Purdue News

March 7, 1989 RICE REVOLUTIONS: FROM GREEN TO GENE West Lafayette, Ind. -- In a breakthrough that could help to reduce crop failure and famine in developing nations, Purdue University researchers have grown a mature, fertile plant from a single cell of an Indica rice plant. Indica rice is grown in the tropics -- where floods, droughts and insect plagues frequently imperil crops. Indica is one of two types of rice that, together, are the primary food source for 40 percent of the world's population, or about 2 billion people. The single-cell regrowth achieved by Purdue scientists opens the way for genetic improvement of Indica rice. "Before you can transfer new genetic coding into a plant to give it new characteristics, you have to be able to grow the plant from a single cell," said Thomas K. Hodges, Purdue botany and plant pathology researcher. He leads a team of scientists at Purdue that is working to genetically redesign Indica rice. The single-cell regrowth -- known in the scientific community as protoplast regeneration -- represents the first step in a new assault on world hunger, Hodges says. For three decades, improvements in rice productivity and resilience have been achieved through conventional plant breeding. New strains released by the International Rice Research Institute in the Philippines have accounted for a substantial increase in production since 1960, Hodges says. But cross-breeding rice plants or any other crops in search of improved strains is time-consuming and unpredictable. Rice productivity increases achieved through plant breeding can't keep pace with population growth, Hodges says, so a short cut to improved strains must be found. "Based on population growth projections, rice yields must increase by over 5 million tons per year, just to maintain current levels of rice consumption per person," Hodges says. Hodges says his single-cell regrowth research is part of a second revolution in crop productivity efforts worldwide. "Release of improved strains of rice and wheat during the 1960s and 1970s was called the Green Revolution," he says. "Work at the cellular level is the beginning of the Gene Revolution in crop improvement. "Some improvements will continue through conventional breeding programs, but these programs will be most effective when coupled with in vitro cell culture of rice and genetic engineering." Two sub-species of rice -- Indica and Japonica -- account for most of the rice grown in the world. Japonica rice is grown in Japan, and in northern China and other temperate regions. Indica is grown in tropical regions -- mostly developing nations from the Indian subcontinent to southern China to the Philippines. In the United States, a hybrid variety of Indica and Japonica is grown. Genetics and cell culture researchers have had more success with Japonica rice than with Indica, Hodges says. In the mid-1980s, Japonica single cells were successfully grown into mature, fertile plants. The Indica single-cell regrowth is the result of months of attempts by Hodges and his research assistant, Lisa Lee. "We evaluated scores of different combinations of nutrients, temperatures, light/dark cycles," he says. "Finally we were able to get the right mix, and we coaxed the cells to grow." Hodges and several Purdue graduate students now are putting their new technique to the test. They have implanted foreign genes in Indica cells. The cells have been successfully grown into calluses -- masses of cells large enough to be seen with the naked eye. "Based on tests, we know that the new genes are expressing themselves in the calluses," Hodges says. It will be several months until the plants grow to maturity. Only then will Hodges know whether the genetically transformed plant can produce seed. Many challenges must be met before an Indica rice plant can be genetically altered with precision, Hodges said. The single-cell regrowth solves the first part of the genetic engineering equation -how to insert new genetic information. What remains a mystery is how to identify what genes make certain plants tolerant of drought or flooding. "The genetic coding for productivity or drought tolerance or any other characteristic isn't fully understood," Hodges said. "That's the next challenge we have to pursue." Hodges will present his findings at the l9th Stadler Genetics Symposium on "Gene Manipulation in Plant Improvement II," March 16 at the University of Missouri in Columbia, Mo. Purdue's Indica rice research is funded by the Rockefeller Foundation. Purdue News Service: (765) 494-2096; purduenews@purdue.edu To the Purdue News and Photos Page