Abstract

Key messageVariations brought about by pineapple genetic transformation do not appear to be physiologically significant in fruitsAbstractIn terms of tropical fruit production, pineapple ranks as one of the major commercially grown fruit crops globally. Our previous research led to the development of a technique suitable for genetic modification of pineapple. The transgenic plants generated were characterized following hardening-off and during the subsequent 8 years of in-situ growth. The current work focuses on the results of a comparison of selected fruit mesocarp physical and biochemical (indicators related to oxidative metabolism) traits across untransformed control plants propagated by cutting, micropropagated untransformed control plants, and micropropagated genetically transformed plants. At the fruit ripening stage, the statistical analysis revealed no biologically meaningful differences in fruit mass (with tops included) (c. 2.0 kg) between transgenic and both groups of control plants. Moreover, contents of aldehydes, soluble phenolics, shikimic acid, phenylalanine, tyrosine, and p-coumaric acid were statistically comparable across the three groups. However, there were small but significant differences in the content of chlorophylls (a, b), carotenoids, malondialdehyde, proteins, 1,1-diphenyl-2-picrylhydrazyl, and cell wall-linked phenolics. This also included small changes in the levels of enzymes (i.e. superoxide dismutase and peroxidase). Furthermore, fruits from micropropagated control plants showed 2.2-fold more catalase activity than control plants propagated by cutting and transgenic plants; transgenic fruits contained 1.8-fold more caffeic acid than those from macropropagated and micropropagated control plants; fruits from micropropagated control plants and transgenic plants showed 3.9-folds higher ferulic acid content than macropropagated control plants; fruit sinapic acid content was 2.5-fold higher in micropropagated control plants than in transgenic and macropropagated control plants. The differences in biochemical traits brought about by transformation do not appear to be physiologically significant, given that the fruit mass was not different from control plants.