus consists of 12 chromosomes and its diploid genome has 24 chromosomes. It belongs to the group known as soft pines and is closely related to western white pine (P. monticola Dougl.) and sugar pine (P. lambertiana Dougl.). It occurs in a broad geographical range, from Newfounland and Maritimes across Canada to southeastern Manitoba, through the United States from Minnesota to New England and southward to northern Georgia (Stearns, 1992). Eastern white pine is a relatively long-lived tree and can live for well over 500 years (Stearns, 1992). In old growth forests many eastern white pine trees reach a height of 50 m and a diameter of over 100 cm. Early European explorers reported some white pine trees which were more than 70 m tall and 350 cm in diameter. Early North American timber industry was founded on vast forests of eastern white pine growing in the great lakes region. Today the importance of eastern white pine has declined considerably in the North American timber industry. This has been partially due to the susceptibility of this species to a number of diseases and pests, the chief among which are the white pine blister rust (Cronortium ribicola J.C. Fisch.) and white pine weevil (Pissodes strobi [Peck]) (Jones, 1992). Efforts for genetic improvement of eastern white pine have been concentrated on developing clones and hybrids which are resistant to blister rust (Zsuffa, 1985).