A review of eucalyptus propagation and conservation

Abstract

Eucalyptus spp. and hybrids remain among the mostly widely-planted species in the world, owed principally to its diverse genome, its site-adaptability, and relatively fast growth rates. Numerous pure species, and yet more hybrid clones have been globally deployed in plantations, as industry seeks to meet growing demands for wood and their products. As a result, various propagation approaches have been explored, from seeds to vegetative propagation by cuttings and trough in vitro method, with a view to remaining cost-effective, yet efficient, and sustainable. Vegetative propagation of eucalypts is preferred, as it conserves valuable germplasm and offers predictability in commercial foplantations. The range of eucalypt species and hybrids in commercial use, however, has resulted in an array of propagation protocols, as researchers seek to optimise growth conditions to enhance the quality and yields of rooted cuttings and in vitro propagules. The exogenous supply of plant growth regulators (PGRs) is central to the objectives of these protocols. The present review traces recent developments in Eucalyptus propagation, and presents a selection of published protocols for a variety of species, explants and PGR supply. With advancements in plant physiology, molecular biology and biochemistry, a clearer picture of the vegetative physiological growth requirements steadily develops, leading researchers to more accurately manipulate and improve Eucalyptus propagation. Furthermore, the recent completion of the E. grandis genome sequence will drive advancements in eucalypt genomics, metabolomics, and proteomics. Collectively, these developments will present future opportunities to accurately decipher, augment and significantly enhance sustainable growth, yields, valuable traits and germplasm conservation of the eucalypts.