Tolerance of seedlings traditional varieties of cowpea (Vigna unguiculata (L.) Walp.) to salt stress

Cowpea is an important source of protein, being the main subsistence crop in the northeast region of Brazil, where water restriction and salinity are limiting factors. Identification of saline stress tolerant varieties can aid crop expansion and improve crop yields. The objective was to study the tolerance of traditional varieties of cowpea to the salinity of irrigation water in the emergency and initial growth phase. The experiment was carried out in a greenhouse using a completely randomized design (DIC), in a 23 x 2 factorial scheme, composed of 23 cowpea varieties (Canapu Vermelho, Boquinha, Pingo de Ouro, Sempre Verde, Ceara, Baeta, Manteiga, Roxao, Costela de Vaca, Feijao Branco, Coruja, Rabo de Peba Branco, Sopinha, Canapu Branco, Lisao, Canapu Miudo, Sempre Verde Ligeiro, Vagem Roxa, Ovo de Peru, Rabo de Peba Miudo, Feijao Azul, Canario, and Paulistinha) and two levels of salinity of irrigation water (S-1 = 0.5 and S-2 = 5.5 dS m(-1)), with four repetitions of 50 seeds. The seedlings were evaluated for emergence, vigor, salinity tolerance index, and dissimilarity. Increased salinity of irrigation water reduced emergence, vigor and dry matter accumulation of cowpea varieties. The cowpea varieties 'Lisao', 'Costela de Vaca', 'Canario', 'Feijao Branco', 'Ceara', and 'Boquinha' are the most tolerant to salinity, while the varieties 'Sempre Verde' and 'Manteiga' are the most sensitive to salinity in the emergency and initial growth phase.