The present work aims to study the biochemical genetic background of wheat resistance to the pathogen; Fusarium culmorum in four Egyptian wheat (Triticum aestivum) varieties, i.e. Sids 1, Sids 8, Sids 9 and Giza 167 by means of tissue culture techniques. It included the study of effects for two concentrations of F. culmorum toxic filtrate (10% and 20%) on peroxidase isoenzymes and protein amino acids in treated calli and regenerated wheat plants. All genotypes turned to be very sensitive to the toxic filtrate, but the level of sensitivity was proven to depend upon on genotype. Gene expression of peroxidase isoenzymes varied in number and activity of isoenzymes. Treated calli revealed a markedly decrease in the concentration of some amino acids e.g. alanine, argnine and an increase in other amino acids as valine.