II. 7. Cytoplasmic male sterility in barley. XIII. Nuclear genes for restoration of msm2 cytoplasm.
H. Ahokas, Department of Genetics, University of Helsinki, P. Rautatiekatu 13, 00100 Helsinki 10, Finland. "R"
The recently found cytoplasmic male sterility msm2 differs from msml by its higher sensitivity to partially restoring genotypes (Ahokas 1982). The Rmfla restorer gene of Sel. 77-1 (Ahokas 1979) completely restored the fertility in msm2 (Ahokas 1982). Evidence is presented below that 13 of the complete restorer genes of msml are also effective in msm2 cytoplasm.
Cv. Adorra-like derivatives with msml cytoplasm and heterozygous for a single dominant restorer gene were used as the pollen parent to a male sterile Adorra-like derivative of msm2 cytoplasm. About 15 F1 plants of each cross were raised to reveal the segregation of male sterility/fertility. The results are listed in Table 1. It appears that all the crosses except for that with Rfm,,l fit to a l:l ratio. All the crosses, however, gave male fertile segregants with the Adorra-like nuclear background which maintains sterility. Therefore, these 13 restorer genes must be capable of restoring in msm2 cytoplasm.
Rfmlb, Rfmlc, and Rfmld of PI 296856, PI 296919, and PI 284755, respectively, are evidently allelic with Rfmla (Ahokas 1980), and therefore most likely restorers of msm2, too. The accessions PI 296853 and 79BS15-B, carriers of genes Rfm,,m and Rfm,,r, respectively (Ahokas 1980, 1981), were found to be restorers in msm2 (Ahokas 1982).
Table 1. Fl segregations of 13 restorer genes in msm2 cytoplasm. The crosses have an Adorra-like nuclear gene background.
PI 296897 is an F1 restorer both in msml and msm2 (Ahokas, unpublished). This accession of the collection of Israeli spontaneum barleys is a carrier of an exceptional 'triplicate' electromorph banding pattern of Est4 locus (Kahler and Allard 1981, Kahler et al. 1981). Electrophoretic zone of a single Est4 gene appears in double bands. The double banded phenotype could be explained by the existence of the enzyme in two cell organelles, e.g. in cytosol and plastids or mitochondria, either of the two enzyme forms being specifically processed to be revealed with the electrophoretic technique. A protein or an enzyme coded by nuclear gene and appearing in a maternally inherited organelle might be associated with restoration of maternal sterility. Rfmla gene is not associated with any triplicate electromorph pattern of Est4 zone at the seedling state studied (Ahokas, unpublished). It will be seen later, if the triplicate Est4 form of PI 296897 is somehow associated with the restoration of that accession. PI 296897 originates from the Judean Foothills region. The spontaneum barley populations of this region of Israel have a high (about 10x) frequency of complete restorers (Ahokas 1981). Therefore, the occurrence of triplicate Est4 and restoration in PI 296897 would more probably be a coincidence.
Ahokas, H. 1979. Cytoplasmic male sterility in barley. Acta Agric. Scand. 29:219-224.
Ahokas, H. 1980. Cytoplasmic male sterility in barley. VII. Nuclear genes for restoration. Theor. Appl. Genet. 57:193-202.
Ahokas, H. 1981. Idem. X. Distribution of m fertility restoration ability in the wild progenitor of barley in Israel. Ann. Bot. Fenn. 18:313-320.
Ahokas, H. 1982. Idem. XI. The msm2 cytoplasm. Submitted.
Kahler, A. L. and R. W. Allard. 1981. Worldwide patterns of genetic variation among four esterase loci in barley (Hordeum vulgare L.). Theor. Appl. Genet. 59:101-111.
Kahler, A. L., M. I. Morris and R. W. Allard. (1981) Gene triplication and fixed heterozygosity in diploid wild barley (Hordeum spontaneum). J. Hered. (In press)
BGN 12 toc
BGN Main Index