The study, which proves a concept already demonstrated on many other plant species, will lead to further research that ultimately will enable scientists to improve the native southern pine with such traits as drought tolerance and disease- and pest-resistance, according to lead researcher Dr. Jean Gould, an Experiment Station molecular biologist.
"Loblolly pine has been challenging to genetically engineer because the genotype is very difficult to regenerate into plants in tissue culture," said Gould.
The transformation was done with a marker gene merely to prove that such genetic transfer could be done and that plants carrying the gene could be regenerated.
Gould's method for transforming plants - using a plant's meristem region for inoculation with Agrobacterium - was patented by the Experiment Station in 1992. The first plants transformed using this method were petunia and corn, followed by cotton and rice. She said using a plant meristem for transformation, rather than the traditional callus method, is a quicker and more universal way to transform plants because plant regeneration is simplified. In addition, the callus method does not work for many types of plants.
Loblolly pines dominate about 29 million acres in the southern United States, according to the U.S. Forest Service. The species grows rapidly as a young tree and lives about 75 years, but does not reach reproductive maturity for as many as 10 years after germination - meaning that traditional breeding programs would take decades to accomplish any improvements for the tree.
"While some crop plants have been selectively bred for more than 10,000 years, programs for the genetic improvement of pine are less than 100 years old," Gould noted.
Though significant improvements have been made in that relatively short period of time, she added, genetic transformation can hasten the improvement of loblolly pines to grow healthier trees with more resistance to environmental stresses such as drought, insects and diseases. The quality of the wood end-products also may be transformed with the new technology, she said.
In the study, transformation of loblolly pines using the meristem-based method resulted in regeneration and survival of 10 percent to 30 percent of the shoots inoculated. And not only did the trees survive, but lab analysis showed that the genes transferred to the genome of the new plants.
"These results suggest that a shoot-based transformation method can be used in the genetic engineering of this important but stubborn species," Gould said.
Acceptable rates of transformation have been documented in other pines such as Afghan, Virginia and Monterey but not in loblolly, she noted.
"There is a broad spectrum of applicability for this technology in the genetic improvement of all commercial pines," Gould said.
Journal
Molecular Breeding