Line 613/2 as a source of a high frequency of spontaneous diploidization in corn
--E. R. Zabirova, O. A. Shatskaya and V. S. Shcherbak

In mass induction of autodiploid lines diploidization of haploid plants becomes one of the problems. Traditionally this is realized by treating the seedlings with 0.12% colchicine solution. In this case a frequency of diploids induced usually ranges from 20 to 30%. Sometimes this value is as high as 50%. However, it is known that the lines passing through a haploid state show a higher percent of diploids. Considering this and the fact that colchicine treatment is a labour consuming process we started searching for a new approach, i.e. a new source of a high frequency of spontaneous diploids. It was found that 33% of the plants originating from 613/2 line in a haploid state became spontaneous diploids (Table 1), in contrast to the lines of the Corn World Collection where no spontaneous diploidization occurred. The selected line was obtained after 4 cycles of selection, i.e. it had passed four times through a haploid state. It seems involvement of the line as a source of a high frequency of diploids into crosses may in part solve the problem of mass induction of haploid lines.

Table 1. Frequency of spontaneous diploids in some corn lines.
 

Line	Number of haploids	Number of pollinated ears	Frequency of diploids (%)
613/2 C4	114	38	33.3
620/1 C1	26	3	11.5
A344	72	3	4.2
A663	26	1	3.8
Kr123CO	20	0	0.0
F2	8	0	0.0

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