Osmopriming improves seeds germination, growth, antioxidant responses and membrane stability during early stage of Moroccan alfalfa populations under water deficit

Mohammed Mouradi1, Abdelaziz Bouizgaren2, Mohamed Farissi3, Bouchra Makoudi1, Ablaa Kabbadj1, Anne-Aliénor Very4, Hervé Sentenac4, Ahmed Qaddoury1, and Cherki Ghoulam1*
Osmopriming has a positive effect on the enhancement of seeds germination and seedlings growth, especially under stress conditions. This study investigated the effects of osmopriming with polyethylene glycol on alfalfa (Medicago sativa L.) seeds germination and seedlings antioxidant responses under drought stress. Seeds of five Moroccan alfalfa populations and an American Moapa variety were used to investigate the effect of osmopriming on seeds germination, seedlings growth, activities of antioxidant enzymes and membrane stability under two water deficit levels (-0.45 and -0.75 MPa). Seeds were primed with polyethylene glycol (PEG6000) (-0.6 MPa) for 24 h at 25 °C. The results showed that treated seeds presented higher germination rate and growth of 8 d-old seedlings than untreated ones. Particularly, osmoprimed seeds of ‘Adis-Tata’ (Ad) and ‘Riche’ (Rc) populations presented the highest final germination percentages of 90.8% and 64%, respectively, and seedlings shoot and root lengths under both levels of water deficit. The priming treatment enhanced the activity of peroxidase (PO) and catalase (CAT) and reduced the malonyldialdehyde (MDA) content and the electrolyte leakage under water deficit. Generally, the success of germination was positively correlated to PO and CAT activities and the degree of membrane stability in drought tolerant populations. However, the positive effect of the osmopriming technique on alfalfa drought tolerance remains limited in some tested populations, and severe water stress could inhibit germination and cause damages of alfalfa seedlings.
Keywords: Catalase, electrolyte leakage, germination, malonyldialdehyde, Medicago sativa, osmopriming, peroxidase, water deficit.
1Université Cadi Ayyad, Faculté des Sciences et Techniques, B.P. 549, Guéliz, Marrakech, Maroc.
*Corresponding author (ghoulam@fstg-marrakech.ac.ma; c.ghoulam@uca.ma).
2Institut National de la Recherche Agronomique (INRA), Unité d’Amélioration Génétique des Plantes, B.P. 533, Guéliz, Marrakech, Maroc.
3Montpellier SupAgro, 2 place Pierre Viala, 34060 Montpellier Cedex 02, France.
4Université Sultan Moulay Slimane, Faculté Polydsciplinaire, B. P. 592, Mghila, Beni Mellal, Maroc.