Improving Heat Stress Tolerance in Camelina sativa and Brassica napus Through Thiourea Seed Priming

Heat stress is a major detriment to crop growth and yield under the current patterns of climate change. Two independent experiments of camelina and canola were conducted to assess the role of thiourea (TU) priming in modulating heat stress tolerance in camelina and canola. The experiment comprised of three factors: (i) seed priming; NP (no priming), HP (hydro-priming), TU500 (thiourea priming at 500 mg L−1), TU1000 (thiourea priming at 1000 mg L−1), and TU1500 (thiourea priming at 1500 mg L−1); (ii) heat stress; control (22/18 °C) and heat stress (35/25 °C) applied at 20% flowering (62 DAS); and (iii) cultivars; camelina (611 and 618) and canola (Hiola-401 and 45S42). The results indicated that the plants exposed to heat stress exhibited a significant decrease in the growth and yield of camelina and canola due to impaired physiological attributes, while activities/levels of superoxide dismutase, total soluble sugars, glycine betaine, and proline were triggered under heat stress compared with control. Heat stress decreased the photosynthetic rate and water potential by 47% and 23% in camelina and 49% and 24% in canola that led to reduction in seed yield of camelina and canola by 53% and 57%, respectively. Seed priming with thiourea improved the growth and yield attributes of both crops by maintaining the gas-exchange attributes, water relations, and upregulating the activities/levels of antioxidants compared with NP; the maximum improvement was observed with thiourea priming at TU1000. Cultivars 618 and 45S42 showed better antioxidant activity to maintain redox potential in camelina and canola, respectively. In crux, these findings indicated that thiourea seed priming improved the heat stress tolerance in camelina and canola, which might be attributed to higher accumulation of secondary metabolites, better antioxidative defense, and maintenance of plant water status in thiourea-primed seedlings.