Advances in barley and wheat straw breeding

IMPROVED STEM STRENGTH WILL HELP TO PREVENT LODGING, WHILE MAKING STRAW MORE VERSATILE

lodging is a serious issue in barley and wheat, which is why researcher Dr. Duane Falk is working on how to most efficiently breed for increased stem strength. Stronger straw may also be a more valuable product for farmers. Because wheat straw and other straws are lightweight, abundant and   environmentally-friendly, straw is being eyed as an ingredient in an increasing number of products.

Lodging results in yield losses, lower grain quality and reduced efficiency at harvest, notes Falk, who is an associate professor of plant agriculture at the University of Guelph. “We’ve been working on increasing straw strength in barley for several years and have had quite good success by increasing the thickness of the straw walls through direct selection for this trait,” he says. “What we have learned with barley we will now apply to wheat.” Falk has been working with graduate student Ingvar Björnsson (also of the Department of Plant Agriculture at the University of Guelph) and Mark Etienne of Hyland Seeds-Dow AgroSciences.

The causes of lodging are complex because environmental factors during the growing season interact with plant characteristics related to lodging. “Individually, disease pressures and the rate of nitrogen fertilization farmers choose to use will affect how much lodging will occur – but these factors also affect each other, which makes selection for plants that resist lodging difficult,” says Falk. “However, several straw characteristics have been shown to have fairly high heritability (are passed on effectively), thus making it feasible to breed for lodging resistance.”

In their barley research over the last ten years, Falk’s team aimed to determine which characteristics are related to lodging, the relationships among them and to develop an efficient method of evaluating the lodging potential of single plants.

harnessing engineering qualities
Their approach turned out to be interdisciplinary. “Most characteristics related to lodging in cereals relate to the physical properties of straw, so we decided to address the lodging problem from an engineering perspective,” says Falk. Since straw is essentially a hollow cylinder, the physics of a hollow cylinder relate to the ability of straw to resist breakage when subjected to a bending force. The factors influencing the strength of a hollow cylinder are length (leverage effect; shorter is better), diameter (larger is better), tube wall thickness (thicker is better) and type of material (stronger with more lignin is better). Falk and his team decided to use straw thickness as the trait to measure and select for.

“There are several advantages to using thickness,” he says. “It can be measured at any time after full stem elongation on intact plants in the field without cutting, drying or weighing the straw.”  This use of indirect selection (selection for a trait which is easy to measure and is related to the trait of interest) can be quite effective for ‘difficult’ traits such as lodging.

In terms of breeding, the process of selection generally begins two generations after the initial cross is made. Individual plants are measured for straw thickness with an electronic calliper and the best ones are harvested; seed from these is sent to California for a winter generation. Individual plants are again measured and selected plants harvested separately; seed from these plants is then used to sow a yield plot back in Ontario in the spring.

“At this point, it may be possible to evaluate the actual lodging, if conditions are right, in addition to measuring straw wall thickness,” says Falk. “The lines with the best lodging resistance, good disease resistance, good agronomic traits and, most importantly, high yield, will then be selected for further evaluation and breeding.”

WHEAT STRAW USES

• Falk notes that traditionally, about 20 percent of the wheat straw produced in Ontario has been used for composting to grow mushrooms, often after being used as bedding by race horses.
• For the past three years, several Ontario farmers have been selling wheat straw that’s been processed to become the main ingredient in the plastic used by Ford. The reinforced resin, which demonstrates good dimensional integrity and weighs a bit less than other reinforced plastics, has been used to make an interior storage bin in the Ford Flex since 2010; it may also be used in future in other vehicle components. (Ford is also using soy-based polyurethane for seat cushions, post-industrial recycled yarns for seat fabrics, and post-consumer recycled resins for underbody systems.) The resin was the first commercialized product from the Ontario BioCar Initiative, a partnership between the auto industry, the Ontario government and several universities.
• In May 2008, Canadian Geographic magazine published a secial ‘wheat sheet’ issue on paper made partially from wheat straw pulp imported from China (there are no pulping facilities in North America). It involved partners such as Canopy, a Vancouver-based environmental group that seeks to shift paper-consuming sectors away from unsustainable sources. In October 2011, Canopy was also involved in the release of a special edition of Margaret Atwood’s new book “In Other Worlds.” The 300 copies for $100 sold out quickly. The paper, a mixture of imported Chinese wheat straw pulp, Alberta flax straw and recycled content, is called ‘Second Harvest’ and was produced by Cascades Fine Papers in Montreal. 
• Wheat straw building panels have been produced in Yangling, China since late 2009, panels designed and patented by scientists at the Alberta Research Council (an applied R&D corporation). China is keen on using wheat straw panels because they have lots of straw available, and buildings made with these panels can better withstand earthquakes compared to other types of buildings. •