Breeding New Stress Tolerant Intermediate Wheatgrass Varieties

Background

Intermediate wheatgrass (IWG) produces a palatable forage for all classes of livestock, and is well suited for pasture forage, hay and late season stockpile grazing. Intermediate wheatgrass is considered moderately saline tolerant forage, performs favorably under saline conditions and may be used to assist in the remediation of saline affected soils. It has been utilized as a high-yielding, high quality forage for decades in Western Canada but like many forage species in Canada the development of improved cultivars has been limited. There has not been a new variety of Intermediate wheatgrass developed in Canada in 40 years and varieties developed in the 1960s-1970s continue to be used today. This team wanted to see if they could improve the salt tolerance of the existing IWG varieties to enhance their survival in mildly and moderately saline soils to balance as an alternative to other forage species that have extreme salinity tolerance, but may be less palatable for livestock.

Objectives

• Identify sources of stress tolerance in intermediate wheatgrass to serve as parents for new cultivars

What they DID

This team evaluated 382 lines collected from around the world held in international genebanks and forage breeding programs to identify materials with the greatest ability to thrive under saline stress. These included lines from Canadian breeding programs within AAFC, the University of Manitoba and the University of Saskatchewan. Lines were tested under hydroponic saline conditions at Canada’s salinity lab facility located at the Swift Current Research and Development Centre. Three evaluations were ran at different levels of salinity, representing moderate to strong salinity (EC_i12 dS/m^-1, 14 dS/m^-1 and 16 dS/m^-1). Metrics of productivity (growth stage, plant height, forage production) and plant health (physiological response to salt stress, plant survival) were evaluated every 2 weeks over twelve weeks of growth.

3,528 plants were included in each evaluation to identify the lines with the greatest potential to survive and produce forage under saline conditions. Over 1.5 million data points were generated across the tests as part of a broad characterization of salinity tolerance in IWG.

What They Learned

We evaluated both existing and pre-release intermediate wheatgrass germplasm from Canadian breeding programs, as well as a  global collection of both American varieties and wild accessions. We found that for the most part, lines that had undergone selection from breeding programs  exhibited the greatest biomass accumulation under three different levels of saline stress. We found that at a strong salinity level (16 dS/m^-1) that multiple lines performed comparably, or surpassed, our salt tolerant check variety of hybrid wheatgrass (AC Saltlander) and existing Canadian varieties of intermediate wheatgrass, such as Chief and Clarke. 

We identified pre-release lines that could be developed into new forage cultivars, and identified traits associated with greater salinity tolerance in this species. The University of Manitoba pre-release lines and USDA varieties developed out of North Dakota tended to produce the highest levels of biomass in our tests and warrant field evaluation.

 As part of our evaluation we also ranked existing Canadian and American varieties of both intermediate wheatgrass and its pubescent morph, pubescent wheatgrass, and identified lines with the greatest salinity tolerance. The AAFC variety Greenleaf was the top performing Canadian line in our hydroponic trials, particularly at 12 dS/m^-1 and 14 dS/m^-1 and within the top 15% of accessions at 16 dS/m^-1. Field evaluation under saline field conditions of this and other identified lines is the next logical step in breeding for enhanced salinity tolerance in this species.

What This Means

These results indicate that there is sufficient genetic variation to support breeding for new and improved varieties of intermediate wheatgrass. We ranked the salinity tolerance of existing varieties and lines and narrowed down lines that may prove useful under saline soil conditions following field evaluation. We identified that there is potential to develop and release varieties that surpass the biomass production of existing Canadian varieties by considerable margins under saline stress. Depending on salinity treatment, experimental lines significantly exceeded the biomass production of Chief intermediate wheatgrass. This data will serve as the basis for the selection of the best parents for developing new high-quality varieties of IWG with improved stress tolerance.