Abstract
BackgroundThe DefH9-iaaM gene fusion which is expressed specifically in placenta/ovules and promotes auxin-synthesis confers parthenocarpic fruit development to eggplant, tomato and tobacco. Transgenic DefH9-iaaM eggplants and tomatoes show increased fruit production due mainly to an improved fruit set. However, the weight of the fruits is also frequently increased.ResultsDefH9-iaaM strawberry and raspberry plants grown under standard cultivation conditions show a significant increase in fruit number and size and fruit yield. In all three Rosaceae species tested, Fragaria vesca, Fragaria x ananassa and Rubus idaeus, DefH9-iaaM plants have an increased number of flowers per inflorescence and an increased number of inflorescences per plant. This results in an increased number of fruits per plant. Moreover, the weight and size of transgenic fruits was also increased. The increase in fruit yield was approximately 180% in cultivated strawberry, 140% in wild strawberry, and 100% in raspberry. The DefH9-iaaM gene is expressed in the flower buds of all three species. The total IAA (auxin) content of young flower buds of strawberry and raspberry expressing the DefH9-iaaM gene is increased in comparison to untransformed flower buds. The DefH9-iaaM gene promotes parthenocarpy in emasculated flowers of both strawberry and raspberry.ConclusionsThe DefH9-iaaM gene is expressed and biologically active in Rosaceae. The DefH9-iaaM gene can be used, under cultivation conditions that allow pollination and fertilization, to increase fruit productivity significantly in Rosaceae species. The finding that the DefH9-iaaM auxin-synthesizing gene increases the number of inflorescences per plant and the number of flowers per inflorescence indicates that auxin plays a role in plant fecundity in these three perennial Rosaceae species.
Highlights
The DefH9-iaaM gene fusion which is expressed in placenta/ovules and promotes auxin-synthesis confers parthenocarpic fruit development to eggplant, tomato and tobacco
In the present study we have shown that introduction of the DefH9-iaaM gene construct causes a significant increase in fruit production which results from an increase in individual fruit weight, an increased number of fruits per inflorescence and an increased number of inflorescences per plant
The two transgenic F. vesca lines used in this study had either one or three copies of the DefH9-iaaM gene (Fig. 1, panel a, lanes 2 and 3, respectively)
Summary
The DefH9-iaaM gene fusion which is expressed in placenta/ovules and promotes auxin-synthesis confers parthenocarpic fruit development to eggplant, tomato and tobacco. Transgenic DefH9-iaaM eggplants and tomatoes show increased fruit production due mainly to an improved fruit set. In the present study we have evaluated, under environmental conditions permitting pollination and fertilization, the effects caused by the expression of the DefH9iaaM gene in fruit species belonging to the Rosaceae. Both wild and cultivated strawberry and raspberry are fruitbearing species cultivated for the high quality and value of their fruits. In Rosaceae, the increase in fruit production is due neither to parthenocarpic fruit development nor to enhanced fruit set but to increased plant fecundity, and only in minor part to enhanced fruit weight
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