Mitochondrial Complementation and Grain Yield in Hybrid Wheat

Abstract

ADP/O ratios, cytochrome c oxidase and adenosine triphosphatase have been measured in mitochondria and mixtures of mitochondria isolated from two day-old shoots of wheat of known F1 hybrid grain yield performance. Mixtures of mitochondria from two varieties, Peko and Cappelle-Desprez, which have considerable F1 hybrid yield heterosis, showed a significantly increased ADP/O ratio over the mean value for mitochondria from the varieties assayed individually, i.e. these varieties showed ‘mitochondrial complementation’. No mitochondrial complementation was detected for cytochrome c oxidase or adenosine triphosphatase. In other mitochondrial mixtures no complementation in ADP/O ratios were found even when the varieties showed F1 hybrid yield heterosis. Mitochondrial ADP/O ratios were studied in six varieties individually and in mixtures. In only one mixture was any significant complementation detected. However, when all the results were considered together, mitochondrial complementation was significantly correlated with F1 hybrid grain yield heterosis when the plants were grown at a low seed density but not at a high seed density. New hypotheses are offered to account for mitochondrial complementation and its statistical relationship with yield heterosis.