II. 19. Natural occurrence of reciprocal translocation in barley.
T. Konishi and K. Takahashi(1), Institute for Agricultural and Biological Sciences, Okayama University, Kurashiki 710, Japan.
(1) Present address: Tohoku Seed Company, Utsunomiya 321-32, Japan.
Among ca. 1,200 cultivars and wild barley strains, used for the study on hybrid weakness, seven strains were found to involve a spontaneous reciprocal translocation of chromosomes. As shown in Table 1, average seed fertility as determined in the central rows of the spikes of the F1 plants derived from the crosses of Turkey 193 with 4 Ethiopian vars and 3 strains of Hordeum spontaneum were somewhat low, ranging from 59% to 82%, whereas those of their parental forms were over 97%. Moreover, in all of the PMC'S of these F1 hybrid plants, chromosome configuration of one quadrivalent and 5 bivalents were observed. Thus, these F1's proved to be heterozygous for a single reciprocal translocation.
In order to identify the translocated chromosomes involved in these strains, a diallel cross was made among 2 Ethiopian vars and 3 spontaneum strains. Seed fertility and chromosome configuration of the resulting 10 different F1's are schematically shown in Fig. 1. The following conclusion are made from the results.
1) Since the hybrid between 2 Ethiopian vars, Debre Zeit 34 and Sululta 16, had highly fertile spikes with 7 bivalents in its PMC's, these two vars seemed to have the sane transloeations.
2) When these two Ethiopian vars were crossed with Spont. II, both of the resulting F1’s showed one quadrivalent besides 5 bivalents in their PMC's. This suggests that the translocated chromosomes of Spon. II are different from those of Ethiopian vars only in the break-points of the same 2 pairs of chromosomes.
3) The crosses of these three strains (2 Ethiopian vars and Spont. II) with 2 strains of H. spontaneum, S-4 and S-7, resulted in F1's with two quadrivalents and three bivalents in their PMC's. This indicates that these two groups of parental strains involve quite different translocated chromosomes. It is mentioned further that F1 hybrid between Spont. S-4 and Spont. S-7 gave one hexavalent configuration in its PMC's, suggesting that these strains had in common one of the translocated chromosomes.
4) At diakinesis of PMC's in all hybrids crossed with Spont. S-7, a quadrivalent or hexavalent was often attached to a nucleolus. It is inferred therefore that translocated chromosomes of Spont. S-7 involve either of the satellited chromosomes, 6 or 7.
5) As is well-known, seed fertility in the hybrids negatively correlated in general with the number of multivalents in their PMC's.
During the course of this experiment, we found other partially sterile
F1 plants which could not be attributed to heterozygous translocations.
This might be due to the heterozygosity of minor change of chromosomal
structure or complementary genes for hybrid sterility.
