ABSTRACT
X-ray-induced deciencies occur at nonrandom positions in chromosomes. Two reports provided conicting results in tomato. Gottschalk (1951) found 73.2% centromeric breaks, 18.4% breaks in heterochromatin and 8.4% in the euchromatin. Khush and Rick (1968a) recorded the highest frequency (60%) of breaks in the heterochromatin. The frequency of breaks in kinetochores was intermediate (20%) and only 15% of breaks occurred in euchromatin.
