Abstract:
NaCl induced salinity stress has been studied for several years. However, development of
salt tolerant cucumber has remained elusive partly due to lack of suitable screening system. Four
cucumber genotypes (11411S and 11432S as salt tolerant whereas 11439S and HH1-8-57 as salt
sensitive) were subjected to two levels of salinity (0 and 80 mM NaCl) under greenhouse conditions to
determine the effect of salinity on growth, leaf gas exchange characteristics and cell membrane stability.
The pre-germinated seeds of each genotype were sown in 1.6 L plastic pots filled vermiculite and peat
in the ratio 2:1 (v/v). The pots were arranged in randomized complete block design with 15 seedlings
per treatment replicated three times. The data on growth, survival, gas exchange characteristics was
taken at the end of 21 days from the start of the experiment. Two cucumber genotypes, 11411S (salt
tolerant) and 11439S (salt sensitive) were selected for the germination experiment. The germination
was assessed at 5 salinity levels (0, 40, 60, 80,100 mM NaCl) and replicated five times. The
germination percentage (GP), mean germination rate (MR) and mean germination time (MT) was
recorded every 24 hours for 8 days. The data collected was subjected to standard analysis of variance
using SAS statistical software and means separated by Dancun’s multiple range tests at P < 0.05. The
results indicated that salt stress significantly reduced growth and survival rates of all cucumber
genotypes but reduction in survival rate was severe in salt sensitive genotypes. Salinity significantly
reduced photosynthetic rate, stomatal conductance, carboxylation efficiency, water use efficiency and
transpiration rate of all genotypes but the decrease was higher in salt sensitive than tolerant cucumber
genotypes. salinity did not affect the germination percentage but increased mean germination time
especially of the salt sensitive genotype. We conclude that survival rate, photosynthetic rate and cell
membrane stability can be used to assess salt tolerance in cucumber.
