UV-B Radiation Affects Canola Yield
Date: March 1998
Term: 2 years
Status: Completed
Researchers: Dr. Malcolm Morrison, Agriculture & Agri-Food Canada; D. Dume, University of Guelph
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: n/a
Project Summary
The amount of UV-B radiation reaching the Earth’s surface is increasing yearly, and UV-B radiation, in sufficient doses, harms sensitive plants and reduces yields. Researchers wanted to determine if there was genetic variability for UV-B tolerance in canola and what the mechanisms of tolerance were to help reduce the impact of increased UV-B on Canadian agriculture. Overall the study confirmed that both B. napus and B. rapa canola cultivars are susceptible to UV-B radiation and yields are at risk. Although there was variability in yield response to UV-B in both species, it appears that yield was affected more in the B. napus varieties. Continued screening and selection of varieties with increased UV-B radiation tolerance is important.
The amount of UV-B radiation reaching the Earth’s surface is increasing yearly. Researchers had estimated that by the years 2005 to 2010 the amount of UV-B radiation bombarding plants would be 20% greater than it was in the mid 1980s. UV-B radiation, in sufficient doses, harms sensitive plants and reduces yields. Preliminary research in the early 1990s on the effect of UV-B radiation on canola revealed that both Brassica napus and B. rapa varieties were sensitive to elevated levels of UV-B radiation.
Researchers wanted to determine if there was genetic variability for UV-B tolerance in canola and what the mechanisms of tolerance were to help reduce the impact of increased UV-B on Canadian agriculture. In a two-year study conducted at the Elora Research Station in 1996 and 1997, five B. napus (Bounty, Cyclone, Garrison, Hyola 401, Shiralee) and three B. rapa (AC Parkland, Horizon, Tobin) canola cultivars were screened for tolerance to UV-B radiation and to determine if there was genetic diversity for UV-B tolerance in canola. Researchers also wanted to determine if UV-B absorbing flavonoid pigment production was related to yield effects.
The eight cultivars were seeded in field plots that had been fertilized prior to seeding with 50 kg/ha N in the form of ammonium nitrate and then seeded at a seeding rate equivalent to 7 kg/ha. All plots were treated with Counter 5-G at a rate of 10 kg/ha to prevent flea beetle damage. The test plots were hand weeded. There were three ultra violet light tolerance treatments, including ambient, +UV-B and control. For the ambient treatment, the plots were exposed to ambient solar radiation. For the +UV-B treatments and control treatments, UV-B lamps and ambient solar radiation supplied visible UV-A and UB-B radiation.
Overall, the results showed that seed yield was reduced with increased UV-B radiation in all of the B. napus lines and with two out of three B. rapa lines. Although there was variability in yield response to UV-B in both species, it appears that yield was affected more in the B. napus varieties. In 1996 and 1997, the results showed a 15 and 12% yield suppression with an increase in UV-B radiation equivalent to a 20% decrease in the ozone layer of 1980 levels. As well, there was a slight decrease in seed size for all cultivars except Bounty, with the varieties Garrison and Hyola 401 showing the most seed size reduction to the increase in UV-B radiation.
Some of the cultivars were tolerant to increased levels of UV-B, but there was a strong interaction with the prevailing environmental conditions. There was no variety that appeared strongly resistant in both years, but Shiralee was clearly susceptible in both years. Although UV-B radiation resulted in an increase in flavonoid pigment production in all cultivars, there did not seem to be a strong association with yield response. Therefore, screening for flavonoid pigment production may not be the best method to determine UV-B tolerance.
Overall the study confirmed that canola is susceptible to UV-B radiation and yields are at risk. Continued screening and selection of varieties with increased UV-B radiation tolerance is important.