Screening of Thirteen Cowpea (Vigna unguiculata L. Walp) Accessions for Salinity Tolerance during Germination under Controlled Conditions

Abstract

Salinity is one of the major abiotic stresses limiting crop establishment and productivity, particularly in legumes such as cowpea (Vigna unguiculata (L.) Walp). This study evaluated the effect of salinity on seed germination and early seedling development of thirteen cowpea accessions under controlled laboratory conditions in a single experimental trial. Seeds were subjected to two NaCl treatments (0 and 150 mM) using a randomised complete block design with three replications. Germination was monitored daily for eight days, and parameters including germination percentage, germination index, germination vigour index, seed vigour index, mean germination time, and time to 50% germination were calculated. Results indicated that salinity significantly reduced germination percentage, germination index, seed vigour index, germination vigour index, and emergence rate across most accessions. In contrast, latency period, mean germination time, and time to 50% germination increased under salt stress, reflecting delayed and reduced germination performance. Substantial variation in salt response was observed among accessions. Cluster analysis grouped the genotypes into four categories: sensitive, moderately sensitive, moderately tolerant, and tolerant. Accessions V3 (WIBALI), V5 (IR16MAP), and V13 (KOMCALLE) exhibited comparatively higher germination performance under saline conditions, whereas V1, V6, V10, V11, and V12 were identified as highly sensitive. These findings highlight significant genetic variability in salinity tolerance among cowpea accessions at the germination stage. The tolerant genotypes identified may be valuable for future breeding programs aimed at enhancing salinity resilience in cowpea. Nevertheless, further evaluation under field conditions and at later developmental stages is required to confirm the stability of tolerance.