EFFECT OF HEAT STRESS ON THE ENZYMATIC AND BIOLOGICAL CHARACTERISTICS OF WHEAT (TRITICUM AESTIVUM) SEEDS COATED AND TREATED WITH YEAST EXTRACT

A laboratory experiment was carried out under the Seed Technology Laboratory conditions, Field Crops Department, College of Agriculture, Anbar University, Iraq, during the 2021 season to study the effect of coating with yeast extract at different concentrations (0, 15, 20, and 25 g L-1) on germination, seedling characteristics, and enzymatic activity under heat stress (5, 10, 15, and 20 °C) of wheat seeds of the Ibaa-99 cultivar. The experiment was conducted using a factorial design in a completely randomized design (CRD) with four repetitions. The obtained results showed a significant response of wheat seeds to the yeast extract treatments, with the 25 g L-1 yeast extract coating treatment showing superiority in germination speed (59.75%), final germination percentage (69.25%), radicle and plumule lengths (9.453 cm, 8.429 cm), seedling vigor index (1662.5), and enzyme activity (10.394 for catalase and 53.46 for peroxidase). Regarding cultivation under heat stress conditions, the temperature of 20 °C was significantly better for germination speed (67.25%), final germination percentage (87.62%), radicle and plumule lengths (10.703 cm and 9.551 cm), seedling vigor index (1812.3), and enzyme activity (catalase and peroxidase: 13.474 and 56.2). The interaction between coating seeds with 25 g yeast extract L-1 and growing at 20 °C achieved the highest values for germination speed, final germination percentage, radicle and plumule lengths, and seedling vigor index, while the same coating treatment at 10 °C recorded the highest activity of catalase and peroxidase enzymes.