AN EVALUATION OF DIFFERENT IONIZING RADIATIONS FOR POSSIBLE USE IN THE GENETIC TRANSFER OF BUNT RESISTANCE FROM AGROPYRON TO WHEAT

Abstract

Ionizing irradiations were employed with the ultimate objective of transferring genes for bunt resistance (Tilletia spp.) from a 56-chromosome wheat–Agropyron derivative to a hexaploid winter wheat, Triticum compactum var. Elgin (2n = 42). Various sources of irradiation, including X-rays, thermal neutrons, and radioisotopes (P32 and S35) were administered to hybrid seeds. The relative "efficiencies" with which these various sources induced chromosome breakage and subsequent translocation were measured by scoring the frequency of multivalents observed in microsporocytes of treated and control F1 hybrid plants. Increments of X-radiation caused a decrease in survival and fertility, as well as in chromosome interchange frequency. Thermal neutrons, on the other hand, caused correspondingly increased interchange frequency with increased dosage. Percentage survival of neutron-treated plants, however, was equal to that of controls. Although percentage survival of hybrid plants treated with the two radioisotopes was low, cytological analyses of P.M.C.'s of surviving plants indicated that the number of translocations induced by these sources remained equal to that of control material.