Autodiploid lines as sources of haploid spontaneous diploidization in corn
--O. A. Shatskaya, E. R. Zabirova and V. S. Shcherbak

In our search for the cultivars displaying a high frequency of spontaneous diploidization of haploids, the 613/2 c4 line was revealed (MNL, 1993). In 1993 the frequency of spontaneous diploidization (the ratio of the number of plants with fertile anthers to the total number of haploids) was as high as 22% in 613/2 c4 (Table 1). Some lines of the fifth cycle of haploidy were derived from 613/2 c4 by genetic marking and spontaneous diploidization. The trait under research, haploids originating in these lines, varies within the range of 11-43%. Stimulation of diploidization shows intermediate inheritance in hybrids.

Genotypes with a high frequency of spontaneous diploidization in some lines and hybrids were selected among the autodiploid lines of 1-3 cycles. In the haploids of these cultivars spontaneous chromosome doubling without a colchicine treatment was observed at a rate of 23-46%. These plants carry a vital ear and some fertile anthers or a fertile sector in a sterile tassel.

Table 1. Frequency of spontaneous diploidization of haploids in corn hybrids and their parents.
 
Origin of haploids No. haploids No. plants with fertile anthers Frequency of diploidization, %
Ts8 57 3 5.3
Ts8 x 613/2 c4 89 12 13.5
Ts16 59 2 3.4
Ts16 x 613/2 c4 220 31 14.0
Intermated Mo17 170 2 1.2
Intermated Mo17 x 613/2 c4 59 8 13.6
613/2 c4 151 33 21.9

Thus, the sources of a high frequency of spontaneous diploidization could be found with a greater success within the cultivars (lines and hybrids) having passed over a haploidy state than within the lines of traditional selection. 


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