Genetic transformation and mutation induced with pollen irradiated with superhigh and high g-radiation doses
--I. M. Romanova and V. N. Lysikov
Pollen was irradiated with superhigh and high g-radiation doses (200-1500Gr). These doses cause loss of pollen fertility due to possible DNA-fragmentation. Utilization of such fragmented pollen, for fetching from which natural pollen is used as a vector, causes mutation and transformational effects.
Marker character transfer was established: sugary endosperm (su1), 0.52% frequency; leaf and stem golden colour (g1), 4.2% out of marker pollen su1 bm2 g1 irradiated with the dose of 800Gr on maize ovule genome in the recipient strain. Mangelsdorf tester irradiated pollen (500Gr dose) caused marker character transfer: su1 in 1.1% frequency, brown midrib (bm2) 2.2%, two gene transfer 1.1% following repollination with natural non-irradiated pollen of recipient strain.
It was also found that g-irradiated pollen (at high doses) produces specific mutagenic activity in generations following the treatment.
Chlorophyll mutations were obtained in H1 during repollination with recipient pollen of the donor strain at the doses of 500, 800 and 1000Gr. The highest percentage of chlorophyll mutation segregation was observed in M2 at the dose of 1000Gr--9.3%. This dose gave the widest variability range--25 characters.
Besides chlorophyll mutations qualitative mutations appeared in leaves, stem, endosperm, seedling colour and male and female sterility. These mutations were inherited in M2, M3 and M4 in different frequencies.
Mutations improving grain quality are the most interesting. Among them are the "sugary" mutation responsible for sugar content and the "opaque" mutation raising lysine and tryptophan content in grain. These mutations were segregating in one family in 0.15% frequency at the dose of 1000Gr.
Induced mutants having a higher number of heads are also of interest. This type of mutation was observed at doses of 300, 800 and 1000Gr, in the highest frequency at the dose of 1000Gr.
Quantitative mutations were obtained in the experiment along with qualitative mutations. The most depressing mutagenic effect of irradiated pollen on quantitative characters was established in M1 and M2.
Maximal variability of the following characters was observed: tassel length, number of branches in a tassel and heads fully developed. The highest mutation frequency (both quantitative and qualitative ones) was obtained by pollen treatment of M2 in K-167 marker strain in the range of 500-1000Gr.
Meiotic mutations were obtained with distinctive infringement of spiralization, partial asynapsis and chromosome fragmentation following pollination of the recipient strain with pollen of the marker strain su1 bm2 g1. Such effect appears at the irradiation doses of 300, 800 and 1000Gr.
The results of the investigation showed the possibility of genetic variability by means of both transformational (su1 g1 bm2 g1) and mutational (white, yellow, su1, br2, o2, barren stalk, stripe, striate, lazy culm, etc.) mechanisms.
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