Foliar Applied Thiourea Improved Physiological Traits and Yield of Camelina and Canola Under Normal and Heat Stress Conditions

Heat stress at reproductive stage is one of the major limiting factors to reduce crop yield. This study aimed at investigating the impacts of thiourea on growth, physiology, and yield traits of camelina and canola genotypes under heat stress. The experiment comprised of three factors: (i) genotypes, Camelina sativa (611 and 618), Brassica napus (Hiola-401 and 45S42); (ii) thiourea spray, TU0 = control-no application, TU1 = 500 mg L−1, TU2 = 1000 mg L−1, and TU3 = 1500 mg L−1 at BBCH scale code-60 in camelina and BBCH scale code-60 in canola; and (iii) heat stress, T1 = control (25 °C) and T2 = heat stress (35 °C). The pot experiment was laid out in a completely randomized design (CRD) with factorial arrangements and three replications. High temperature stress reduced the growth attributes, gas exchange, and water relations in camelina and canola genotypes with more reduction in control (no thiourea spray) compared to thiourea spray. The photosynthetic rate (A) decreased by 23% in camelina and 30% in canola under heat stress compared to control-no heat stress, whereas all the physiological traits were negatively affected by heat stress. The yield traits including number of siliques per plant, number of seeds per silique, 1000-seed weight, and seed yield per pot were adversely affected under heat stress. However, supplemental thiourea applications alleviated heat stress damages by improving the photosynthetic efficiency, water potential, and other physiological attributes in both tested crops. Moreover, foliar applied thiourea had improved the seed yield by 39% in camelina and 38% in canola under heat stress. Among thiourea levels, thiourea applied at 1000 mg L−1 was more effective to improve heat stress tolerance as compared to other levels. The camelina genotype 618 was found more tolerant to heat stress than 611. Similarly, in canola, the genotype 45S42 performed better than Hiola-401 under heat stress conditions. While among both crops, camelina showed better resilience against heat stress as compared to canola. Application of thiourea at 1000 mg L−1 improved the growth, physiology, and yield of camelina and canola under heat stress. The camelina genotype 618 and canola genotype 45S42 were more tolerant to heat stress than 611 and Hiola-401, respectively.