Two new Clearfield releases did well in 2019 with high yield potential, good blast resistance
• By Vicky Boyd,
University of Arkansas rice breeder Dr. Xueyan Sha made the initial crosses for the Clearfield varieties, CLL15 and CLM04, shortly after relocating to the university’s Rice Research and Extension Center in Stuttgart in 2013.
By using the university’s winter nursery in Puerto Rico, Sha was able to double the number of crops he could harvest each year, speeding the breeding process. Both varieties were released just five years later for seed production during the 2019 season.
They are commercially available to producers through Horizon Ag for 2020 planting. In addition, they have received high marks from producers who grew them for seed during 2019.
But Sha, who previously was a rice breeder at the Louisiana State University AgCenter, isn’t about to rest on his laurels and has a number of advanced Clearfield semi-dwarf varieties in the pipeline.
In addition, Dr. Karen Moldenhauer, also a University of Arkansas rice breeder, has a conventionally statured Clearfield long-grain variety — CLL16 — that appears to have even better yield potential than some current Clearfield long grains.
Using integrated weed management
Although weedy rice has become resistant to imidazolinone herbicides in spotty locations throughout the Mid-South and especially in South Louisiana, the chemistry still has a place in many growers’ weed control tool boxes, says Tim Walker, general manager of Horizon Ag, which markets the Clearfield varieties.
Newpath, Clearpath and Beyond herbicides from BASF are paired with Clearfield rice varieties. They all belong to the imidazolinone herbicide family.
“There are certainly areas in addition to many in Southern Louisiana where (the Clearfield technology) doesn’t work as well as it did, but I think there are a lot of areas where it still works well,” Walker says.
The Clearfield system has been available to growers commercially for almost 20 years — longer than many had expected when it was first launched. In areas where the system may not work as well as it once did, he says the Provisia system offers growers another tool for integrated weed management.
“Our hope and goal is we get into a Provisia-Clearfield-conventional rotation along with soybeans, and we’re not putting so much selection pressure on one technology,” Walker says. “More and more I’m seeing people are using a pre-emerge type of chemistry in their soybeans, especially in the upper Delta. But upon further investigation, there are still a lot of people who are just spraying Roundup. In those rice-bean rotations, we’re putting so much selection pressure on the Clearfield technology and other rice herbicides.
“If they would use a residual in soybeans, it opens up those acres to different types of chemistries that wouldn’t put so much selection pressure on the weeds.”
CLL15 long grain
Variety CLL15 is a high-yielding long-grain Clearfield cultivar with excellent milling characteristics, including good grain length and low chalk. In fact, it has better grain quality than CL151, an industry standard.
In field-scale demonstrations throughout the Mid-South rice-production area, CLL15 had consistent yields, Walker says.
“Last year (2018), we had it in 1-acre strip trials side by side with other varieties from South Louisiana to Missouri, and it just was a consistent variety with 190-plus bushels (per acre).
“This year it did the same thing. We had a lot of 200-bushel-plus rice, but it was just very, very consistent whether it was a demonstration or seed field.”
Sha saw similar performances.
“This year was a little bit strange. In our advanced yield trials for four years in a row, what I saw is (CLL15) seems to have better stability compared to CL153. CL151 is another one that is stable across the whole area as disease isn’t an issue. CLL15 has better stability than CL153 from what I saw.”
CLL15 is a semi-dwarf and about 1 inch shorter than CL153 and CL151, he says.
The newly released Clearfield long grain has two genes — the Pi-ta and Pikm — that impart improved blast resistance to most of the common races found in the South.
Darren Walker, who farms in Prairie County, Arkansas, had two fields of CLL15 for seed production in 2019 with good yields.
He says he didn’t treat the fields differently from what a producer would do with a commercial crop. One field yielded 195 bushels dry, the other 186 bushels dry.
“It’s a wonderful variety — the best Horizon variety I’ve ever grown,” says Darren Walker, no relation to Tim. Unlike commercial growers, he says seed producers don’t have samples run for milling yields, so he couldn’t comment on that trait.
Darren Walker planted the CLL15 April 20 during a break in the rains after planting his other seed fields. He applied a premix of azoxystrobin and propiconazole fungicide early to pick up sheath blight and kernel smut. Because of the two-gene blast resistance, he says that disease was not an issue.
Harvest also was easy, since the grain comes off the panicles cleanly and without cracking.
“It would be my No. 1 pick out of the Horizon varieties,” Darren Walker says. “If they will let me, I’ll grow some more of it.”
Tim Walker says Horizon Ag should have seed available to plant about 100,000 acres of CLL15 for the 2020 season.
CLM04 medium grain
The medium-grain CLM04 was one of the very first crosses Sha made in spring 2013 in his new role as a University of Arkansas rice breeder.
Like Jupiter, CLM04 contains the Pi-ks gene for blast tolerance. CLM04 also contains the Pi-z gene for improved blast tolerance.
CLM04 is a couple inches taller than Jupiter, so growers need to pay close attention to nitrogen applications to reduce the chances of lodging, Sha says. Maturity also is very similar to Jupiter.
The grain size is similar to CL272 and Titan but larger than Jupiter. CLM04 also has less chalk than Jupiter.
Sha has been working closely with Kellogg’s to provide the Battle Creek, Michigan, food company with samples to test.
“We’ve sent samples three years in a row, and from everything they’ve told us, it’s good,” he says. “I’m pretty optimistic, because so far I haven’t heard anything negative from Kellogg’s.”
This winter, Sha shipped the company 1,000 pounds to run through a pilot plant.
One reason for Sha’s upbeat outlook may be that CLM04 has almost identical amylose content and gelatinization temperatures — two critical processing traits — as Jupiter, a medium grain from the LSU AgCenter breeding program.
Jupiter, as well as Titan, a previous University of Arkansas medium-grain release, successfully completed Kellogg’s lengthy testing process and were approved.
Tim Walker is equally optimistic about CLM04 based on what he’s seen in the field.
“It looks like we’re finally getting a Clearfield variety that’s right there with Jupiter and Titan with respect to yield performance,” he says. “CL272 wasn’t always competitive from a yield standpoint in South Louisiana, and in certain situations in Arkansas, it also wasn’t competitive. Jupiter was more consistent, but CLM04 has shown to be a lot more stable.”
CLM04 averaged 196 bushels per acre from 2016-2019 in the statewide Arkansas Rice Performance Trials. In those same trials, Jupiter averaged 197 bushels and Titan 201 bushels — not statistically different.
Of all the Clearfield seed production fields in South Louisiana this season, CLM04 performed the best, averaging 50 to 51 barrels (180 to 184 bushels) per acre.
“All the grain quality is almost identical to the Jupiter and Titan, and we would hope that Kellogg’s sees that,” Tim Walker says.
Horizon Ag should have seed available to plant about 30,000 acres of CLM04 for the 2020 season, he says.