Evaluation of the effect of drought stress on fruit quality of transgenic strawberry plants with cell wall encoding genes down-regulated.

Abstract

Strawberry is an important crop in our country. One of the main challenges of this crop is to produce high-quality fruits with a prolonged post-harvest shelf life. Strawberries are particularly susceptible to water stress so climate change will pose a significant challenge for quality fruits production. This study aimed to characterize, under water restriction conditions, the performance of several transgenic lines of strawberry (Fragaria × ananassa, Duch.) with genes encoding cell wall enzymes involved in fruit softening down-regulated. The lines used were: PG29 and 18A13, modified in the polygalacturonase gene FaPG1; βGal28, with the β-galactosidase gene FaβGal4 silenced; RGli26, with the ramnogalacturonan lyase gene FaRGLyase1 silenced. All these lines produced ripe fruits significantly firmer than the control. The plants were grown in a greenhouse under sufficient (3.3 L·m-2·dia-1) or deficient (0.5 L·m-2 ·dia-1) irrigation conditions. The vegetative growth of the plants under stress conditions decreased significantly in the same proportion in all lines tested. Likewise, a similar reduction in fruit weight and size was observed in all genotypes tested, as well as in the number of fruits produced per plant. In terms of fruit quality, all transgenic lines produced firmer fruits than the control under sufficient water conditions. In the water stress treatment, the two lines with the modified FaPG1 gene produced fruits firmer than the control. However, the RGli26 and βGal28 lines showed a decrease in fruit firmness, obtaining values similar to the non-transformed control. No significant variations in colour and soluble solids were detected in any of the analysed lines. These results indicate that FaPG1 gene manipulation is a viable alternative to increase the postharvest shelf life of strawberry plants cultivated under water restriction; nevertheless, the increase in firmness obtained by β-galactosidase or RGlyase silencing is reversed under water stress