Commercialization of Eucalyptus species mainly depends on its growth rate and ease of propagation. Most species that are commercially available are fast growers that can be easily propagated, have good form and are adapted to various soil conditions. Growth and yield of Eucalyptus varies from species to species as well as with the geographical area (Tables 9.1 and 9.2). Generally, the faster growing species such as E. grandis, E. urophylla and E. urograndis, which are usually the ideal species for tropical areas, have higher yields (Table 9.2). On the other hand, these tropical varieties do not tolerate the cold winter temperatures of subtropical areas. Therefore, their planting range in the United States is limited to South Florida and Hawaii. When these tropical species are planted further north, trees are killed back to the ground during winter months and coppice every year. Even if they survive the cold winter, their growth is compromised due to cold stress.

ArborGen has genetically engineered E. urograndis by inserting a freeze tolerant gene (Figure 9.1). Results from field trials suggest that the superior line has growth rates and productivity similar to the conventional base clone, with better freeze tolerance up to about -8 to -9°C [9]. With this freeze tolerance achievement, the species can be planted as far north as N 30.5°. TheU. S. Department of Agriculture’s Biotechnology Regulatory Services is currently reviewing the species for deregulation.