Improvement of Screening Techniques for Salinity Tolerance in the Cowpea Genotypes (Vigna unguiculata) on the Seedling Growth Stage.

Salinity is one of the main destructive abiotic stresses, affecting crop production. About 800 million ha of global land are salt affected. The salinity increase of soils or water supplies used for irrigation will result in decreases in productivity for most crop plants, especially in legume crops. Cowpea an important legume species, is widely growing as a fodder crop for animals, green vegetable and for dry beans. Many varieties are grown in tropical and sub-tropical agricultural areas of the world, where soil salinity is a yield-limiting factor. The complexity and polygenic nature of salt stress tolerance make the breeding of salt-tolerant verities difficult. Therefore, understanding the genetic basis for salt tolerance is essential to establish an efficient salt tolerance breeding system in legumes. The objective of this study is the evaluation of salinity effect on the vegetative growth of some cowpea genotypes, develop a screening method according to the height, number of leaf, color of leaf, fresh and dry weight of shoot and root as a basic study to identify QTLs are associated with the plant survival during the salt stress.

Seeds of 12 genotypes of cowpea were sown in small pots containing silica sand. Fourteen-day–old seedling with 2 true leaves will be subjected to salt treatment (NaCl solution with different salinity levels of 45, 90 and 180 mM). The experiment is conducted under greenhouse at 25±1°C and 16hr light. Salt stress responses of the genotypes were evaluated using 14-day-old seedling after 40-day exposure to 180 mM NaCl for height, number and color of leaf and biomass. Based on salt response index (SRI) values BigJohn and 476-8 had highest and lowest values for height, number and color of leaf respectively. However, for biomass analysis we got different response so that for each trait we got different genotype had highest and lowest values.

Key words: Vigna unguiculata, Salt stress, salt response index