Effects of water stress and constitutive expression of a drought induced chitinase gene on water-use efficiency and carbon isotope composition of strawberry

Abstract

Recombinant DNA technology and tracer technique are being widely used for different purposes. Plant genetic transformation is a common practice for increasing crop tolerance to biotic and abiotic stresses and stable isotopes is a good tool to track the effects of environmental stresses on crop productivity. In this research, the effect of water stress on plant carbon isotopic composition (δ¹³C) and water use efficiency (WUE), as indicators of physiological processes and environmental factors, were evaluated for transgenic strawberry (Fragaria x ananassa) plants continuously expressing a chitinase gene and non-transgenic plants. To implement water stress, strawberry plants were grown in pots and were assigned to three different soil water contents (SWC) of well-watered, moderately-watered and water-stressed. Treatments were implemented for two months, in a growth chamber. At the final stage of the experiment, leaves were randomly collected from each experimental unit. After oven-drying and powdering, subsamples of 4 to 5 mg of plant materials were combusted under vacuum, using Vycor tubes containing cupric oxide and silver wire. Combustion took place at 520 degrees C for 5 hrs to produce carbon dioxide. Carbon isotope composition (δ¹³C) was measured relative to Vienna Pee Dee Belmnite (VPDB). Both SWC and the expression of chitinase gene in transgenic strawberry plants significantly affected δ¹³C and WUE (p < 0.001). Highly significant (p < 0.01), but negative correlations were found between δ¹³C and plant dry matter components, such as lead dry matter (r = -0.92; p = 0.009) and total dry matter (r = -0.92; p = 0.008). High correlations were found between δ¹³C and water use per plant (r = -0.93; p = 0.006), and between δ¹³C and leaf area per plant (r = -0.93; p = 0.006).