Y. YAMAMOTO and M. SASAKI
Faculty of Agriculture, Tottori University, Tottori, Japan
It is of interest to know whether or not there is any difference between F1 hybrid plants (2n=28, ABDR) of conmon wheat x rye and of synthesized 6x-wheat x rye in regard to their meiotic behavior.
The F1 hybrid plants used in this experiment were obtained from crosses between each of the five strains of synthesized 6x-wheat, ABD 1b, 2, 4, 5 (WIS No.1) and Sears', and the rye variety Petkuser. In comparison to the aforementioned hybrid plants, the F1 hybrid plants between common wheat (T. aestivum var. Sanshu-kochiku) and rye were observed, too. One to three plants for each of the cross combinations were selected for observations, and three heads per plant were collected on different dates. Microsporocytes were studied at MI in order to record the chromosome configurations and their frequencies until observations of 100 MI cells had been recorded. The results obtained are presented in the following table.
The number of conjugated chromosomes at MI varies from 0 to 2 with mode of 0 for cross No. 1 and 2, from 0 to 3 with mode of 0 for cross No. 3 and 5, from 0 to 5 with mode of 1 for cross No. 4, and from 0 to 4 or 5 with mode of 0 for cross No. 6 (control).
According to their metaphase configurations the F1 bybrid plants are classified into two groups : of those which consist of cross No.1, 2 and 5, and of those which consist of cross No. 3, 4 and 6 (control), and there is statistically a significant difference between those two chromosome configuration types since no significant variation among heads of each plant and among plants of each cross number is observed with respect to the number of conjugated chromosomes and their frequency. However, it may well be said that there is no significant difference between the chromosome configuration types of the F1 hybrid plants of synthesized 6x-wheat x rye and those of common wheat x rye because according to my previous studies on wheat-rye hybrids, there are many varieties of common wheat which show the some chromosome configuration type in the F1 hybrid plants with rye as that in the F1 hybrid plants of cross No.1, 2 and 5.
In some microsporocytes of cross No. 3 and 6 (control), it is noticed that there is a tripartite or tetrapartite besides usual conjugated chromosomes. This kind of observations has been previousely mentioned in the reports on wheat-rye F1 hybrids by many investigators. It is also of interest that a ring-shaped bivalent is found besides zero or one conjugated chromosome in some microsporocytes of cross No. 3, 4 and 6 (control). No certain relationships are found between the chromosome configuration types in the F1 hybrid plants of the synthesized 6x-wheats with rye and the crossability between their parents.
In conclusion, it might be said that there are no significant differences between synthesized 6x-wheat and common wheat regarding chromosome pairing at MI of F1 hybrid plants with rye.
