Towards barley that does well even in dry weather
November 30, 1999 By Carolyn King
Too wet, too dry, too hot, too cold, or just right – wouldn’t it be great to have crop varieties that could perform well no matter what crazy Prairie weather hits your area? For barley, low moisture can really limit yields. So a team of Alberta researchers is working towards barley lines with improved water-use efficiency that will produce good yields even under dry conditions
It’s challenging work. “Just by merely looking at the barley plants in a field, you wouldn’t be able to say this one plant is water-use efficient and that one is not. So you have to identify what attributes make a plant more efficient at using water and determine how to measure those attributes. Then after you measure them, you have to find a mechanism for incorporating those attributes into breeding programs, because breeders deal with thousands of breeding lines, so they need a quick way to screen for the traits,” says Dr. Anthony Anyia with Alberta Innovates – Technology Futures.
That’s the path followed in Anyia’s recently completed multi-agency project, which included researchers at the Field Crop Development Centre (FCDC) of Alberta Agriculture and Rural Development and the University of Alberta. The project was funded by the Alberta Crop Industry Development Fund, Alberta Agricultural Research Institute (now part of Alberta Innovates – Bio Solutions), Alberta Barley Commission, and Brewing and Malting Barley Research Institute.
“Enhancing water-use efficiency means to increase crop yield per millimetre of moisture available,” explains Dr. Pat Juskiw, a barley breeder at FCDC who was part of the research team. The project focused on three physiological attributes related to water-use efficiency: early seedling vigour, increased transpiration efficiency and increased carbohydrate storage in stems.
Barley plants with good early seedling vigour are able to very quickly produce a lot of leaves very early in the growing season. As a result, the crop canopy is better able to shade the soil and reduce evaporation of soil moisture. As well, the barley plants are able to outcompete weeds, so the crop gets more of the available moisture than the weeds do.
Increased transpiration efficiency is critical if dry conditions occur as the crop begins to set seed. Anyia says, “At that stage, the crop needs to be able to use most of the water it has taken up to make carbohydrates, rather than just transpiring the water – letting it go into the air [through openings on the leaves, called stomata].” The stomata let out water and take in carbon dioxide. Both water and carbon dioxide are essential for photosynthesis, so the plant can form carbohydrates (sugars and starches). In response to dry conditions, the plant closes its stomata, which reduces the plant’s ability to assimilate carbon dioxide into carbohydrates.
Increased carbohydrate storage is a crucial attribute if hot, dry weather occurs during grain filling. “If it’s dry and hot, the plant can no longer undergo the process of photosynthesis to make more sugars. But if it has good stem carbohydrate reserves, it can mobilize those reserves to complete grain filling. That can make a big difference to whether the crop makes the bushel weight you’re looking for,” notes Anyia.
For this project, the researchers evaluated the water-use efficiency of a wide range of barley breeding materials. And they investigated ways to measure the three attributes related to water-use efficiency. For example, they evaluated a technique called carbon isotope discrimination (CID), which is an indirect way to measure transpiration efficiency. They found that CID could be a good tool for selecting stable yielding barley lines in some situations. CID is faster and easier than the traditional way of measuring transpiration efficiency, which involves time-consuming, labour-intensive measurement of water and biomass in a greenhouse. As well, CID has high heritability, which is important for breeding programs.
The research team also made some important progress towards incorporating the three attributes into breeding programs. Using the lines that have superior water-use efficiency, the researchers developed recombinant inbred lines through single-seed descent – in simple terms, that’s a process to produce plant populations that are very useful for mapping the location of genes in the chromosomes.
The researchers used those inbred lines to map the locations of chromosomal segments containing genes for water-use efficiency attributes. And then they used that locational information to start work on some genetic markers. A genetic marker is a small portion of DNA associated with a specific trait, and is usually located near the gene for the trait.
Breeders use markers to rapidly screen breeding material for desired traits. Anyia has recently applied for funding to further refine the markers developed so far with the goal of improving their accuracy.
Overall, the project’s results show that breeders will likely need to develop varieties that exhibit more than one of the three attributes related to water-use efficiency. That’s because selecting for just one of these traits could result in plants that do very well in a drought situation, but don’t perform well when conditions are optimal. For example, the plants might conserve water even when there is no need to, and may not be able to take advantage of optimal moisture conditions.
Anyia notes, “We want to have barley lines that will do well when conditions are optimum, and when it gets dry we want the lines to do better than others.”