THE ARTIFICIAL INDUCTION OF ANEUPLOIDS IN AVENA

Abstract

In order to produce a monosomic series in Avena sativa, a number of different methods for inducing aneuploids in this species was studied. Pre-flowering panicles of the varieties Garry and Rodney of A. sativa and of the tetraploid A. barbata and diploid A. strigosa, were X-irra-diated at 75 r, 150 r, 300 r, and 600 r. In A sativa, the frequency of aneuploids increased with the level of irradiation. Although the 600 r treatment produced the most aneuploids, it also induced the greatest degree of chromosome damage and the monosomic frequency was not increased above that obtained from the 300 r dose. Most of the monosomics derived from the 300 r treatment were meiotically normal. Although the 150 r level produced fewer aneuploids than the higher doses, all were monosomics (except one trisomic) and the meiotic pairing was normal. It is concluded that the most effective treatment is from 150 x 300 r. Rodney appeared to be more sensitive than Garry to the effects of irradiation as a much higher relative frequency of aneuploids was obtained from the 300 r and 600 r treatments; i.e. 13.3% and 23.1% respectively for Rodney as compared with 7.7% and 9.9% in Garry. Sonic vibration produced a low frequency of monosomics and appeared to have some promise. Preflowering treatment with the chemicals Myleran and 8-ethoxycaffeine by injection into the florets and into the stem was not successful in inducing aneuploidy. At present there are 126 monosomics and potential monosomics available for classification in Garry and 60 in Rodney. X-irradiation of A. barbata and A. strigosa panicles induced a number of aneuploids parti-cularly in A. barbata where the frequency increased with the dose. Monosomic plants with 27I chromosomes were sterile but 4 with 27 + f set seed. Deficiencies in A. strigosa were either lethal or sterile.