Key message

Temporary immersion bioreactors can improve hybrid sweetgum somatic embryo conversion and somatic seedling growth rates compared to semisolid medium, significantly improving somatic seedling production efficiency for hybrid sweetgum, an emerging woody biomass crop.

Abstract

Fast-growing hybrid southern hardwood trees should make excellent material for woody biomass production in the Southeastern US, if elite clones can be identified and efficiently propagated. We have enhanced the potential of sweetgum (Liquidambar styraciflua) as a biomass species by generating hybrids between the tree and its Chinese relative, Liquidambar formosana, and propagating the most promising clones via somatic embryogenesis. Some of the hybrid clones have already demonstrated superior biomass productivity compared to elite L. styraciflua trees. However, production of somatic seedlings from these clones remains labor-intensive. Bioreactors, specifically temporary immersion designs, such as the RITA^®, have been applied to improve the efficiency of in vitro propagation of a number of woody species. We tested RITA^® bioreactors for their potential to improve the production efficiency of high-quality hybrid sweetgum somatic seedlings. In one tested genotype, a RITA^® with 50 somatic embryos had about 66% higher conversion frequency (p < 0.05) and produced about 40% more “high-quality” somatic seedlings (p < 0.05) than when somatic embryos were germinated on semisolid medium in GA-7 vessels. In all the genotypes we tested, somatic seedlings produced in RITA^® bioreactors had higher survival percentages by the end of acclimatization than somatic seedlings produced on semisolid medium in GA-7 vessels.