Olivia McClure | 3/13/2015 10:30:22 PM
Rice, sugarcane and sweet potatoes are staple crops around the world. Here at home, they’re signatures of Louisiana cuisine and culture.
Together, those three crops annually contribute about $1.5 billion to the state’s economy — a sizeable impact that wouldn’t be possible without the LSU AgCenter. Much of the rice, sugarcane and sweet potato acreage in Louisiana is planted in varieties developed by the AgCenter.
New varieties of soybeans and corn, for example, are typically bred and owned by large companies that sell seeds nationwide. Crops like sugarcane, however, are significant in Louisiana but not in many other states.
That’s where the AgCenter comes in. Louisiana farmers need varieties that are viable in both the state’s unique environmental conditions and the marketplace. At 17 research stations around the state and in laboratories on LSU’s campus, AgCenter scientists are working to meet those needs.
THE TREASURE HUNT
A plant breeder’s job is never quite done because even the best varieties don’t last forever. New diseases and insect pests arise, and new varieties surpass the yields and quality of old ones.
One characteristic of all good varieties is good yields.
“Increased yield is the easiest thing to help farmers because it gives them more profit,” said Don LaBonte, AgCenter sweet potato breeder and director of the School of Plant, Environmental and Soil Sciences. “But sometimes that also means developing resistance to diseases that reduce yield.”
The challenge in sweet potatoes has been finding something better than the successful Beauregard variety, which the AgCenter released in 1987. Even today, the Beauregard dominates Louisiana sweet potato acreage because it provides high yields. It tastes good, making it a consumer favorite.
But the Beauregard is not perfect. The newer Orleans variety is gaining popularity because its taste and appearance is similar to the Beauregard — but it produces more uniformly shaped potatoes, which translates to a higher marketable yield, LaBonte said.
The Beauregard also can’t tolerate some herbicides, and it’s not resistant to insects such as the sweetpotato weevil.
“For almost two decades, we’ve been making improvements, but not at a level to reduce insecticide use yet,” LaBonte said.
Those improvements are slow but important. Chemicals cost money, and growers want to be confident in their crop.
In general, breeding a new sweet potato variety takes six to eight years. It takes longer if breeders have to hunt for genes that provide specific traits, such as resistance to insects and herbicides.
“If you’re developing a source of resistance, that can take 15 years, and then you have to cross it with other varieties so you get it in a form that growers like,” LaBonte said. “You might look at what cells from this plant can tolerate this herbicide, and keep adding to see which ones survive.”
LaBonte likens that process to a treasure hunt.
“You pick and choose puzzle pieces to get something better than what you have now,” LaBonte said. “You’re taking what’s out there and recombining it.”
If sweet potato breeding sounds difficult, consider sugarcane.
Unlike row crops that are planted and harvested every year, sugarcane is perennial and allows three to four harvests from a single planting. That means sugarcane varieties must be able to withstand potential hurricane winds and cold winter weather.
Breeding takes a long time — usually 12 years — because sugarcane is genetically complex. AgCenter molecular biologist Niranjan Baisakh said sugarcane has eight to 10 copies of each gene, whereas other crops have one to a few copies.
“It is difficult to combine all the traits you want, so often a variety comes with one or two flaws,” said AgCenter sugarcane breeder Collins Kimbeng. For example, a variety may have good sugar content, but not yield well after the first harvest, or have poor disease resistance.
The sugarcane breeding process begins with about 100,000 single seedlings that are carefully selected based on data and observations.
“We look for plants with vigorous growth, disease resistance, a good number of stalks and good height,” Kimbeng said. “It’s a tedious process, but you know the right plant when you see it.”
Each of the 100,000 seedlings is hand-planted in flats, then transplanted into the field. Over the next several years, various tests and trials across southern Louisiana help the breeders choose about 40 plants.
After undergoing intense scrutiny from the AgCenter, U.S. Department of Agriculture and American Sugar Cane League, just one variety usually emerges as a winner and is released.
“We won’t know if the seedlings planted this April will go commercial until 2027,” said AgCenter sugarcane breeder Michael Pontif. “It’s a big difference from other crops. It takes a long time.”
Technology has sped things a bit. Since 2007, Pontif and Kimbeng have used infrared technology to measure sugar content earlier on the breeding timeline. Those tests once required “very involved wet chemistry,” Pontif said.
Breeders, however, will always have to contend with sugarcane’s complex nature. LCP 85-384, an AgCenter variety that was once grown on 91 percent of Louisiana sugarcane acreage, was a good variety, Pontif said — but crosses made from it did not produce similarly good results.
“The genes just didn’t match up the same way,” Pontif said. “You got something different every time.”
LCP 85-384 became popular because it was initially resistant to brown rust disease, which is a major problem. That resistance faded over time.
Brown rust can often adapt quickly because only one resistance gene, Bru1, has been identified in the past 20 years. The disease only has to overcome one source of resistance.
Baisakh, the molecular biologist, is looking at varieties of sugarcane and related wild species that don’t contain Bru1, but still have resistance qualities. He is trying to identify those genes and combine them with Bru1 to create “gene pyramids,” which would give sugarcane varieties multiple defenses against brown rust.
“The genes may have small effects, but together, they are stronger and can resist several strains of fungus,” he said.
As Baisakh makes discoveries about plant genes, breeders can make better decisions.
CLEAR FIELDS AND BETTER YIELDS
Baisakh is applying the same gene pyramid concept to rice as he works to make it salt and drought tolerant. Several genes control that tolerance, so it will take time to identify them all and breed varieties with multiple tolerance genes.
New rice varieties are bred in five to seven years, said Steve Linscombe, AgCenter rice breeder and director of the Rice Research Station. Rice breeding typically begins by making a cross, the progeny of which is planted and selected for several generations. The first generation of plants is uneven, showing traits from both parents.
During the selection process, breeders pick out the plants they like and grow those seed, concentrating desirable genes with each generation, Linscombe said. The plants also become more uniform, or pure, over time.
One of the AgCenter’s biggest contributions to the rice industry has been the Clearfield rice system, which was introduced in the early 2000s and tolerates herbicides that kill the difficult-to-control red rice weed. Several Clearfield varieties have been released and successfully grown over the years.
While the conventional tactics that made Clearfield rice possible remain viable, the AgCenter is also exploring newer approaches, such as hybrid breeding.
Hybrid rice is grown from the seed from the initial cross of two lines. Although grain quality is usually lower, the advantage of hybrids is a 10 to 15 percent increase in yield — meaning more profit for farmers — and sometimes better disease resistance, Linscombe said. The AgCenter hasn’t released a hybrid variety yet, but hopes to do so in the next year or two.
AgCenter breeders are also using marker-assisted selection technology to pinpoint genes that are resistant to blast disease, which causes lesions on plants and threatens yields.
The process involves taking a small amount of leaf tissue from a young rice plant and mapping where resistance genes are in the plant’s DNA, Linscombe said. That saves time that would normally be spent growing the variety and waiting to see how it performs in the field.
Technology, however, cannot replace variety trials and the time scientists spend walking fields, looking for signs of disease, pests, poor plant growth and other issues.
Fortunately, AgCenter breeders can continue that work year-round at a winter nursery in Puerto Rico. It once took eight years to release a new variety, but the nursery has helped reduce that time to five to seven years.
“It expedites the work because it extends the research season,” Linscombe said. “You have to go through a number of generations to get a variety.”
Being able to complete that process a bit faster is helpful because problems like diseases can arise and change quickly.
“If a variety lasts five or six years in the industry, that’s doing good,” Linscombe said. “If we can improve the variety and offer a higher yield, but keep the same inputs, that helps the industry.”
Linscombe said the impact of the AgCenter’s breeding programs can be seen across Louisiana.
“Much of what we grow in Louisiana are AgCenter varieties,” he said. “The industry is dependent on variety development at the AgCenter. In the case of rice, if we didn’t have our breeding program, we might not have much of a rice industry.”
But the value of the AgCenter’s work stretches beyond Louisiana’s borders. LaBonte said the innovation that takes place here is valuable worldwide.
“Feeding a growing world population is a reality today,” he said.
Louisiana farmers play an important role in doing just that — and the AgCenter is committed to supporting them through research and outreach.
Olivia McClure is a graduate assistant with LSU AgCenter Communications.