The effect of salinity on germination and seedling growth in Cowpea genotypes (Vigna unguiculata)

One of the constraints in development of cowpea cultivation in growing areas of this crop is soil salinity. In order to investigate the effect of salinity on germination and seedling growth of cowpea (Vigna unguiculata), an experiment was conducted as factorial based on completely randomized design with 4 replications. The study was carried out June 2013 at the genetic and gene nation bank laboratory of Seed and Plant Improvement Institute, Karaj, Iran. Treatments were including of 4 levels of salinity (0, 50, 100 and 150 mM), 15 genotypes of cowpea (mashhad, omid bakhsh1, omid bakhsh 2, 001, 002, 7245, 7254, 7262, 7288, 7244, 7256, 7291, 7289, 7278 and 7305). The results showed that the effects of genotypes and salinity levels on different measured traits were significant at 5% probability level. Germination under saline conditions gave significant reductions for each treatment tested. The interaction effects of genotype and salinity, cultivar Mashhad in 150 mM NaCl salinity had the highest final germination percentage (84 %) and vigor germination (8.1). Also, the highest and lowest germination rate in high salinity (150 mM NaCl) had obtained in 7291 (5.3 seed per dar) and omid bakhsh 2 (3.7 seed per dar) cultivar, respectively. Increasing NaCl applications generally decreased the fresh and dry weight of Plumule and fresh and dry weight radicle. In high salinity level (150 mM NaCl), the highest of fresh and dry weight of Plumule had obtained in cultivar Mashhad (0.76 and 0.995 gr). Decrease in Plumule and radicle weight by NaCl application is due to increase in osmotic pressure of soil and decrease in availability of soil water because of NaCl Genotypes mashhad and 001 in NaCl salinity were evaluated as the most resistant and susceptible genotypes, respectively. Based on the results of this experiment, there is necessary genetic diversity among the Cowpea genotypes of Iran for selection of salinity resistant cultivars.