Seed hydropriming to alleviate drought stress in germination of two cotton (Gossypium hirsutum L.) varieties

AbstractBackground Drought is a serious threat to the farming community, biasing the crop productivity in arid and semi-arid regions of the world. This study aims to evaluate effect of hydropriming on seed germination of two varieties of cotton, STAM 129A and STAM 190, under drought stress. The seed imbibition kinetics allowed to fix various hydropriming delays (3, 6, 9, 12, 15 and 18 hours). The germination test was conducted in four completely randomized repetitions of 25 seeds for each of the four induced osmotic water stress modalities (0 bar, -3bar, -6 bar, -9 bar), which required the use of PEG-6000 for adjustment. Calculus of germination percentage (GP), mean germination time (MGT), germination index (GI) and the relative PEG injury rate (RPIR) made it possible to evaluate the germinative behavior of the seeds following the different treatments. Results Drought stress-induced damage to seed germination was significantly reduced by priming seeds for 12 hours for both cotton varieties. Under drought stress (average of values measured at -3 bar, -6 bar and − 9 bar), 12H-hydropriming increased the GP by 206.25% for STAM 190 and 179.26% for STAM 190. Germination, previously nil at -6 bar and − 9 bar for unprimed seeds, becomes possible with priming and better with 12H-hydropriming. Increases of 250.76% and 289.55% of GI for respectively STAM 129A and STAM 190 are noted under drought stress. In general, primed seeds germinated one day earlier than unprimed seeds under normal hydrous conditions. Under drought conditions, however, MGT did not vary significantly from the control, approximately 4.56–4.77 days. Longer priming (18H-hydropriming) had a repressive effect on seed germination with total PEG damage, the few seeds that germinated doing so earlier than all the other treatments, at around 3.83–4.02 days under normal hydrous conditions, and 4.33–4.46 days under drought conditions. RPIR was reduced 35.89% (for STAM 129A) and 27.10% (for STAM 190) with 12H-hydropriming. Conclusions Thus, for growing cotton varieties STAM 129A and STAM 190, hydropriming seeds for 12 hours can be recommended to maintain germinative vigor whatever rainfall conditions may arise.