Jeffrey W. Hoy and Lester P. Cannon
The most damaging diseases of sugarcane are caused by pathogens that infect the total plant. These diseases are important because sugarcane is propagated by planting stalk sections, and what we call systemic diseases can be spread and increased by planting infected seed cane. Healthy stalks are vital for successful management of sugarcane diseases. However, this has been hard to achieve.
The most important disease affecting sugarcane worldwide is ratoon stunting disease. It is caused by bacteria that live in the plant water vessels and stunt growth without causing visible external symptoms. Farmers do not know where the bacteria are or how much they have and unknowingly spread it during harvesting and planting operations. As a result, ratoon stunting disease reduced yield and profits for the sugarcane industry for many years. An important step forward was the development of a healthy seed cane program based on hot-water treatment of stalks to be used for planting. However, this method was hard on the cane and difficult to accomplish technically and logistically. Also, it did not provide complete control. As a result, ratoon stunting disease continued to be a widespread problem. In addition, heat treatment did not control other important systemic diseases, including leaf scald, mosaic and smut.
In 1984, Freddie Martin of the LSU AgCenter and a private investment group discussed a different idea for a healthy seed cane program for the Louisiana sugarcane industry. The idea was to use a lab technique, tissue culture, to mass produce healthy planting material of sugarcane varieties to sell to farmers. This idea was met with interest and considerable skepticism, so a group of industry representatives from the LSU AgCenter, the U.S. Department of Agriculture, the American Sugar Cane League, and the Louisiana Department of Agriculture and Forestry (LDAF) was assembled to explore whether the concept was feasible and if it might be possible to develop standards that would independently verify the quality of the product produced. LDAF had been responsible for seed certification for other important field crops, but these programs were focused on ensuring varietal purity and low weed seed infestation, whereas the sugarcane program would be focused primarily on disease control.
There was a problem in that the technology for rapid, sensitive, large-scale disease detection was not yet available. Nevertheless, the group moved forward, and the Sugarcane Seed Certification Program was established in 1986 with the first field inspections conducted on 879 acres of seed cane the following year. In 1995, the LSU AgCenter Sugarcane Disease Detection Lab was established with industry support to provide disease monitoring. The program represented a unique public and private-sector partnership with a goal to provide sugarcane farmers high quality seed cane with little or no disease. The end result would be effective disease management for the Louisiana sugarcane industry.
LDAF would be responsible for administration of the program, inspections and certifying that all specified standards had been met. The LSU AgCenter would be responsible for obtaining the initial source material of varieties from the LSU and USDA breeding programs, producing healthy plant material in local quarantine to be used by the companies as the source for tissue culture, disease testing (once appropriate methods became available), and training for LDAF field inspectors. Commercial seed cane companies would maintain foundation stock plants of the different varieties as the source for tissue culture. They would also mass produce plantlets in the lab and increase the material in the field. Upon certification, companies would then sell and deliver certified seed cane to farmers. The program utilized the varied expertise and capabilities of the different entities in a complimentary way to jointly accomplish a more effective healthy seed cane program. In addition, the sugarcane industry and the companies were both happy to have an independent verification of product quality.
The program starts every year with a small group of experimental varieties from the Louisiana Cooperative Sugarcane Breeding Program that are three years away from possible release as commercial varieties. There are detailed certification standards for every step of the process, including how the initial varieties are collected from the breeders, how healthy plant material is produced and delivered to companies, how “foundation stock” plants to be used as a source for tissue culture are maintained, and how vegetative increases of plants are done in the field. There are standards specifying limits for variety mixtures, tissue culture off-types, weeds, diseases and insects that are applied through multiple visual inspections, tissue sampling and disease testing. The program has proven to be adaptable, periodically making adjustments to better ensure the quality of the product.
The Sugarcane Seed Certification Program has resulted in successful management of multiple important diseases of sugarcane in Louisiana. Ratoon stunting disease continues to be the most important disease of sugarcane around the world, but it has not been detected in Louisiana sugarcane fields in many years. The program also minimizes losses from other historically important diseases, including smut, mosaic and leaf scald. The program has helped to prevent our most recent disease, yellow leaf, from building up to damaging levels. One significant benefit of the program has been that it has allowed successful cultivation of high yielding varieties with moderate susceptibility to certain diseases. By continuously introducing healthy material, the disease may occur, but it does not build up to damaging levels by the end of the crop cycle. The current number one commercial variety, L 01-299, which is grown on nearly 60% of the acreage, is susceptible to smut. If farmers had to produce and increase their own seed cane on the farm, smut would steadily increase and not allow successful cultivation of this critically needed variety.
A mark of success for the program is that no one even thinks about ratoon stunting disease anymore. Young farmers do not even know what it is. The Louisiana sugarcane industry has been doing well and produced a new crop record for the total amount of sugar produced during 2020. The effective management of sugarcane diseases accomplished during the past 35 years by the unique public and private sector partnership that provides healthy planting material through seed cane certification has played an important role in that success story.
Jeffrey W. Hoy is a professor in the Department of Plant Pathology and Crop Physiology, and Lester P. Cannon is the seed programs director for the Louisiana Department of Agriculture and Forestry.
(This article appears in the spring 2021 issue of Louisiana Agriculture.)
Jeff Hoy, LSU AgCenter plant pathologist who works with sugarcane diseases, is in the local quarantine greenhouse with sugarcane plants that will be the source for tissue culture to be used in the production of healthy seed cane for the sugarcane industry. Photo by Olivia McClure