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Contamination affects rice planting decisions in 2007
By Robert H. Wells
Delta Research and Extension Center
STONEVILLE -- Rice producers will need to consider other variety options this year after losing the popular variety Cheniere to contamination.
“The discovery in August of Liberty Link Rice 601 contamination in U.S. commercial long-grain rice supplies will significantly affect variety selection for Mississippi rice producers in 2007,” said Tim Walker, assistant agronomist at Mississippi State University's Delta Research and Extension Center in Stoneville.
Liberty Link 601 is a genetically modified trait in rice that provides resistance to the Liberty Link herbicide. Lucrative markets, such as the European Union, will not purchase rice with this trait.
“As of now, the only known variety that has been contaminated with the Liberty Link 601 line is Cheniere,” Walker said. “Cheniere was planted on about 25 percent of the rice acreage in Mississippi in 2006. However, in an attempt to purge the rice supply of the Liberty Link 601 line, the industry has decided not to plant Cheniere in 2007. Growers must select other varieties for fields where Cheniere was popular.”
Growers primarily planted Cheniere on silt-loam soils and on recently land-leveled fields because of the variety's tolerance to the physiological disorder straighthead.
“Variety selection is critical for Mississippi rice growers,” Walker said. “Factors such as lodging, disease resistance, yield potential and milling qualities are all very important factors that growers consider when selecting which varieties to plant. Few, if any, varieties offer a complete package where there are essentially no weaknesses. Therefore, growers should choose what negative factors they can live with.”
Growers' check-off dollars through the Mississippi Rice Promotion Board have sponsored Walker's research on variety performance. Walker, who has conducted yield trials on silt-loam soils and land-leveled fields, said growers need to know their options for planting rice in the environments where Cheniere was popular. Replacement options include the hybrid rice XL723, Cocodrie, Wells, Cybonnet, Trenasse and Sabine.
Pros and cons of XL723…
“As we have come to expect, the hybrid XL723 outperformed all inbred varieties for the last three years with an average yield advantage of 18 to 25 percent more bushels per acre,” Walker said. “XL723 offers excellent milling quality as long as the rice is harvested at optimum moisture.”
Other advantages of XL723 are its field tolerance to straighthead and its resistance to the rice disease blast.
Some drawbacks Walker pointed to include XL723's potential to lodge and shatter during severe weather and its expense. The seed cost for all hybrids is considerably higher than inbred varieties.
Dwight Kanter, rice breeder and agronomist at the Stoneville center, said another variety replacement option is Cocodrie.
“Cocodrie was grown on about 42 percent of the production acreage in Mississippi in 2006,” Kanter said. “It is a popular commercial, semi-dwarf, long-grain cultivar noted for its sustained, good to excellent yields and milling percentages.”
However, Walker found Cocodrie to be the most susceptible variety to straighthead on silt-loam soils and recently land-leveled fields. Growers can almost eliminate the potential for straighthead if they drain the fields and allow the soil to crack so oxygen will return to the soil.
“However, Cocodrie reaches mid-season almost one week earlier than most other varieties,” Walker said. “As a result, draining and re-flooding is often difficult due to the narrow window between initial flooding and midseason.”
MSU Extension rice specialist Nathan Buehring said the variety Wells also will be a good replacement for producers who grew Cheniere in 2006.
“This variety is taller than most varieties we grow, so lodging may be an issue,” Buehring said. “We do recommend going with a lower preflood nitrogen rate to help prevent lodging.”
Walker suggested reducing Wells' preflood nitrogen rate to 90 pounds of nitrogen per acre and reducing its seeding rate to about 65 to 70 pounds of seed per acre.
Yield potential for Wells is good to excellent.
“If field conditions prevent a continuous flood being maintained during the growing season, the risk of having blast increases tremendously,” Walker said.
Cybonnet also may be considered in 2007, but yields may not match Cocodrie or Wells. It has moderate to good lodging resistance.
“Cybonnet was released recently as Arkansas' first semi-dwarf variety,” Walker said. “It has good field tolerance to straighthead and is also rated moderately resistant to blast. Sheath blight can inhibit Cybonnet from reaching its maximum yield potential, but foliar fungicides have been worth their price when the pathogen is aggressive.”
Another option for some growers is Trenasse.
“It is Louisiana's newest non-Clearfield, long-grain, semi-dwarf variety,” Walker said. “For growers who do not mind harvesting rice about five days earlier than normal, Trenasse may be of interest.”
Walker said because of Trenasse's earliness, insect and disease monitoring will be critical. It is rated very susceptible to sheath blight and is subject to lodging under high-yielding conditions.
“As with Wells, preflood nitrogen rates for Trenasse should be dialed back to about 90 pounds per acre, and seeding rates should be reduced to 65 to 70 pounds per acre,” Walker said.
Yields for Trenasse are typically not as high as other varieties due to its earliness.
Growers may consider Sabine as another possible option.
“Sabine is a new release from Texas that has Dixiebelle cooking qualities,” Walker said.
Dixiebelle qualities are grain processing characteristics that make a variety desirable for use in the canning and parboiling industries.
“In limited observations, Sabine has shown average yield potential and excellent milling quality,” Walker said. “Because of its susceptibility to sheath blight, a fungicide may be necessary to protect yields.”
Walker said little is known about Sabine's field tolerance to straighthead, but in limited observations, straighthead has not been detected in Mississippi.
Buehring said Sabine typically yields lower than other varieties such as Cocodrie and Wells in trials.
“However, growers get a premium for growing this variety because of its superior cooking qualities,” he said.