Germination and seedling growth responses of Sri Lankan grown Sesame/Thala (Sesamum indicum L.) for simulated drought conditions

The agriculture sector is often challenged by dry weather, thus a better understanding of growth responses of crops to changes in climate is imperative. However, drought responses of many economical crops are yet to be comprehensively studied. "Therefore, this research was carried out to investigate the responses of 10 Sri Lankan grown sesame varieties/cultivars: Lima, Malee, Idal, Pokuru, Black-seeded sesame and its wild relatives, to reduced water availability during germination and seedling growth. Drought conditions were simulated in a laboratory with three different treatments [polyethylene glycol (PEG) 6000, mannitol and sodium chloride] at 0, - 0.25, - 0.5 and -1.0 MPa water potentials under complete randomised design with 10 replicates each having eight seeds per petri plate per variety/cultivar. The final germination percentage of sesame seeds after 10 days was calculated. Seedlings were further exposed to the same treatments and their root and shoot lengths were measured after 10 days. Germination was assessed using binary data analysis and the seedling data were subjected to ANOVA. Results revealed that the highest tension of PEG (-1.00 MPa) inhibited seed germination and the emergence of seedlings, while that of mannitol (-1.00 MN) negatively affected seedling growth only (p < 0.001). It is concluded that sesame varieties/cultivars were drought susceptible at a tension of -1.00 MPa during germination and seedling development. Improved cultivars alma and Make) showed to be more drought tolerant during germination and landraces (Idal and Pokuru) were the least susceptible to drought during seedling growth. Seedlings of Black(1), Wild(1), Wild(2), Pokuru and Uma varieties/cultivars developed morphological adaptations to display drought avoidance responses during the period of drought stress.