Resistance of wheat genotypes to boron toxicity is expressed at the cellular level

The effects of toxic boron (B) concentrations on the growth of wheat genotypes at organ level and cellular level were investigated using excised root culture techniques. At the organ level, wheat genotypes differed for root elongation and lateral root development in response to toxic B concentrations. Genotypes classified as resistant from field studies had longer root axes and more lateral roots than sensitive or moderately sensitive genotypes, but there was no difference in axis elongation between sensitive and moderately sensitive genotypes. At the cellular level, callus production of root explants among genotypes still different at toxic B concentrations: resistant genotypes could produce more callus than sensitive or moderately sensitive genotypes. These results suggest that differences among genotypes in resistance to toxic B concentrations may be related to cell membrane permeability to B since they were also expressed in undifferentiated callus cells. The distinct and consistent differences among genotypes in response to B toxicity both at the organ level and at the cellular level could serve as a basis for selection in a breeding program. The methods were precise and efficient.