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Photosynthesis trackers shine light on new rice varieties

Photosynthesis trackers shine light on new rice varieties

Photosynthesis monitoring Looking for better varieties Measures light interception

What looks like a flock of giant, robotic geese in a field near Beaumont, Texas, is actually new technology shedding light on how scientists can develop better varieties of rice.

Specially designed equipment is monitoring photosynthesis in 14 rice varieties at the Texas AgriLife Research and Extension Center in Beaumont, according to Dr. Ted Wilson, director and lead scientist on the study.

"Photosynthesis is the engine that drives crop growth, development and yield. By understanding the physiology behind photosynthesis better, we can use this information to determine what plants to select in a plant breeding program, with the end result being a more efficient and faster rate of developing new varieties," Wilson said. "In a nutshell, the faster one can develop a new variety, the greater the rate of yield increase and thus grower income."

In field studies, Wilson and his team are looking at a series of inbred rice varieties and their offspring, which are called hybrids. The idea is to try to determine the inheritance of different traits and how much of the photosynthetic rates of a variety can be inherited from the male and female plants.

Grown in cages

Each variety is grown under a different cage which is automatically measured 58 times in 15-second increments during a three-day period. This is repeated over the growing season, totaling more than 635 measurements of five minutes for the plants in each cage, Wilson explained.

"We also measure detailed information on light interception, allocation of carbohydrates to different parts of the plant and uptake of nitrogen. We can get information on how much we're able to predict how a particular variety responds to a particular environment," Wilson said.

He said the more light a plant is able to intercept, the greater the plant's growth and, hence, its yield. The study is comparing results of different varieties to see if some are able to intercept light better than others.

Wilson explained that a plant uses sunlight to convert carbon dioxide and water into oxygen and sugars, the building blocks for plant growth and respiration.

"The plant allocates the sugars to different parts of the plant -- the roots, leaves, stem, and grain -- dynamically throughout the season as the crop grows," he said. "The manner in which this allocation occurs determines whether you end up with a plant that is largely vegetative at one extreme, or ends up using a lot of its 'energy' to produce, say, grain at the other extreme."

Breeding goal

The goal of a rice breeding program, Wilson added, is to produce a plant that has enough vegetation to support the greatest amount of grain yield.

"This is very much a balancing act. If you select for a plant type that sends most of its energy to producing grain too soon, the plant will be small and stunted," he said. "At the other extreme, if you select for a plant type that puts most of its early and mid-season growth into vegetation, you can end with a very late maturing plant that has too much vegetation that costs the plant too much energy to maintain, which can result in a plant that either matures its grain too late or which cannot support much grain."

The team is considering three years of detailed data as part of its continuing rice breeding program.

"Our ultimate goal is to develop a new variety of rice, so we are working very closely with Dr. Omar Samonte, a plant breeder and partner on this research, and Jim Medley, the lead technician who keeps the project going," he said.

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