CARBON PARTITIONING IN AN APPLE MUTANT DEFICIENT IN MALIC ACID

J. Berüter
In the present study carbon partitioning was investigated in the Usterapfel (Malus domestica Borkh.), a variety in which a sweet-tasting form and an acid-tasting mutant is known. The high concentration of malic acid, which was increased 10-fold up to 800 μmol/g DW when compared to the low-acid or sweet-tasting form, accounted for the elevated acid content in the mutant. Fruit from the high-acid mutant was larger but showed the same total dry weight as the sweet form. The difference in fresh weight is therefore the result of enhanced water retention in the high-acid mutant.

To elucidate the biochemical background with respect to the different ability of the two apple forms to store malic acid, enzyme activities related to malate metabolism were compared. The activity of phosphoenolpyruvate carboxylase (PEPC) was slightly increased in the-low acid apple and for the activity of phosphoenolpyruvate carboxykinase (PEPCK) a 3-fold activation in the same fruit was found. There was no difference in the activity of NAD-dependent malic acid dehydrogenase (MDH) and NADP-dependent malic enzyme (ME). It is suggested that in the low-acid fruit, in which there was no decrease in the activity of the enzymes involved in malate metabolism, it is an inability to accumulate malate that is responsible for the low-acid content of the apple.

Berüter, J. (1998). CARBON PARTITIONING IN AN APPLE MUTANT DEFICIENT IN MALIC ACID. Acta Hortic. 466, 23-28
DOI: 10.17660/ActaHortic.1998.466.3
https://doi.org/10.17660/ActaHortic.1998.466.3
apple fruit, carbohydrate storage, Malus domestica Borkh., cv. Usterapfel

Acta Horticulturae