Effects of Salinity on the Growth Characteristics, Yield, Quality, and Physiological Parameters of Wakegi (Allium wakegi A.) of Okinawa

Abstract

We investigated salinity effect on growth, yield and quality of Wakegi (Allium wakegi A.) of Okinawa. We examined the effects of foliar application of different salt concentrations (0.02%, 0.1%, 0.2%, 1%, and 5% bittern) on the growth parameters, rate of leaf tip burn, soil and plant analyzer development (SPAD) value, mineral content, proline content, and sugar content during 2012 and 2013. In this study, with the exception of the number of tillers, none of the growth parameters were significantly influenced by the investigated salt concentrations in 2012 and 2013. With the exception of 0.02% bittern in 2012, an increase in the salt concentration resulted in a slight increase in the number of tillers. The rate of leaf tip burn decreased under saline conditions, whereas the SPAD value increased with increasing salt concentrations. With the exception of 5% bittern in 2013, an increase in the salt concentration resulted in a slight increase in N content. In 2012 and 2013, we found negative correlations between the rate of leaf tip burn and N content (r = −0.835 and r = −0.960, respectively), and positive correlations between the SPAD value and N content (r = 0.888 and r = 0.528, respectively). An increase in the salt concentration up to 1% bittern resulted in an increase in the proline content; in 2012 and 2013, the proline contents in the presence of 1% bittern were 1.75 times higher than those of the controls. The glucose and fructose contents increased in response to increasing salt concentrations, especially in the presence of 0.2% bittern in 2013. Our results suggest that the proline and sugar contents of Wakegi increase under saline conditions and function as osmolytes, thereby enabling the plant to survive. Thus, Wakegi of Okinawa could be cultivated under saline conditions and near seashore area for improving quality parameters without decreasing yield.