Effects of Salinity on Biofortified Common Bean (Phaseolus vulgaris L.) Varieties for Seed Germination and Seed Vigour

Abstract

Soil salinity threatens global food security, affecting over 800 million hectares of farmland, including approximately 2 million hectares in Tanzania. Common bean (Phaseolus vulgaris L.) is susceptible to salt stress during germination and early seedling development. The performance of recently released biofortified common bean varieties in Tanzania remains unexplored, raising concerns about potential trade-offs between enhanced nutrition and stress resilience. This study evaluated the effects of salinity on seed germination and seedling vigour in biofortified common bean varieties to identify those with superior salt tolerance for salt-affected areas. Seven varieties, six biofortified cultivars (SELIAN14, JESCA, TARIBEAN 2, TARIBEAN 4, TARIBEAN 5, TARIBEAN 6), and one non-biofortified control (TARIBEAN 1) were tested under four NaCl concentrations (0, 50, 100, and 150 mM) using a completely randomized factorial design with three replicates. Two-way ANOVA revealed that salinity significantly affected (p < 0.001) germination, shoot length, fresh and dry weight, and seedling vigour indices. Increasing salinity reduced cumulative germination from 98-100% to 59-67%, decreased shoot length by 25-35%, and lowered vigour index I by 50-60% at 150 mM NaCl. Significant varietal differences were observed for root length (p < 0.05), fresh weight (p < 0.001), dry weight (p < 0.001), and vigour index II (p < 0.01). SELIAN14, TARIBEAN 5, and TARIBEAN 6 demonstrated greater salt tolerance, maintaining higher biomass and vigour indices, while TARIBEAN 2 was more sensitive. These salt-tolerant, biofortified varieties are recommended for cultivation in salt-affected regions and as donor parents in breeding programs to develop climate-resilient, nutrient-rich common beans in sub-Saharan Africa.