KRASNODAR, USSR

Krasnodar Research Inst. of Agriculture

Relationship between frequency of autodiploid corn inbred occurrence and origin of initial stock

--O. A. Shatskaya, V. S. Shcherbak, M. S. Chumak and E. R. Zabirova

Methods of experimental haploidy may be used successfully in corn breeding in particular to obtain new inbreds faster. At first some promising crosses and public line populations were utilized as the initial stock to produce matroclinal haploids through gene marking. After obtaining some autodiploid inbreds and evaluating their combining ability and identifying promising crosses, these crosses were widely employed as parents to produce new haploids and autodiploids. Thus, there came an idea to use recurrent selection for combining ability together with experimental haploidy. At present the inbreds of the first, second, third and fourth cycles of recurrent selection were obtained. It is worth mentioning that from year to year the frequency of matroclinal haploid occurrence was higher in the initial stock including haploid inbreds. On an average for 8 years their frequency was 40% higher than that of the stock containing the inbreds obtained by traditional selection (Table 1).

Table 1. Relationship between the frequency of matroclinal haploid occurrence and origin of the initial stock (1982-1989).
 
Initial stock Number of kernels studied Number of haploid plants Frequency of haploid (%)
Populations and crosses of autodiploid inbred origin 1,719,746 3,672 0.214
Populations and crosses of public line origin 2,590,156 3,853 0.153

In some hybrid combinations originating from autodiploid inbreds frequency of haploidy reached 1%. It is necessary to emphasize in the haploid plants obtained from autodiploid initial stock chromosome number doubled more easily after colchicine treatment. In certain genotypes we succeeded in 50% doubling.

Four year data showed that on an average the frequency of haploids of autodiploid origin was 2-3 times higher than that of the haploids of public line origin (Table 2).

Table 2. Relationship between the frequency of haploid diploidization and origin of initial stock.
 
Initial stock Number of haploid plants treated with colchicine Number of inbreds obtained Frequency of diploidization (%)
Populations and crosses of autodiploid inbred origin 1,988 522 26.3
Populations and crosses of public line origin 3,724 406 10.9

Thus, the use of autodiploid inbreds, their crosses and their combinations with the best inbreds and hybrids from the World Corn Collection allows increasing the number of produced haploids up to 4,000-5,000 a year and the number of new inbreds originated from them up to 500. It surely results in wider application of experimental haploidy in corn breeding.


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