Factors in wheat drought resistance
Optimization of soil water and N addition is essential to improving wheat drought resistance. Overall, the results showed that moderate drought priming along with nitrogen application can improve drought resistance, yield, and grain quality in spring wheat.
One of the significant challenges for crop production is the impact of drought. Although the negative effects of drought can be reduced through crop management practices such as plant stress priming and nitrogen (N) application, little is known about their interactive effects in wheat. Plant stress priming, also known as stress hardening, training, or conditioning, can help make plants be more tolerant to additional stress events in present or future generations.
The objectives of the study were to examine the impacts of drought priming and/or N addition on drought resilience, growth, yield, and grain quality of spring wheat. A second objective was to assess the suitability of high-throughput plant phenotyping techniques to quantify drought resistance and resilience in wheat. Factors such as plant biomass, grain yield and grain quality were assessed for impacts of soil water and N treatments.
The project was conducted under both growth chamber and greenhouse conditions. Spring wheat seeds (variety Stettler) were grown in pots in growth chambers with high, moderate, and low soil water levels. Nitrogen (N) treatments compared urea N applications with a control or no N application. Once the plants reached the tillering stage, half of the plants were exposed to acute drought by withholding water for 10 days followed by rewatering for another 10 days. The other half, or the control treatment, continued to receive the three soil moisture and N treatments.
The growth chamber was maintained at 25C during the day for 16 h, 16C during the night for 8 h, and a relative humidity of 70 per cent. To quantify drought resistance and resilience, measurements were taken at three-day intervals for canopy temperature, maximum efficiency of photosystem II, and normalized difference vegetation index (NDVI) during drought-recovery periods.
At the end of the acute drought and rewatering treatments, all of the wheat plants were moved to a greenhouse and grown under the same watering and growing conditions until maturity. After harvest, above-ground dry matter, straw dry matter, seed dry matter, harvest index, and grain N, phosphorus (P), and zinc (Zn) concentrations were determined.
Early water stress improved drought resistance
The study showed that over the drought period both moderate- and low-water-grown plants had higher drought resistance than high-water-grown plants. However, wheat plants grown with low-water had a higher canopy temperature than high-water-grown plants. The results also showed that the addition of N was beneficial for high-water- and medium-water-grown plants to cope with stress and improve drought resistance, but exacerbated drought stress in low-water-grown plants. The study shows that optimization of soil water and N addition is essential to improving wheat drought resistance.
Soil water content had a significant effect on yields, with both high- and moderate-water-grown plants resulting in higher yields than low-water-grown plants. However, low-water-grown plants had a lower harvest index. The high-water-grown plants had the highest yields, while the low-water had the lowest. Along with improved grain yields and protein, the addition of N also increased straw dry matter, above-ground dry matter and grain N concentration, but decreased zinc levels in grain.
Overall, this study showed that moderate drought priming along with N application can improve drought resistance, yield, and grain quality in spring wheat. The results also indicated that canopy thermal imaging is very useful for high-throughput plant phenotyping to examine the drought resistance, growth, and yield of wheat.
Funding for the study was provided by the Saskatoon Research Development Centre (SRDC) — Agriculture and Agri-food Canada (AAFC), the AgriScience Program as part of the Canadian Agricultural Partnership, a federal, provincial, and territorial initiative, with funds provided by Agriculture and Agri-Food Canada, Western Grains Research Foundation, Saskatchewan Canola Development Commission, Saskatchewan Wheat Development Commission, Alberta Wheat Commission, Alberta Pulse Growers, and Manitoba Crop Alliance.
Dilip Biswas, Branimir Gjetvaj, Mervin St. Luce, Kui Liu, and Haben Asgedom. 2023. Effects of soil water and nitrogen on drought resilience, growth, yield, and grain quality of a spring wheat. Canadian Journal of Plant Science. 103(4): 401-410. https://doi.org/10.1139/cjps-2022-0210
Photo courtesy of Haben Asgedom
