II.17 Mitochondrial efficiency in eight-paired barleys.
Robert G. McDaniel. Department of Plant Sciences, The University of Arizona, Tucson, Arizona 85721, USA.
Eight-paired barley has been produced by adding a pair of homologous translocated chromosomes to the normal genome complement of seven pairs. Preferential synapsis of the translocated chromosomes has been insured by eliminating the ends of these chromosomes, thus negating the possibility of their pairing with other chromosomes, which would result in abnormal meiosis.
Mitochondria were isolated from scutella and embryos of 18 hr. old germinating eight-paired barley seedlings and assayed polarographically (l, 2). Seed for this study was obtained from G. A. Wiebe, who also provided seed of seven-paired Atlas 57 barley as a control (3).
Replicated experiments designed to measure phosphorylative efficiency and degree of respiratory coupling showed a range of efficiencies for the eight-paired lines, averaging slightly less than control, but not significantly so. The conclusion drawn from these experiments is that presence of an extra chromosome pair does not significantly alter phosphorylative efficiency of mitochondria of these barleys. Growth control by mitochondria would not be considered a factor in possible reduced yield potential of these lines (2). Evidence of variability of mitochondrial activity in eight-paired barleys, though not significant in the present experiments, indicates potential for increasing yield of these lines through selection for superior mitochondria, as is now underway in hybrid barley programs.
1. McDaniel, R. G., 1969. Relationships of seed weight, seedling vigor and mitochondrial metabolism in barley. Crop Sci. 9: 823-827.
2. McDaniel, R. G., 1972. Mitochondrial heterosis and complementation as biochemical measures of yield. Nature, New Biol. 236: 190-191.
3. Wiebe, G. A., R. T. Ramage, and R. F. Eslick, 1974. Eight-paired barley lines. Barley Genetics Newsletter 4: 93-95.
