Genotypic Difference of Sorghum bicolor in the Callus Formation and Callus Growth on Aluminum–Containing Medium

Abstract

We examined the genetic variation in the callus performance of the Al–tolerant and Al–susceptible genotypes of sorghum (Sorghum bicolor L.) on Al–containing medium. Addition of Al to the medium with a low pH, low Ca and low phosphate resulted in a severe decrease in the percentage of callus formation (GF) in both Al–tolerant and Al–susceptible genotypes. However, the percentage of callus formation in the expiants from Al–tolerant genotypes was higher than that from susceptible genotypes on Al–containing medium. The genotypic difference in the relative growth of calli on Al–containing medium and in the suppression of callus formation by Al was in agreement with that in the hematoxylin staining score. Al might have been considered as a limiting factor that affected the callus growth. There was a significant correlation (r= –0.664*) between the percent relative suppression of callus formation by Al and the percentage of callus formation on Al–containing medium. The callus growth in fresh weight and size on Al –containing medium relative to that on Al–free medium (relative growth on Al–containing medium) was greater in Al–tolerant genotypes than in the other genotypes. The relative growth of callus in fresh weight and size on Al–containing medium significantly correlated (r=–0.820** and r=– 0.956**, respectively) with the percent relative suppression of callus formation by Al. The tissue culture is considered to be a useful tool for selecting Al–tolerant haploids at the callus stage.