Evaluating the effectiveness of electrical conductivity method in determining the viability of common bean seeds of different storage periods

Abstract

This study evaluates the effectiveness of the electrical conductivity (EC) method in determining the viability of common bean seeds (Phaseolus vulgaris L.) across different storage periods (3, 9, and 18 months), conducted at Makerere University Agricultural Research Institute Kabanyolo (MUARIK). The research aims to assess the EC method’s accuracy in predicting seed viability, establish its correlation with germination rates, and compare its practicality with traditional germination tests. Experimental data were obtained by measuring EC after soaking 30 seeds per replicate in 250 ml distilled water for 24 hours using a BlueLab pH pen (700 ppm resolution), alongside germination tests on 50 seeds per replicate over 5 and 8 days, with additional data for seedling vigor (seedling height and weak seedlings). Results indicated a significant increase in EC with storage duration, with mean values of 210.0 ppm (3 months), 232.5 ppm (9 months), and 340.0 ppm (18 months), reflecting greater membrane leakage in older seeds. Germination rates decreased correspondingly, from (34.7/50) at 3 months to (29.7/50) at 9 months, and (15.3/50) at 18 months after 5 days, with slight improvements to (46.3/50), (37.7/50), and (25.7/50) after 8 days. Seedling vigor, measured as height, declined from 17.8 cm (3 months) to 14.0 cm (9 months) and 8.7 cm (18 months), while weak seedlings increased from (2.0/50) to (5.0/50) and (10.7/50) for 3 months, 9 months and 18 months respectively. Statistical analysis using ANOVA confirmed significant differences across storage periods (p < 0.05), with a strong negative correlation between EC and germination (r = -0.893 for 5-day germination and r = -0.912 for 8-day germination). The EC method proved effective as a rapid indirect predictor of viability (24 Hours) and offered a cost-effective alternative to the 5–8 day germination test, though the latter provided direct and detailed vigor data (Height and weak seedlings). Recommendations include; standardizing EC protocols for NAROBEAN 1 and other Ugandan bean varieties to establish cultivar-specific EC thresholds to improve accuracy, refining the EC method to obtain reference electrical conductivity values (similar to logbooks or MPN tables) for different bean varieties which indicate a specific level of seed viability and vigor to account for varietal differences in deterioration rates and integrating EC with automated systems to eliminate repetitive operations.