| A new amphiploid from a cross between Triticum durum
and Agropyron elongatum (2n = 14) B. C. JENKINS and A. MOCHIZUKI Division of Plant Science, University of Manitoba Winnipeg, Manitoba, Canada The senior author successfully crossed Triticum durum variety Stewart with Agropyron elongatum (2n=14) in the greenhouse late in 1955. The badly shrivelled grains obtained were planted on nutrient medium (Difco Orchid Agar) and four plants were established. Two of the plants were treated with colchicine and two were left untreated. A colchicine treated plant and an untreated plant were transplanted to the field while the remaining two plants were left to grow in the greenhouse during the summer of 1956. All four plants produced seeds in an unexpected high frequency. Cytological observation indicated that non-reduction was permitting the development of pollen grains with 21 chromosomes, consequently natural doubling was taking place resulting in the formation of a new hexaploid from the cross. Extensive cytological observations indicate that on the average 2.6 bivalents were formed at first metaphase in F1 plants and unreduced PMC's were observed mixed with normal dyad cells. Offspring with somatic chromosome numbers of 42, 41 and 40 were obtained from these F1 plants but the majority had 42 chromosomes. In backcrosses with the durum parent, plants having 35 and 34 chromosomes were obtained. The fertility in all of these plants is unexpectedly high. Despite considerable variation in chromosome pairing some of the plants show fairly regular pairing of 21 bivalents and these will be selected to maintain the new amphiploid. Attempts are being made to establish a series of addition lines, and also to determine the genome homology of the Agropyron chromosomes. It is suggested that this Agropyron genome be called E despite the fact that this letter has already been used to designate a genome of polyploid Agropyron species as well as for the genome of rye. (Received April 18, 1957) |