More resistant sugarcane fields
A variety of genetically modified sugarcane developed by a company from Piracicaba is approved for planting
Brazil is the world leader in sugarcane production, with 8.9 million hectares planted and an estimated harvest of 647 million metric tons this year. The only reason this number is not higher is the sugarcane borer, the larval phase of the moth Diatraea saccharalis, the most common pest on sugarcane plantations. The annual losses generated by this insect in Brazil average almost R$5 billion plus the cost of control measures, and affect an average area of 521,000 hectares. In an attempt to resolve this issue, the Sugarcane Technology Center (CTC), a Brazilian company located in Piracicaba, São Paulo State, developed a genetically modified sugarcane variety resistant to the pest. Named CTC 20 Bt, the variety was approved in June of this year by the Brazilian National Technical Biosafety Commission (CTNBio), the governing body responsible for assessing the biosafety of genetically modified organisms (GMOs) in Brazil.
Antonio de Padua Rodrigues is the technical director of the Brazilian Sugarcane Industry Association (UNICA), the members of which are responsible for more than half of Brazil’s sugarcane production. He explains that the development of the CTC’s genetically modified sugarcane reflects the technological advances of the Brazilian sugarcane industry. “With the definitive arrival of these genetically modified versions on the market, producers will have more profitable sugarcane plantations that will be more resistant to diseases and pests,” UNICA declared in an official statement.
Once approved by CTNBio, the genetically modified sugarcane will be introduced gradually, and the planted areas will be monitored. It will initially be sold only to selected producers mainly from the Central-Southern region of Brazil (to which this variety is better adapted), and these producers will commit to following standards for control and reproduction without industrialization. For two to three years, all of the sugarcane produced will be used as a seedling. “We will also develop genetically modified varieties for other regions and different soil types,” says agricultural engineer William Lee Burnquist, director of Genetic Improvement at the CTC.
The moth’s life cycle begins when it lays its eggs on the leaves of the sugarcane plant. After they hatch, the larvae begin to eat the pulp of the culms (stems). The holes they make weaken the plant, which is then more easily blown over by the wind. This damage also leaves the plant more prone to attacks by fungi such as Colletotrichum falcatum and Fusarium moniliforme. These species cause red rot, a disease that reduces the purity of sugarcane juice and the quality of both the sugar and alcohol produced from the plant.
Genetically modified sugarcane was developed to address these problems. “We introduced the Cry1Ab gene from the soil bacterium Bacillus thuringiensis into the plant genome. This is the same bacterium used to develop genetically modified insect-resistant corn, soybeans, and cotton,” Burnquist explains. Cry1Ab is cloned in the laboratory using genetic engineering. Next, gold microparticles are coated with copies of the gene and introduced into the sugarcane genome, which then produces a protein toxic to the moth (see infographic). The modified plant is reproduced in a nursery and then grown in the field. “Larvae are in contact with this toxin as soon as they are born,” says Burnquist. “When they hatch, they begin to feed on the plant. They ingest the protein and die before they can bore holes into the stem.”
Currently, producers fight the sugarcane borer with chemical insecticides and biological controls—in this case, small wasps of the species Cotesia flavipes are released into fields to parasitize caterpillars (see Pesquisa FAPESP, issue No. 195).
Research at the center began in 1994, which later benefited from the professional training provided by the Sugarcane Genome Project between 1998 and 2004. This project was implemented by several groups from different universities and research institutions, and it was financed by FAPESP and the CTC. “There was a lot of professional training in sugarcane biotechnology at that time. Here at the CTC, many of the professionals were part of the Sugarcane Genome Project at Alellyx [the corporate spin-off of the Genome Project, later acquired by Monsanto] or took classes with those who participated,” says Burnquist.
At the end of 2015, the company filed a CTNBio application for commercial release. The biosafety of the genetically modified plant has been analyzed by several subcommittees within CTNBio. These committees have considered the new variety to be safe for the environment, human health, animal health, and the plant itself. CTC studies have shown that the Cry1Ab gene is eliminated from sugarcane derivatives during the sugar and ethanol manufacturing process and does not cause damage to the soil.
The CTC has already asked the authorities in the United States, Canada, and other countries to approve the sale of sugar produced from genetically modified sugarcane, though this approval is not likely to occur for another few years. Of the 150 nations to which Brazil exports this crop, approximately 40% currently have laws limiting or prohibiting sugar from genetically modified sugarcane.
Another study to make sugarcane immune to pests is being performed at the Luiz de Queiroz College of Agriculture at the University of São Paulo (ESALQ-USP) in Piracicaba. There, agricultural engineer Márcio de Castro Silva Filho has been dedicated to understanding how sugarcane reacts to insect attack since the 1990s (see Pesquisa FAPESP, issue No. 125).
A few years ago, the researcher discovered a gene in the sugarcane itself that exhibits antifungal properties. Known as sugarine, this gene stimulates the production of toxic substances that kill the fungi that cause red rot. “We found that genes that expressed proteins against Diatraea saccharalis when larvae attack the plant do so in a systemic way; in other words, all of the tissues in the plant produce these proteins,” explains Silva Filho. “In the case of sugarine it is different: the gene is expressed only at the point where the moth larva has attacked.”
This discovery led the researcher to study the phenomenon. “We then found that the protein expressed by sugarine affects not the caterpillar, but the fungi C. falcatum and F. Moniliforme,” he recalls. “Recently, we discovered that sugarcane varieties with higher sugarine expression exhibit lower levels of fungal infestation. This discovery could aid in the development of more tolerant varieties.”