Cassava plant (Manihot esculenta) is a primary food source in many African nations, explains Richard Sayre, professor of plant cellular and molecular biology at Ohio State University.
The researchers used a gene from the bacterium E. coli to genetically modify cassava plants. The plants, which were grown in a greenhouse, produced roots that were an average of 2.6 times larger than those produced by regular cassava plants.
“Not only did these plants produce larger roots, but the whole plant was bigger and had more leaves,” Sayre said. Both the leaves and the roots of the new giant strain are edible are after processing and cooking.
Cassava is the primary food source for more than 250 million Africans – about 40 percent of the continent’s population. And the plant’s starchy tuberous root is a substantial portion of the diet of nearly 600 million people worldwide.
Sayre collaborated with Ohio State colleague Uzoma Ihemere and scientists from BASF Plant Science in Research Triangle Park, N.C., and BARC-West in Beltsville, Md., who formerly worked on this project in his laboratory.
The researchers used a variety of cassava native to Colombia (cassava was brought to Africa from South America by the Portuguese in the 1500s.) They inserted into three cassava plants an E. coli gene that controls starch production. A non-modified fourth plant served as a control.
“Cassava actually has this same gene,” Sayre said. “But the bacterial version of the gene is about a hundred times more active.”
The modified plants converted more of their sugar into starch, as shown by an increase in root size as well as the number of roots and leaves produced by each modified plant.
The roots of the modified plants were up to 2.6 fold larger than the roots of a non-modified plant (an average of 198 grams for the biggest roots vs. 74 grams for the roots of the non-modified plant.) The modified plants produced a maximum of 12 roots, compared to the seven roots produced by the non-modified plant. These modified plants also produced a third more leaves – a maximum of 123 leaves per modified plant vs. 92 leaves per non-modified plant.
Sayre and his colleagues previously created a genetically modified cassava that contained none of the cyanide-produucing compounds common to the normal plant, which means it requires concentrated cooking before it is edible. The giant cassava contains the cyanogens and so Sayre and his colleagues will have tocombine their various efforts if they are to produce a giant cyanide-free cassava.
SOURCE: OSU press releases based on early online issue of Plant Biotechnology Journal.