Effect of Temperature of Seed Incubation on Salinity and Drought Tolerance of Moringa peregrina in the UAE

Moringa peregrina is a native small tree in the mountain of the UAE. It has ecological, traditional, nutritional, industrial, and medicinal importance. Adopting M. peregrina as a cash crop necessitates information about seed dormancy, germination requirements, and adaptation to the major abiotic stresses in the Arabian Desert, such as high temperatures, salinity, and drought. This study examined temperature, salinity, drought effects, and their interactions on the final germination and germination rate index (GRI) of M. peregrina. Seeds of M. peregrina were collected from the Hafeet Mountains, Al-Ain, UAE. Seeds were allowed to germinate under six concentrations of NaCl (0, 50, 100, 150, 200, and 250 mM) and four levels of polyethylene glycol (PEG) 6000 solutions (0.0, −0.2, −0.4, and −0.6 MPa) and incubated in three growth chambers adjusted at 15/25 °C, 20/30 °C, and 25/35 °C in alternating 12 h light/12 h darkness. There is little dormancy in M. peregrina seeds; germination rates ranged from 82 to 97%. Final germination and GRI were significantly reduced with the increase in both salinity and PEG solutions, but the reduction was temperature dependent. The salinity tolerance was higher at 15/25 °C and 20/30 °C in lower salinities but was lower at only 20/30 °C in higher salinities. Seed germination was very sensitive to drought; around 22.5% of the seeds germinated at −0.4 MPa PEG at 20/30 °C, but none at the lower and higher temperatures. Germination was significantly greater at lower temperatures than at higher temperatures in −0.2 MPa PEG.