Author(s):

S Das, S Mohanty, GBN Jyothi and D Dash

Abstract: An investigation was conducted during summer season of 2016-17 and 2017-18 in the Department of Seed Science and Technology, College of Agriculture, OUAT, Bhubaneswar to study the role of osmoprotectants on rice crop physiology and seed yield under high temperature stress. Rice variety Naveen (120 days duration) was chosen for the experiment. The experiment was laid out in SPD, the main plot factor being date of sowing (D₁ – 30^th November, D₂ – 15^th December and D₃ – 30^th December) and the sub-plot factor being foliar spray of chemicals at vegetative and seed filling stage. The foliar sprays included Glycine betaine 600 ppm (T₁), Salicylic acid 400 ppm (T₂), Salicylic acid 800 ppm (T₃), Ascorbic acid 10 ppm + Citric acid 1.3% (T₄), α-Tocopherol 150 ppm (T₅), KCl 1% (T₆), Brassinolides 5 ppm (T₇) and Brassinolides 10 ppm (T₈). One control (T₀) was also taken in which equal volume of water was sprayed. Significantly higher superoxide dismutase (SOD), peroxidase and catalase activity of leaves, proline content of leaves, pollen viability and seed set were recorded from leaves of first date of sowing both at vegetative and seed filling stages, as compared to the second and third dates of sowing. The treatments T₂ and T₈ were most effective in increasing the pollen viability to almost at par with the Control from the first date of sowing (D₁T₀). Similar trend was observed with regards to percent seed set and 1000-seed weight. Highest seed yield was obtained from the first date of sowing, while it declined as the sowing was delayed. Among the treatments, T₈ and T₃ gave the highest seed yields (5243 kg/ha and 5195 kg/ha, respectively), followed by T₂ and T₄ (5193 kg/ha and 5147 kg/ha, respectively). The treatments T₂ and T₈ gave highest harvest index as compared to untreated control. From the experiment, it can be concluded that rice seed production is adversely affected under heat stress leading to lower seed yield and quality. Spray of chemicals such as Salicylic acid 400 ppm, Salicylic acid 800 ppm, Brassinolides 10 ppm or Ascorbic acid 10 ppm + Citric acid 1.3% at vegetative and seed filling stages was effective in mitigating the effects of heat stress on physiological parameters, yield attributing characters, seed yield and quality to a considerable extent.

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