Keeping switchgrass from “growing up” will make it easier to convert into cellulosic ethanol, according to a recent USDA-Agricultural Research Service (ARS) study.

A gene called “corngrass” – from corn – which is inserted into switchgrass, will keep its plants from flowering, producing seeds and from going through a dormant growth phase. The sugars making up the plant starch are more readily available.

The starch in these transgenic plants stays inside stems because it isn't needed for nourishing flower buds and blossoms, according to ARS geneticist Sarah Hake. That increases starch levels as much as 250%, which increases sugars that can be fermented into ethanol.

Transgenic switchgrass leaves aren’t nearly as stiff as leaves in unmodified switchgrass cultivars because leaf lignin isn’t the same, observed Hale, director of the ARS Plant Gene Expression Center in Albany, CA, and George Chuck, University of California-Berkeley plant geneticist. That fact could lead the scientists to find ways to break lignin down and release sugars for fermentation – essential to commercial production of cellulosic ethanol.

The researchers are now introducing DNA segments called genetic promoters that would “turn on” the expression of the corngrass gene just in aboveground switchgrass shoots. This could help increase root mass development that otherwise would be inhibited by the gene.

Developing non-flowering switchgrass varieties would eliminate the possibility of cross-pollination between transgenic switchgrass cultivars and other switchgrass cultivars, Hake and Chuck suggest.

Results from this work were published in 2011 in Proceedings of the National Academy of Sciences.