Diplontic Selection and Its Modification by Gamma Radiation in a Colchicine-Treated Grass Hybrid. 2. Comparative Radiosensitivity Studies in the Gramineae (proposed). Progress Report, 1964-1965.

摘要

The principal objectives of the research conducted in 1964-1965 were: (1) To determine whether gatama radiation could inhibit the growth of triploid tissue in shoot meristem of an inter-specific hybrid while colchlclne-produced hesaploid tissue in the same merlstem continued to develop because of the differential radiosensitivity of the tissues. (2) Calculate the average interphase chromosome volume for Agropyron cristatum and A. subsecundum, the presumed parents of the hybrid. (3) Produce a controlled hybrid between A. cristatum and A. subsecundum. (4) Prepare a karyotype analysis of the natural triploid hybrid between the above Agropyron species which would permit us to determine whether total chromosome length is a reliable index of radiosensitivity. Objectives (2) and (4) were achieved. The data from (2) will be utilised in our investigations of comparative radiosensitivity. The data from (4) clearly Indicate that total chromosome length is not useful in predicting radiosensitivity. The primary objective (1) was not achieved, despite this second year of concentrated effort. We are, however, by no means ready to abandon our idea since the hypothesis has not yet been fully tested. We have had extraordinary difficulty In producing hexaploid tissue, and, in addition, we have only recently been able to determine with certainty that our gaoma dosages have been too high. Objective (3) also was not achieved. We have no reasonable explanation for this other than the intrinsic difficulties associated with such wide crosses.