Seedling Emergence and Seedling Growth of Mustard and Rapeseed Genotypes under Salt Stress

Core IdeasVarietal differences in salt tolerance were observed.There were differences in salt tolerance between the seedling emergence and seedling growth stages.Growth and photosynthesis decreased at high salinity, indicating osmotic stress.Chlorophyll fluorescence did not decrease at high salinity, indicating no stress on photosystem II.Leaf chloride concentrations varied among genotypes, suggesting different salt tolerance mechanisms.Salt-tolerant energy crops can be grown on marginal lands for sustainable biofuel production without competing with food crops for arable land. However, salt tolerance is a variable trait among plant species, varieties, and growth stages. In this study, the relative salt tolerance of seven mustard (Brassica juncea) genotypes and four rapeseed (Brassica napus) genotypes was evaluated at the seedling emergence and seedling growth stages. In the first experiment, seeds were sown in a growth chamber with reverse osmosis water or saline solution at an electrical conductivity (EC) of 10 mS cm(-1) for 10 d, and emergence was determined daily. In the second experiment, seedlings were grown in a greenhouse and irrigated with nutrient solution (control) with an EC of 1.5 mS cm(-1) or saline solutions (EC 5 and 10 mS cm(-1), respectively) for 4 wk. For the seedling emergence stage, the relative emergence percent, and emergence index showed great variation among genotypes (range, 11-112% and 7-110%, respectively). For the seedling growth stage, the saline treatments caused reductions in leaf area and fresh and dry biomass that averaged 63, 65, and 65% relative to the control, respectively. Overall, hierarchal cluster analyses showed differences in salt tolerance between the seedling emergence and seedling growth stages. Net photosynthetic rate decreased with salinity, but soil-plant analysis development readings increased by an average of 18% in the EC10 treatment. Chlorophyll fluorescence did not change, but performance index tended to increase in response to salinity. Chloride concentrations in the leaf tissue increased with salinity and ranged from 32 to 111 mg g(-1), with significant varietal differences.