The zymogram phenotypes of 11 enzymes were determined for 22 Triticum aestivum cv. Chinese Spring-Elytrigia elongata disomic and ditelosomic chromosome addition lines. Eleven isozyme structural genes were located in specific arms of six E. elongata chromosomes, as follows: Gpi-E1 in 1ES, Est-E1 in 3ES, Got-E3 in 3EL, Adh-E1 and Lpx-E1 in 4ES, Adh-E2 and Lpx-E2 in 5EL, Amp-E1 in 6Eα, Adh-E3 and Got-E2 in 6Eβ, and Ep-E1 in 7EL. The E. elongata chromosomes present in five disomic addition lines have previously been designated 1E, 2E, 4E, 6E, and 7E to indicate their homoeology with Chinese Spring chromosomes. The results of this study support these designations. The development of disomic putative 3E and 5E addition lines is reported. The added chromosomes designated IV, V, and VI that are present in three of the seven original disomic T. aestivum-E. elongata addition lines are translocated. Evidence that VL and VIL are opposite arms of 2E and that IV is partially homoeologous to 3E has been published. The results reported in this paper indicate that IVS = 3ES, IVL = 7EL, VS = 3ES, and VIS = 5ES and are consistent with VL and VIL being opposite arms of 2E. The synteny relationships of the 11 E. elongata isozyme genes identified in this study are fully consistent with those of homoeologous T. aestivum cv. Chinese Spring genes and thus provide evidence that the gene synteny groups which these two species inherited from their common ancestor are conserved. This study further documents the valuable role that studies of isozyme genes can play in the isolation, characterization, and maintenance of alien chromosomes, telosomes, and chromosomal segments in wheat strains.

This report describes the existence of a mutation in a proA1 pabaA6 yA2 strain of Aspergillus nidulans, which prevents it growing on elevated concentrations of nitrite. The nitrite toxicity marker (nihA) resulted from a mutation in a single gene representing a new locus in linkage group I, and behaved as a recessive character. The observed recombination frequencies between nihA and proA1 and between nihA and pabaA6 were about 1 and 11%, respectively. Nitrite toxicity was not due to a defect in nitrite reductase, because the mutant grew well on nitrate. Furthermore, ammonium protected both nis-5 and niiA− strains against nitrite toxicity, which was not observed for the nihA strain. Since growth of the mutant was inhibited more by a mixture of ammonium and nitrite, compared to nitrite alone, it is proposed that the proA1 pabaA6 yA2 strain has a mutation leading to increased efficiency in nitrite uptake, which is not repressed by ammonium.

RP4::Mu was used to insert Tn3171 into the Acinetobacter calcoaceticus EBF65/65 chromosome. Insertions occurred at a frequency of approximately 10−7 per recipient cell. Auxotrophic mutations resulted from 28% of the Tn3171 insertions examined, with a possible ‘hot-spot’ for insertion in a gene for arginine biosynthesis. The frequency of subsequent precise excision of Tn3171 from the chromosome was less than 10−10. When attempts were made using RP4 derivatives to mobilize the chromosome from a strain containing an arg::Tn3171 insertion, it was found that the enhanced transfer frequency of the adjacent region of the chromosome was dependent on the original Tn3171 insertion, but was independent of the presence of Tn3171 on the mobilizing plasmid.

Genet. Res., Camb. (1982), 39, pp. 157–168

The relationship between heterochromatic homology and meiotic segregation of compound second autosomes during spermatogenesis in Drosophila melanogaster

By Arthur J. Hilliker, David G. Holm and R. Appels

Several errors occurred in the headings of Table 4, on p. 162: the table should read as follows:

Structural genes for the isozymes of shikimate dehydrogenase (E.C. 1.1.1.25) have been located on chromosome arms 5AS, 5BS and 5DS of wheat, 5RS of cereal rye and on chromosome 5Cu of Aegilops umbellulata by electrophoretic techniques. This character provides a useful genetic marker for these previously unmarked chromosome arms, and the results support the notion of the conservation of gene synteny groups within the Triticinae.