Response of chinese spring and Capelle-Desprez substitution lines to chronic and acute gamma irradiation

It was found in a preliminary experiment that hexaploid wheat varieties show a great deal of variability in response to radiation, Chinese Spring and Capelle-Desprez in particular differing in their radiosensitivity. The entire set of substitution lines between the latter two varieties being available, an approach to elucidate the genetic basis of radiosensitivity has been attempted. 21 Chinese Springdiffering from the genetic background of the recipient variety (Chinese Spring) by the substitution of a homologous chromosome pair, originating from the donor variety (Capelle-Desprez). Acute gamma irradiation was carried out on selected seeds of the substitution and parenteral lines in a dose ranging from 10 to 25 kR. Chronic gamma irradiation (dose rates from 120 to 40 r/20-hrs day) was carried out from the three-leaf stage throughout the whole life cycle until harvest time (92 days). The radiosensitivity was evaluated by the following parameters: reduction of plant height and plant dry weight, the ear fertility (measured as a ratio for the total number of seeds to the total number of ears in each plant) and chromosome aberrations yield scored in the first mitotic cycle after acute irradiation of the seeds. The results obtained indicate that different chromosomes 2 D, 5 A, 7 D, 6 B and 7 B condition hexaploid wheat radiosensitivity. In the case of all parameters analysed, the 5 A chromosome and 7 D, to a lesser extent, are the ones that affect radiosensitivity, while the 6 B, 7 B and 2 D chromosomes of Capelle-Desprez probably carry factors of radioresistance. (A.B.)