THE USE OF ELECTROLYTIC CONDUCTIVITY IN BREEDING SUGAR-BEET FOR QUALITY

Sugar beet varieties from 2 trials (1990 and 1991) were analysed for quality. Pulp samples were analysed for K+, Na+, alpha-amino nitrogen, glucose and polarimetric sugar (sucrose). The electrolytic conductivity of the samples was measured. In both trials, 1990 and 1991, conductivity was positively correlated with K+ (r = 0.7 and 0.8), Na+ (r = 0.5 and 0.2), alpha-amino nitrogen (r = 0.2 and 0.6) and molasse sugar (r = 0.3 and 0.7). It was negatively correlated with sucrose (r = -0.3 and -0.6) and glucose (r = -0.4 and -0.3). The variation of electrolytic conductivity was explained by a multiple regression equation with different independent variables according to the trial: K+, glucose, Na+, sucrose in 1990, with R2 = 0.65 and K+, sucrose, alpha-amino nitrogen, glucose in 1991, with R2 = 0.81. Genotypic (r(G)) and micro-environmental (residual) (r(e)) correlations were computed for conductivity and the other traits. r(G) had a high absolute value for: sucrose (-0.68), K+ (0.71), Na+ (0.71) and glucose (-1.15), but was medium for molasse sugar (0.50). Selection for low conductivity should be efficient in improving quality only if a large variability exists among genotypes for cation concentration.